The Buzzer is a self-contained, low-voltage, battery-operated device. A buzzing sound is heard when a patch cord is plugged into the two polarized jacks, thus completing the external circuit.

The test buzzer is an audible signalling device used by electricians to identify wires and terminals that are directly interconnected. It determines whether switch contacts are open or closed, or whether wiring is short circuited. Unlike an ohmmeter, the buzzer will not indicate circuit continuity if any appreciable resistance is present.