Abstract: A lamp unit having an electromechanical ball including first and second electrically-conductive hemispheres separated by an insulator region, the ball being pop-fit insertable and removable anywhere along a guide track apparatus providing first and second oppositely-disposed conductor strips, the lamp unit being rotatable with respect to the conductor strips to provide on-off switching. The lamp unit-track combination provides the multiple capabilities of aiming and on-off switching, as well as lamp insertion and removal, while eliminating conventional fixturing.