| 摘要 |
PROBLEM TO BE SOLVED: To provide a call signal transmission circuit that eliminates the need for a relay and an external ringer signal generating circuit or the like and that is advantageous in the cost and mount space. SOLUTION: Transistors(TRs)1-4 configure a push-pull emitter follower circuit. A zero level is given to a control terminal CNT2 to make a TR6 conductive, which deactivates the TR3 and makes the TR4 conductive to bring a terminal B to a ground level. A 16 Hz clock signal is given to a control terminal CNT1 to turn on/off a TR5, which alternately turns on/off the TRs1, 2, and a ringer signal of -200 V is generated from a terminal A and given to a telephone set.
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