Abstract: A device for monitoring and compensating for changes in the flight time of the print hammers of impact printers is disclosed. The flight time of the respectively monitored hammer is calculated from the elapsed time between the moment of firing of a hammer and the moment of impact of the print type carrier against the impact platen. In order to ensure automatic self-adjustment of all print hammers in predetermined test cycles, without the actual printing process itself being affected, and without there being any test imprints on the record carrier, the print type carrier includes, in addition to the standard print types, an additional test type. The impact surface area of the test type is large enough such that no visible imprint is made upon its impact on the record carrier because of the low impact pressure.