| 摘要 |
<p>PURPOSE:To drop a spare bit to exchange a clock at the inside of a station through a simple circuit by recognizing a frame which is selecting and reading plural buffer memories of the transmission line side at the inside of the station. CONSTITUTION:At the inside of a station, buffer memories 5 and 6 are selected alternately by a selector 7 to read out frames A and B. A counter 9 forms a drop pulse by a selector signal SR and a clock of the intra-station side of a clock pulse generating circuit 8. a drop pulse for a spare bit X1 of the frame A is obtained by having an AND between the first one of eigth intra-station side clocks corresponding to the frame A and the signal SR. Then said drop pulse is supplied to a clock input terminal of an FF circuit F1 of a spare bit extracting circuit 10. The bit X1 is dropped since the frame A is supplied to a data input terminal of the circuit F1 from the memory 5 via the selector 7. so is with spare bits X2 and Y1-Y5 of the frame B.</p> |
