| 摘要 |
1,029,163. Loud-speaking telephones. STANDARD TELEPHONES & CABLES Ltd. May 29, 1964, No. 22299/64. Heading H4R. A loud-speaking telephone has a microphone amplifier A1 and a loud-speaker amplifier A2 whose gains are differentially varied by a control circuit C in response to the direction of signals in the line L as sensed by the unit D which may be of the type disclosed in Specification 969,916. In addition an auxiliary gain control circuit Ca may further reduce the gain of microphone amplifier A1 when signals are present in the output of the loud-speaker amplifier A2. |
