Abstract: A connector for interconnecting or mutually isolating two circuits one of which is connected to a first connector element (1) and the other of which is connected to a second connector element (2) which is interengageable with the first. One of the connector elements supports a first contact (12) connected to a respective circuit and a displaceable contact holder (4) carrying interconnected second (14) and third (15) contacts. The contact holder is displaceable between a first position in which the first (12) and second (14) contacts are separated and a second position in which the first and second contacts are interconnected. The connector elements are formed such that on interengagement the contact holder is displaced from the first to the second position after the third contact is interconnected with a contact (34) of the other connector element (2). The arrangement is such that on disengagement of the connector elements (1, 2) the contact holder is displaced from the second to the first position.