We are at the weekend and, without a doubt, there is nothing better than daring ourselves with a good project in which to have a good time, especially if in the end we achieve such amazing things as creating a fully functional rotary phone like the one that you see on these lines. The project has been dubbed PiTelephone and it is nothing more than an old phone connected to a Raspberry Pi which is the one that «does all the magic«.
If you want to recreate as much as possible the result that you can see in video right at the end of this same post, tell you that its creators chose the phone GPO model 746 of 1970, specifically we speak of an English model. To get the phone to ring, it has been necessary to connect both sides of the coil to a 16 volt source, while to power the Raspberry Pi a converter is required, specifically the model used is a OKI-78SR.
The photo you have on these lines corresponds to the system necessary to achieve the typical frequency of the telephone exchanges of the time which, in the United Kingdom and at that time was 25 hertz, for this dyou reread SPDT, one for current and one for oscillating between the two coils. To count the pulses they leaned against the library raspberry-sharp-io and a simple C # script that counts the time in milliseconds between pulses, so you know what number has been dialed. You have all the code in GitHub.
We reached the final point where, thanks to technologies such as FreeSwitch, a multiplatform solution designed to connect the most popular communication protocols using voice, audio, image or other multimedia resources, PJSIP, an open source library for multimedia communications as well as the Skype SDK. I leave you with the aforementioned video.