Telephone
Goal: using an rotary phone as input and output device
Step 1: Reading rotary numbers
Connecting the phone
Dutch connector: http://www.matilo.eu/technish/oude-telefoon-aansluiten/?lang=en
Connect pin A (red) to +5V
Connect pin B (blue) to input Arduino
Connect gnd (yellow) to GND => not really needed
Tested: 12...15V, 50Hz is minimal needed to rinkle bell (only tested when B is conneced to GND)