A turret phone is a phone system that allows other phone stations to be connected to a master phone station. The systems can connect to standard phone lines and active phone calls can be monitored through the other phone stations connected to the network.
The first patent for the phone system was in 1983 by Thomas E Feil. He invented the multistation telephone communicating system.
Turret systems allow someone to use multiple phone lines at once. They also allow voice recording on every call for protection from unnecessary litigation.
The phone system is used in hotels, trading jobs, and other companies requiring many phone lines. It is used all over the world.