Also, it's 8P8C, not RJ45, and sometimes it's more important to use the term from a standard body, but usually it's more important to use the term everyone knows. When documenting, I recommend saying something like this:
J3 is an 8P8C jack (commonly RJ45) for IEEE P802.3bz 2.5GBASE-T communications, backward compatible with Gigabit and Fast Ethernet
A lot of connector series are are multi-sourced because big clients tend to require this. For example the 38999 series connectors used in military and aviation applications are made be TE, Amphenol, Souriau, ITT Cannon, Eaton...
So it's really not uncommon to have manufacturers make something thing that a different company is known for. I think it's basically just luck that Molex got the credit for it
"Molex" usually refers to flat 4 pin AMP 1-480424-0 or Molex 8981-04P connectors(part number taken from random pdf on the Internet[1]). Confusing as it is... Actual Molex Mini-Fit are rarely colloquially referred to as Molex.
And "JST" is used for any small white plastic connector with one side open showing the pins. "DuPont" means "Amphenol Mini-PV" or "Harwin M-20" or any other Mini-PV clone.
I work a lot with connectors and I'm not really sure what you mean by extruded pin connectors. Typically the terminals are formed from sheet, unless you're using fancy 38999-style pins, which I believe are machined (and very expensive).
At a certain point, the genericized trademark is the correct term, like how aspirin is the correct term (only term, really) for a specific preparation of acetylsalicylic acid, even though it was a trademark of the Bayer corporation.
Ah, so it does appear that Mate-n-Lok is a name that AMP/TE uses for some Molex-compatible products. For example, TE’s Micro Mate-n-Lok appears to be compatible with Molex’s Micro-Fit.
It’s the one the diagram of connectors calls “peripheral power connector” but the document doesn’t seem to go into details for it. Basically the original PC drive power connector, so 5.25” drives, older hard discs, optical drives etc. use it, in the latter cases it’s been replaced by the SATA power connector.
...and Berg (0.1") connectors are now Dupont, even though Dupont doesn't make them anymore, and has had nothing to do with them since 1993. Everyone called them "Berg" in 1978 when I was first exposed to them, even though Dupont had acquired the product line from Berg in 1972.
2.5GBASE-T? But I do 10GBASE-T over one. Provided it has Cat 6A cable inside it and has been tested to IEC 60512-9-3 & IEC 60512-99-002. (See https://ieee802.org/3/bt/public/oct15/Draft%20of%20IEC%20605... for some fun photos of what happens when PoE is disconnected on a connector before IEC 60512-99-002...).
The combination of "When documenting" and referencing "J3" indicates that dlcarrier is referencing a limitation of a specific port on a product that they worked on, not a set of global limitations on any 8P8C connectors
I had assumed that the wires in the jack would rest along the bottoms of the blades in the plug, but I guess if it was never designed for high current applications, the contact area wouldn't be a consideration.
It took a few tries to get it right, but it's amazing that PoE is even an option given how far it is outside of the scope of what the cables and connectors were designed for. I've heard of locations that use it for power, instead of 120 V outlets, because it's cheaper and safer and most portable high-current appliances use batteries, while fixed high-current appliances use 240 V outlets.
Hot plugging is always a challenge, especially with direct current, and negotiation prevents that from being a problem while making a connection, but I never considered that unplugging isn't negotiated first. I wonder if IEC has ever considered using a locking latch, like an EV charger.
I have a PoE camera that I sometimes unplug to restart it, when it freezes up and I can't restart it from the web interface. I'll be sure to turn that port off first, before unplugging it.
If you can turn the port off and then back on remotely, perhaps you can skip the unplugging part completely? I know that some managed PoE switches even offer a button to power cycle a port.
Good point, now that you mention it, it's not turning off PoE, just stopping data. I don't know if there's a great way to handle it, and there's no way I'm shutting off the entire switch. I'll just unplug the patch panel end of the cable, instead of the switch end, so the jack I'm wearing out is one that's easy to replace.
While your preferred specification is excellent, It’s “an ethernet port” in ordinary usage. Or “ethernet jack” in more technical contexts and entirely sufficient for Ali Express.
> While your preferred specification is excellent, It’s “an ethernet port” in ordinary usage. Or “ethernet jack” in more technical contexts and entirely sufficient for Ali Express.
Right, in your average 2020s home or office, "Ethernet" is almost certainly 8P8C (commonly known as RJ-45). In decades past it was more ambiguous – in the 1990s, coax – ThinNet/10Base2 – was still reasonably common; even the older ThickNet/10Base5 would still occasionally be encountered. So to some extent, being specific is a bit of an "old timer" trait–a habit picked up decades ago when it was still important, now maintained when it is rarely still necessary.
But even in the 2020s – in a factory, it could easily be M12 instead. Or even a mix of both – 8P8C in the offices, but M12 on the factory floor.
Honestly, even in a home environment, I hate how fragile and easily unplugged 8P8C connectors are (the worst part is when they get slightly pulled out, so they still look like they are plugged in, but the connection is dead or flaky). I've thought about using M12 at home before, but it probably wouldn't be very practical.
RJ45S and RJ45M are ordering codes for so-called “registered jack” configurations for terminal connections to the U.S. telephone network. These codes were defined until 2000 in the FCC Rules (47 CFR § 68.502(e)) and later in the TIA/EIA-IS-968 standard, and they refer to single and multiple arrangements of two wires and a programming resistor on a miniature eight-position keyed jack.
Unfortunately, the “RJ45” part of these codes has become a metonym for the unkeyed version of the miniature eight-position jack and plug, now widely used for Ethernet and other purposes, but strictly speaking, RJ45 refers to a different connector with totally incompatible wiring.
RJ45 is a keyed 8-position jack, not a normal 8-position jack. ("Keyed" means that there's a notch in the side making it a different shape; you would not be able to fit an "Ethernet" connector into it.)
Closer is RJ38X, which is a series 8-position jack, not a normal 8-position jack. ("Series" means that the jack shorts pint 1 to pin 4 and pin 5 to pin 8 when there's not a cable plugged in to it; you would be able to fit an "Ethernet" connector into it, but even so it's probably not what you want.)
AFAICT (skimming 47 CFR part 68, and the historical AT&T documents that became 47 CFR part 68), there is no RJ-number for a normal 8-position jack.
> you would not be able to fit an "Ethernet" connector into it
Because of the size being different? Surely a keyed female plug will take a male connector with or without the key. Or did you mean you couldn't fit a RK45 connector into a Ethernet plug because then the key would interfere?
RJ45 is a mechanically (slightly) different connector, but indeed all RJ specs were for phone lines, with RJ45 focused on several lines for high speed modem connections.
The regular ethernet 8P8C connector was defined by both an ANSI and ISO spec, neither of which gave the connector an actual name as it covers modular connector designs. :/
To be fair, 5 out of the 6 phone support agents I talked to at Optimum (an ISP) did not know what IPv6 is, so saying you used to do phone support for an ISP isn't really saying much.
RJ45 is a connector with a key notch sticking out and a "programming" resistor joining two of the pins. It won't work for Ethernet at all, the plug side can't even fit in the 8P8C socket Ethernet uses. If you grind off the key it'll still not work, because of the embedded resistor. Also the pinout is totally wrong, so even if you didn't have the resistor it wouldn't work. None of the RJ connectors have the correct pinout for Ethernet.
Specifically, what is colloquially an "RJ45" or "Ethernet" connector is an 8P8C "Bell System Miniature Plug/Jack" (AT&T's original name; it is a smaller version of the older Bell System connectors) / "miniature plug/jack" (FCC genericization of the name by removing "Bell System", even though the word "miniature" is no longer meaningful without context) / "modular jack" (ANSI/IEC genericization). That is what is meant when just "8P8C" is said.
Pedantically speaking, RJ45 (as first defined by AT&T internally[1], and later by the FCC's 47 CFR part 68) is not that. The RJ45 socket is a keyed 8P8C modular jack, not a regular 8P8C modular jack. Here is a photo: https://commons.wikimedia.org/wiki/File:RJ45_female_connecto...
[1]: The "RJ45" designation was originally an AT&T "USOC" (Universal Service Order Code). In the '70s, the FCC told AT&T that they had to allow interoperability from other companies, so the FCC had to publish a bunch of specifications; the meaning of "RJ45" became publicly specified in Bell System Communications' Technical Reference PUB 47101 "Standard Plugs And Jacks" (1979, though I think there might be an older number/revision from the early '70s that I haven't been able to track down). That (in combination with a few other technical references, such as PUB 47102), later became part of the Code of Federal Regulations, as 47 CFR part 68.
Well you definitely SHOULD say RJ45. We do a lot of networking at my job and if I asked for an 8P8C connector, I would get confused stares. Say Ethernet cable, Cat 6 cable (or whatever cat), or RJ45. Sometimes being correct isn’t the right thing to do.
If a contractor installed exactly what he asked for, an RJ45 jack which would be unusable for his needs he would have no grounds to stand on to demand it be corrected without paying more. By specifying the technically correct name as well as the colloquially recognized name he is being precise and accommodating.
If a contract requires RJ45 terminated Ethernet patch cables and the contractor delivers keyed RJ45, they have not delivered because RJ45 doesn’t even have the correct conductor layout to act as an Ethernet cable. Contracts call for RJ45 all the time and there are no mixups. You’d probably find it quite difficult to even find vendors for keyed RJ45
I know this feels like a technically correct gotcha, but in fact is not. Do some parametric searches on digikey and flip through some manufacturer catalogs. If you go out of your way to misinterpret industry standard jargon you won't be paid for your work and you'll lose the contract.
I take issue with referring to the DB-25 as the connector you'd see for old parallel ports. I'm old enough to remember when the DB-25 was universally used for RS-232 serial ports, and parallel used an oddball larger Centronics connector.
D-sub has got to be one of the longest enduring connector standards I can think of, apart from wall outlets. They're from the 50s, originally for military use, and we're still speccing them in new space hardware today. Now they've got coax/twinax, high power, fiber, and even pneumatic "contacts" if you know where to look (and can afford it). I can't say that they'd be my first choice, personally, but it's quite remarkable to see how well they've fared over the better part of a century.
XLR used (mostly) in audio is also from the 1950s.
The biggest problem with these standards is they are used for everything and so you cannot be sure that if the cable fits it will work. If a USB cable fits it will almost always work - but if it doesn't it will be obvious to your average idiot way (that is you can plug a mouse into a power supply - but nobody expects it will work). USB-C somewhat violates that, but even still it mostly is a case if you can get the connectors to fit it works.
When the plug is inserted, the jack "breaks its normal connection." Like they didn't want to leave the audio output like a floating pin to reduce stray voltage?
Scribner calls the switch "spring-jack" after "jack-knife" where the "jack" part of it comes from the name Jack and in the 1300s meant a mechanical device. So the "female" component of the connection was thereby given a "male" name.
Charles E. Scribner filed a patent in 1878 to facilitate switchboard
operation using his spring-jack switch. In it, a conductive lever pushed by a
spring is normally connected to one contact. But when a cable with a
conductive plug is inserted into a hole and makes contact with that lever,
the lever pivots and breaks its normal connection. The receptacle was called
a jack-knife because of its resemblance to a pocket clasp-knife. This is said
to be the origin of calling the receptacle a jack. Scribner filed a patent in
1880 which removes the lever and resembles the modern connector and made
improvements to switchboard design in subsequent patents filed in 1882.
late 14c., jakke "a mechanical device," from the masc. name Jack. The proper
name was used in Middle English for "any common fellow," and thereafter
extended to various appliances which do the work of common servants (1570s).
