Radio beacon, in order to locate persons distress

摘要

1516740 Radio signalling PHILIPS ELECTRONIC & ASSOCIATED INDUSTRIES Ltd 14 Oct 1975 [17 Oct 1974] 42032/75 Heading H4L In a portable transmitter-receiver e.g. for locating a person buried by an avalanche, a receiver 8 has a changeover switch 9 arranged to select either an omnidirectional aerial 10 or a directional aerial 12 and further switching means ganged to the contacts 9 and arranged so that when used with the omnidirectional aerial, the receiver 8 is arranged to initiate operation on the same frequency as a transmitter 1 so that the device behaves as a transponder and, when the contacts 9 are in the other position, the device behaves as a direction finding receiver. As described, the receiver 8 comprises an aerial tuning circuit 11, frequency converter 13 with local oscillator 14, pre-selector 15, IF amplifier 16, filter 17 and detector 18. The transmitter 1, arranged to operated on the same frequency as the receiver 8, includes an RF oscillator 3, power amplifier 4, tuned filter 5...7 feeding an aerial 2. In the normal mode e.g. when the person carrying the equipment is likely to be buried by an avalanche, contacts 9, 27 and 24 are set into the positions shown so that the battery 20 supplies the receiver 8 via an electronic changeover switch 21. At the end of a received signal, an integrator 26 initiates operation of a 15 second timer 25 which enables electronic switch 21 to changeover the power supply to the transmitter I which thereupon radiates a 15 second signal. The device thus operates as a transponder. In the other positions of contacts 9, 24, 27, the transmitter 1 can be operated by depressing push button 23 which initiates a one second timer 22 so as to cause radiation during that period. During the following 15 seconds, receiver 8 is used as a direction finder with an alarm 28 and loudspeaker 29 so as to attempt to locate a person carrying a similar equipment. A switch 30 may be closed so that the transmitter repeats its operation at the end of each signal received by the detector 18.