Abstract: Control apparatus of the kind disclosed in our U.K. patent application No. 2173887 wherein the `mover` or rotor of a linear or rotary electrical stepper motor is coupled to a manual operating member so that, not only can the motor drive the operating member to give an automatic mode of the apparatus, but can exert a controlled resistance to manual movement of the operating member thereby giving a degree of `feel` to the operator and/or one or more electrically generated discreet detent positions within the range of movement. Herein the apparatus incorporates an improvement whereby the movable operating member is pivotably mounted so that the manual movement is arcuate--flexible cables connected to the drive motor mover and/or control switches incorporated in the operating member can pass from the operating member to a fixed part of the apparatus at or near the pivotable mounting where the movement to be taken up is less.

Abstract: In an electric discharge machine in which the machining gap between an electrode and a workpiece is maintained suitably by a control device having sampling, logic operation and holding functions, an up-down counter is provided for integration, over a predetermined period corresponding to the sampling period, servo signals from a discrimination circuit adapted to discriminate the conditions of the machining gap, so that sampling for all periods of time within the sampling period can be achieved.