I don't think it was about not wanting to leave the audio input floating. Rather the "normal connection" is that the telephone subscriber is connected directly to the switchboard operator's annunciator (a display panel) so that the subscriber can light up a bulb on the annunciator when that subscriber wishes to ask the operator to reroute that subscriber's connection to another subscriber (instead of to the switchboard operator). This is why the switch ought to act like a double-throw, not just a single-throw switch. I think something along those lines is the reason...
> In a telephone-exchange system the wires of the several subscribers are run into a cen tral office, where, upon request, any wire may be connected with that of any other subscriber.
> In Fig. 4 is shown the cut-out connected with subscriber's wire in and the relay and annunciator P and O, and also, with the operator's telephone J, by means of the plug A, which is provided with a metallic point, and conducting-cord d. The connections are formed as follows: The subscriber S, by throwing on his local battery, sends a current along the wire in through the relay P, which, closing, the annunciator number of S is indicated at O, and the current passes along the Wire H, and thence through the switch to the ground Wire G.
Didn't even think of that, yes of course XLR and for that matter, 1/4" TS/TRS connectors were originally for switching phones at AT&T, before automated switching. Incidentally, you can also blow up quite a bit of stuff with them, depending on whether they are at consumer "line level", pro audio "line level", or even speaker level. We're definitely too comfortable with "if it fits, it works" (or at least isn't harmful".
There was a wild period in early transistor electronics where DC power adapters sometimes used 1/8" phone jacks - before the barrel-style DC plugs became common. Having 9V DC in a form that could be plugged into a microphone input always seemed like a pretty insane choice.
I'd like to mention my USB-stick-shaped audio recorder/player who's headphone jack (only uses built-in mic in any case, though iirc the headphone button skips to the next file) functions as the computer and charging connector.
The device was shipped with a cable (USB-A male) <> (TRRS 3.5mm aka 1/8") for this usage. It reports as mass storage.
Though that’s both older and better than RCA plugs. Somehow both RCA and NEMA managed to spread, the former world-wide, the latter only US + colonies, despite much better alternatives already existing and the drawbacks being obvious even 100 years ago.
I always thought this was really interesting. The Coast Guard's Electrician's Mate training program taught electron-flow theory, so it was tough to switch my brain to hole-flow theory when I went to college. Technically the math is the same but man it threw me off with schematics.
Ben Franklin's coin flip landed the wrong way - nowadays electronics circuits are calculated and drawn assuming movement of positive charges, when in reality it's the negatively charged electrons that flow.
Nothing wrong with saying that an absence of electron is moving. Both electrons and electron holes are just excitations in a quantum field anyway... ;-)
It can, but nobody would do that as it would be cheaper to use a DB-25 connector and not use all the pins. If they went for the cursed true DB-9 they would need to meet the minimum order quantity for a special order, pay for the manufacturer's tooling, and any required certifications. If you needed the spacing between pins for some reason you would probably just specify the use of crimp-and-insert.
That being said, the DE-0 is real, but it can't hurt you.
It's just a filler that in the form of a DE connector with no holes for any pins. It was an old full-rack CISC AS/400 for what it's worth, but I scrapped it 30 years ago.
I have a vague memory of a computer (probably in the 16 bit era?) saving money on providing two joystick ports by using a DB25 housing with the middle pins removed, leaving two 9 pin clusters at the ends, into which two DE9 joysticks could be plugged. The case plastic covered over the middle of the connector.
Could well have been, though I’m still picturing a computer in my mind. Wasn’t the SAM Coupe, but that’s the sort of thing I’m recalling.
But: it was probably quite common on joystick interfaces, now you mention it. Thinking along those lines and searching for ‘twin joystick adapter’ let me actually find an example: https://www.ebay.com/itm/276075015721
Worth noting that in the image that shows two joysticks plugged in they really don’t look like they fit all that well…
I’ve seen (many… many years ago) a DB housing with 9 connectors but with the spacing of 25 pins. Would this then be a DB25C9P?
In retrospect, I think this may have been an adapter from DE9 to DB25, but it would have been a quick way to save a few pennies when only 9 pins were used for serial communication.
True. However, mine were for connecting to modems, so they were definitely only 9 pin serial cables. I didn't have the pleasure of seeing the 13W3 connectors until I was in grad school, and I still think they look weird. It didn't occur to me until today that they were the exact same size/shape as the DB connectors. They were so different that the thought never occurred to me!
How would you even count those 3 giant pins? If I recall correctly, they were for coax cables that ran within the main cable. So each of those pins would have a contact for the shield and the conductor.
The cables I saw were handmade. You can get connectors which are just the shield and an insulator with holes in the place of the pins. You crimp the pins onto the wires, then slide the pins into the insulator. You may have saved a few cents by not inserting the unconnected pins, but the reality is that most people left them out because there was no point in going to the trouble of putting them in.
"DB" already means 25 pins, so well, it's quite hard to both have 25 and 9 pins at the same time.
That is still pedantically different from a DB-25 of which we ripped out pins until it had only nine. The result would be "a DB-9" in big quotes, as it would't be "a", but more like "3/4 of a DB-25".
There’s also a now-quite-rare 23pin variant, which was used for the Amiga video port. Those connectors are getting harder to find these days, some people have resorted to modifying 25pin connectors when making Amiga video cables
DB housing can fit 25 pins in 2 rows. But it can also fit 9 really honkin big pins in 1 row, with a custom mold & pins. 3x groups of 3x12-gauge pins for 60A 3-phase delta power connector in a DB sized shell would probably work for a while before you burn your house down.
Heh flashback, I had an ati all in wonder, which was a video card with built in video capture. Now this involves a lot of ports so the model I had used a port breakout dongle for the video capture stuff, and some engineer had the bright idea to run all these pins through a mini-din connector. Think a ps/2 connector with about 10 pins crammed into it. Now ps/2 connectors are sort of stupid in the first place. why a round connector that is keyed to only go in one way? But this 10 pin variant was a nightmare to insert and by about the third time I made a firm resolution to never unplug it again if I could help it.
Footnote: keyed round connectors are not actually that bad, super strong, easy to seal and you can fit a large nut or bayonet clamp to them to make them extremely secure. However, this depends on having a well placed shell/key and mini-din doesn't, it is a bad connector. Not enough shell and key for solid locating so the pins tend to ride on the face while you try and orient it.
Sure you could do it. You could even put 25 pins in 9 pin housing if you made the pitch smaller.
They just don’t exist, and hopefully never will.
Maybe not as a standard, but I've seen a several companies stuff a crazy number of pins into a DE9 shell. I think one of them was my old GRiD Compass.
Beast of a machine. Heavy as hell, magnesium case, bubble memory, a screen that caused all televisions it was pointed at to lose their signal, and a sticker on the bottom saying it was illegal to use it in a whole list of countries, including Israel.
Seems like it has 19 pins in a DE9 shell. That's a lot. VGA connectors were also in a DE9 shell, but had 15 pins.
The funny thing about the GRiD DE9 connector is that it's labeled "Serial", but every DE9 serial port connector I've ever seen is 9-pin. I have to wonder what else they are cramming into that 20-pin DE9 "serial" port.
Originally? Because that was the naming convention that Cannon designated. Later, because the shell size wasn't sufficient to determine the number of pins.
> And how do you explain DE15 (popularized by VGA)?
Cannon's D-series connectors started with 2 rows, at the "normal density" of 326/3000 of an inch between pins. They later expanded the range of connectors with "high density" and "double density" connectors that put more pins at greater densities into the original shell sizes. DE15 is in the "high density" range.
VGA connectors were a DE-9 shell with 15 pins in them, and were used widely for many years to connect monitors to computers. There are other connectors that crammed 19 pins into a DE-9 shell. 25 might be a bit too much, but 19 is pretty close.
There's a lot of things like this, especially when the connector is commonly used for just one thing. One is "composite video" which at one point or another I have heard items on this list used interchangeably (though not always at the same time):
composite video
- RS-170
- monochrome video
- EIA-170
- NTSC
- black and white video
- CVBS
- B&W video
- RS-170A
- analog video
- PAL
- yellow RCA plug
- just plain "video"
These don't even all refer to the same thing, and some are definitely more correct than others, but all are used even by technical people.
Here's another one: "Amphenol connector", "Cannon connector" or "Molex connector". It's the same as saying "Ford car".
Not connector related, but I can't tell you how many people use time zones like PST year-round. The ST stands for "standard time," meaning not Daylight Saving Time. Right now, PDT would be appropriate.
The thing that kills me is that they could just say "PT" or "Pacific time" and be right, with less effort.
I always know what they mean, but it's wrong for more than half the year.
The 1.44 MB diskette is my canonical "dear God what happened"-named thing.
The traditional diskette is 1440 KiB. I.e., base-2, today named "kibibyte" though in that day that word didn't exist yet & it was just a kilobyte and the base 2 inferred from context. Clearly, someone didn't infer, and moved the decimal, so that 1.44 "MB" is 1.44 * 1000 * 1024 bytes. The actual capacity is thus either 1.41 MiB or 1.47 MB.
IMO it's the ISP's who are intentionally misleading people. Average Joe might have some inkling of how big a gigabyte is these days, but nobody except a network engineer cares what a gigabit is. I can't imagine how many people buy gigabit fiber expecting a gigabyte. It would sound much less impressive if it were marketed as 125MB/s like it should be. They should at least be required to show both, not make people convert units if they want to find out how fast their advertised internet is supposed to download their 50GB game.
I don't think that counts as intentionally misleading since bits/second is the correct measurement for any serial connection and has been since the days of Baudot. Joe Blow might misunderstand it but that's on Joe.
It's not like the situation with hard drives where they're going against industry convention for marketing purposes.
I have had to debug enough fires because of stupid unit confusion that I now make the point of being extremely pedantic with the use of the right unit.
> today named "kibibyte" though in that day that word didn't exist yet & it was just a kilobyte and the base 2 inferred from context
That is still what most people do. Only very pendantic individuals insist on using KiB, etc. Normal people are just fine inferring from context whether base-2 or base-10 is meant.
My opinion is use KiB as the abbreviation but pronounce it as kilobyte. It pisses off both sides but makes the most sense to me for both being technically and historically accurate at the same time.
Perhaps the formatted capacity, or the safe capacity, but I can specifically recall being able to format those same floppies up to... I forget, maybe ~2MB? Something like that.
Yeah, the unformatted capacities of 3.5” floppy disks were:
SS-DD - 512KB
DS-DD - 1MB
HD - 2MB
ED - 4MB
LS (floptical) - 21MB
Technically you could format some of the lower density media in the high density drives and get the expanded capacity (although you may have needed to modify the media a little - holepunch to make an HD drive see a DS-DD disc as “HD”), although it wasn’t always very reliable and depended on the physical media and the capabilities of the individual drives.
Different file systems used the 2*80 tracks differently, hence the different formatted capacity, DOS usually had the lowest, Macintosh in the middle, Amiga had the most (although the Amiga HD floppies were a bit of a cludge - the drive spun at half speed due to a limitation of the Amiga floppy controller, which was also the reason you couldn’t just use a “PC” HD floppy in an Amiga without modification).
Same with older floppy disk formats. Using FAT16 (or FAT12 on some systems) you can often format DD 3.5" disks to 830K instead of the usual 720K. On the Amiga the same disks are usually 880K.
My favorite example of this is using "aux cable" to refer to an audio cable with a 3 or 4 pin 3.5mm connector on the end (because car stereos would have a 3.5mm jack labeled "Aux" for "Auxiliary input")
I usually call those "headphone cables" just to be contrary.
You have been misusing the D-sub connector terminology
No I haven’t and the same is true for approximately everyone else.
Because we have not been using D-sub connector terminology at all. We have been talking about the things that come with (and without) DB9 connectors. We have been (mostly) playing —- as the witty Wittgenstein would say — a different language game.
That’s why you know what I mean. So bring me a slab.
