| 摘要 |
PURPOSE:To simplify the discrimination in a magnetic recording and reproducing device by providing a different index depending on a different storage capacity to a recording medium, detecting the difference of the indexes and switching the circuit constant automatically so as to eliminate the need for the discrimination at the host system side. CONSTITUTION:As an index provided to the recording medium, whether or not a notched part exists at a part of the recording medium is used. When the notched part 4 is provided to the recording medium 1, the light irradiated from a light emitting element 2 passes through the notched part 4 and reaches a photodetector 3. In this case, a photo current flows to the photodetector 3 in this case, switches SW1, SW2 in a low pass filter circuit 7 are in the open state and the circuit is activated by the constant of capacitors C1, C2 only. When no notch 4 is provided to the recording medium 1, the switches SW1, SW2 are closed, the circuit acts like a circuit provided with capacitors C3, C4. The recording medium of different storage capacity is discriminated easily by the recording and reproducing side to switch the circuit.
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