Sounds like you and I have essentially the same system. Let me describe mine.
My home was built in 1954, and came with (even then) what was called ‚ÄúRemote Control Switching‚Äù from GE. It is comprised of little 24-volt (DC) rocker switches in place of normal 110v switches. When you push the rocker switch up, a relay is switched to on, and your light/receptacle is turned on. Push the rocker switch down, the reverse happens, and the power to the light/outlet is turned off. Each rocker switch has 3 wires; one is power from the transformer, and the other 2 go back to the relay. The wire is basically solid-core bell wire.
All of my relays, and most of my transformers are located in a central place, which is neat because I can add switches and power things from anywhere. I even have master switches which can turn on all lights inside and out in case of emergency. It‚Äôs only drawback is that one cannot get a dimmer switch for a light without running 110v wire and bypassing the low-voltage system, but I got around that with the introduction of wireless dimmer switches.
It was an idea that never caught on in the residential side, but it did on the commercial, so all the components are still widely available, a point which led me to decide to keep the system instead of ripping it all out, which would be very expensive to do. The switches fit in sets of 1 to 3, in a space the size of a regular outlet box, although mine use something like phone or cable TV brackets instead of actual electrical boxes. The little plate that the switches snap into lines up, screw-wise, with regular outlet box screw holes. The cover plates have the same hole pattern as d√©cor switch plates, and although I do not know if the originals could still be purchased, I buy blank d√©cor plates and cut out the holes, or make decorator ones out of wood. We bought the home last June, I checked, and the components cost less than in 1994 when the last owners last bought a part..
I have about 35 relays, and 50 switches, and it looks like maybe 5 relays and 3 switches have been replaced in 45 years. Does this sound like something you could use? If so, I have copies of the original installation manual, which I could fax you. You could also call your local electric supply company and ask if they can get GE low-voltage relays or switches.
At any rate, let me know more about your system. Until now, I did not know there were other similar systems out there.
TomR - [email protected]