Abstract: A printing apparatus includes a supply of printing material, a drive assembly coupled to the printing material and capable when enabled of advancing the material along a predetermined path past a printing station, and a detection device for detecting when the printing material fails to be advanced by at least a first predetermined amount when the drive assembly has been enabled to advance the material by at least a second predetermined amount.

Abstract: A hammer protection circuit automatically disconnects a power supply from a hammer actuating coil in order to inhibit current flow through the coil when such current flow is either greater than a predetermined level or present for greater than a predetermined time period. The circuit comprises charging means coupled to the coil for charging up to a voltage level proportional to the level and duration of the current flow through the coil, comparator means coupled to the charging means for comparing the voltage level with a reference voltage and for generating an output signal when the voltage level bears a predetermined relationship toward the reference voltage, and means coupled to the comparator means and to the power supply and responsive to the output signal for disconnecting the power supply from the coil.