Abstract: A system for transmission of binary signals between components of an alarm installation and across a transmission path, including an external wire network, comprises a converter for converting each of two logical conditions of two binary signals into respective signal frequencies, a coupler for coupling the alarm installation to the external wire network, a clamping circuit for clamping both binary signals to the same amplitude, providing the binary signals representing the two logical conditions with respective signal frequencies within a given range of frequencies and with a given frequency separation, and a band pass filter circuit at the receiving end of the transmission path for detecting the information signals, and exhibiting a narrow band pass responsive characteristic which is symmetrical with respect to the mean frequency of the two binary signals. Components of the system include a modulator, transmitting point, coupler, band pass filter, demodulator, and associated amplifiers.

Abstract: A method for transmitting binary signals having two logical states over a foreign wiring network, in particular for transmitting signals between structural elements of an alarm installation over an electrical supply wiring network. At least one of the two logical states of the binary signals is converted into a particular frequency, provided to the foreign network, and selected on a receiving end by filtering devices. The method includes the steps of recovering the binary signals on the receiving end, and passing the recovered binary signals through first and second differentiating networks which form an interference trap to identify and block interference pulses present in the signal.