The paper trays have a complex set of sensors and pickup mechanisms that must all be functioning properly. Each tray in a laser printer has a set of tabs that contact sensor switches to tell the control circuitry that the tray is installed and what size paper is in it. A mechanical arm and photo detector are used to sense the presence of paper in the tray.

A thermal fuser protects the fuser assembly from overheating and damaging the printer.

The drops are formed by one of two methods: thermal shock or mechanical vibration. Thermal shock heats the ink in a capillary tube, just behind the nozzle. This increases the pressure of the ink in the tube and causes it to explode through the opening. Mechanical vibration uses the vibrations from a piezoelectric crystal to force ink through a nozzle.

Socket-mounted devices should be reseated (removed and reinstalled to establish a new electrical connection) as a part of an anti-corrosion effort. This also overcomes the chip-creep effect that thermal cycling has on socket-mounted devices.

A branch circuit is the portion of a wiring system that extends beyond the last over current-protection device. In interpreting this, you must not consider the thermal cutout or the motor overload protection as the beginning of the branch circuit. The branch circuit actually begins at the final fusing or circuit breaker point where the circuit breaks off to supply the motor.

A thermal printer generates images by pushing electronically heated pins against heat sensitive paper.