Comment by SAI_Peregrinus

Comment by SAI_Peregrinus 7 hours ago

RJ45 isn't even actually the same connector, at least not in the original FCC naming. That was an 8P8C keyed modular connector. RJ45 connectors had only two of the positions connected to wires (one phone line) an internal resistor between two of the other positions, and a keying bar that stuck out of the plug so they wouldn't even go into the unkeyed 8P8C jacks we use for Ethernet.

So I'll still call them RJ45 connectors. Because nobody has time to say "8P8C unkeyed modular connector" every time!

necovek 7 hours ago

Weren't phone lines something like RJ11 or RJ12?

FWIW, TIL about 8P8C.

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SAI_Peregrinus 4 hours ago

Yes, and RJ45. It used to be defined by the US FCC[1] in 47 CFR Part 68 Subpart F. Along with others, like RJ31X, RJ38, etc. The "RJxxy" numbers were the Universal Service Order Codes (USOCs), the `y` value described the use (e.g. W for wall-mounted jacks). Pages 143 & 144 of the PDF (403 & 404 of the print version) have the electrical connection diagram and the USOCs, pages 125-129 (385 -389 print) have the mechanical drawings. The unkeyed 8p8c connector we use today is also in there (pdf pgs 103-113), but the RJ45 series used the keyed connector! It's RJ31X & RJ38X that used the unkeyed 8-position series jack & 8-position plug we call RJ45 today (pdf pages 137-138).
[1] https://web.archive.org/web/20170705131407/http://www.tscm.c...

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Brian_K_White 3 hours ago

Similarly, it's DE9 not DB9

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SAI_Peregrinus an hour ago

Yep, and these days ribbon cables are rare, instead we have Flexible Flat Cables or Flexible Printed Circuits. Ribbon cables are the old cables like IDE hard drives used, with insulation displacement connectors, while FFCs and FPCs are much thinner and use integral connection schemes (tinned pads on the cable itself get clamped by some sort of connector on a PCB).

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