Abstract: The resolver drive circuit on a numerical control system includes a microprocessor system which monitors the phase and amplitude of the sinusoidal wave forms applied to the resolver. Any changes in amplitude or phase shift of the applied wave forms due to such factors as time and temperature are automatically corrected by the microprocessor system. A highly accurate resolver position feedback system is thus formed with a minimal number of temperature sensitive components and a minimal number of required manual adjustments to analog circuitry.

Abstract: A set of circuit boards are mounted side by side and electrical connection is made to terminal pads disposed along one edge of each circuit board by connectors which are carried by swing arms. The swing arms are rotatably mounted on a support rod which also mounts a set of lower guide rails supporting the set of circuit boards. A set of status indicator lights are disposed along the same edge of each circuit board above each swing arm. A swing arm latching mechanism holds the swing arm in a vertical operating position. A circuit board latching mechanism holds the circuit board in place when the swing arm is pivoted to a maintenance position.