Abstract: A socket (1) comprises a plurality of contacts (10, 11, 12 and 20, 21, 22) arranged for electrical connection with a plug (2, 2?), electrical connection between the plug and socket being made by insertion of the plug into the socket and subsequent relative rotation (9R) of the plug and socket about a common axis (9A), at least a first electrical contact (10, 11, 12) having a contact face (14, 14?, 14?) in a plane (1P, 1P?, 1P?) substantially parallel to the common axis (9A), and at least a second electrical contact (20, 21, 22) having a contact face (24, 24?, 24?) in a plane (1Q) substantially perpendicular to the common axis (9A). Each of the said contact faces arranged for making electrical contact with the plug (2, 2?).