For me, if I ever say IEC mains lead I get a blank expression. C13 even more so.
"Kettle lead" (Which is notched to indicate it can take a higher temperature and most of cables aren't that, they will be the c13 type), and their face lights up and a cable will be handed to me.
Just one of those things that's wrong, but it's not worth being pedantic over it, imo.
Given the paucity of electric kettles in the USA, I wonder how that term became so widespread.
Ironically in Europe where the IEC cables were familiar from kettles, they've largely been superceded by cables hardwired into a base pad onto which the kettle is set.
I always just called it a serial port, because I could never remember DB9 to begin with. I really hope I remember this so I can impress some nerds in the future with how pedantic I can be. (I don't know how to write that last sentence without it sounding sarcastic, but I really meant it.)
Some other pedant might come along if you keep just calling it a serial port. They might mention that it’s specifically RS-232, and that DB-25 is also used for that. They might also mention that “serial port” could include ports for RS-422 and RS-485. They might even mention SIO and USB.
Null modem, crossover, DTE, DCE, straight-through, full handshaking, no handshaking, RS-232 or TTL levels. Plus CAN, RS-485, RS-422, CGA video, RGB video, and any number of industrial things use or can use the same DE9 connector (including sometimes for power).
DEC equipment had something similar. A 6 pin "MMJ" connector. It almost looks like RJ45 except the clip was off center.
I also remember some 90's terminal servers that had enormous "octopus" cables. There was a single connector on the box that broke out to 8 to 16-ish DB25 serial ports.
Are you sure those weren't using RS-232 over TCP/IP over Ethernet?
That is quite common in the pro audio/video installation world, where RS-232 is common but needs extenders for longer distances.
Within A/V, the norm for local RS-232 lines is actually not DE9 but 3-pin terminal blocks! (RX/TX/GND)
I've seen those even on Cisco video codecs, priced $10'000+.
No, most Cisco devices has an RJ45 shaped RS232C port that needs a special cable to do anything with. It's proprietary, but there's one in every networking guy's backpacks so the situation is only as bad as Lightning cable for iPhone. Most(but not all!!) networking gears that compete with Cisco uses the same cable as well.
Eh, depends on "proprietary", I guess. In the PLC world, using an RJ45 for a variety of serial uses is not uncommon. I've never touched a Cisco router in my life, but I've got a few things like these laying around:
Those are some interesting connectors since they have a REAL RJ45 socket. Also interesting that they come prewired and not some assembly required like the ones from amazon do.
The pinout is also called a Yost Cable. You can read about it on https://yost.com/computers/RJ45-serial/ but its an interesting solution to converting DTE and DCE sides to using a standard port and cable. The downside is that the DIY adapters online need some soldiering to bridge the ground wires and more.
I do believe the DTE and DCE pinouts on the yost page are swapped though. I recently tested the pinouts of a Cisco DE-9 to 8P8C (DB-9 to RJ45) with a multimeter and came up with the DCE pinout instead of the DTE one. I then built an adapter with the DCE pinout to connect to my servers serial port and use them as a make shift null modem cable for terminal access.
If I would have know more about this 5 years ago while still at a previous employer, there was some old equipment that used an unknown pinout that would have gotten a DB-9 to RJ45 adapter slapped on it to change it to Cisco/Yost pinout. I was told not to loose the serial cable in the rack with the device because it was the only one that worked on it but never investigated more into it to find out if it was a straight through, null modem, or something else entirely.
I've got a "Sentry Commander" remote power switch and serial server, with four 6P6C connectors for its serial ports to hook to machines and two 8P8C connectors for its own serial console and modem port. I'm sure it shipped with its own proprietary cables long since lost, but I just use RJ12 cables and those "RJ45"->DE9 modular adapters.
The thing I don't get about this is why did people think it was a good idea to have a serial connection over DB-25? You honestly need only 3 wires. Not 25
For a Parallel port, sure 25 wires is right there. But not for a serial port
Plus the differential versions of most of those signals for long distance doubles the number of pins. And they have optional synchronous clocks. I did some WAN work for 3Com back in the day... :)
My VGA (DE-15) and keyboard and mouse (Mini DIN #6) ports disagree. The printer port (DB-25) could not be reached for comment, as it is still set for uni-directional.
Being on the sharp edge of professional "do you want what you're asking for, or what I assume you want?" misunderstandings, you learn that it breaks in both directions often enough that sometimes not being pedantic up front isn't an option.
I don't think shittalking "well actually" conversations in the context of an equipment vendor making a cutely-titled article that is very sympathetic to the inexact language around designators for products they offer is the play.
This is why I've learned to present people with the concrete consequences and results of their service request. Especially if I get the feeling that someone does not comprehend what they are asking for.
"Your service request will result in X hours of downtime, as well as ireversible data loss between T1 and T2, and a reset of your system back to the state it was in at T1. All changes and interactions after T1 will be lost. Is this what you expect and want?"
Beyond a certain amount of service disruption or monetary investment, asking twice and making sure is prudent, not pedantic.
Normally I agree. The only time I ever raised my voice at a subordinate was because they were consistently lax and inaccurate with technical details. Things like mixing up C and C++ in conversations where it mattered.
But things like DB9 and RJ45 are so commonly used that anyone taking them literally is either being obstinate or are completely new to the field.
In this case, is it that helpful? Since only a lunatic would want a true DB9 and no one’s ever made a giant connector with 9 pins, I fail to see the importance.
> But language is for communication, and the most correct language is that which communicates best.
This seems to be biased in US-American culture. In Germany, people are in my observation much more prone to analyze words and sentences (often by their origins), and many people wouldn't accept a "wrong" way to express things to be correct.
Just to give one example (which also works in English): "[die] Alternative" (the alternative): this word comes from Latin "alter, altera, alterum" (the other). This means, that there exists only one other. So educated people love to point out that talking of multiple "Alternativen" [alternatives] is wrong; by the word origin there can only exist one alternative (the other one). If more than one "alternatives" exist, so, to be precise, you likely want to use a different word.
I think this implies a meaning of "the" that doesn't actually exist in modern english.
"The" often refers to a group or category.
"The other" is actually a phrase I would take to be incredibly inclusive in meaning if not followed by another specifier (it means "the category of everything that is not us").
"The alternative" is similarly a category structure. It's a singular category, made of many possible members, or alternatives.
You may still only pick a single alternate for each case, but that does not mean that a category of multiple possible alternative choices does not exist.
---
All that said, sparkfun is messing up by labeling this DE9. Spoken as someone who's done quite a bit of serial communication work. The defacto industry term is DB9, whether they like it or not, and most searching/purchasing will be done using that term. This is a "technically correct" fun article, with a name that would immediately mean I don't ever find this product (and would not purchase this product) unless they highlight that this is a DB9 breakout board with a bad name.
Simple test? Amazon has more than 4000 results for "db9 cable" and only ~110 results for "de9" cable. Even specialty sites like McMaster, which are usually pretty particular with their terms are happily calling this a db9 connector: https://www.mcmaster.com/products/connectors/computer-connec...
> I think this implies a meaning of "the" that doesn't actually exist in modern english.
> "The" often refers to a group or category.
But this does not hold for the meaning of Latin "alter, altera, alterum" (the other one), from which the German and English word "Alternative"/"alternative" is derived.
Our language started out as a bad habit shared between French soldiers and English barmaids. And the barmaids were speaking a language that started as a bad habit shared between Viking raiders and Anglo-Saxon villagers.
I think you're proving my point. If the people I am talking to and the language I am using both demand precision in word choice, then I would be foolish to use the wrong term and then say "well, you should have known what I meant."
But that is a communication context, and there are other contexts where implications and assumed meanings are expected, and spelling everything out would be considered pompous, self-important, and ridiculous.
Perhaps not in Germany? But certainly elsewhere (but i believe that in German the pronoun "sie" can require assumed context to understand).
> But that is a communication context, and there are other contexts where implications and assumed meanings are expected, and spelling everything out would be considered pompous, self-important, and ridiculous.
> Perhaps not in Germany? But certainly elsewhere (but i believe that in German the pronoun "sie" can require assumed context to understand).
I would indeed claim that in German such assumptions are often spelled out more explicitly than in English.
I do wonder why they decided to have have separate shell size and pin designations given there appears to be a 1:1 correlation between shell sizes and pins (i.e. the 'B' shell is always 25 pins, the 'E' shell is always 9 pins). Perhaps there was plan to have fewer pins in the same shell at some point?
There's also 13-W3: DB shell, 13 pins, 3 of them coax: https://en.wikipedia.org/wiki/DB13W3. They were used for high-end workstation video back in the day.
And for reasons I don't fully understand, somewhat unrelated - if you look around almost any small business in my area, it's almost always VGA, rarely DVI, almost never HDMI or DisplayPort.
My theory is just that the cables came in the box and are screw-on when more modern connectors are friction fit, and the IT departments don't want the hassle of "they just got pulled out." Which should have been predictable - but I can literally see 12th gen Intel, paired with 1080p display, over VGA fairly regularly.
It's 100% because the VGA cable came in the box. Nothing about cables pulling because my lazy counterparts would not even screw in the DE15 cables half the time.
Source: Too many years experience in the desktop support trenches.
Confusingly enough, I’ve actually seen real, properly named DB-9 connectors. They were a cheaper version of a DB-25 to DE-9 converter. Instead of combining the extra pins properly, they just had a DE-9 on one end connected to only 9 pins on the DB end. They sometimes occasionally even worked properly at low enough line rates.
Coax and high-current/voltage pins are not that weird. You can also get truly weird semi-proprietary pins like fiber optics or even pneumatics/fluidics.
I use both DA-15 and DE-15 all the time in my line of work, and I am fastidious about using the correct terminology on all my drawings. Manufacturers are ironically some of the worst at getting this right.
Wouldn't it fit into the nomenclature with another shell type? DF, perhaps?
It is not like there is any real sensibility to the naming anyway. Of the common types, DA, DB, and DC seem to follow a pattern, but DD and DE then go completely off the rails.
If you keep calling it DB9 everybody knows what you're talking about. They don't think you're weird and they also don't waste time talking about terminology.
Words mean things. Especially in engineering disciplines.
It's perfectly fine for a product manager to say "DB9", but the guy who has to order the part from a supplier will probably want to use the correct terminology. If there's a mistake, it's the supplier's fault.
I struggle with someone I work with because of this :( They might as well call a DB9/DE9 a USB connector and expect everyone to understand them. They're both connectors after all, right?
And this reminds me of the time that my colleague put DB15 on a whole bunch of drawings, and we ended up with DA15 connectors instead of DE15. If I see DB9 on any drawing that comes across my desk, it will be corrected.
One of the more confusing versions of this I came in contact with recently is the 23 pin amiga rgb port. It has no real official D-subminature name as there is no such designation for the shell of a 12+11 pin port, which I assume is due to the fact that it was for a non-IBM machine...BUT some sellers (on aliexpress) DO call it a DB-23 port...I did figure it out eventually and got a few but it did take a while after searching for "12+11 serial" and being a bit frustrated at not finding anything.
The real reason is that in the 1980s this illustration ( https://cdn.sparkfun.com/assets/home_page_posts/1/4/2/9/8/DS... ) was not shown to people. And an illustrator, probably who hadn't seen it either, is who got it wrong. I don't blame them. The existence of an arbitrary letter invariably joined with a useful and descriptive number is the fault here. And the illustrator could NOT show the whole thing anyway because it contained diagrams of products not sold. The perfect setup.
That is all. Everything else is blah blah blah (about DB9, love all the examples of other goofy identifiers!)
People strive for accuracy and remember things. I love people-in-general and they have an impressive track record. They improved on the standards committee.
