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So when people call the (smaller) PC serial port connector DB9, they're technically wrong? TIL
by gugagore 2y ago
So when people call the (smaller) PC serial port connector DB9, they're technically wrong? TIL
- ssl-3 2y agoFor some versions of "technically," yes: A DB9 isn't really a thing. But ostensibly, everyone who needs to know will know what is meant when a person says "DB9," and thus it works fine. (Relatedly, the connector used for Ethernet is not an RJ45.)
- javawizard 2y ago> (Relatedly, the connector used for Ethernet is not an RJ45.) Wait, what? I cannot find a single source on Google for this - they all say RJ45 is the correct term. If it's not an RJ45, what is it?
- andrewshadura 2y ago8P8C
- formerly_proven 2y agoRegistered Jacks are always for phone stuff, the general-purpose name would be 8P8C.
- atombender 2y agoWikipedia has a good explanation: https://en.m.wikipedia.org/wiki/Modular_connector#8P8C https://en.m.wikipedia.org/wiki/Modular_connector#8P8C
- colejohnson66 2y agoRJ45 is/was the pinout/wiring of an 8P8C[1] (eight pin/eight contact) connector designed for the telephone system.[0] The wiring specification of Ethernet is ANSI/TIA-568[2]. The only thing RJ45 has in common with Ethernet is that it used the same 8P8C-sized connector. But even then, RJ45 had a key notch on the side and Ethernet does not. [0]: https://en.wikipedia.org/wiki/Registered_jack#RJ45S https://en.wikipedia.org/wiki/Registered_jack#RJ45S [1]: https://en.wikipedia.org/wiki/Modular_connector#8P8C https://en.wikipedia.org/wiki/Modular_connector#8P8C [2]: https://en.wikipedia.org/wiki/ANSI/TIA-568 https://en.wikipedia.org/wiki/ANSI/TIA-568
- jes5199 2y agoall the examples with the notch say “RH45S” - what does the S stand for?
- ssl-3 2y agoThe antiquated Registered Jack standard is RJ45S, which always gets butchered to RJ45 in common parlance [and this sans-S version has never actually existed]. For RJ standards, an S suffix signifies that it is a "single line" circuit. https://en.wikipedia.org/wiki/Registered_jack#Types https://en.wikipedia.org/wiki/Registered_jack#Types https://en.wikipedia.org/wiki/Registered_jack#RJ45S https://en.wikipedia.org/wiki/Registered_jack#RJ45S
- gumby 2y agoI have always loved that the 6P4C fits into the 8P8C such that when wired up as RJ11 or RJ12 it interoperates properly.
- ssl-3 2y agoIIRC, that was one of the reasons we had the center pair available with Ethernet for such a long time: A given jack on a wall in a given office could be wired for a regular single-pair phone, or for Ethernet, or for both -- even at the same time (using the same cabling), as a design intent. Of course this doesn't work with the gigabit spec we all wound up using, but it was never a popular option to begin with (and nowadays, we usually have VOIP if we even bother with desk phones at all).
- somat 2y agoThe original idea was to have the first pair in the middle, the next pair outside of that, etc.. so that a smaller pair plug could fit in a larger sized jack. However when it came time to specify the pinout when designing ethernet over utp they found the separation required to place the wires like this was too great and degraded the characteristics of the line so they placed a pair on each side keeping the center as is for some sort of compatibility. Like said you could have a phone line in the center of your ethernet. suck to be you it you did that then later wanted to upgrade to gigabit. It also suck if you had some idiot doing the wiring who had the bright idea "herp derp, two pairs of this are not used... I could run two ethernet lines over this cable" Which is sort of my next complaint, tia-568, the intent was to have the A standard be used with the B standard for compatibility with existing phone lines . Every place I have ever been they just used the B standard. I mean it is not a huge deal, but it always bugged me. https://en.wikipedia.org/wiki/ANSI/TIA-568 https://en.wikipedia.org/wiki/ANSI/TIA-568
- Suzuran 2y agoThere actually WAS a DB9 connector, that is 9 pins in the B-side shell. They were used for manufacturing equipment. They carried 4 high-voltage differential pairs and a common signal for negotiation/detection. IIRC part of the specification was that the signal pins had to be milled solid parts rather than the much cheaper/more common rolled hollow pins.
- blueflow 2y agoYes, and this is a common problem with language. There are many instances where colloquial knowledge is just wrong and its not clear how people even came up with their alternative interpretation. Maybe you have seen me previously ranting about such things.
- dylan604 2y agoA recent one used around these parts is "hallucinating". There have been multiple pro/con threads on using it when discussing the failing of LLMs.