[John Graham-Cumming] has shown us one exquisite example, with his teardown of a simple Czech telephone. The model in question is a DS3600 telephone built by Tesla Stropkov in the early 1980s.

Then in 2004, he happened to connect with a friend of a friend who also was into the old telephone technology and discovered there was a whole world of phone aficionados. That led to a trip to the ...

The schematic for the project shows how to connect the rotary dial (salvaged from an old telephone) to both a 7-segment display and a collection of ten LEDs.