Abstract: The device comprises an input unit for generating coded data to be transmitted, an FSK coder-modulator for modulating, by frequency shift, the coded data to be transmitted, in a frequency range located between about 15 and 18 KHz, a mixer circuit for superimposing, with an attenuation of 20 to 40 dB, the signals modulated by frequency shift on a low-frequency signal of a traditional program to be applied to a frequency modulation radio transmitter, a decoder comprising filter circuits and an FSK demodulator for separating the coded data from the signals delivered by a standard frequency modulation receiver, and a display or recording unit for displaying or recording the demodulated, filtered, transmitted coded data.

Abstract: In an installation comprising a master assembly for reading the sound information signals and the end-of-program sequence signals recorded on a master tape, and at least one slave assembly to record a second time the read out signals, the slave assembly comprises circuits for detecting and regenerating end-of-sequence signals, which circuits are connected to the output of the said recording amplifier, digital coding circuits by derivation from a pilot frequency for producing a coded auxiliary digital signal, means to modify the digital coding at each new detection of end-of-sequence signals and an adder circuit to add the coded auxiliary digital signal with the sound information signal before re-recording the latter.