AP21-BH1 is a self-contained, plug and play extra loud break buzzer signal system for factories, warehouses, auto and truck shops. It includes a high quality, low-voltage, 4-inch, high output buzzer (100dB), which is pre-wired with a 90ft cable for easy installation. Mounting hardware is included. No wiring is required. Simply hang the enclosure and the buzzer, plug it in, and enter program. This Buzzer must be mounted at least 10ft above employee work areas.