Abstract: A radio frequency transmission and reception system, for use as an active decoy, includes a receiver 10, a transmitter 12 and a signal generator 20 for providing wideband noise signals for transmission during the interpulse period of pulsed signals transmitted by the transmitter 12. A feedback circuit 21, including an adaptive transversal filter 23 combines signals for transmission with output signals from the receiver to adaptively modify the wideband signals in the signals for transmission so as to render the receiver 10 substantially insensitive to received signals which are derived from the transmitter.

Abstract: A signal generator produces a spread-spectrum bandwidth signal in the frequency range 40 to 90 KHz for use in a domestic mains signalling system. In the generator, sixteen individual frequencies, equi-spaced in that range, pass to samplers operating at a clock frequency of 204.8 KHz and then to quantizers before storage. The resultant signals are then assembled in appropriate manner by selector switch before being filtered when (temporarily) in the frequency domain.The resultant signals duly reach catalogue store, whose output can be used for programming an EPROM in a mains signalling interface unit.

Abstract: In a line network communication system coded data signals are transmitted on a base band carrier signal and are recovered in a receiver. The receiver includes an exclusive OR gate and a shift register which operate in conjunction to compare, during successive time intervals, a series of coded reference signals and a succession of received signals shifted in phase relative to one another by respective amounts to generate respective comparison signals forming a set. A control unit causes a change in the relative phases of compared signals until the value of a comparison signal in a set indicates a degree of correlation exceeding a threshold value. Then, in a tracking mode, the control unit monitors the values of comparison signals generated in successive sets to verify that a degree of correlation exceeding the threshold value persists. If the verification is successful the control unit, in a locking mode, adjusts the relative phases of the compared signals to maintain a desired degree of correlation.