PURPOSE: To detect the temp. of a solenoid accurately and prevent its burning properly.

CONSTITUTION: The driving voltage of a solenoid is measured by a driving voltage measuring means 20 and the energizing time required for the driving current of the solenoid to reach at least a predetermined value is measured by a current value monitoring means 30 and an energizing time measuring means 50. The driving voltage and the energizing time thus obtained are converted into the temp. of the solenoid element by a solenoid temp. converting means 70. The printing operation is controlled according to the temp. of the solenoid element so obtained. In this way the solenoid temp. can be detected accurately and an excessively long print stopping action is eliminated.