| 摘要 |
PURPOSE:To improve the reliability and the transmission quality of a line, to increase the number of channels, and also, to simplify the maintenance by executing a detection of a transmission and an incoming of a telephone by utilizing a light emission diode and a photodiode. CONSTITUTION:When a service telephone set 6 is busy, a light emission diode 2 is ignited by 48V sent from an exchange 7, a phototransistor 3 and a transistor operate, a contact of the lower part of a capacitor 1 is opened, and an information transmitting circuit is cut off. On the other hand, in an idle time of a telephone line, the light emission diode 2 is extinguished, therefore, the contact is closed and a voice information transmitting equipment becomes operable. When a PB signal of a channel switching request for sending out voice information is sent from a subscriber's telephone set at a speech idle time, a PB signal frequency is discriminated by a filter of a transmitting/incoming signal detecting circuit and a controller 8 is started. By a control of the controller 8, a switch 5 is operated, and a CH signal from an amplifier 10 is send out of a loudspeaker 12 through telephone lines L1, L2, and a reproducing amplifier 11.
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