Abstract: A printed circuit board has two contact areas on each surface near one end. The board is sandwiched between two halves of a shell to form a plug in such a way that the contact areas are exposed. The contact areas on one surface are nearer the exposed end than the contact areas on the other. The tip and ring conductors of a pair of wires in a test cord are connected, respectively, with the two contact areas which are nearer the exposed end. A keeper spring which is connected to the shield of the jumper cable, the ground potential, insures that the plug will be retained within a jack into which the plug is inserted by engaging a detent. The detent is connected to ground potential. The jack has two long electrical contacts and two short electrical contacts. The long electrical contacts engage the two contact areas which are farther away from the exposed end and the two short electrical contacts engage the nearer contact areas.