| 摘要 |
<p>PURPOSE:To perform mode changing over stably with a simple constitution by comparing the output frequency of a speed detector for tape running driving motor and the reproduction frequency of reproduction control signal. CONSTITUTION:The frequency of a speed detection head is 480 Hz in the case of a low speed mode and made to 240 Hz by a 1/2 frequency divider 32. The output 120 Hz of a frequency divider 47 is applied to the FFIC1 being a 1/2 frequency divider 47 and the collector or emitter of a transistor TrQ1 being a changeover switch. On the other hand, the output of the frequency divider 32 is applied to an IC2 being a 1/16 frequency divider 31 and the output having been reset by the control signal (IC2 a No.4 terminal) is converted to DC by an integrator 45. At this time, the base potential of TrQ2 has been set at 0.4V or under and therefore this becomes cut off and the (+) potential of the collector is applied to the base of TrQ1. The input signal 240 Hz from the frequency divider 32 is directly outputted to the output terminal to a speed multi 33. In this way, the mode may be changed over stably with the simple constitution.</p> |
