Abstract: A digital teleconferencing control device, system and method are disclosed for use in telecommunications. A digital conference control circuit having pulse code modulation and time division multiplexing is used in connecting a plurality of telephone subscribers together for conference purposes. When so connected, a plurality of then selected speakers can be heard by all other subscribers connected into the conference with the number of subscribers connectable into the conference being unlimited. Logic gates at the digital level in the control circuitry prevents return of signals generated by a speaking subscriber back to that subscriber.

Abstract: Apparatus for detecting and measuring an electrostatic field is disclosed which includes two sensing plates and a rotary blade that is rotated to move over the sensing plates to vary the amount of area of each of the sensing plates exposed to an electrostatic field being measured. A particular width and a particular arrangement of the sensing plates are used for producing a non-symmetrical electric output signal with a repetitive wave-form having a reversal of the peaks in each half-cycle. The dissymmetry of the peaks indicates field polarity information and the amplitude indicates field intensity information. Each sensing plate has a non-linear varying width that decreases from a wide end to a narrower end to develop distinctive characteristics in the wave-form.