Federal Signal's Model 300SSC Supervised SelecTone Command Unit is the heart of a fully supervised plant and employee protection signaling system. A steel enclosure, locking door and a plexi–glass window protect the hand–held microphone and local control switches from unauthorized access.

This visual and audible annunciator system alerts any alarm or trouble conditions. All initiating and signal lines, control circuitry and switches are supervised. Up to four audible warning signals, including voice can be broadcast in a SelecTone system.

Signals are prioritized. Local mic has highest priority, followed by tones 1–4 and auxiliary PA. Higher priority signals interrupt lower priority signals.

Two auxiliary relay circuits are programmable to control door locks, fire doors, fan circuits or other process control functions. Circuitry is provided to activate the local municipal box.

The annunciated control panel provides easy control and analysis of system conditions. Tone signals can be tested on a monitor speaker without sounding false alarms or activating peripheral equipment.