Abstract: A multiterminal socket suitable for mounting on a printed wiring board together with one or more jumper plugs is disclosed for providing various circuit options. The jumper plugs have a pair of interconnected male terminals projecting from one end and a pair of resilient extensions straddling the male terminals. When a plug is inserted in a correct socket position the plug extensions flex outwardly to pass over a pair of socket shoulders and lock the plug in place with a snap action. When an attempt is made to insert the plug in an incorrect position which would cross-connect circuits, a pair of opposing projections on the socket body interfere with the plug extensions to prevent insertion. Double throw switching functions and single throw functions with idle plug storage are described together with a visual indication of the option in effect.