Two channel ship to shore communication system - uses local receiver with diode bridge attenuator operated by vocal transmission

摘要

The two channel radio system is used for ship to shore voice communication. since simultaneous transmission and reception are required an attenuator activated by voice signals from the transmitter is located in the receiver antenna circuit. The vocal transmission from a local transmitter received by the local receiver antenna (10) is detected by a circuit comprising a rectifier in series with a differentiating circuit and a d.c. amplifier followed by a threshold detector. A diode bridge (D1 to D4, 14) in series with the antenna circuit is bridge (D1 to D4, 14) in series with the antenna circuit is controlled by the output from the voice detector which is applied to the bridge through two resistors (R1, R2). Presence of a predetermined signal level causes reciver signal attenuation.