Abstract: Three or more listening devices (A1, A2, A3) are dispersed over the water area where the location of a sound source is to be determined, and transmit radio signals over respective channels to a master station upon detecting sound. The master station correlates the signals from selected ones of the listening devices to derive the position of the sound source relative to those listening devices. If the positions of those listening devices are unknown, for example if the devices are floating free, their positions are determined by the master station by comparing the relative times at which an identifying radio signal transmitted by each listening device is received by the master station directly and relayed from each of two stationary radio stations with known positions. The listening devices may also be provided with receivers for receiving radio command signals from the master station, for example relating to activation of certain listening devices and assignment of radio channels.

Abstract: A method of and a system for remote control of individual electronic equipments which are spread out across a large geographical area. Particularly activation of radio transmitters spread over the water surface and cooperating with hydrophones for picking up sound waves from submarines in order to locate submarines. To selectively activate the electronic equipments electromagnetic waves or sound waves are transmitted with given relative time positions from at least three fixed stations having known geographical positions. In each electronic equipment the waves are received and compared as regards their relative time positions at reception, activation of an equipment taking place only if a given criterion as regards said mutual time positions is fulfilled. Activation of equipments will take place only within a given small zone of said large area. The location of said small zone is determined by the relative time positions of the transmitted waves, which can be varied in order to select different zones.