Phone tap consoles are usually built in a security room. They require a guard and electricity to operate. They must be connected to phone booths or visitation booth in order to tap into that particular phone booth's calls.
When a booth with an ongoing call is found the cycling stops and the guard listens to that phone call. If a call is being monitored, the light on top will appear green. If no call is being monitored, the light will appear yellow. Please be aware that a Guard listening to a Phone Call will not stop other Guards from listening to the same Phone Call. This causes multiple Phone Taps connected to a bulk of phones to be ineffective.
The information gathered from phone taps will be utilized automatically by the guards and given to the player.
It is a good idea to run your phone taps on an isolated electrical line and then put a switch and a door timer on it. That way you can automatically disable phone taps when they are not needed, which will free the guards controlling them.