The HSE-HA Microdrive Controller Type 864 is a single-axis control unit with microprocessor control for operating motorized micrometer drives (vernier controls) with DC motor. It has been specially developed to meet the requirements in physiological and pharmacological research. It is ideally suitable as control unit for the remote operation and vibration-free movement of microelectrodes or capillaries, e.g. in intracellular potential recording, patch clamp experiments or stereotaxic investigations in the brain. When used with either the micrometer drive HSE-HA 864/1 or 864/2, the Microdrive Controller thus represents a complete alternative to hydraulic micro drives which have now become very expensive. Apart from its compact size, similar to a remote control for a TV set, a special feature is the combination of continuous and stepping linear operation. In the continuous mode the micrometer drive is operated by the joystick shift in the direction IN or OUT. The drive speed is proportional to the displacement of the joystick. In the switch mode the micrometer drive is moved by the joystick either IN or Out by a preset step. The size of the step can be adjusted continuously with the STEP BS4DTH potentiometer from ~0.5 µm to approx. 0.1 mm per step. This operating mode is particularly useful when advancing glass microelectrodes into the cell membrane for intracellular potential recording. In order to reduce interference emission to a minimum, e.g. in the input circuit of a microelectrode amplifier, special attention has been paid in the design of the instrument to good electrical de-coupling and screening. The system consists of the Microdrive Controller 864, mains adapter, ground cable, foil-screened connecting cable for micrometer drive and operating instructions.