An electrical switch, in a generator or motor, that periodically reverses the direction of an electric current.
A binary map in a given group G, given by [g, h] = ghg⁻¹h⁻¹, where g and h are elements of G, which yields the group's identity if and only if the group operation commutes for g and h.
A binary map in a given ring R, given by [a, b] = ab − ba, where a and b are elements of R, which yields the ring's zero element if and only if the multiplication operation commutes for a and b.
Any of a number of mechanical or electrical devices which cause a component to oscillate between two states.
A device with multiple (often two), alternately flashing lights which is installed at a railway level crossing (or grade crossing), a movable bridge, etc., to warn vehicular traffic to stop.
An instrument that creates a wigwagging motion for polishing.
A grade crossing signal with a swinging motion used to indicate an approaching train.
A device that causes one or more lights to flash in a preset pattern.
A red light near the door of a sound stage that flashes to indicate that cameras are rolling inside the stage and that all people and vehicles outside should remain quiet; a red-eye.
A device used to cause lamps installed on a motor vehicle, especially an emergency vehicle such as an ambulance or police car, to flash as a warning.
A signal sent by waving a flag to and fro.
A warning device inside the cabin of a truck that causes a mechanical arm to drop into view when the pressure in the airbrake system of the truck becomes too low for the brakes to be reliably deployed.
To send a signal by waving a flag to and fro.
An act of wigwagging.
To oscillate between two states.
To move gently in one direction and then another; to wig or wiggle, to wag or waggle.
With a wigwagging or to-and-fro motion.