Print Head Used As an Audio Alarm
Original Publication Date: 1988-Nov-01
Included in the Prior Art Database: 2005-Feb-16
A dot matrix print head can be used as an audio alarm by delivering to the firing coils controlled amounts of energy that are below the firing thresholds. The energy vibrates the print wires without actually firing them. Referring to the figure, the head strobe is turned on to gate the power to all coils for all wires in the print head. The wire fire select line is turned on, but then turned off prematurely to reduce the delivered power. The on time is controlled so that the coil current increases sufficiently to cause the print wire to vibrate, but is interrupted before the coil current reaches the firing threshold, indicated in dotted lines.