Printer having identifiable interchangeable heads

Claim 1

A dot matrix printer, comprising: a movable printhead carriage; a print media; means for advancing said print media in a direction orthogonal to printhead carriage movement; single color and multicolor thermal inkjet printheads; a nozzle plate on each printhead having a plurality of nozzles and means for admitting ink to said nozzles; each multicolor printhead having a nozzle group for each color of ink in the nozzle plate thereat, each nozzle group having the same nozzle format as the nozzles of a single color printhead but of a lesser number of nozzles than the number of nozzles for the single color of ink of the single color printhead; means for mounting single color or multicolor printheads on said printhead carriage; motor means for driving the printhead carriage to move the printhead thereon across said print media; a resistor network on each printhead having a resistor at each nozzle, which resistor when energized heats and expels ink from the nozzle thereat; a print control system for selectively energizing resistors of said resistor network of said printhead for printing on said print media during printhead carriage movement; printhead identification means on each printhead comprising patterns of resistors forming part of said resistor network providing a unique code for each printhead; detection means for energizing said patterns of resistors of said printhead identification means for providing electrical signal identifying a specific printhead; and means in said print control system responsive to said electronical signals for initiating operation of said print control system to selectively energize resistors at the nozzles of said specific printhead.