Circuit Board Construction

I spent a most enjoyable afternoon with my friend and neighbor building simple alarm circuit boards that detect a break in an an electric wire.
These alarms are used in many ways, for example as a burglar alarm if opening a door breaks a circuit  thus triggering the alarm.
We will use the alarms we make in the hearing loop wire we install that allows people with hearing aids to have a speaker's microphone audio signal go directly into their hearing aid. 
We are presently doing a job in building being renovated and the flooring workers come in after us to install new flooring.
They may inadvertently cut the loop wire which must be detected immediately before the flooring material is put over the wire.
We built six of these gizmos this afternoon.