A system in which one or more alarm sources (10), can wirelessly communicate with a receiver (30), to activate an alarm and does not contain any identification that indicates the communication's source (10). The system may include “repeaters” (40), whose function is to relay the communication from one station to another over distances longer than can be reached by a single transmitter (10), Apparatuses for transmitting (10), repeating (40), and receiving (30), are also disclosed, as well as a communication system comprised of various elements of these.