| 摘要 |
PURPOSE:To remarkably decrease the cost by providing a switch switching a telephone set and a connection device so as to select talking and data communication and coupling the switch and the connection device via a DC circuit and a communication transformer thereby simplifying the circuit constitution and decreasing number of relays. CONSTITUTION:A switch 23 is a switch to change over a telephone set 21 and a Captain receiver 22, a call collision prevention circuit 25 and the telephone set 21 are connected to the normally closed contact, and the Captain receiver 22 is connected to the normally open contact via a DG circuit 26, a communication transformer 27 and a changeover relay 28. When it is confirmed by other circuit that the telephone set 21 is not in use at present, the switch 23 is changed over to the position of the normally open contact. In inputting a pulse dial mode signal from an input terminal 341, a shunt contact 33 of the DC circuit 26 is closed to short-circuit the primary side of the communication transformer 27. In this state, when a pulse signal is inputted from an input terminal 36, the switching section 32 is turned on/off synchronously with the dial signal and the pulse signal is sent via a telephone line. Finally, the shunt contact is opened and communication or line is monitored.
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