| 摘要 |
<p>PURPOSE:To detect the change of a recording mode by measuring the operation time of an intermittently operated capstan by a counter and comparing a result with time data determined as a threshold value. CONSTITUTION:The counter 1 receives clock pulse (CP) supplied from a clock pulse (CP) generation circuit 2 through a switch 3, performs counting during the arrival of capstan driving signals SCD and becomes operable with signals delayed in a delay circuit 4. A count value is supplied to a latch circuit 5 and the fall of the signals SCD is latched by the latch pulse LP of a differentiation circuit 6. A comparator circuit 7 compares the latched count value with the threshold of a memory 8 and performs transmission to an AND circuit 9 and one of the thresholds is selected by a mode switching signal MSW. The counter 10 counts control signals CTL out of a magnetic tape during the rotation of the capstan and performs operation only during the arrival of the signals SCD. The output is supplied to the AND circuit 9. When either the output of the counter 10 or the output of the comparator circuit 7 or the both change, the output of the AND circuit 9 also changes from 'H' to 'L'. The change is detected in a control circuit and the mode is surely recognized.</p> |
