| 摘要 |
PURPOSE:To automatically release a line close state even if the on-hook dial switch of a telephone set is unconsciously or erroneously turned on, by connecting a timer circuit and a switch circuit, which is controlled by the output of this timer circuit, in parallel with the on-hook dial switch. CONSTITUTION:When an on-hook dial switch 8 is depressed, a dial pulse sending circuit 2 is operated to close a line and reset of a counter circuit 104 is released to start the counting operation. If dial transmission is performed within T seconds, the counter circuit 104 is reset. When T seconds elapse after depression of the on-hook dial switch 8, an output terminal O of the counter circuit 104 is switched to the high level from the low level and a switch circuit 81 is turned on, and the state is equivalent to depression of the on-hook dial switch 8, and the telephone set is released to the initial state of on-hooking.
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