The DET-16 is an indoor mounted sixteen-zone solid state telegraph transmitter that employs a unique code for each zone. It includes a CAM lock, display and keypad, AC transformer, standby battery and built-in charger. The unit is housed in a steel enclosure suitable for indoor mounting. Telegraph codes unique to each of the sixteen zones for Alarm, Trouble, and Secure, Low Battery, & AC Power Failure are transmitted over 100 milliampere circuit using positive non-interfering successive (PNIS) line current detection to avoid clashes between more than one transmitting box. Automatic ground return, a watchdog timer, and a software selected internal trouble buzzer assure continued main system operation and operator notification in the event of box failure.  NFPA-72 compliant.