| 摘要 |
PURPOSE:To protect a heat generating element of a recording head against runaway of a CPU by comparing to decide whether a conducting time exceeds a maximum time or not, judging occurrence of a malfunction when a decided result is yes, and stopping conducting means. CONSTITUTION:A heat error timer 17 starts counting when the output HEATEN of a NOR circuit 13 is 'H', i.e., when a head driver is ON. When a level of a TOUT signal is not varied due to occurrence of the malfunction and a level 'H' holding state of the signal HEATEN is elapsed for a predetermined time or longer, an overflow signal TOV is output from the timer 17, and latched to a D type latch circuit. Since the output of the latch circuit is connected to the other input of the NOR circuit, when the timer 17 overflows, the output of the latch circuit becomes 'H', the output HEATEN of the NOR circuit is shifted from 'H' to 'L', and heat of a heat driver 5 is automatically (forcibly) turned OFF. |
