A circuit for conditioning and digitising an analogue signal (x(t)) comprises a regulator circuit which is in the form of a delta modulator and comprises a comparator (1), a clocked flip-flop (2), a digital accumulator (3) and a digital-to-analogue converter (4). The comparator (1) compares the analogue input signal (x(t)) with a tracked signal (y(t)). The digital output signal of the accumulator is converted into a rectangular signal (COUT) corresponding to the analogue input signal (x(t)) by a digital low-pass filter (7) and a threshold value comparator (9) to which the mean value (M) of the digital output signal (DOUT) is supplied as the threshold value.