Abstract: A receiver circuit for audio frequency modems, comprising an input module (11) for receiving and sampling an analog input signal representing digital data, an adaptive equalizer (12, 14, 15) having a transversal filter (12) with a plurality of complex multiplier coefficients ordered relative to a usually central highest norm coefficient to generate symbols at a given symbol rate from the sampled analog signal, and a timing recovery device comprising devices (12, 16, 18, 19) responsive to displacement of at least one of the coefficients, relative to said central position, to control an oscillator (20) supplying a timing signal.

Abstract: A data communication system comprises two links between two terminal equipments, a standby link being used in the event of malfunctioning of a normal link. A method of returning to the normal link after using the standby link comprises, in parallel with transmission on the standby link, preliminary verification of the continuity of the normal link. The preliminary verification involves simultaneous transmission of a data signal by the terminal equipment initiating the continuity verification procedure, on the normal link and on the standby link, and detection by the other terminal equipment of the presence or absence of power on the normal link. This is done for each transmission medium of the normal link if the latter comprises separate media for each transmission direction.