Abstract: The correlator responds to an input of N code sequences each having E code elements, each N sequence corresponding to a given state of a local coder. Each E element consists of one of W frequencies received for a time T. In the absence of an input an N-counter will advance under control of a timer. When the N-counter advances, an E-counter is reset. A local frequency synthesizer is set to one of W frequencies under control of the state of the coder, state of the E-counter and the state of the N-counter which will make the correlator receptive to the first element of the N-sequence corresponding to the value N at which the N-counter is sitting. If this frequency input is present for a time T, the E-counter will advance by one count and wait for the next element. The E-counter produces an output when advanced through E counts in a time interval to ET. This output advances the coder and delivers a correlator output corresponding to the state of the N-counter.

Abstract: 15. In a secure communication system a transmitter comprising first means to modulate a carrier wave with a sub-carrier wave and a desired signal, a code generator synchronized to said sub-carrier wave, second means to modulate the output of said first modulating means with the output of said code generator, and means to transmit the output of said second modulating means to a distant receiver.

Abstract: A signal modulated with information is hopped to discrete frequencies and its phase is selected to be 0.degree. or 180.degree. in each frequency hop interval under control of a pseudo noise binary code signal produced by a code generator. The discrete frequencies are generated in a binary frequency synthesizer and the phase is selected by a balanced modulator. One embodiment is a transceiver employing a single code generator for both transmission and reception. In another embodiment, a code generator is employed at the transmitter and another code generator is employed at the receiver of a communication system. In each embodiment, acquisition circuitry is employed to synchronize the code signal to the received frequency hopped and phase selected signal for synchronous detection of the information.