Abstract: A low probability of intercept communication system (CCSK)--modulates information signals onto an inverse fast Fourier transformation of a large number of simultaneous frequencies that have been determined to be reasonably `quiet` within a given system bandwidth, so as to produce a time domain pulse waveform. The amplitude of each transmitted frequency is weighted. Within the receiver equipment of each participant in the system, the incoming pulse waveform produced by the inverse fast Fourier transformation mechanism at the source is coupled to a fast Fourier transform operator, so as to separate the time domain signal into a plurality of frequency components that contain the modulated data. These components are then convolved with a replica of the plurality of quiet channels to derive a time domain output waveform from which the data modulation can be identified and recovered.

Abstract: An evolutive coding process using a pseudo-random discontinuous function for coding remote controls, such as for automobiles. A message containing at least two pseudo-random values calculated by the pseudo-random discontinuous function is transmitted. Preferably the pseudo-random values are successive values of the pseudo-random discontinuous function, and the message optionally includes a code derived as a function of a specific base code associated with the system. The general preferred form of complete code message may take the form T(C) plus FA(C,n-1), plus FA(C,n) where T is a continuous function and FA is a pseudo-random discontinuous function.