Abstract: A single stepper motor is utilized in a printing device to lift a print head from the surface of recording material upon the initial angular rotation of the stepper motor output drive shaft and to move the recording material within the printing device upon further rotation of said drive shaft. The print head is returned to the surface of the recording material by operating the stepper motor in the reverse direction until the output drive shaft of the stepper motor traverses an angular displacement equal but opposite to the initial angular displacement. A cam surface couples the output drive shaft of the stepper motor to a drive gear and transforms the initial angular displacement of the output drive shaft into linear motion to lift the print head from the surface of the recording material. Further rotation of the stepper motor drive shaft rotates the drive gear to move material within the printing device.

Abstract: A transistorized circuit is used for controlling the flow of current through a high voltage source, such as a battery. The high voltage source must be capable of being tapped at voltages less than the critical voltage of the transistors in the circuit, that is, that voltage at the maximum current through the transistor, above which the breakdown characteristics or maximum power dissipation ability of the transistor is exceeded. A plurality of transistor arrays are connected in series with each other, and each array is connected to a tap on the voltage source. Each array includes parallel connected transistors in sufficient quantity to achieve the desired current flow. The current through each array is made equal by control circuits so that no current flows through the tapped connection to the voltage source. The transistorized circuit may be used to control both the charging and the discharging rate of current through a high voltage battery.