[drewzero1]

I have a couple of those around. I had to learn to dial them as a kid when we moved to a house that still had them hard-wired to the wall.

Someday I'd like to try to use them as an intercom/hotline between the house and workshop, but I haven't figured out how to power the circuit and (especially) the ring signal. (Grandpa always did his own phone wiring and told me you really didn't want to be touching the terminal when a call came through, something like 100V AC!)

[timonoko]

Connecting two rotary phones (via 40 volt battery) is the easiest thing. They work as-they-are without modifications. When the phone is off-hook, the dialling rotator makes pulses and when the phone is on-hook those pulses cause the bell to ring. But not very loudly, because the real ringing pulses are 80 volts.

Source: I am rotary-telephone-era Telecommunication Engineer.

[drewzero1]

Thanks for the info! Sounds a lot easier than anything I was imagining. I'll have to dig up a couple of those 4-pin sockets and see if I can source a battery.

[ipdashc]

Completely overkill for just an intercom, but an analog telephone adapter would let you connect those to a VoIP server (like Asterisk, etc). Could be cool.

For just a hotline/intercom setup, I think a telephone line simulator might do the job, but those seem stupidly expensive!

EDIT: The other reply seems a lot more knowledgeable, ignore this one

[drewzero1]

Thanks! I was looking into a line simulator, but yeah they're expensive!

I thought about setting something up with an old PBX from work, but they're too new for pulse dialing. I was trying to figure out if I could build something with old modems but never got anywhere with that.