| 摘要 |
PURPOSE:To simplify the structure and to obtain a high reliability by using a dial switch which has a switch matrix having the single contact structure. CONSTITUTION:A dial switch 31 has the principal part constituted of a switch matrix 32 where individual switches have the single contact structure. Normally, a DC voltage V1 is out putted to a line 28 from the stabilized power supply circuit of a main device and is supplied to a control circuit 19 and a control switch circuit 21, and the control switch circuit 21 receives the voltage V1 to connect row signal lines 34 of the switch matrix 32 to the control circuit 19. At the time of a power failure, a DC voltage V2 is outputted from a telephone circuit to a line 35 and is supplied to a dial transmission circuit 20 and the control switch circuit 21, and the control switch circuit 21 connects row signal lines 34 of the switch matrix 32 to the dial transmission circuit 20. Thus, the structure of the dial switch 31 is simplified and the reliability is improved. |
