Abstract: A system and method for automatically compensating for inaccuracies in the positioning of the timing mark sensor of a band line printer. A selected hammer is operated to impact a test character and an adjacent space between characters or a space provided by a blank character on the type band. The flight times of the hammer for the character and space impacts are measured under control of a microprocessor programmed to locate the edge of the test character and to compute a timing adjustment value for use by the printer control to obtain centered impacts of characters during printing.

Abstract: A fault protection system for impression devices of a printer detects fault current in the impression devices during non-print operation, checks the impression devices individually to determine the location of the fault and then disconnects the impression devices from the power supply. The fault protection system also includes means for recording the fault location data in a storage means which can be called out for later use in repairing the impression devices.