The wig-wag is mounted atop the washing machine's transmission, where it oscillates back and forth like a railroad signaling wigwag (hence the name). When either solenoid is engaged, a rod catches and engages the transmission in the desired mode. A wig-wag is a form of servomechanism; the coils are not powerful enough to engage the belt clutch themselves, but they can move their pins within the cam bar, then the mechanical oscillation of the wig-wag provides the force to push the cam bar and engage the belt clutch. When a solenoid is de-energized, the pin drops due to gravity.