| 摘要 |
<p>PURPOSE:To make it possible to change the reproduction mode over to the recording mode automatically by judging by the frequency of a reproduced control signal whether recording has been done in NTSC mode or PAL mode. CONSTITUTION:The turning speed of capstan 1 is detected by the frequency generator consisting of gear 6 and magnetic head 7, amplified 8 and then applied to NTSC and PAL mode speed detecting circuits 9 and 10. A control signal reproduced by control head 5 is applied to Schmitt trigger circuit 18 by way of voltage converting circuit 17 to generate trigger signals of hysteresis characteristics with the 1st and 2nd threshold voltages, thereby controlling change-over switches 11 and 15. As a result, when a magnetic tape recorded in NTSC mode is reproduced in PAL mode, the period of the reproduced control signal exceeds the 1st threshold level and switches 11 and 15 are controlled by outputting an NTSC mode signal to place them at the sides of circuit 9 and NTSC reference signal generator 13, thereby increasing the speed of motor 1.</p> |
