Vintage Connecticut Telephone intercom

[blickcd]

I have a pair of these which used to belong to my Grandfather. They look like old phones but are really an intercom system.

You pick up the handset on one phone and press a button on the side, which rings the other phone for as long as you hold in the button. A person on the other end picks up their handset and you speak into the mouthpiece to talk. If people on both ends pick up at the same time they can talk without first ringing the other phone as the bell is only a signal.

My Grandfather wired these up at a house I lived in while I was a kid and we had some fun with them and they were useful for my Mom to call down from the kitchen to the basment when supper was ready. We moved though, several times, and never hooked up the phones again.

I've now dug them out of some old boxes of junk and want to hook them up but don't remember exactly how it was done. I am hoping that someone knows of these phones and can make a suggestion. I'm generally good with electricity but my trial and error has gotten me nowhere.

Each phone has identical wiring terminals on the back. Bell, Bell/Line, and Line. I suspect that Bell/Line is a common positive or negative. As I recall, three wires run from one phone to the other and batteries are hooked up at one end somehow. Large lantern batteries were used but I don't remember if it was 3, 6, or 12 volts.

I can attach photos of the backside if that will help anyone, though there isn't much to look at. This is a really promitive system.

Thanks,
Christopher

[Excella CM]

They need to be connected by two conductors. Either two wires or one wire and a chassis ground return. Probably batteries inside since they need low voltage DC to operate.

[Jammer]

Not sure without experimenting. That design was common, I've seen many.

I would expect that the battery goes in series on the wire between the line terminals with a blocking capacitor in series with the battery. The value is not critical, 47 uF, 470 uF, anywhere in between, maybe less will work.

There may be a blocking capacitor built into the phones but if it is there's a good chance that it's shot and will have to be replaced.

I believe the other two wires just go between the phones.

Not sure how you get power to the bell.

[cclarkego]

Gosh, how long is your Airstream? Can't you just yell down the hall?

[blickcd]

There was never a capacitor in the circuit, though one might be in the phones, and the batteries were outboard. For our installation, the batteries were in a storage room behind the basement phone.

The way it works, there is power to the bell circuit all the time. Pushing the button on phone 1 completes the cricuit to ring phone 2 and vice versa.

I'm a bit confused on the wiring descriptions given so far. I need something like, Bell to Bell, Line to Line, Bell on phone 1 to +, etc.

Christopher

[safari62]

Originally Posted by cclarkego

Gosh, how long is your Airstream? Can't you just yell down the hall?

Must be a 34'.....

[blickcd]

Special thanks to my brother-in-law Dave who helped me figure this out. See the attached schematic.