The unit is activated by a solid state, voltage sensing relays and responds to a 16-70 Hz ringing frequency. Operation of the unit matches the ringing cycle of the telephone. The unit has a 4" (102mm) steel gong.
Installs with three screws using the three external mounting lugs.For use in areas that have medium ambient noise levels such as small warehouses, garages, car lots, gas stations, taxi stands, and construction sites.