Abstract: In a fire, smoke or intruder detection system including a master unit and satellite units with remote sensors, the satellite units send alarm transmissions to the master unit over a radio frequency channel. In order to register satellite units with the master unit each satellite unit is provided with a unique identification code and, after suitable triggering, sends a signal including this code to the master unit over a line-of-sight communications channel. The master unit registers satellite unit identification codes received on the line-of-sight channel and disregards radio frequency transmissions if they include unregistered satellite unit identification codes.

Abstract: A security installation at one Site has remote sensors which detect intrusion, fire, etc. and transmit corresponding signals by radio to a master station. Similar installations are provided at other Sites. The sensors of each Site precede their data signals with an access code which is particular to that Site and prevents their signals being received by the master station of any adjacent Site within radio range. When a new installation is to be installed at a new, adjacent Site, an arbitrary value is initially selected for its access code and the master station there transmits a special code to all adjacent Sites. In response to this special code, the master station in each such adjacent Site transmits its own access code back to the new installation, where it is compared in value with the arbitrarily selected access code. The latter is automatically changed until it becomes different from that of any and all adjacent Sites. The remote sensors of the new installation are then set to this value.

Abstract: A security installation comprises a plurality of sensors in and around a building and which transmit digital information to a central station by radio, in each case preceded by an access code specific to the particular installation; signals inadvertently received from the sensors of an adjacent installation are rejected. The information is transmitted by encoding a multiple bit word incorporating the access code, a code indentifying the particular sensor, and the actual data. The sensor transmitters may drift over a wide bandwidth. To avoid using a wide band receiver in the master station, the receiver bandwidth is narrow but swept over the wide bandwidth. As soon as a signal is detected, the sweep is halted until the recognition process has been completed.