System for activating a remote underwater device

Claim 2

In a remote underwater device actuable by at least two predetermined frequencies fA and fD, the improvement comprising: detecting and logic means responsive to each incident acoustic wave for activating the device only upon the detected joint presence of at least two predetermined frequencies fA and fD and the absence of at least two other predetermined frequencies fB and fC where fA<fB<fD<fC; the detecting and logic means including: n narrow band filters tuned to the predetermined frequencies fA, fB, fC, and fD, the filters providing corresponding output signals eA, eB, eC, and eD indicating the presence of the desired frequency; a first logic arrangement coupling the n arrow band filters for providing an output signal S1 where S1 eA$eB$eD$eC; a second logic arrangement also coupling the n narrow band filters for providing an output signal S2 where S2 eA$eB$eD$eC; and a third logic arrangement for generating a signal S3 for activating the device when S3 S1$S2.

Claim 3

The detecting logic according to claim 1, wherein the third logic arrangement includes: an AND gate coupling the first and second logic arrangements; and means interposed between the first logic arrangement and the AND gate for applying the S1 signal to the corresponding AND gate input if a predetermined number of S1 signals have been detected within a given time after receipt of the first S1 signal.

Claim 4

In combination: means for generating a sequence of signal pulses, having a predetermined spectrum in which certain predetermined frequencies are present and in which other predetermined frequencies are absent; means responsive to said sequence of signal pulses for detecting the presence and absence of said predetermined frequencies of said spectrum and providing a first signal indicating such presence and such absence of said frequencies; means responsive to said first signal of said detecting means for providing a second signal at a predetermined time subsequent to said first signal; and means, responsive to the temporal concurrence of said second signal with said first signal in response to a subsequent one of said sequence of said signal pulses, for providing a signal indicating the simultaneous presence of said second signal and said subsequent first signal of said detecting means.

Claim 5

In combination: means for generating a sequence of signal pulses, having a predetermined spectrum in which certain predetermined frequencies are present and in which other predetermined frequencies are absent; means responsive to said sequence of signal pulses for detecting the presence and absence of said predetermined frequencies of said spectrum and providing a first signal indicating such presence and such absence of said frequencies; means responsive to said first signal of said detecting means for providing a second signal at a predetermined time subsequent to said first signal; and means, responsive to the temporal concurrence of said second signal with said first signal in response to a subsequent one of said sequence of said signal pulses, for providing a signal indicating the simultaneous presence of said second signal and said subsequent first signal of said detecting means.

Claim 6

The combination in accordance with claim 3 wherein said response of said frequency detecting means will occur only upon the simultaneous presence of at least two of said frequencies and the simultaneous absence of At least two of said frequencies.

Claim 7

The combination in accordance with claim 3 wherein said frequency detecting means comprises a plurality of frequency responsive filters and said sequence of signal pulses are pulses of acoustic energy.

Claim 8

A sonic communication system comprising: means for generating a sequence of signal pulses having a predetermined spectrum in which certain predetermined frequencies are present and in which other predetermined frequencies are absent; and means for receiving said sequence of signal pulses, said receiving means being responsive to the difference in the times of occurrence of one of said signal pulses and of a subsequent one of said signal pulses of said sequence for providing a first signal indicating the presence of said subsequent pulse at a predetermined time after the occurrence of said one of said signal pulses, said receiving means being furthermore responsive to the presence of said present frequencies and to the absence of said absent frequencies of said spectrum for providing said first signal only if said certain predetermined frequencies are present and if said other predetermined frequencies are absent.

Claim 9

A sonic communication system comprising: means for generating a sequence of signal pulses having a predetermined spectrum in which certain predetermined frequencies are present and in which other predetermined frequencies are absent; and means for receiving said sequence of signal pulses, said receiving means being responsive to the difference in the times of occurrence of one of said signal pulses and of a subsequent one of said signal pulses of said sequence for providing a first signal indicating the presence of said subsequent pulse at a predetermined time after the occurrence of said one of said signal pulses, said receiving means being furthermore responsive to the presence of said present frequencies and to the absence of said absent frequencies of said spectrum for providing said first signal only if said certain predetermined frequencies are present and if said other predetermined frequencies are absent.

Claim 10

In combination: means for generating a sequence of signal pulses, a first pulse in said sequence of pulses having a first frequency spectrum in which certain predetermined frequencies are present and in which other predetermined frequencies are absent, a second pulse in said sequence of pulses having a second frequency spectrum different from said first spectrum, said second spectrum having certain predetermined frequencies which are present and other predetermined frequencies which are absent; means responsive to said sequence of signal pulses for detecting the presence and absence of said predetermined frequencies of said first spectrum and providing a first signal indicating such presence and such absence; means responsive to said sequence of signal pulses for detecting the presence and absence of said predetermined frequencies of said second spectrum and providing a second signal indicating such presence and such absence; means for delaying said first signal for a predetermined interval of time; and means responsive to the temporal concurrence of said delayed first signal and said second signal for providing a third signal indicating the simultaneous presence of said delayed first signal and said second signal.

Claim 11

In combination: means for generating a sequence of signal pulses, a first pulse in said sequence of pulses having a first frequency spectrum in which certain predetermined frequencies are present and in which other predetermined frequencies are absent, a second pulse in said sequence of pulses having a second frequency spectrum different from said first spectrum, said second spectrum having certain predetermined frequencies which are present and other predetermined frequencies which are absent; means responsive to said sequence of signal pulses for detecting the presence and absence of said predetermined frequencies of said first spectrum and providing a first signal indicating such presence and such absence; means responsive to said sequence of signal pulses for detecting the presence and absence of said predetermined frequencies of said second spectrum and providing a second signal indicating such presence and such absence; means for delaying said first signal for a predetermined interval of time; and means responsive to the temporal concurrence of said delayed first signal and said second signal for providing a third signal indicating the simultaneous presence of said delayed first signal and said second signal.

Claim 12

The combination according to claim 7 wherein said sequence of signal pulses are pulses of acoustic energy.

Claim 13

A secure communication system comprising: means for radiating pulse train signals into a medium, said pulse train signals having a predetermined frequency spectrum in which a plurality of predetermined frequencies are present and in which a plurality of predetermined frequencies are absent, one of said absent frequencies being located between two of said present frequencies and one of said present frequencies being located between two of said absent frequencies in said frequency spectrum; means spaced from said radiating means in said medium for receiving said pulse train signals; and means fed by said receiving means and responsive to said pulse train signals for decoding said pulse train signals, said decoding means having logic means responsive to the relative spectral positions of said present frequencies and said absent frequencies in said spectrum for providing a signal if, and only if, there is an absence of said absent frequency between two of said present frequencies and if, and only if, there is a presence of said present frequency between two of said absent frequencies.

Claim 14

A secure communication system comprising: means for radiating pulse train signals into a medium, said pulse train signals having a predetermined frequency spectrum in which a plurality of predetermined frequencies are present and in which a plurality of predetermined frequencies are absent, one of said absent frequencies being located between two of said present frequencies and one of said present frequencies being located between two of said absent frequencies in said frequency spectrum; means spaced from said radiating means in said medium for receiving said pulse train signals; and means fed by said receiving means and responsive to said pulse train signals for decoding said pulse train signals, said decoding means having logic means responsive to the relative spectral positions of said present frequencies and said absent frequencies in said spectrum for providing a signal if, and only if, there is an absence of said absent frequency between two of said present frequencies and if, and only if, there is a presence of said present frequency between two of said absent frequencies.