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By smartlight
I have recently discovered a bunch of old phones in a very dingy theater basement. I polished one up and would like to get it going for use as my office phone. It is a classic black, 5-line with hold,Western electric "hand-set" type (500 series?). But the cable coming out of it appears to be a parallel port style....multi-pin (50), 90 deg. jack.

Does anyone know where I can find a shematic or pinology chart so I can fabricate an adapter? Even one line would be cool. Not quite as cool as the "port-o-rotary" but nonetheless cool.
Thanks in advance....
By wiml
There are a bunch of those lines where I work, mostly unused since we've gone to a VoIP PBX... hmm, some googling (eg here) suggests that it's an RJ-21X connector. Does this pinout look like what you have?
By eejake52
The blue pair will be line 1. Everything else is related to the lamps and other lines.

By awright
My building is wired with these 50-pin connectors, a legacy of the time it was an office with many separate, active phone lines. Each office has a 25 pair cable coming in from the telephone equipment room and terminated in one of those 50 pin, 90 degree connectors. To connect a phone, I have to select an available, unused pair on the cable (which is pretty arbitrary, since there are not many lines presently in use), punch the corresponding wire pair in the cable to an available line coming into the building to one of the 25-line punch-down blocks in the telephone room, and connect the two signal wires from the telephone to the appropriate pins in the 50-pin connector. So for a single-line phone, I'm only using two pins on the 50-pin connector (always seemed like such a waste).

For a 5-line phone (assuming you have 5 active lines available to connect to your phone), you arbitrarily select 5 pin/wire pairs, connect the 5 pairs to the punch-down block in the phone room, and wire your phone connector to match the lines selected.

It was a method of wiring a building for many phones in a very flexible manner, leaving the installer to select which of the available wire pairs went to which phone by the way he wired the connector.

If you don't want to use 5 lines with your vintage phones, I'd suggest just getting a 1 or 2-pair cable from Radio Shack with ring terminals on the phone end and a modular plug on the line end and tossing the 50-pin connector. (They were always a pain anyway, due to the stiffness of the cable and their bulk.)