Abstract: A hands-free telephone terminal includes a loudspeaker (HP), a microphone (MI) and loudspeaker gain control means (AUG, DIM, PP). A loudspeaker gain correction method cyclically determines a listening comfort index to deduce gain modification parameters. If the local user modifies the loudspeaker gain using the control means, the gain modification parameters weight the loudspeaker gain to optimize listening comfort during a telephone conversation for the local user and for the remote user.

Abstract: The invention concerns a switching device for a telephone set having a handset enabling an auxiliary device to be substituted for the handset. In an embodiment, the switching device includes a casing provided with at least one compartment, the compartment being intended to receive one end of the handset. The compartment includes a switch actuated by the presence of the handset which triggers the aforementioned substitution. The invention finds application in hands-free telephoning and teleconferencing.

Abstract: Several microphones (M1, M3) are arranged substantially in the same plane (P) and are distributed symmetrically with respect to a direction of symmetry (D) perpendicular to this plane (P). A phase shift is applied between the signals output respectively by different microphones (M1, M3) and the signals thus phase shifted are added, in such a way as substantially to cancel the signals relating to any sound wave arriving in phase and with the same intensity on each of the microphones (M1, M3).

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.