| 摘要 |
PURPOSE:To prevent malfunction, by controlling data of on/off-state so as to represent the ON of the hook switch succedingly, and storing a dial key data inputted continuously correctly, even if the power source fed from a lne is temporarily disconnected. CONSTITUTION:Resistors 4a, 4d, a Zener diode 5, a diode 6, a TR 8a and capacitors 12a, 12b constitute an on/off state data forming circuit, which produces the on/off state data of the hook switch based on a current of a line via the hook switch 1a and a rectifier 3, and when the line 2 is interrupted, the data is kept to on-state for a prescribed time. The hook switch 1b itself interlocked with the hook switch 1a forms a state detection circuit, and when the switches 1a, 1b are turned off, the on/off state data is brought to the off-state. An IC7 detects on-hook once and when a redialing key, for example, is depressed, a DP signal corresponding to a data in a storage section 11 is transmitted, and when a new dial key data is inputted, the data of the storage section 11 before T4 is cleared, and the new data is written. |
