Abstract: Thermal inkjet printhead temperature control is provided in a temperature control system responsive to printhead temperature, which in the presence of printhead overheating selectively causes the printhead to stand idle, or, if multiple nozzles are available, shifts to a nozzle which, is not overheated, which in the event a nozzle is unused for some time and the dye transport agent may have evaporated leaving a viscous plug in the nozzle, employs warm up pulsing and/or nozzle spitting to clear the nozzles, and which when the temperatures of the nozzle is below acceptable printing temperatures, employs nozzle pulsing for warm up and/or nozzle spitting to clear the nozzles, all such decisions and actions being provided in advance of beginning a printing operation.

Abstract: The single channel encoder comprises a transparent scale in which the scale divisions are defined by transverse opaque lines having a width greater than the width between the opaque lines. An emitter holder and a detector holder snap together, clamping an aperture plate there between. The aperture plate has a slit therein which is disposed in the optical path between the emitter and the detector. Projections functioning as scale supports on the opposite sides of the emitter holder and the detector holder are disposed in longitudinally spaced positions and define a gap therebetween for engaging the outside edges of the encoder scale outside of the opaque transverse lines to precisely position the scale in the optical path for maintaining a constant gap between the encoder scale and the aperture plate.