| 摘要 |
<p>PURPOSE:To prevent a heater from being energized for more than a prescribed time if it occurred such a state that a printing control signal remains outputted due to a failure, by providing a time control means to drive an electric power supply means through the outputting of a control signal for less than a prescribed time at a printing control signal. CONSTITUTION:A printing control signal outputted to a control wire 26 from a control part 21 switches ON transistors 39, 40 of a heater drive circuit 22. As a result, an electric current runs into a heater 38 and the transistor 40 from an electric power supply part 24 and in turn, the heater 38 generates heat, printing a thermosensitive paper. If an unusually long signal such as ''e'' signal was outputted from the control part 21 for some reasons, an output from a differential circuit consisting of a condenser 28 and a resistance 29 becomes ''f'' signal and this signal enters a transistor 32 from a resistance 31. However, if a base emitter voltage stands at approx. less than 0.6V, the transistor 32 turns OFF. Accordingly a time constant of the differential circuit shall be set at approx. 4-5msec.</p> |
