Abstract: A circuit for putting a plurality of participants into a conference call in a PCM telecommunications system. The signals of the participants are numbered linearly and are arranged in time rasters and carried on a plurality of time multiplexes (i.e. all PCM channels). To each participant is allocated at participant circuit (CAi.1-30) which comprises a sample selection circuit (SW), an addition circuit (CAD), and a circuit for converting (COM) the numerical sum supplied by the addition circuit into a speech signal transmitted to the corresponding participant. The selection circuit (SW) comprises as many gate circuit as there are time multiplexes. The gate circuits selectively become conductive at determined instants in each time raster in order to select the samples which come from the other participants forming part of the same conference as the corresponding participant and which are to applied to the addition circuit (CAD) the output signal of which is transmitted to the corresponding participant.