Abstract: A secure communication system comprising:a first cyclical pseudo-random noise generator comprising determinable vable starting point means and an output;transmitting means for transmitting said pseudo-random noise generator output;receiving means for receiving said transmitting means transmissions, said receiving means having an output;recycling storage means for storing said receiving means output;a second cyclical pseudo-random noise generator identical to said first pseudo-random noise generator having an output and a reset input, said receiving means output connected to said reset input;a correlator having a first input connected to said storage means and a second input connected to said second pseudo-random noise generator output and an output from said correlator; andtiming means connected to said receiving means output and said correlator output for measuring time elapsed between any output of said receiver and said correlator.

Abstract: The secure communication keying system has a noise generator whose output a predetermined finite band of noise within, for example, the zero to eleven hundred cycle per second range. The noise generator may be a pseudorandom noise generator that is synchronized with a given clock frequency. The output of the system may have noise-like characteristics, but it is encoded with any type of intelligence desired to be transmitted. The output signals simulate the ambient noise occurring within the communication medium and has the same frequency spectrum regardless of the frequency of the modulating signals supplied thereto.

Abstract: 2.

Abstract: A secure sonar communication system for transmitting and receiving intellnce signals within an aqueous medium comprising in combination means for generating an electrical pseudo random noise signal within a predetermined bandwidth, means connected to said pseudo random noise generating means for selectively driving same at one of a plurality of predetermined frequencies, keying oscillator means adapted to selectively produce an output of one of a plurality of predetermined frequency signals, a balanced modulator means coupled to said pseudo random noise signal generating means and said keying oscillator means for mixing the output signals therefrom, bandpass filter means connected to the output of said balanced modulator means for passing the upper sideband thereof, means for receiving an electrical pseudo random noise signal, transducer means, said transducer means being capable of broadcasting acoustical energy upon excitation by the upper sideband from the aforesaid bandpass filter means and in proportion

Abstract: 1. An encoded echo-ranging signal generator comprising in combination;A digital shift register having a plurality of binary encoded stages,A shift pulse generator coupled to said digital shift register for the tiy shifting thereof,An anti-coincidence circuit having a pair of inputs and an output with one of said inputs being connected to a predetermined stage of said digital shaft register and the other input thereof coupled to the output of said digital shift register and with the output thereof connected to the input of said digital shaft register, to randomly recirculate through said register the binary contents of said encoded stages,An echo-ranging system coupled to the output of said digital shift register,And a digital message encoder coupled to said digital shift register for the respective binary bit encoding of each stage thereof.