| 摘要 |
PURPOSE:To circulate a frame with an integer number around a loop without requiring a large capacity of frame buffer memory by varying the transmission speed so as to adjust a frame electric length. CONSTITUTION:The output of a VCO 4 is inputted to a frame generating circuit 5 in a master station, and a frame generated in the circuit 5 is sent to a transmission line via a transmission switching circuit 6. Further, a frame clock is sent to a phase comparator 2. A feedback frame sent from the circuit 6 and circulated through the loop 6 is inputted to a memory 7 and a frame extraction section 1. The extraction section 1 generates a feedback frame clock representing the frame phase and sends it to the comparator 2. The comparator 2 compares the phase shift of both the clocks and gives a bias voltage to the VCO 4 via an LPF 3. Then the output frequency of the VCO 4 is adjusted so that the phases of the generated frame clock and the feedback frame clock are coincident to synchronize the clock. When the synchronization is taken, the circuit 6 sends the frame from the memory 7 to a transmission line synchronously with the feedback frame clock.
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