GB1399313A - Electronic system for locating - Google Patents

Abstract

1399313 Electronic locating system RECOGNITION DEVICES Inc 14 May 1973 22891/73 Heading G4H [Also in Division H4] A locating system (e.g. in a building) comprises means 13 in a central console 10 for transmitting a VHF or UHF signal 19 identifying a person being sought, portable units 20 comprising means 25 for generating an ultrasonic signal in response to reception of a signal whose frequency corresponds to the carrier of the unit, stations 30 in fixed locations having means responsive to an ultrasonic signal generated by a nearby unit to generate in turn a signal 37 having a frequency identifying the station, and means 47-51 in the console responsive to this signal to indicate the station 30 and hence the location of the person being sought. The frequency 19 to be transmitted is selected by depressing a key 17 on the console. Each unit 20 includes a button 26 which the person carrying the unit may depress to actuate an audible or visual alarm on the console. The console and each station 30 may be provided with ring-counter actuated reed switch networks for scanning the locations of all the persons in the building (Fig. 2, not shown). The system may make use of the ordinary building electricity supply network, and stations 30 may be arranged to transmit signals of different polarities as well as of different frequencies (Fig. 3, not shown). One transmitter may be shared among a group of stations 30 (Fig. 5, not shown), the central console then incorporating means to accept only the first frequency received from stations of the group, which identifies the station of the group nearest the person sought. The above system may be adapted to cause a telephone 115, Fig. 4, to ring near the person being sought. An access code and a code identifying the person to be contacted are dialled on a phone 111 connected to a switching network 101 (e.g. a private branch exchange). An access network 103 thereby signals a decoder 105 (which causes transmitter 13 to generate a signal of there. quired frequency) and also opens a gate 109 so that the incoming location-identifying signal can pass from receiver 47 to a decoder 107. Decoder 107 translates the received A.C. signal into one recognizable by network 101 as being directed to a particular extension 115, which is thus caused to ring, after which a network 120 blocks gate 109 and turns off decoder 107.