The ringer of the phone is actuated by a hammer and an electromagnet. Alternating current through a solenoid, continuously polarises the magnet two different ways. This makes the hammer swing both ways, hitting the bells.
During the days of the actual phone this was done with around 100 Volts at a frequency of 20 Hz, but I am hoping that 12 V and 50 Hz will do the trick.
I want the phone to be working continously and not have to hassle with batteries. Since I anyway need the AC circuit for the bell, I plan to use the power from an outlet, convert it to 12 V DC for the electronics and tap from the incomming AC supply for the bell. The ACDC converter I ended up buying is very similar to this one.
A simple 5V relay shall be used to actuate the solenoid intermittently with 1s intervals. The figure below shows the electromagnetical actuator in this phone: