Abstract: A security system for a building uses the telephone system. Telephone receivers are located in various rooms in the building and linked through a telephone exchange. Persons that live or work in the building are provided with wireless alarm transmitters. Wireless receivers are located in the building, each coupled to one of the telephone receivers. Each wireless receiver, when receiving an alarm signal from one of the transmitters, initiates a call to the telephone exchange in response. The wireless receiver message will identify the individual associated with the particular transmitter and provide the location of the receiver that received the alarm signal.