Abstract: A microphone unit particularly suitable for conference applications is provided, wherein an acousto-electric transducer is disposed between two dish-like back-to-back sound collectors, each having a central aperture exposing one side of the transducer, which preferably has a single planar diaphragm.

Abstract: A method and apparatus for alleviating sound-coupled feedback in a conference room having a conference table for the seating of human participants, the room sound system including one or more loudspeakers for outputting amplified sound from a given source in sufficient volume for all to hear plus one or more microphones for picking up the voice of any given participant. By locating the loudspeaker(s) below the board-like table top, preferably at floor level attached to the table foot structure, and by locating the microphone(s) above the table top, preferably in the central region, sound waves from the loudspeaker(s) are directed with high efficiency coupling to the participants' ears, but are constrained by the table top to "feedback" to the microphone(s) only with low efficiency coupling. "Rain barrel" effects are reduced. The invention finds advantageous use in purely local conference room sound amplification systems and in teleconferencing systems.

Abstract: A method and system for establishing an interactive audio and video conference. A plurality of geographically dispersed interactive sites are connected via the ordinary message telephone system to a central conferencing bridge. The bridge mixes the audio signals received from any of the interactive sites and distributes it to all such sites. The video signal is created in a television studio and transmitted as a conventional television signal via satellite. Steps are taken to bring the moderator at the studio site into the interactive conference while avoiding the echo problems which would normally be created. Moderator audio is conveyed to the bridge site via ordinary telephone lines where it is delayed by a period sufficient to compensate for the difference between satellite and telephone transmission times. The so-delayed signal is added to the mix such that moderator audio is received at each interactive site in synchronism with the satellite received video.