Abstract: A telephone signalling receiver comprising speech detectors for respective voice-frequency signalling components of push-button (TDK) signals which are in a frequency band divided into lower and upper frequency subgroups. Each detector calculates the Discrete Fourier Transform (DFT) of the corresponding signal frequency component, the frequency characteristic of such detector having a main lobe for such signalling frequency component and two side lobes. Such calculation employs DFT product coefficients calculated for the lower and upper frequency subgroups and which are stored in memories, such coefficients being for particular Kaiser-Bessel window functions and for pairs of frequencies in the lower and higher subgroups. The coefficients are selected so that the peaks of the side lobes are lower, such as 6 dB below, the peaks of the associated main lobes.