A favourite paper: “ A Microfluidic D-subminiature Connector” “ Standardized, affordable, user-friendly world-to-chip interfaces represent one of the major barriers to the adoption of microfluidics. We present a connector system for plug-and-play interfacing of microfluidic devices to multiple input and output lines.”
https://pmc.ncbi.nlm.nih.gov/articles/PMC3786702/
Previous discussion: https://news.ycombinator.com/item?id=32886596
We used the DD-50 connectors in the telephony world and called them "DD-50 connectors." I always wondered why they were "DD-50" and the 9 and 25 pin connectors were "DB-9" and "DB-25". Now I know... we were just using the nomenclature wrong.
IMO this is a case where being correct causes confusion rather than clarity. Everyone calls this connector DB9, so calling it DE9 is going to make people wonder if it's really a DB9 or only looks like it ...
Surprised that no one has corrected them that it's not RS232 anymore. It was eventually ratified and it's technically called EIA-232-F (at least for the most recent 1997 version).
The examples would illustrate the issue a little better if there were two pin counts with the same shell, eg DE9 and DE15 and maybe two shells with the same pin count (though I'm not aware of such an example).
Yep, was going to comment on this aspect. If you can't have a DB-9 (which would be the large shell but with a bunch of missing pins) they should have just called the m DA-DE or D-(number of pins)
Could the name "DB9" have come from 25-pin serial ports with only the minimum 9 pins populated? That would be a correct "DB9" and would also be valid electrically. I think I've even seen one of those in the wild before.
Interestingly they have 25 to 9-pin adapters and the majority of DB25 devices I worked with were fine either way. So, the devices generally used 9 pins or less (or at least 9 or less pins were "important").
There are, of course, devices that use more than that, but most things seemed to use less. Maybe that's part of the reason the 9-pin became more standard.
Well, I admire the nerd logic, but it seems like it would just unnecessarily cripple sales if people searching for it under the common name can't find it.
Doesn't a DB9 connector include all the DB25 RS-232 handshaking lines, even if not all devices actually use them?
I grew up in the 70s-80s with serial connectors and a drawer full of cables, DB25-DB9 adaptors, gender-benders, null modems, breakout boxes, etc, and the only (very common) source of incompatibility that I can recall was connecting devices where one side wanted hardware handshaking but the other didn't provide it, so having to make custom cables with handshaking tied hi/lo to fake it.
Some devices used software XON/XOFF handshaking, so for example on a typical terminal, depending on what you were connected to, you could pause text being sent to the terminal with XOFF (Ctrl-Q), and resume with XON (Ctrl-S).
I've got a softspot for serial communications - used be more a source of fun rather than frustration to dip into the draw of cables/etc and get two devices happily talking to each other.
> Doesn't a DB9 connector include all the DB25 RS-232 handshaking lines
Handshaking yes, but not all potential RS232 signals, of which there are 11.
I work with RS232 frequently and even CTS/RTS is rare to use. Never personally seen anything use DTR, DCD, DSR, or RI though I know they did see historical use.
But it is kinda important to know if something is using TTL or RS-232 voltages before connecting to it. Using the wrong one might let the magic smoke out.
Given that DB9 is so pervasive (and I admit this is new information to me), I thought AI training data might include the error but no, ChatGPT knows DB9 is wrong:
This might not prevail in the world of tech, but in language studies, words mean what the majority of their users think they mean. Examples:
* Decimated. How many of you know this means (or once meant) reduced by 1/10?
* Literally. Often used to mean figuratively, to the degree that it can be relied on to mean nothing at all.
* Reign, as in "reign him in". Clearly now an accepted misuse, reign once defined what a monarch does to a kingdom, not what a cowboy does to a horse (i.e. rein).
* Fewer / less. Sadly interchangeable in modern writing, "fewer" was once reserved for enumerable things, while "less" referred to continuous measures. Less water, fewer liters of water.
* Double precision. In computer science, defined in IEEE 754 as a floating-point data format with a 53-bit mantissa, therefore 15.95 decimal digits (53 * log(2)/log(10)). Now the norm, the default, to the degree that people may forget what "double" refers to. Because of double's ubiquity, in the fullness of time I expect single precision will come to be known as ... wait for it ... half precision.
Lexicographers are at pains to point out that words mean what people think they mean. I think they have a point.
The correct technical designation for a D-sub connector with nine pins is DE9.
It’s early and eyes are still a little blurry, but I’m not seeing a cite?
Wikipedia fleshes it out a bit:
The D-sub series of connectors was introduced by Cannon in 1952.[3] Cannon's part-numbering system uses D as the prefix for the whole series, followed by one of A, B, C, D, or E denoting the shell size, followed by the number of pins or sockets
No links to a primary source, but seems plausible.
Also, it's 8P8C, not RJ45, and sometimes it's more important to use the term from a standard body, but usually it's more important to use the term everyone knows. When documenting, I recommend saying something like this:
Right. RJ45 was sort of like an 8P8C, but had a thing on the side so you actually couldn't plug a "real" RJ45 cable into a "normal" 8P8C slot.
And Molex power connectors are actually AMP Mate-n-Lok connectors.
I didn't learn this until this year...
A lot of connector series are are multi-sourced because big clients tend to require this. For example the 38999 series connectors used in military and aviation applications are made be TE, Amphenol, Souriau, ITT Cannon, Eaton...
So it's really not uncommon to have manufacturers make something thing that a different company is known for. I think it's basically just luck that Molex got the credit for it
Which “Molex connector” are you referring to? The ATX spec specifically specifies Molex Mini-Fit part numbers, and claims this is for compatibility with PCIe: https://cdn.instructables.com/ORIG/FS8/5ILB/GU59Z1AT/FS85ILB...
Is Mate-n-Lok perhaps a compatible product from a competitor?
"Molex" usually refers to flat 4 pin AMP 1-480424-0 or Molex 8981-04P connectors(part number taken from random pdf on the Internet[1]). Confusing as it is... Actual Molex Mini-Fit are rarely colloquially referred to as Molex.
1: https://community.intel.com/cipcp26785/attachments/cipcp2678...
I've heard it argued that "Molex" means any extruded-pin connector.
Like "Kleenex" means any facial tissue that is meant to be sneezed on.
(Both uses are wrong, but both also tend to promote efficient communication.)
And "JST" is used for any small white plastic connector with one side open showing the pins. "DuPont" means "Amphenol Mini-PV" or "Harwin M-20" or any other Mini-PV clone.
I’ve seen Molex’s part catalogue, and would expect that almost any connector could be a molex part ;)
I work a lot with connectors and I'm not really sure what you mean by extruded pin connectors. Typically the terminals are formed from sheet, unless you're using fancy 38999-style pins, which I believe are machined (and very expensive).
At a certain point, the genericized trademark is the correct term, like how aspirin is the correct term (only term, really) for a specific preparation of acetylsalicylic acid, even though it was a trademark of the Bayer corporation.
Ah, so it does appear that Mate-n-Lok is a name that AMP/TE uses for some Molex-compatible products. For example, TE’s Micro Mate-n-Lok appears to be compatible with Molex’s Micro-Fit.
It’s the one the diagram of connectors calls “peripheral power connector” but the document doesn’t seem to go into details for it. Basically the original PC drive power connector, so 5.25” drives, older hard discs, optical drives etc. use it, in the latter cases it’s been replaced by the SATA power connector.
ATX should call out Molex Mini-Fit Junior connectors. There are many Mini-Fit.
...and Berg (0.1") connectors are now Dupont, even though Dupont doesn't make them anymore, and has had nothing to do with them since 1993. Everyone called them "Berg" in 1978 when I was first exposed to them, even though Dupont had acquired the product line from Berg in 1972.
https://www.reddit.com/r/electronics/comments/ioc6sf/i_final...
2.5GBASE-T? But I do 10GBASE-T over one. Provided it has Cat 6A cable inside it and has been tested to IEC 60512-9-3 & IEC 60512-99-002. (See https://ieee802.org/3/bt/public/oct15/Draft%20of%20IEC%20605... for some fun photos of what happens when PoE is disconnected on a connector before IEC 60512-99-002...).
The combination of "When documenting" and referencing "J3" indicates that dlcarrier is referencing a limitation of a specific port on a product that they worked on, not a set of global limitations on any 8P8C connectors
I had assumed that the wires in the jack would rest along the bottoms of the blades in the plug, but I guess if it was never designed for high current applications, the contact area wouldn't be a consideration.
It took a few tries to get it right, but it's amazing that PoE is even an option given how far it is outside of the scope of what the cables and connectors were designed for. I've heard of locations that use it for power, instead of 120 V outlets, because it's cheaper and safer and most portable high-current appliances use batteries, while fixed high-current appliances use 240 V outlets.
Hot plugging is always a challenge, especially with direct current, and negotiation prevents that from being a problem while making a connection, but I never considered that unplugging isn't negotiated first. I wonder if IEC has ever considered using a locking latch, like an EV charger.
I have a PoE camera that I sometimes unplug to restart it, when it freezes up and I can't restart it from the web interface. I'll be sure to turn that port off first, before unplugging it.
If you can turn the port off and then back on remotely, perhaps you can skip the unplugging part completely? I know that some managed PoE switches even offer a button to power cycle a port.
Good point, now that you mention it, it's not turning off PoE, just stopping data. I don't know if there's a great way to handle it, and there's no way I'm shutting off the entire switch. I'll just unplug the patch panel end of the cable, instead of the switch end, so the jack I'm wearing out is one that's easy to replace.
It's just the chip the NSA put in the cable, failing to initialize first try.
You'll also enjoy annex H of https://usb.org/sites/default/files/USB%20Type-C%202.4%20Rel...
While your preferred specification is excellent, It’s “an ethernet port” in ordinary usage. Or “ethernet jack” in more technical contexts and entirely sufficient for Ali Express.
> While your preferred specification is excellent, It’s “an ethernet port” in ordinary usage. Or “ethernet jack” in more technical contexts and entirely sufficient for Ali Express.
Right, in your average 2020s home or office, "Ethernet" is almost certainly 8P8C (commonly known as RJ-45). In decades past it was more ambiguous – in the 1990s, coax – ThinNet/10Base2 – was still reasonably common; even the older ThickNet/10Base5 would still occasionally be encountered. So to some extent, being specific is a bit of an "old timer" trait–a habit picked up decades ago when it was still important, now maintained when it is rarely still necessary.
But even in the 2020s – in a factory, it could easily be M12 instead. Or even a mix of both – 8P8C in the offices, but M12 on the factory floor.
Honestly, even in a home environment, I hate how fragile and easily unplugged 8P8C connectors are (the worst part is when they get slightly pulled out, so they still look like they are plugged in, but the connection is dead or flaky). I've thought about using M12 at home before, but it probably wouldn't be very practical.
M12 gets old quick if you do a lot plug/unplug cycles.
That does you no good in my line of work, where it's just as likely to be a serial port.
After googling for an image of that, jesus christ you learn something new everyday.
Yeah, I learned that rencently, engineers are dumb on naming things and remember the namings.
_o/
100% guilty here, ouch.
also never saw a 8P8C "keyed, real rj45" connector in person.
Most 8P8C other connectors are incompatible with RJ45.
Why wouldn't you say RJ45?
RJ45S and RJ45M are ordering codes for so-called “registered jack” configurations for terminal connections to the U.S. telephone network. These codes were defined until 2000 in the FCC Rules (47 CFR § 68.502(e)) and later in the TIA/EIA-IS-968 standard, and they refer to single and multiple arrangements of two wires and a programming resistor on a miniature eight-position keyed jack.
https://www.govinfo.gov/content/pkg/CFR-2000-title47-vol3/pd...
