Home-Made VOIP Phone/Modifying an Analogue Telephone for VOIP use

Some of my family and friends have started to use Skype. I know its not compatible with SIP etc etc (at the time of writing anyway), but they found it easy to install and use, and to be able to communicate with them in this way I'm going to have to join them!

The idea is very straightforward. We bypass the phone circuitry, and connecting straight to the microphone and speaker of the handset. This design has two main disadvantages over the £35 Skype handsets (a) it ties up the audio card - if you wish to listen to music you'll have to unplug the handset and (b) it doesn't have the integration of the official handset - you'll still have to click the red button to hang up for example.

  • So, I disassembled the telephone.
    etc
  • Within the base of the handset found a convenient location for the two jack sockets. These are labelled 'Speaker In' and 'Mic Out'.
  • Located the wiring from the speaker of the handset. The connections to the speaker are normally red and green. I soldered two short links from the PCB to one of the jack sockets.
  • Located the wiring from the microphone of the handset. The connections to the microphone are normally black and yellow. I soldered two short links from the PCB to the other jack socket. The polarity matters for this set of connections.
  • Reassembled the telephone.
  • Connected the telephone to my computer.

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