| 摘要 |
PURPOSE:To check the state of a writer by inserting switching elements into two current lines connected to a current direction switching circuit for a writing head, comparing the potential difference of a contact between the current lines and the switching circuit with a reference potential and checking the change of a logical value. CONSTITUTION:Transistors (TRs) TR1, TR2 are inserted into the current lines 2, 3 for registers R1, R2 between a power supply +V and the current direction switching circuit 1. When the outputs Q, the inverse of Q of a toggle type switch FF1 are '1' the TR1, TR2 are turned on. The TR1, TR2 are alternately turned on and off every input of a pulse '1' to a terminal T3. A comparator CMP having the intermediate threshold of a potential generated between two contacts is connected to the contact P between the current lines 2, 3 and the switching circuit 1. When the state of the output terminal T2 of the comparator CMP is turned on and off by turning on and off the elements TR1, TR2 under said constitution, the whole direction switching circuit can be decided as a normal state, a pulse '1' is applied to the FF1 at a proper timing, and immediately after the impression of the pulse '1', the state of the terminal T2 is read out to check the operation of the magnetic writer.
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