| 摘要 |
PURPOSE:To lengthen the life of a heat-sensitive head by bringing one section of a current controlling means to a high impedance condition interrupting the recording energizing currents of a group connected to the one section of the means when the number of the recording energizing heat generating sections exceeds a fixed number. CONSTITUTION:When the values of a resistor RB1 and a resistor RA1 are set at fixed values because the voltage of the RB1 is the base voltage in the forward direction of a transistor QS2, the transistor QS2 is at ON when the number of the ON of the first pair switching circuits 51-5216, the number of recording picture elements, is a fixed number or more and is at OFF when the number is less than the fixed number. Even when a transistor QS1 is made ON and energized by the output of a group selective circuit 2, the transistor QS2 is at ON and a section between a base and an emitter of the QS1 is short-circuited when the number exceeds the fixed number, thus resulting in no ON of the transistor QS1. Consequently, the recording energizing currents do not flow through the heat generating sections R1-R216 when the number of the recording picture elements exceeds the fixed number. The transistor QS1 is at ON by the output of the group selective circuit 2 when the transistor QS2 is at OFF, and the recording energizing currents flow through the heat generating sections connected to the ON circuits among the switching circuits 51-5216. |
