| 摘要 |
PURPOSE:To make light emitting elements of a telephone set needless to reduce power consumption, by modulating the photosignal, which is transmitted from the exchange, by the dial signal of the telephone set, the call signal, and so on and by returning the photosignal to the exchange. CONSTITUTION:In exchange 1, light emitting element 13 is driven by the call signal and the incoming signal to generate a photosignal for call, and light emitting element 11 is driven by a constant current to generate a photosignal for returning, and they are subjected to wave length multiplexing by coupler 14 and are transmitted to optical fiber 21. In telephone set 3, the photosignal for call is applied to telephone set circuit 33 by branching filter 32 to drive the incoming display unit, and the receiver is driven by off-hook. Meanwhile, the photosignal for returning is applied to returning part 31 and is modulated by the dial signal and the call signal and is transmitted to down optical fiber 22. Receiving control part 15 transfers the dial signal and the call signal to the common control unit and so on and the other-party subscriber respectively. |
