Because the two lights flash alternately on and off, the signal could have been entirely dark at regular intervals.

Other signs also flash alternately between a number indicating the speed and an emoticon.

The light from the window alternately flashed and was cut off.

Flashing headlights (typically the high beams, flashed alternately) are known as a wig-wag.

It must be retroreflective and/or equipped with alternately flashing red lights.

Each door on the platform also has a set of red lights that flash alternately to warn that the doors are closing.

The escape behavior consists of alternately flashing its white sides when running away.

The Left and Right eye images are flashed alternately on the screen at a high frame rate (100 times a second or more).

The lights begin to flash alternately, and a bell (or bells) mounted at the crossing begins ringing.

A coded signal activates a 120db siren and the vehicle's indicators flash alternately.