in which the feeler varies an electrical characteristic in a circuit, e.g. capacity, frequency

Full Title

Control systems or devices for copying directly from a pattern or a master model; Devices for use in copying manually > using a feeler or the like travelling along the outline of the pattern, model or drawing; Feelers, patterns, or models therefor > Feelers; Feeler units > designed for a physical contact with a pattern or a model > for control of an electrical or electro-hydraulic copying system > in which the feeler varies an electrical characteristic in a circuit, e.g. capacity, frequency