GB1214050A - A system for activating a remote underwater device - Google Patents

Abstract

1,214,050. Acoustic signalling. RAYTHEON CO. 21 Oct., 1968 [1 Nov., 1967] No. 49910/68. Heading G4F. In a frequency coded system for activating a remote underwater device, a receiver is arranged to respond only to the presence of at least one "assertion" frequency f A , f D and to the absence of other "negation" frequencies f B , f c . The transmitter (Fig. 2A, not shown) may comprise four oscillators each coupled via respective AND gates to two amplifiers feeding transmitting transducers. The AND gates are arranged so that one transducer first transmits frequencies from two of the oscillators whilst the second transducer later transmits frequencies from the other two i.e. providing the logical complement of the first signal. Receiver.-In Fig. 2B the receiving transducer 50 is housed in a pressure proof lead zirconate titanate sphere and its output is separated by filters 56-59 into four channels 60-63 corresponding to the frequencies of the four oscillators in the transmitter. After detection and further filtering at 71-74 the outputs of channels 60 and 62 are fed to AND gate 79 together with the outputs from channels 61 and 63, after inversion at 76, 78. AND gate 79 thus only provides an output following reception of the first signal from the transmitter i.e. in the presence of frequencies f A and f D and the absence of frequencies f B and f c . After a delay due to one shot multivibrator 82, a signal is supplied on one input 97 of a further AND gate 84 for a period determined by a second multivibrator 83. If, at this time the complementary second signal is received from the transmitter, then an output from AND gate 80 will pass AND gate 84 so as to operate a relay, motor, radio transmitter, valve or to detonate an explosive. The system may be arranged to transmit different codes corresponding to various control functions.