I should have been a little more specific. The Overdrive cable is for the lockout for the freewheeling clutch. With the handle out, the freewheel and overdrive are locked out, and it operates like a normal 3 speed. When pushed in, at speeds under 28 MPH, the freewheel allows for coasting without compression braking, which helps save feul at lower speeds. It also allows the overdrive to engage without shock on the system when 28 MPH is reached and you let up off the gas for a second ot two. As far as the electric part, it is on whenever the ignition switch is on, if wired like the factory did it.
