| 摘要 |
<p>1,185,514. Substation anti-side-tone circuits. WESTERN ELECTRIC CO. Inc. 30 March, 1967 [6 April, 1966], No. 14450/67. Headings H4K and H4R. A telephone subset circuit contains a resistive anti-side-tone network to which the transmitter and receiver are connected via transistors, the receiver inductance being thereby isolated from the network rendering the circuit impedance substantially resistive. As shown in Fig. 1. a resistive hybrid comprises resistors R7, R8 and R9, with transmitter T1 and transistor Q1 on the one hand and receiver U1 and transistor Q2 on the other hand forming conjugative branches. Variable diode D1 and varistor D2 compensate for variations in line voltage. Capacitor C6 and resistor R11 avoid dialling clicks in the receiver. In another arrangement (Fig. 2, not shown) the parallelled transmitter T1, diode D1 and resistor R3 appear in the emitter circuit of transistor Q1.</p> |