Unfortunately, the “RJ45” part of these codes has become a metonym for the unkeyed version of the miniature eight-position jack and plug, now widely used for Ethernet and other purposes, but strictly speaking, RJ45 refers to a different connector with totally incompatible wiring.
RJ45 is a specific AT&T USOC order code to slap a normal 8P8C jack on someone's wall to provide something like multi-line analog telephone service.
RJ45 is a keyed 8-position jack, not a normal 8-position jack. ("Keyed" means that there's a notch in the side making it a different shape; you would not be able to fit an "Ethernet" connector into it.)
Closer is RJ38X, which is a series 8-position jack, not a normal 8-position jack. ("Series" means that the jack shorts pint 1 to pin 4 and pin 5 to pin 8 when there's not a cable plugged in to it; you would be able to fit an "Ethernet" connector into it, but even so it's probably not what you want.)
AFAICT (skimming 47 CFR part 68, and the historical AT&T documents that became 47 CFR part 68), there is no RJ-number for a normal 8-position jack.
> you would not be able to fit an "Ethernet" connector into it
Because of the size being different? Surely a keyed female plug will take a male connector with or without the key. Or did you mean you couldn't fit a RK45 connector into a Ethernet plug because then the key would interfere?
RJ45 is a mechanically (slightly) different connector, but indeed all RJ specs were for phone lines, with RJ45 focused on several lines for high speed modem connections.
The regular ethernet 8P8C connector was defined by both an ANSI and ISO spec, neither of which gave the connector an actual name as it covers modular connector designs. :/
I used to do phone support for a phone company / isp and I have no idea what you just wrote.
To be fair, 5 out of the 6 phone support agents I talked to at Optimum (an ISP) did not know what IPv6 is, so saying you used to do phone support for an ISP isn't really saying much.
you tell him!
RJ45 is a connector with a key notch sticking out and a "programming" resistor joining two of the pins. It won't work for Ethernet at all, the plug side can't even fit in the 8P8C socket Ethernet uses. If you grind off the key it'll still not work, because of the embedded resistor. Also the pinout is totally wrong, so even if you didn't have the resistor it wouldn't work. None of the RJ connectors have the correct pinout for Ethernet.
He said RJ45 is an AT&T part/reference number. Just like RJ11 which is your small phone plug that had 6pins, more rare.
Nit: RJ11 has two contacts.
RJ11, RJ14 and RJ25 all used the same 6P housing though, making them 6P2C, 6P4C and 6P6C connectors, respectively.
Things sold as RJ11 is often 6P4C, making for another error. The rule of thumb is that anything referred to as RJ-something is likely wrong.
Specifically, what is colloquially an "RJ45" or "Ethernet" connector is an 8P8C "Bell System Miniature Plug/Jack" (AT&T's original name; it is a smaller version of the older Bell System connectors) / "miniature plug/jack" (FCC genericization of the name by removing "Bell System", even though the word "miniature" is no longer meaningful without context) / "modular jack" (ANSI/IEC genericization). That is what is meant when just "8P8C" is said.
Pedantically speaking, RJ45 (as first defined by AT&T internally[1], and later by the FCC's 47 CFR part 68) is not that. The RJ45 socket is a keyed 8P8C modular jack, not a regular 8P8C modular jack. Here is a photo: https://commons.wikimedia.org/wiki/File:RJ45_female_connecto...
[1]: The "RJ45" designation was originally an AT&T "USOC" (Universal Service Order Code). In the '70s, the FCC told AT&T that they had to allow interoperability from other companies, so the FCC had to publish a bunch of specifications; the meaning of "RJ45" became publicly specified in Bell System Communications' Technical Reference PUB 47101 "Standard Plugs And Jacks" (1979, though I think there might be an older number/revision from the early '70s that I haven't been able to track down). That (in combination with a few other technical references, such as PUB 47102), later became part of the Code of Federal Regulations, as 47 CFR part 68.
Well you definitely SHOULD say RJ45. We do a lot of networking at my job and if I asked for an 8P8C connector, I would get confused stares. Say Ethernet cable, Cat 6 cable (or whatever cat), or RJ45. Sometimes being correct isn’t the right thing to do.
If a contractor installed exactly what he asked for, an RJ45 jack which would be unusable for his needs he would have no grounds to stand on to demand it be corrected without paying more. By specifying the technically correct name as well as the colloquially recognized name he is being precise and accommodating.
If a contract requires RJ45 terminated Ethernet patch cables and the contractor delivers keyed RJ45, they have not delivered because RJ45 doesn’t even have the correct conductor layout to act as an Ethernet cable. Contracts call for RJ45 all the time and there are no mixups. You’d probably find it quite difficult to even find vendors for keyed RJ45
I know this feels like a technically correct gotcha, but in fact is not. Do some parametric searches on digikey and flip through some manufacturer catalogs. If you go out of your way to misinterpret industry standard jargon you won't be paid for your work and you'll lose the contract.
Another, it's not an API it's an backend to backend http server, (but we know what you mean)
I take issue with referring to the DB-25 as the connector you'd see for old parallel ports. I'm old enough to remember when the DB-25 was universally used for RS-232 serial ports, and parallel used an oddball larger Centronics connector.
D-sub has got to be one of the longest enduring connector standards I can think of, apart from wall outlets. They're from the 50s, originally for military use, and we're still speccing them in new space hardware today. Now they've got coax/twinax, high power, fiber, and even pneumatic "contacts" if you know where to look (and can afford it). I can't say that they'd be my first choice, personally, but it's quite remarkable to see how well they've fared over the better part of a century.
XLR used (mostly) in audio is also from the 1950s.
The biggest problem with these standards is they are used for everything and so you cannot be sure that if the cable fits it will work. If a USB cable fits it will almost always work - but if it doesn't it will be obvious to your average idiot way (that is you can plug a mouse into a power supply - but nobody expects it will work). USB-C somewhat violates that, but even still it mostly is a case if you can get the connectors to fit it works.
DIN connectors also date from the 1950s, so do coax F connectors (the screw-coupled connectors for cable TV).
RCA/phono jacks are from the 1930s - when record players and radios were first a thing.
But headphone jacks - originally phone switchboard jacks - are way older, dating to the 1870s.
The 1878 one is fascinating:
When the plug is inserted, the jack "breaks its normal connection." Like they didn't want to leave the audio output like a floating pin to reduce stray voltage?
Scribner calls the switch "spring-jack" after "jack-knife" where the "jack" part of it comes from the name Jack and in the 1300s meant a mechanical device. So the "female" component of the connection was thereby given a "male" name.
https://en.wikipedia.org/wiki/Phone_connector_%28audio%29 https://www.etymonline.com/word/JackI don't think it was about not wanting to leave the audio input floating. Rather the "normal connection" is that the telephone subscriber is connected directly to the switchboard operator's annunciator (a display panel) so that the subscriber can light up a bulb on the annunciator when that subscriber wishes to ask the operator to reroute that subscriber's connection to another subscriber (instead of to the switchboard operator). This is why the switch ought to act like a double-throw, not just a single-throw switch. I think something along those lines is the reason...
> In a telephone-exchange system the wires of the several subscribers are run into a cen tral office, where, upon request, any wire may be connected with that of any other subscriber.
> In Fig. 4 is shown the cut-out connected with subscriber's wire in and the relay and annunciator P and O, and also, with the operator's telephone J, by means of the plug A, which is provided with a metallic point, and conducting-cord d. The connections are formed as follows: The subscriber S, by throwing on his local battery, sends a current along the wire in through the relay P, which, closing, the annunciator number of S is indicated at O, and the current passes along the Wire H, and thence through the switch to the ground Wire G.
Are barrel connectors also as old as phono jacks?
Didn't even think of that, yes of course XLR and for that matter, 1/4" TS/TRS connectors were originally for switching phones at AT&T, before automated switching. Incidentally, you can also blow up quite a bit of stuff with them, depending on whether they are at consumer "line level", pro audio "line level", or even speaker level. We're definitely too comfortable with "if it fits, it works" (or at least isn't harmful".
Here I thought you meant they were also used in demolition or pyrotechnics.
Any electronics are pyrotechnics if you use them wrong enough.
There was a wild period in early transistor electronics where DC power adapters sometimes used 1/8" phone jacks - before the barrel-style DC plugs became common. Having 9V DC in a form that could be plugged into a microphone input always seemed like a pretty insane choice.
I'd like to mention my USB-stick-shaped audio recorder/player who's headphone jack (only uses built-in mic in any case, though iirc the headphone button skips to the next file) functions as the computer and charging connector. The device was shipped with a cable (USB-A male) <> (TRRS 3.5mm aka 1/8") for this usage. It reports as mass storage.
Apple shipped a few iPods that were like this, too: https://en.wikipedia.org/wiki/IPod_Shuffle#2nd_generation
Apple even used the 1/4” jack for the Lisa keyboard https://archive.computerhistory.org/resources/access/physica...
i blew up my atari in the 1980s with one of those plugs.
Right, but the alternative of having 1 protocol per connector sounds awful as well, wouldn't you agree ?
European TVs still use an antenna connector that was introduced in 1922.
https://en.wikipedia.org/wiki/Belling-Lee_connector
Though that’s both older and better than RCA plugs. Somehow both RCA and NEMA managed to spread, the former world-wide, the latter only US + colonies, despite much better alternatives already existing and the drawbacks being obvious even 100 years ago.
The https://en.wikipedia.org/wiki/Edison_screw is from 1880.
Phone jacks. Invented in the late 19th century. Still in use today.
I assume you're talking about these, right?
https://en.wikipedia.org/wiki/Phone_connector_(audio)
I assume you're referring to the 1/4" jacks, not RJ series?
Sparkfun should take it upon themselves to correct the centuries-old mix-up of "conventional current" next :)
I always thought this was really interesting. The Coast Guard's Electrician's Mate training program taught electron-flow theory, so it was tough to switch my brain to hole-flow theory when I went to college. Technically the math is the same but man it threw me off with schematics.
Was that in the context of vacuum tubes? There, electron flow definitely makes sense.
What's that?
Ben Franklin's coin flip landed the wrong way - nowadays electronics circuits are calculated and drawn assuming movement of positive charges, when in reality it's the negatively charged electrons that flow.
Nothing wrong with saying that an absence of electron is moving. Both electrons and electron holes are just excitations in a quantum field anyway... ;-)
> To be blunt, the term "DB9" is plainly inaccurate because it pairs the 25-pin "B" shell with a 9-pin count, a physical contradiction.
Why couldn't a DB shell house a 9 pin connector? I don't see the physical contradiction (even if nobody actually manufactures such a thing).
It can, but nobody would do that as it would be cheaper to use a DB-25 connector and not use all the pins. If they went for the cursed true DB-9 they would need to meet the minimum order quantity for a special order, pay for the manufacturer's tooling, and any required certifications. If you needed the spacing between pins for some reason you would probably just specify the use of crimp-and-insert.
That being said, the DE-0 is real, but it can't hurt you.
> That being said, the DE-0 is real, but it can't hurt you.
That depends on several factors, like its current velocity.
While your statement is perfectly accurate, I just wanted to blithely add that it's not the velocity that hurts you, it's the change in velocity :))
Velocity alone can also kill: https://what-if.xkcd.com/1/
Randall Munroe rules this space IMHO.
Doesn't VGA use DE-15?
Edit: I was wrong, it is DE-15 connector. They squeeze 15 smaller pins into 9 pin housing.
You can remove pins from D-sub connectors. There are dedicated tools made for doing so.
In a pinch, a pair of pliers works too.
Searching google for DE-0 didn't bring any results but now I am curious to see it.
https://uk.rs-online.com/web/p/d-sub-connectors/0481049 https://uk.rs-online.com/web/p/d-sub-connectors/2748593
Isn’t that just a normal bring-your-own-contacts connector housing?
