Rotary Telephone Teardown

20 August 2019 Link


I had a chance to have a look at an old rotary telephone at my son's school. The inner mechanics and lack of printed circuit boards looked refreshing. Here are the internals of the phone


THis image shows the front of the phone

This image shows the ringer bells and the gong in between. The electromagnet which pulls the gong is seen as the red coil on the right. The box with all the wire connections on the left is the impedance matching network. The spring assembly is where the handset rests.

Here we see the handset resting arm assembly more clearly. We can also see the markings on the impedance matching network box.

Here we see the speaker of the handset

Here I have taken out the microphone out of the handset.


I found the datasheet for the impedance matching network box. It is here, although it is not very clear how the ringer and the telephone line connect to it.