Abstract: The present invention relates to a method and to an arrangement for regenerating timing pulses from an information-carrying pulse train of the NRZ-type. The method can be used in a telecommunication system to create a timing signal which is synchronous with the information-carrying pulse train, so as to enable the pulses of the generated timing signal to be used as clock pulses when reading information from the original pulse train. The information-carrying pulse train is differentiated and rectified in a known manner, wherein the rectified pulse train signal will contain solely positive or solely negative pulses originating from level shifts of the pulse train signal. A commutating filter is given a resonance frequency which corresponds to the frequency of the NRZ-signal, and the rectified pulse train signal is supplied to the commutating filter, which generates timing pulses during those periods in which no pulses occur in the rectified pulse train signal.

Abstract: A method of detecting hazardous line voltages over a two-wire line for transferring digital information. At one end, the line is terminated by a hybrid coupler (G) and an apparatus for adaptive echo elimination. This apparatus generates a digital signal (d) constituting an unambiguous measure of the difference between the line impedance (Z.sub.L) and the hybrid impedance (Z). This signal is compared with two digital limiting values (d.sub.1,d.sub.2) an alarm being given should either these two values be reached or exceeded.