Yep. Though if you don't place any of them - depending on how technical you want to get - that's a DE0.
It's just a filler that in the form of a DE connector with no holes for any pins. It was an old full-rack CISC AS/400 for what it's worth, but I scrapped it 30 years ago.
I have a vague memory of a computer (probably in the 16 bit era?) saving money on providing two joystick ports by using a DB25 housing with the middle pins removed, leaving two 9 pin clusters at the ends, into which two DE9 joysticks could be plugged. The case plastic covered over the middle of the connector.
It was an accessory to let you use Amiga joysticks on the PC, from the mid 90s. I had one.
Could well have been, though I’m still picturing a computer in my mind. Wasn’t the SAM Coupe, but that’s the sort of thing I’m recalling.
But: it was probably quite common on joystick interfaces, now you mention it. Thinking along those lines and searching for ‘twin joystick adapter’ let me actually find an example: https://www.ebay.com/itm/276075015721
Worth noting that in the image that shows two joysticks plugged in they really don’t look like they fit all that well…
I’ve seen (many… many years ago) a DB housing with 9 connectors but with the spacing of 25 pins. Would this then be a DB25C9P?
In retrospect, I think this may have been an adapter from DE9 to DB25, but it would have been a quick way to save a few pennies when only 9 pins were used for serial communication.
Another possibility is Sun or SGI 13W3 display connector. They were DB25 shaped connectors with 10 regular pins and 3 giant pins for video signals.
Also the NeXT “Megapixel” displays. But note that none of these were compatible.
True. However, mine were for connecting to modems, so they were definitely only 9 pin serial cables. I didn't have the pleasure of seeing the 13W3 connectors until I was in grad school, and I still think they look weird. It didn't occur to me until today that they were the exact same size/shape as the DB connectors. They were so different that the thought never occurred to me!
How would you even count those 3 giant pins? If I recall correctly, they were for coax cables that ran within the main cable. So each of those pins would have a contact for the shield and the conductor.
I’ve seen this also - I am unsure if it was a cost cutting measure or something else, but I’ve seen more than one connector with many missing pins.
The cables I saw were handmade. You can get connectors which are just the shield and an insulator with holes in the place of the pins. You crimp the pins onto the wires, then slide the pins into the insulator. You may have saved a few cents by not inserting the unconnected pins, but the reality is that most people left them out because there was no point in going to the trouble of putting them in.
It was pretty common for RS232 (-ish) DB25 connectors not to populate unused pins.
"DB" already means 25 pins, so well, it's quite hard to both have 25 and 9 pins at the same time.
That is still pedantically different from a DB-25 of which we ripped out pins until it had only nine. The result would be "a DB-9" in big quotes, as it would't be "a", but more like "3/4 of a DB-25".
> "DB" already means 25 pins, so well, it's quite hard to both have 25 and 9 pins at the same time.
No, it doesn't. All of the D-Subs are readily available in high density versions:
The high density versions are commonly used in aerospace applications. Garmin is pretty fond of them.There are also double density connectors putting 52 pins in a DB housing and whopping 100 connectors in the DD housing.
Also DE-15 is the standard connector used for VGA.
There’s also a now-quite-rare 23pin variant, which was used for the Amiga video port. Those connectors are getting harder to find these days, some people have resorted to modifying 25pin connectors when making Amiga video cables
DE-15 is none other than VGA.
DB housing can fit 25 pins in 2 rows. But it can also fit 9 really honkin big pins in 1 row, with a custom mold & pins. 3x groups of 3x12-gauge pins for 60A 3-phase delta power connector in a DB sized shell would probably work for a while before you burn your house down.
You mean this?
https://adamconn.com/product/8w8-connector
It's 8 pins, so, sorry, I'm not accepting it as DB9-of-doom. Maybe DB-8-of-doom.
Sure you could do it. You could even put 25 pins in 9 pin housing if you made the pitch smaller.
They just don’t exist, and hopefully never will.
Heh flashback, I had an ati all in wonder, which was a video card with built in video capture. Now this involves a lot of ports so the model I had used a port breakout dongle for the video capture stuff, and some engineer had the bright idea to run all these pins through a mini-din connector. Think a ps/2 connector with about 10 pins crammed into it. Now ps/2 connectors are sort of stupid in the first place. why a round connector that is keyed to only go in one way? But this 10 pin variant was a nightmare to insert and by about the third time I made a firm resolution to never unplug it again if I could help it.
Footnote: keyed round connectors are not actually that bad, super strong, easy to seal and you can fit a large nut or bayonet clamp to them to make them extremely secure. However, this depends on having a well placed shell/key and mini-din doesn't, it is a bad connector. Not enough shell and key for solid locating so the pins tend to ride on the face while you try and orient it.
I think this was the one I had.
https://www.techpowerup.com/gpu-specs/all-in-wonder-9600.c86...
[delayed]
Sure you could do it. You could even put 25 pins in 9 pin housing if you made the pitch smaller.
They just don’t exist, and hopefully never will.
Maybe not as a standard, but I've seen a several companies stuff a crazy number of pins into a DE9 shell. I think one of them was my old GRiD Compass.
Beast of a machine. Heavy as hell, magnesium case, bubble memory, a screen that caused all televisions it was pointed at to lose their signal, and a sticker on the bottom saying it was illegal to use it in a whole list of countries, including Israel.
Seems like it has 19 pins in a DE9 shell. That's a lot. VGA connectors were also in a DE9 shell, but had 15 pins.
The funny thing about the GRiD DE9 connector is that it's labeled "Serial", but every DE9 serial port connector I've ever seen is 9-pin. I have to wonder what else they are cramming into that 20-pin DE9 "serial" port.
http://raster-burn.net/wordpress/wp-content/gallery/grid-113...
What's the physical contradiction, then? I don't get it.
The physical contradiction is that the standard requires a particular pitch of the pins, and a specific distance of the pins from the shell.
What's the point of "9", then? And how do you explain DE15 (popularized by VGA)?
> What's the point of "9", then?
Originally? Because that was the naming convention that Cannon designated. Later, because the shell size wasn't sufficient to determine the number of pins.
> And how do you explain DE15 (popularized by VGA)?
Cannon's D-series connectors started with 2 rows, at the "normal density" of 326/3000 of an inch between pins. They later expanded the range of connectors with "high density" and "double density" connectors that put more pins at greater densities into the original shell sizes. DE15 is in the "high density" range.
VGA connectors were a DE-9 shell with 15 pins in them, and were used widely for many years to connect monitors to computers. There are other connectors that crammed 19 pins into a DE-9 shell. 25 might be a bit too much, but 19 is pretty close.
They're just DE shells, not DE-9
In a world with 3D printers, everything can potentially exist.
So if I put USB type C into a DB shell should I call it a DB-USB-C?
Yes, of course. You should be able to fit more than one in there, with a hub in the connector housing!
Man-made horrors etc.
There's a lot of things like this, especially when the connector is commonly used for just one thing. One is "composite video" which at one point or another I have heard items on this list used interchangeably (though not always at the same time):
composite video - RS-170 - monochrome video - EIA-170 - NTSC - black and white video - CVBS - B&W video - RS-170A - analog video - PAL - yellow RCA plug - just plain "video"
These don't even all refer to the same thing, and some are definitely more correct than others, but all are used even by technical people.
Here's another one: "Amphenol connector", "Cannon connector" or "Molex connector". It's the same as saying "Ford car".
Not connector related, but I can't tell you how many people use time zones like PST year-round. The ST stands for "standard time," meaning not Daylight Saving Time. Right now, PDT would be appropriate.
The thing that kills me is that they could just say "PT" or "Pacific time" and be right, with less effort.
I always know what they mean, but it's wrong for more than half the year.
The 1.44 MB diskette is my canonical "dear God what happened"-named thing.
The traditional diskette is 1440 KiB. I.e., base-2, today named "kibibyte" though in that day that word didn't exist yet & it was just a kilobyte and the base 2 inferred from context. Clearly, someone didn't infer, and moved the decimal, so that 1.44 "MB" is 1.44 * 1000 * 1024 bytes. The actual capacity is thus either 1.41 MiB or 1.47 MB.
Hard drives continued to make that mistake, and once you got to GB size they were overselling the disk space by an appreciable amount.
hard drives intentionally use giga and tera rather than gibi and tebi. They're right; it's the memory sticks that are usually wrong :-)
IMO it's the ISP's who are intentionally misleading people. Average Joe might have some inkling of how big a gigabyte is these days, but nobody except a network engineer cares what a gigabit is. I can't imagine how many people buy gigabit fiber expecting a gigabyte. It would sound much less impressive if it were marketed as 125MB/s like it should be. They should at least be required to show both, not make people convert units if they want to find out how fast their advertised internet is supposed to download their 50GB game.
I don't think that counts as intentionally misleading since bits/second is the correct measurement for any serial connection and has been since the days of Baudot. Joe Blow might misunderstand it but that's on Joe.
It's not like the situation with hard drives where they're going against industry convention for marketing purposes.
You could also blame Windows. Linux counts storage bytes in base 10. But still counts RAM in base 2.
Nobody says "gibibyte" out loud without giggling or getting giggled at. I think we should start saying "gigglebyte".
Know that several of your coworkers are laughing at you in their minds every time you utter such foolishness.
I have had to debug enough fires because of stupid unit confusion that I now make the point of being extremely pedantic with the use of the right unit.
I've been calling them Kibbles, Marbles, Gerbils and Tribbles
Pebble scale computing is all the rage right now.
jigglybits works too in the correct company
also cal state irvine had a compsci prof who said "jigga-byte"
One point twenty one jiggabytes??? Great Scott!
> today named "kibibyte" though in that day that word didn't exist yet & it was just a kilobyte and the base 2 inferred from context
That is still what most people do. Only very pendantic individuals insist on using KiB, etc. Normal people are just fine inferring from context whether base-2 or base-10 is meant.
My opinion is use KiB as the abbreviation but pronounce it as kilobyte. It pisses off both sides but makes the most sense to me for both being technically and historically accurate at the same time.
I thought they tossed the fool that tried to make mebibyte a thing off a bridge and we tried to forget about that.
Back in the day -- when used for a disk drive -- we used to call 1000 * 1024 bytes a "marketing megabyte" and 1024*1024 bytes a "megabyte". YMMV.
Perhaps the formatted capacity, or the safe capacity, but I can specifically recall being able to format those same floppies up to... I forget, maybe ~2MB? Something like that.
Yeah, the unformatted capacities of 3.5” floppy disks were:
SS-DD - 512KB
DS-DD - 1MB
HD - 2MB
ED - 4MB
LS (floptical) - 21MB
Technically you could format some of the lower density media in the high density drives and get the expanded capacity (although you may have needed to modify the media a little - holepunch to make an HD drive see a DS-DD disc as “HD”), although it wasn’t always very reliable and depended on the physical media and the capabilities of the individual drives.
Different file systems used the 2*80 tracks differently, hence the different formatted capacity, DOS usually had the lowest, Macintosh in the middle, Amiga had the most (although the Amiga HD floppies were a bit of a cludge - the drive spun at half speed due to a limitation of the Amiga floppy controller, which was also the reason you couldn’t just use a “PC” HD floppy in an Amiga without modification).
Yes, the typical formatted capacity. The word "traditional" was the brevity which was attempting to sum that up.
There were also other, weirder setups where you could get various other capacities. It was a wild time.
Same with older floppy disk formats. Using FAT16 (or FAT12 on some systems) you can often format DD 3.5" disks to 830K instead of the usual 720K. On the Amiga the same disks are usually 880K.
My favorite example of this is using "aux cable" to refer to an audio cable with a 3 or 4 pin 3.5mm connector on the end (because car stereos would have a 3.5mm jack labeled "Aux" for "Auxiliary input")
I usually call those "headphone cables" just to be contrary.
