Turn your old phone into an security alarm When the door opens you get a call to your phone You can make a security device with an old phone and microrupteur you have to set the phone on speed call first  solder 2 wire on the key you set solder microrupteur you can get the microrupteur from microwave or in electric store

The copper wire is taken from an old transformer. it is coated with insulating material and does not take a lot of space

Source: Youtube