Abstract: A receiver for FFSK modulated signals operating in the time domain so as to effect a rapid acquisition of the data signal and the generated clock signal and to maintain the synchronization irrespective of the data pattern. For that purpose the receiver comprises a zero-crossing detector and a window generator for selecting by means of this window generator from the zero-crossings detected by the zero crossing detector two consecutive zero-crossings of the lower frequency of the two signal frequencies of the FFSK signal for sychronization of the regenerated clock signal.

Abstract: A transmitter for transmitting FSK-modulated signals by way of an inductive aerial. A large frequency deviation, such as with FFSK-modulated signals, and a high transmission rate may cause the occurrence of a non-constant envelope. Electronic equipment arranged in the vicinity is then subjected to a greater degree of interference than with a small modulation depth and a low transmission rate. By generating in the transmitter an aerial current whose amplitude is inversely proportional to the frequency, tuning is not necessary to obtain a constant voltage envelope.

Abstract: Apparatus for preventing the simultaneous energization of a pair of traffic lights includes a detection device for monitoring any leakage current in the cables between the traffic lights and a control box. A threshold voltage related to a predetermined level of leakage current to be monitored is coupled to the detection device which actuates an alarm if the leakage current across at least one traffic light exceeds said predetermined level of leakage current.

Abstract: Vehicle identification system comprising a carrier period detector in which, to increase the accuracy of identification signals received, the identification signal is rejected and a new identification signal is requested whenever one period is absent from the carrier signal received.