The GEM-HEAT is a high-quality 135°F (57°C) Fixed temperature detector with Rate of Rise. It is compatible with the NAPCO Express and Gemini series GEM-RECV Series supervised security receivers. The GEM-HEAT incorporates circuitry which will transmit an alarm signal upon an alarm condition, generate an hourly supervisory test signal to the receiver and also monitor and annunciate low battery. Coding switches are not required or used in the GEM-HEAT. Each transmitter is assigned a unique identification code number at the factory. The transmitter is powered by one 3V Lithium battery (supplied) which can power the unit for up to two years. If the battery voltage drops below normal, a low-battery report will be sent to the receiver with any status or alarm transmission. If a low-battery condition is indicated, replace the battery.