| 摘要 |
PURPOSE:To keep excellent communication quality and to simplify the constitution by sending a control signal from a transmission terminal equipment to a reception side counter communication equipment and applying communication when the return of a ring back tone is stopped so as to utilize no superimposition of a control signal on a communication signal. CONSTITUTION:When a handset of a four-wire telephone set 100 is lifted up, a signal is inputted to a hook-off detection circuit 10 of a counter communication equipment 1 at the reception side, a decision circuit 16 gives a control command to a control signal generating circuit 13 based on the detected output to send the control signal to a line L via an amplifier 17 and a hybrid transformer 19. On the other hand, a counter communication equipment 2 being the reception side uses a decision circuit 26 to give a control command to a call signal generating circuit 25 and an RBT generation circuit 24 based on the detection output of a control signal detection circuit 21 to call a telephone set 200, and the RBT generated from the RBT generation circuit 24 is returned to the said counter communication equipment 1 at the transmission side via an amplifier 27, a hybrid transformer 29 and the line L.
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