The jack socket connector for inserting into the holes of a matrix circuit board for making through contacts consists of a cylindrical jack (22) whose upper end (62) has an opening (36) into which conductors can be inserted, and a circular eye (16) spaced apart from the opening but electrically connected to the upper end. The centres of the eye and the opening are spaced apart by the pitch of the matrix board. The opening (18) in the eye is the same size as the holes in the matrix board. The eye may be bent at right angles to the longitudinal axis of the jack. The eye may be integral with the jack. The point at which the eye is attached to the jack may be of reduced cross-section. The jack may have elastically deformable portions which extend into the bore jack, these portions extending over only part of the circumference of its body.
