| 摘要 |
A system for preventing abnormal heating of a thermal head, which is configured with pure hardware. In the system, when a temperature of the thermal head becomes an abnormally high temperature exceeding a predetermined temperature and/or an active time of a print-time setting signal cyclically issued from a microcomputer for activating the thermal head only for a time period necessary for printing of one line of picture image becomes abnormally long, a flip-flop is set so that three sorts of switch circuits are respectively operated in such a manner as follows, whereby the abnormal heating of the thermal head can be prevented at a very high reliability. (1) The supply of a drive voltage to the thermal head for heating the thermal head is forcibly stopped. (2) The input of the print-time setting signal to the thermal head is forcibly stopped. (3) A picture image signal supplied from the microcomputer to the thermal head is cut off and, instead of the picture image signal from the microcomputer, a signal indicative of a non-printing picture image, e.g., all-white picture image, is forcibly supplied to the thermal head as the picture image signal.
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