(IDEA) RePhone in Old dial phone

Hi all,

Just got my RePhone GSM module and excited to get play with it.

I plan to put a RePhone GSM module in an old British dial phone (GPO type 706).

I have the arduino Xadow board for the dial rotor, I think that will work, I did see the GSM board has IO so that might work too.

The ringer is going to be fun have to make 60v AC from somewhere.

What I don’t know is how you connect the microphone and speaker. From all the research I have done the speaker doesn’t look like a problem a simple audio amp should do it? It’s the microphone input that I don’t get.
What I found is that the dial phone uses a carbon powder mic.
I made a test circuit using a carbon mic voltage divider and preamp. This makes a signal about 1.8v peak to peak at full but I don’t know what the rephone can take before it goes pop.
Power wise I have had the mic running off 3.3v so will work on a LiPo, there is also the micbias pin which looks like a power pin? What’s different what that from the 3.3v rail?



My thought as well … I’m still awaiting my RePhone but have collected a few tutorials relevant to the project at


[ My bookmarks at the DELICIOUS bookmark cloud service . ]

Please share your tips … I’ll do the same when I get my stuff working.

One thought: the rotary phone I will be using is cast iron and hence is a Faraday cage (hard to get a signal out). A friend suggested I embed an antenna in the cord of the rotary phone …

Charlie in Houston

Hi seeedstudio201407,

sorry compleatly missed your reply there.

Though on the up side I have info on how to get it to work :slight_smile: I do need to write this stuff up which is going to talk time, if you have any part to want info on just ask.

This was a big help with the ringer side sparkfun.com/tutorials/51

I can imagine that case if going to be interesting with signal. I got a little sticky antenna with mine so you could stick that on the outside, it’s only a 20mm ish cable. I do find when I turn on the boost converter the signal drops sometimes.

My phone is a GPO 746 (not the 706 I though it was) so not a problem for me.

Best of luck