A description is given of a contact device of the high-pressure small-area type, capable of carrying 75 amp at 20 Mc/s, and 150 amp at power frequencies. Whilst relative movement and rotation is provided between the various parts of the assembly, all contacts are of the high-pressure type, and there are no flexible leads or springs carrying current. Examples of its use are illustrated with special reference to improvements in the design of variometers or coupling coils.