| 摘要 |
<p>In a thermal printer, data in the form of character data separated by gaps is supplied over a data line (38) to a shift register (15), the latched outputs of which cause operation of thermal elements (R1-RN) in a thermal printhead (11). During a test mode of operation, test data is supplied to operate the thermal elements (R1-RN) in succession, a sensing resistor (RS) providing corresponding test signals which are digitized by an AD converter (39). Each digitized test signal is compared with an associated initial, stored, digitized test signal, and if the current value deviates by more than a predetermined amount from the initial value, a failure signal is provided. A processor (19) is thereupon effective to cause the subsequent character data to be shifted such that the defective element is aligned with a location which is not used for printing, such as an intercharacter gap. In a modification, the test signals for all the thermal elements (R1-RN) are compared with a common fixed, predetermined reference level. </p> |
