| 摘要 |
PURPOSE:To discriminate the tape recording speed with high reliability by breaking forcibly an automatic frequency control loop at a reproduction starting time point to drive a motor and to check whether or not the reproduction speed is coincident with the record speed, detecting the reproduction speed from the revolving frequency of a driving motor for magnetic tape and discriminating the tape recording speed based on said two detection outputs. CONSTITUTION:In a reproduction mode a control circuit 27 sets switch switching signals S8 and S9 at high levels and connects mobile bars a1 and a2 to fixed terminals C1 and C2 respectively. Thus an AFC loop of a motor 11 is broken and the revolving frequency of the motor 11 is set by a signal S6 applied to a terminal 23. The circuit 27 decides that the reproduction speed is equal to the record signal when a DC signal of a high level is obtained continuously for a prescribed period from a window comparator 26. Then the circuit 27 delivers a mode designating signal S7 showing a speed equal to the reproduction speed obtained from an FG signal given from a waveform shaping circuit 15 and at the same time sets the signal S9 at a low level to switch on the AFC loop.
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