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?