Configuration for ETR print head triggering

In an apparatus having an ETR printing unit with an ETR print head having a plurality of electrodes for printing individual pixels of a print image, a configuration for triggering the ETR print head, comprising:

• a microprocessor control unit and a memory connected to said microprocessor control unit;
• a controllable constant current source connected to said microprocessor control unit;
• a switching unit connected between said control unit and the electrodes of the ETR printing unit for temporarily connecting a number of the electrodes to said constant current source and for supplying a current from said constant current source to the number of the electrodes connected during a predetermined actuation time by said switching unit;
• said constant current source being controlled by said control unit in accordance with the number of the temporarily connected electrodes such that a relatively greater number of electrodes is supplied with a relatively greater current than a relatively smaller number of electrodes;
• and
• said microprocessor control unit having means for calculating a control parameter for controlling said constant current source from a first constant and from a second constant multiplied by the number of the temporarily connected electrodes.

A configuration for triggering a print head having a plurality of print head elements for printing individual pixels of a print image, the configuration comprising:

• a microprocessor control unit and a memory connected to said control unit;
• a regulated voltage source connected with said microprocessor control unit;
• a switching unit connected to said control unit, said switching unit connecting said control unit to the print head elements of the print head and said control unit triggering said switching unit so as to supply the print head elements during a predetermined time period with energy from said regulated voltage source for individual pixels of a print image, and said control unit controlling the energy supplied to the print head in accordance with a number of temporarily triggered print head elements and supplying a relatively greater number of print head elements with a relatively greater voltage and supplying a relatively smaller number of print head elements with a relatively smaller voltage;
• said microprocessor control unit forming a control voltage for operating the print head by adding a first, constant voltage and a second voltage corresponding to a constant voltage multiplied with the number of temporarily triggered print head elements and by factoring in a factor representative of an adjusted print intensity.