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
...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.
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.
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.
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.
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".
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 hypothesize that the car cigarette lighter port is the only truly standard, widely-used connector remaining. Wall outlets, just for 120V in the US, have at least three variants. 3.5mm audio plugs have at least four variants.
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.
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.
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.
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.
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.
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.
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.
"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 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.
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".
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.
> 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.
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.
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.
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.
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.
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.
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.
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
Readit News
The “what” was of course not Ethernet.
I didn't learn this until this year...
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
Is Mate-n-Lok perhaps a compatible product from a competitor?
https://www.reddit.com/r/electronics/comments/ioc6sf/i_final...
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.
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.
100% guilty here, ouch.
also never saw a 8P8C "keyed, real rj45" connector in person.
Why wouldn't you say RJ45?
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.
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.
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.
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.
https://en.wikipedia.org/wiki/Belling-Lee_connector
I have soldered a lot of these into cable assemblies for automated welding fixtures. They are also found on some servo motors and cables.
https://en.wikipedia.org/wiki/Phone_connector_(audio)
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).
That being said, the DE-0 is real, but it can't hurt you.
That depends on several factors, like its current velocity.
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.
They just don’t exist, and hopefully never will.
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.
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...
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".
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.
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".
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.
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.
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I usually call those "headphone cables" just to be contrary.
https://pub.smpte.org/doc/st170/20041130-pub/st0170-2004_sta...
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.
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.
Deleted Comment
DB9 or DE9 isn't even the end of it. There are lots of ways to run a serial line.
For a Parallel port, sure 25 wires is right there. But not for a serial port