You forgot SMPTE 170M, which is probably the definitive standard at this point:
https://pub.smpte.org/doc/st170/20041130-pub/st0170-2004_sta...
You have been misusing the D-sub connector terminology
No I haven’t and the same is true for approximately everyone else.
Because we have not been using D-sub connector terminology at all. We have been talking about the things that come with (and without) DB9 connectors. We have been (mostly) playing —- as the witty Wittgenstein would say — a different language game.
That’s why you know what I mean. So bring me a slab.
For me, if I ever say IEC mains lead I get a blank expression. C13 even more so.
"Kettle lead" (Which is notched to indicate it can take a higher temperature and most of cables aren't that, they will be the c13 type), and their face lights up and a cable will be handed to me.
Just one of those things that's wrong, but it's not worth being pedantic over it, imo.
Given the paucity of electric kettles in the USA, I wonder how that term became so widespread.
Ironically in Europe where the IEC cables were familiar from kettles, they've largely been superceded by cables hardwired into a base pad onto which the kettle is set.
British English, most likely.
I always just called it a serial port, because I could never remember DB9 to begin with. I really hope I remember this so I can impress some nerds in the future with how pedantic I can be. (I don't know how to write that last sentence without it sounding sarcastic, but I really meant it.)
Some other pedant might come along if you keep just calling it a serial port. They might mention that it’s specifically RS-232, and that DB-25 is also used for that. They might also mention that “serial port” could include ports for RS-422 and RS-485. They might even mention SIO and USB.
Aren't Cisco switches (and a large number of other switches) loaded with Serial Port / RS232 over RJ45?
DB9 or DE9 isn't even the end of it. There are lots of ways to run a serial line.
Null modem, crossover, DTE, DCE, straight-through, full handshaking, no handshaking, RS-232 or TTL levels. Plus CAN, RS-485, RS-422, CGA video, RGB video, and any number of industrial things use or can use the same DE9 connector (including sometimes for power).
DEC equipment had something similar. A 6 pin "MMJ" connector. It almost looks like RJ45 except the clip was off center.
I also remember some 90's terminal servers that had enormous "octopus" cables. There was a single connector on the box that broke out to 8 to 16-ish DB25 serial ports.
Some DEC equipment in the QBUS era also used DE9 serial ports, with a different pinout than IBM's.
I haven’t touched Cisco gear in years, but that at least was true for a long time.
Are you sure those weren't using RS-232 over TCP/IP over Ethernet?
That is quite common in the pro audio/video installation world, where RS-232 is common but needs extenders for longer distances.
Within A/V, the norm for local RS-232 lines is actually not DE9 but 3-pin terminal blocks! (RX/TX/GND) I've seen those even on Cisco video codecs, priced $10'000+.
No, most Cisco devices has an RJ45 shaped RS232C port that needs a special cable to do anything with. It's proprietary, but there's one in every networking guy's backpacks so the situation is only as bad as Lightning cable for iPhone. Most(but not all!!) networking gears that compete with Cisco uses the same cable as well.
It's proprietary...
Eh, depends on "proprietary", I guess. In the PLC world, using an RJ45 for a variety of serial uses is not uncommon. I've never touched a Cisco router in my life, but I've got a few things like these laying around:
https://www.networktechinc.com/serial-rj45-adapters.html
Those are some interesting connectors since they have a REAL RJ45 socket. Also interesting that they come prewired and not some assembly required like the ones from amazon do.
The pinout is also called a Yost Cable. You can read about it on https://yost.com/computers/RJ45-serial/ but its an interesting solution to converting DTE and DCE sides to using a standard port and cable. The downside is that the DIY adapters online need some soldiering to bridge the ground wires and more.
I do believe the DTE and DCE pinouts on the yost page are swapped though. I recently tested the pinouts of a Cisco DE-9 to 8P8C (DB-9 to RJ45) with a multimeter and came up with the DCE pinout instead of the DTE one. I then built an adapter with the DCE pinout to connect to my servers serial port and use them as a make shift null modem cable for terminal access.
If I would have know more about this 5 years ago while still at a previous employer, there was some old equipment that used an unknown pinout that would have gotten a DB-9 to RJ45 adapter slapped on it to change it to Cisco/Yost pinout. I was told not to loose the serial cable in the rack with the device because it was the only one that worked on it but never investigated more into it to find out if it was a straight through, null modem, or something else entirely.
I've got a bunch of Cisco switches with RJ45 connectors for the serial console ports.
Here's the cable they use: https://www.bhphotovideo.com/c/product/1263972-REG/comprehen...
I've got a "Sentry Commander" remote power switch and serial server, with four 6P6C connectors for its serial ports to hook to machines and two 8P8C connectors for its own serial console and modem port. I'm sure it shipped with its own proprietary cables long since lost, but I just use RJ12 cables and those "RJ45"->DE9 modular adapters.
I'm talking about this thing
https://www.amazon.com/Console-Female-Serial-Ethernet-Rollov...
The thing I don't get about this is why did people think it was a good idea to have a serial connection over DB-25? You honestly need only 3 wires. Not 25
For a Parallel port, sure 25 wires is right there. But not for a serial port
CTS, DCD, DSR, DTR, GND, PG, RI, RTR, RTS, RxD, TxD (alphabetically) makes around 11, I think.
If I recall correctly, the DB-25 RS-232 cables also facilitated two serial connections.
You do. (I've never seen that used, though.)
Yes and then we came up with soft flow control for the win
Plus the differential versions of most of those signals for long distance doubles the number of pins. And they have optional synchronous clocks. I did some WAN work for 3Com back in the day... :)
and V.35 and X.21!
My VGA (DE-15) and keyboard and mouse (Mini DIN #6) ports disagree. The printer port (DB-25) could not be reached for comment, as it is still set for uni-directional.
This is like King Canute and the tide. Technical pedantry is often interesting, as this is, and can lead to deeper understanding, though this doesn’t.
But language is for communication, and the most correct language is that which communicates best.
A conversation burdened with “well actually” tangents about one participant’s personal passion gets pretty tiresome.
Being on the sharp edge of professional "do you want what you're asking for, or what I assume you want?" misunderstandings, you learn that it breaks in both directions often enough that sometimes not being pedantic up front isn't an option.
I don't think shittalking "well actually" conversations in the context of an equipment vendor making a cutely-titled article that is very sympathetic to the inexact language around designators for products they offer is the play.
This is why I've learned to present people with the concrete consequences and results of their service request. Especially if I get the feeling that someone does not comprehend what they are asking for.
"Your service request will result in X hours of downtime, as well as ireversible data loss between T1 and T2, and a reset of your system back to the state it was in at T1. All changes and interactions after T1 will be lost. Is this what you expect and want?"
Beyond a certain amount of service disruption or monetary investment, asking twice and making sure is prudent, not pedantic.
Normally I agree. The only time I ever raised my voice at a subordinate was because they were consistently lax and inaccurate with technical details. Things like mixing up C and C++ in conversations where it mattered.
But things like DB9 and RJ45 are so commonly used that anyone taking them literally is either being obstinate or are completely new to the field.
In this case, is it that helpful? Since only a lunatic would want a true DB9 and no one’s ever made a giant connector with 9 pins, I fail to see the importance.
Gotta love that sharp edge.
Nothing saves money like a good well actually.
> But language is for communication, and the most correct language is that which communicates best.
This seems to be biased in US-American culture. In Germany, people are in my observation much more prone to analyze words and sentences (often by their origins), and many people wouldn't accept a "wrong" way to express things to be correct.
Just to give one example (which also works in English): "[die] Alternative" (the alternative): this word comes from Latin "alter, altera, alterum" (the other). This means, that there exists only one other. So educated people love to point out that talking of multiple "Alternativen" [alternatives] is wrong; by the word origin there can only exist one alternative (the other one). If more than one "alternatives" exist, so, to be precise, you likely want to use a different word.
I think this implies a meaning of "the" that doesn't actually exist in modern english.
"The" often refers to a group or category.
"The other" is actually a phrase I would take to be incredibly inclusive in meaning if not followed by another specifier (it means "the category of everything that is not us").
"The alternative" is similarly a category structure. It's a singular category, made of many possible members, or alternatives.
You may still only pick a single alternate for each case, but that does not mean that a category of multiple possible alternative choices does not exist.
---
All that said, sparkfun is messing up by labeling this DE9. Spoken as someone who's done quite a bit of serial communication work. The defacto industry term is DB9, whether they like it or not, and most searching/purchasing will be done using that term. This is a "technically correct" fun article, with a name that would immediately mean I don't ever find this product (and would not purchase this product) unless they highlight that this is a DB9 breakout board with a bad name.
Simple test? Amazon has more than 4000 results for "db9 cable" and only ~110 results for "de9" cable. Even specialty sites like McMaster, which are usually pretty particular with their terms are happily calling this a db9 connector: https://www.mcmaster.com/products/connectors/computer-connec...
> I think this implies a meaning of "the" that doesn't actually exist in modern english.
> "The" often refers to a group or category.
But this does not hold for the meaning of Latin "alter, altera, alterum" (the other one), from which the German and English word "Alternative"/"alternative" is derived.
Our language started out as a bad habit shared between French soldiers and English barmaids. And the barmaids were speaking a language that started as a bad habit shared between Viking raiders and Anglo-Saxon villagers.
Meanings have shifted since Roman times.
"(The/an) alternate" is probably the ahem _alternative_ term you're looking for...
I am not a native English speaker, so I honestly was not aware of this English word.
Addendum: nevertheless: "alternate" is also derived fron "alter, altera, alterum" (the other one), so my point above still holds.
I think you're proving my point. If the people I am talking to and the language I am using both demand precision in word choice, then I would be foolish to use the wrong term and then say "well, you should have known what I meant."
But that is a communication context, and there are other contexts where implications and assumed meanings are expected, and spelling everything out would be considered pompous, self-important, and ridiculous.
Perhaps not in Germany? But certainly elsewhere (but i believe that in German the pronoun "sie" can require assumed context to understand).
> But that is a communication context, and there are other contexts where implications and assumed meanings are expected, and spelling everything out would be considered pompous, self-important, and ridiculous.
> Perhaps not in Germany? But certainly elsewhere (but i believe that in German the pronoun "sie" can require assumed context to understand).
I would indeed claim that in German such assumptions are often spelled out more explicitly than in English.
It depends on context. If you're working from a document that is otherwise correct, and you come across a mistake like this, it's worth checking.
In casual language, sure, whatever.
I do wonder why they decided to have have separate shell size and pin designations given there appears to be a 1:1 correlation between shell sizes and pins (i.e. the 'B' shell is always 25 pins, the 'E' shell is always 9 pins). Perhaps there was plan to have fewer pins in the same shell at some point?
it's not always 9 pins. you can get pretty creative regarding the number and type of pins (high current, coax) you can fit in that shell:
DE with 2 High current contacts:
https://de.wikipedia.org/wiki/D-Sub#/media/Datei:D-Sub_conne...
DE with 15 contacts ("VGA"):
https://de.wikipedia.org/wiki/D-Sub#/media/Datei:D-SUB_DE-9-...
There's also 13-W3: DB shell, 13 pins, 3 of them coax: https://en.wikipedia.org/wiki/DB13W3. They were used for high-end workstation video back in the day.
I came here to share this cursed connector. I remember it well from Sun workstations
https://en.wikipedia.org/wiki/File:D-Sub_connectors_size_DE_...
https://en.wikipedia.org/wiki/File:D-SUB_DE-9-F_BLUE_VGA_IMG...
VGA connectors used the same shell as the DE-9 but had three rows for a total of 15 pins.
An excellent example I really should have been able to think of myself!
