Circuit for detecting pulses, and video recorder comprising the circuit

Abstract

A circuit for detecting pulses in an electric input signal, which pulses are superposed on a specific reference level (U.sub.ref), has an input terminal for receiving the electric input signal, at least a first and a second comparator device, switching means (S.sub.1), an output terminal and control signal generator means. The control signal generator means supply a control signal to the switching means (S1) to control the position of the switching means. The input terminal (1) is coupled to a first input of the comparator devices, whose outputs are coupled to a terminal (c and a respectively) of the switching means (S.sub.1). The output terminal (b) of the switching means is coupled to the output terminal. The first comparator device transfers only pulses whose relative amplitude in relation to the reference level exceeds a first value (U.sub.D1). The second comparator device transfers only pulses whose relative amplitude in relation to the reference level exceeds a second value (U.sub.D2). When input terminal receives N1 consecutive pulses whose amplitude relative to the reference level exceeds a specific (third) value (U.sub.D3) the switching means (S.sub.1) have been/are set to position c-b in such a manner that the first comparator is coupled to the output terminal. When subsequently N2 consecutive pulses are counted whose relative amplitude lies between a fourth and a fifth value (U.sub.D4 and U.sub.D5 respectively), such that U.sup.D5 <U.sub.D4 <U.sub.D3, the switching means (S.sub.1) have been/are set to position a-b in such a manner that the second comparator device is coupled to the output terminal. N1 and N2 are integers larger than or equal to 1.