| 摘要 |
PURPOSE:To prevent color development of a printing paper and fatigue of heating resistor elements from being generated, by a method wherein a voltage lower than a printing voltage is used as a voltage impressed on the heating element, when discriminating the condition of the heating element. CONSTITUTION:A central processor 26 sets the number (n) of the heating resistor elements 2-1-2-n on an appropriate register X. Then, the first stage of a shift register 6 is made to be H level by a data signal 34, and an output enable signal 36 is mad to be H level. By this, an H-level signal is supplied to the base of a transistor 4-1, and an electric current from a discriminating power source line 20 of a voltage of 5V is passed to the transistor 4-1 and the heating resistor element 2-1. However, since a transistor 12 is in a non-conductive state, an electric current from a printing power source line 14 of a voltage of 10-30V is not passed to the resistance element 2-1 or the transistor 4-1. At this moment, the voltage V28 at a junction point 28 is measured by a voltage-detecting part 30, and is compated with a predetermined upper limit value and a predetermined lower limit value. When the lower limit value <V28< the upper limit value, it is discriminated that the heating element 2-1 is in a normal condition. |
