| 摘要 |
PURPOSE:To improve the performance of traffic control by obtaining an information transmission line between control parts of switchboards by making use of the unused frequency band of a trunk line. CONSTITUTION:Once terminal equipment 11 makes a call, signal distributing circuit 13-3 of switchboard 13 distributes a switching control signal and operation control data, received from control part 13-2, to modulator 13-4. A FSK output signal from the modulator and an output signal from terminal equipment 11 are synthesized by filter 13-5 in one, which is sent out to trunk line 14-1. Filter 15-1 of switchboard 15 separates two signals from the trunk line mutually and demodulator 15-2 is supplied with the separated FSK signal. Here, the FSK signal is transmitted by using the frequency band 3,000-3,400Hz of the trunk line. |
