| 摘要 |
PURPOSE:To execute a tripartite call by a calling telephone set, a transfer destination telephone set and a transfer origin telephone set, by executing a transfer by a telephone transfer device, and thereafter, transmitting a calling- back signal from the transfer destination telephone set side. CONSTITUTION:When an incoming telephone set 4a of a transfer origin receives a call, a telephone line 10a of a transmitting telephone set 5a is held so as to be dialable. Also, a telephone number of a transfer destination telephone set 6 stored in a memory 26, and a transfer origin code signal from a transfer origin code transmitter 12a are sent out successively through a dial pulse sending-out device 20 and a touch tone transmitter 27, and connected so that a call can be executed. In this state, when a switch 34 of a calling-back use signal transmitter 30 is operated in the course of a call, a calling-back use signal transmitter 30 is operated in the course of a call, a calling-back signal is sent out through the telephone line 10a, and inputted to an annunciator 33 through a transformer 16, a transformer 31 and a switch 32. In this way, a sign can be given to pick up a transmitter-receiver of the telephone set 4a or 5a by a buzzer, etc., and a tripartite call containing them can be executed.
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