| 摘要 |
PURPOSE:To obtain a miniature and lightweight subscriber's circuit which does not need large power for control, by employing the constitution of a differential amplifier, arithmetic circuit, in-phase amplifier, and inverting amplifier and by combining a hybrid circuit with a semiconductor switch for howler signals. CONSTITUTION:An audio signal, applied in the form of ground balancing between terminals 200 and 203, is inputted via capacitors 201 and 204 to differential amplifier 205, where it is converted into the form of ground unbalancing, and the conversion output is transmitted from terminal 207 to a converting circuit by way of adding circuit 208. An audio signal, applied from the converting circuit to terminal 206 is converted into the form of ground balancing through adding circuit 210 and inverting amplifier 212, and the conversion output is sent to a subscriber via a resistance. Although this signal is applied to circuit 208 via amplifier 205, part of the signal from terminal 206 is applied and canceled to prevent echoes, thereby constituting a hybrid circuit. The output of howler signal supply 213 is applied to the subscriber by way of switch element 214, circuit 210 and amplifier 212. Since the adder circuit and amplifier are high in input impedance, a little switch current only is required and semiconductors can be employed for constitution. |