And for reasons I don't fully understand, somewhat unrelated - if you look around almost any small business in my area, it's almost always VGA, rarely DVI, almost never HDMI or DisplayPort.
My theory is just that the cables came in the box and are screw-on when more modern connectors are friction fit, and the IT departments don't want the hassle of "they just got pulled out." Which should have been predictable - but I can literally see 12th gen Intel, paired with 1080p display, over VGA fairly regularly.
It's 100% because the VGA cable came in the box. Nothing about cables pulling because my lazy counterparts would not even screw in the DE15 cables half the time.
Source: Too many years experience in the desktop support trenches.
DisplayPort has latching connectors, but they're easily broken when pulled out without unlatching.
For some reason DisplayPort monitors are more rare, and even when you get one like the MSI Pro MP241, it comes with an HDMI cable in the box!
Confusingly enough, I’ve actually seen real, properly named DB-9 connectors. They were a cheaper version of a DB-25 to DE-9 converter. Instead of combining the extra pins properly, they just had a DE-9 on one end connected to only 9 pins on the DB end. They sometimes occasionally even worked properly at low enough line rates.
DE15 and DA15 both exist and are pretty commonly used, I'm not aware of any other conflicts in normal versions.
However, you can get weird Dsub connectors with things like COAX in there, so having the shell sizes have names can be useful.
Coax and high-current/voltage pins are not that weird. You can also get truly weird semi-proprietary pins like fiber optics or even pneumatics/fluidics.
I use both DA-15 and DE-15 all the time in my line of work, and I am fastidious about using the correct terminology on all my drawings. Manufacturers are ironically some of the worst at getting this right.
I vaguely remember there being some proprietary connectors that were the same as the standard with a single pin missing.
IBM did that pretty often. And well, the original VGA connector had pin 9 missing and used as a key.
IMO, the issue is less that there is a shell designation and more that the shell designation is hard to interpret.
A single letter doesn't have a lot of meaning on its own, and the A-E order is not consistent with the E shell being smaller than all the others.
By making it fully adjacent to the 'D', it makes the letter sound like it's part of the standard's name, like the 'RJ' in 'RJ45'.
It would have been better to focus on pin count and row count, as those along with standard pin spacing drive the shell size.
D-2R-15 for a two row 15 pin connector equivalent to DA-15, D-3R-15 for a 3 row 15 pin equivalent to DE-15 / VGA.
Could trim out the 'R' and go with "D2-15" for 2 row and "D3-15" for 3 row, if brevity is preferred.
There also existed non-standard D-subminiature connectors that didn't fit within that nomenclature.
For instance, the Amiga used 23-pin connectors to connect displays and disk drives. They had the same pin spacing as DB25 but were slightly smaller.
And there's the infamous DB-19: https://www.bigmessowires.com/2025/06/30/bulk-lots-of-db-19s...
Wouldn't it fit into the nomenclature with another shell type? DF, perhaps?
It is not like there is any real sensibility to the naming anyway. Of the common types, DA, DB, and DC seem to follow a pattern, but DD and DE then go completely off the rails.
If you keep calling it DB9 everybody knows what you're talking about. They don't think you're weird and they also don't waste time talking about terminology.
Words mean things. Especially in engineering disciplines.
It's perfectly fine for a product manager to say "DB9", but the guy who has to order the part from a supplier will probably want to use the correct terminology. If there's a mistake, it's the supplier's fault.
> If you keep calling it DB9 everybody knows what you're talking about.
But might question what your wiring has to do with a 2000s-era Aston Martin.
AI image generation can finally express what I picture when hearing Aston Martin DB9: https://chatgpt.com/s/m_6883b37e1fc881919e3af8f862aa7900
"DE10 isn't real, it can't hurt you"
And this reminds me of the time that my colleague put DB15 on a whole bunch of drawings, and we ended up with DA15 connectors instead of DE15. If I see DB9 on any drawing that comes across my desk, it will be corrected.
One of the more confusing versions of this I came in contact with recently is the 23 pin amiga rgb port. It has no real official D-subminature name as there is no such designation for the shell of a 12+11 pin port, which I assume is due to the fact that it was for a non-IBM machine...BUT some sellers (on aliexpress) DO call it a DB-23 port...I did figure it out eventually and got a few but it did take a while after searching for "12+11 serial" and being a bit frustrated at not finding anything.
DB is easier to say, and everyone knows what I mean, so I will continue to say DB9.
Standards that ignore human frailties will be corrupted by humans, and that's a good thing.
It's completely clear what you mean, so DB9 is fine. In most contexts calling it a DE9 will be more confusing.
If you ever find yourself wanting to order the connectors or backshells, it might be useful to know it's actually DE-9.
DB15 is the only one I have issues with. The company I work with has one container with "DB15" connectors (DA-15), and one with "DB15HD" (DE-15)
The real reason is that in the 1980s this illustration ( https://cdn.sparkfun.com/assets/home_page_posts/1/4/2/9/8/DS... ) was not shown to people. And an illustrator, probably who hadn't seen it either, is who got it wrong. I don't blame them. The existence of an arbitrary letter invariably joined with a useful and descriptive number is the fault here. And the illustrator could NOT show the whole thing anyway because it contained diagrams of products not sold. The perfect setup.
That is all. Everything else is blah blah blah (about DB9, love all the examples of other goofy identifiers!)
People strive for accuracy and remember things. I love people-in-general and they have an impressive track record. They improved on the standards committee.
Why are almost all data connectors designed with male/female pairings and not a unisex connection?
(like half the contacts pins are half are slits and you can plug any cable in)
A favourite paper: “ A Microfluidic D-subminiature Connector” “ Standardized, affordable, user-friendly world-to-chip interfaces represent one of the major barriers to the adoption of microfluidics. We present a connector system for plug-and-play interfacing of microfluidic devices to multiple input and output lines.” https://pmc.ncbi.nlm.nih.gov/articles/PMC3786702/ Previous discussion: https://news.ycombinator.com/item?id=32886596
We used the DD-50 connectors in the telephony world and called them "DD-50 connectors." I always wondered why they were "DD-50" and the 9 and 25 pin connectors were "DB-9" and "DB-25". Now I know... we were just using the nomenclature wrong.
This is exactly the kind of technical pedantry I keep coming back to HN for.
IMO this is a case where being correct causes confusion rather than clarity. Everyone calls this connector DB9, so calling it DE9 is going to make people wonder if it's really a DB9 or only looks like it ...
Surprised that no one has corrected them that it's not RS232 anymore. It was eventually ratified and it's technically called EIA-232-F (at least for the most recent 1997 version).
Frankenstein’s monster!
I was looking for this one. Three angles for a potential retort:
a) Frankenstein is the real monster in the book
b) The monster is Victor's son, so inherits the family name and thus is also (a) Frankenstein
c) A modern adaptation gives the reader explicit permission to use "Frankenstein" as the name for the monster: https://xkcd.com/1589/
I prefer to calm them “Frankensteins”, like:
“Look out, there’s a Frankenstein to push into that lake!”
But can never resist the Frankenstein’s monster pedantry, I find it hilarious.
https://connectorbook.com/identification.html?N=&n=d_sub_con...
See the online interactive adjuncts here: https://connectorbook.com
I love these sparkfun boards. I built this little web app just to be able to play with them in the browser too
https://webserialconsole.com/
The examples would illustrate the issue a little better if there were two pin counts with the same shell, eg DE9 and DE15 and maybe two shells with the same pin count (though I'm not aware of such an example).
Without that it is barely worth the distinction.
Yep, was going to comment on this aspect. If you can't have a DB-9 (which would be the large shell but with a bunch of missing pins) they should have just called the m DA-DE or D-(number of pins)
Could the name "DB9" have come from 25-pin serial ports with only the minimum 9 pins populated? That would be a correct "DB9" and would also be valid electrically. I think I've even seen one of those in the wild before.
Interestingly they have 25 to 9-pin adapters and the majority of DB25 devices I worked with were fine either way. So, the devices generally used 9 pins or less (or at least 9 or less pins were "important").
There are, of course, devices that use more than that, but most things seemed to use less. Maybe that's part of the reason the 9-pin became more standard.
Frequently only 3 pins are used in a DE-9.
Well, I admire the nerd logic, but it seems like it would just unnecessarily cripple sales if people searching for it under the common name can't find it.
DB25 and DB9? Oh, you mean parallel port and serial port? :)
DB-25 is the standard RS-232 connector. DE9 is just the cheap alternative for cases where you don't need all control lines
Doesn't a DB9 connector include all the DB25 RS-232 handshaking lines, even if not all devices actually use them?
I grew up in the 70s-80s with serial connectors and a drawer full of cables, DB25-DB9 adaptors, gender-benders, null modems, breakout boxes, etc, and the only (very common) source of incompatibility that I can recall was connecting devices where one side wanted hardware handshaking but the other didn't provide it, so having to make custom cables with handshaking tied hi/lo to fake it.
Some devices used software XON/XOFF handshaking, so for example on a typical terminal, depending on what you were connected to, you could pause text being sent to the terminal with XOFF (Ctrl-Q), and resume with XON (Ctrl-S).
I've got a softspot for serial communications - used be more a source of fun rather than frustration to dip into the draw of cables/etc and get two devices happily talking to each other.
> Doesn't a DB9 connector include all the DB25 RS-232 handshaking lines
Handshaking yes, but not all potential RS232 signals, of which there are 11.
I work with RS232 frequently and even CTS/RTS is rare to use. Never personally seen anything use DTR, DCD, DSR, or RI though I know they did see historical use.
Maybe next they can work on getting people to stop calling Category 3 - 8 cables Ethernet cables.
What's about the 19 and 23 pin variant
Some discussion on the 19 pin variant from last year:
https://news.ycombinator.com/item?id=40397593
This is great. Maybe having total or stats/tools for comparison will be awesome plus.
Set input and output and check cost.
While we're at it, RS-232 is not serial. It's a voltage specification.
But it is kinda important to know if something is using TTL or RS-232 voltages before connecting to it. Using the wrong one might let the magic smoke out.
9 pin D connector sounds clearer, and doesn’t waste a letter. D9 works for the same reason.
If everyone calls something by a name, that's its name, whether you like it or not. "ask" is now also a noun.
I spent years wishing (and pretending) that this wasn't the case, but you can't fight the wind.
Given that DB9 is so pervasive (and I admit this is new information to me), I thought AI training data might include the error but no, ChatGPT knows DB9 is wrong:
https://chatgpt.com/share/6883b2ff-d26c-8002-bc4d-b184d7afd4...
This might not prevail in the world of tech, but in language studies, words mean what the majority of their users think they mean. Examples:
Lexicographers are at pains to point out that words mean what people think they mean. I think they have a point.So, the [ABCDE] in D?-N is redundant and useless, so it doesn't matter what letter you use. Humanity triumphed, eliminating useless redundancy.
No, because a VGA port is a DE-15 and a DA-15 is used for, uh, something?
ETA: Oh hey, just to make things confusing, Apple used DA-15 for video on older Macs.
https://en.m.wikipedia.org/wiki/D-subminiature
DA15 was used for amongst other things Mac video outputs in the beige era, PC joystick / MIDI ports and Ethernet AUI ports.
The correct technical designation for a D-sub connector with nine pins is DE9.
It’s early and eyes are still a little blurry, but I’m not seeing a cite?
Wikipedia fleshes it out a bit:
The D-sub series of connectors was introduced by Cannon in 1952.[3] Cannon's part-numbering system uses D as the prefix for the whole series, followed by one of A, B, C, D, or E denoting the shell size, followed by the number of pins or sockets
No links to a primary source, but seems plausible.
https://www.ittcannon.com/d-sub
https://ittcannon.canto.com/direct/document/h10hf84e3l4n77ck...