Portable thermal desk top printer - has electrical control and thermal printing heads for colouring thermically sensitive paper

摘要

A variable resistance (R2, R4) is provided in the electrical circuit to vary the input voltage to the thermal printing heads. In this way the ink density is varied on the thermally sensitive paper. The control circuit also provides a constant voltage circuit with which the variable resistance (R2) is connected so as to vary the level of the input voltage which is applied to the thermal printing heads after receiving the printing trigger impulse. The resistance of the variable resistance (R2, R4) can be altered manually using a hand knob (A). The desk-top printer operates on direct current produced by a transformer (2) whose input plug (1) is inserted into an alternating current source.