Abstract: The analogue to digital converter is of the bipolar mark-space type and includes an integrator for integrating the analogue input signal to be converted. A square wave generator is connected to the input of the integrator so as to superimpose a triangular periodic signal on the output signal produced by the integrator.First and second level detectors are connected to compare the output signal from the integrator with first and second detector levels respectively to produce first and second control signals respectively when the magnitude of the output signal from the integrator exceeds the first level and falls below the second level respectively. Switch means responsive to the first and second control signals are provided to respectively apply first and second reference signals. The conversion interval is set equal in duration to the duration of an integral number of cycles of the periodic triangular signal.