The Post Office

Edward G Johnson

Ian S Groves

David R Guard

John G Bunting

Adrian J Morgan

Robin C Cross

Alan E Stevens

An electroacoustic transducer for a microphone comprises an electret wherein an additional capacitance substantially greater than the capacitance normally inherent in the electret is connected in parallel with the electret. The additional capacitance may be of the order of 10 times greater than the capacitance normally inherent in the electret and may be produced inherently in the transducer or by a separate component connected to the transducer.

Electret microphone circuit

An electro-acoustic terminal unit for use in an audio teleconferencing system comprises a loudspeaker and one or more microphones each having a sensitivity which is directionally dependent and exhibits at least one null or substantially null position. The loudspeaker and microphones are rigidly mounted on a boom and the microphones are so located and orientated relative to the loudspeaker that the null position is directed towards the loudspeaker.

Audio teleconferencing

Growing community of inventors

Woodbridge, United Kingdom

Edward G Johnson