| 摘要 |
PURPOSE:To detect any failure in many thermal elements individually and sensitively with high accuracy by determining that the indication of higher than a fixed value of a differential signal obtained by the falling of a test signal is a failure, if the thermal element driver of a thermal head is in 'ON' state in spite of its functional trouble. CONSTITUTION:If there is any abnormality exists during the energization of a thermal head 11, a differential pulse DEF.IN is obtained from a differential circuit 15. Then an inverter output INV.OUT obtained by slicing the differential pulse with an inverter at a fixed slice level is transmitted to a printer control circuit 14. This printer control circuit 14 maintains a test signal RLYD at 'L' level 'O'(OV) to prevent the thermal head from proceeding to a further printing action. In addition, said control circuit causes the LED of a thermal head abnormality display section 16 to light as a warning to an operator. |
