| 摘要 |
PURPOSE:To enable the protection of a printing head by components in few numbers, by a construction wherein a circuit interrupting a supply voltage to the printing head when a clock pulse from a microprocessor stops is provided in a power supply element for the printing head. CONSTITUTION:A false operation or the like occurs assumedly at a time T1 in a microprocessor 1, a clock pulse 10 stops and a high level is held. Then a counter 21 is put out of a clear state and counts '1' '2' ... incrementally. When a count value reaches '16' at a time T2, a carry-out terminal CT of the counter 21 turns to be at high level, and therefore an output 220 of an inverter 22 turns to be at low level. Consequently an output 230 of a NAND circuit 23 turns to beat high level and an output 240 of a NAND circuit 24 at low level. Therefore an output 250 of an inverter 25 turns to be at high level and a transistor 26 is put in an ON state. Accordingly, a base voltage of a transistor 27 lowers and consequently an output voltage 20 lowers. |
