Audible and visual warnings will attract workers' attention over a wide area to a potential or actual hazard.

With no radio communication between the two, news of the approaching ship depended on visual warning.

But wouldn't there be a visual warning, too?

At present it gives audible and visual warnings to suggest a break.

The first warning stage includes audible and visual warnings to brake.

The active visual warnings are usually in the form of flashing lights.

The passive visual warnings involve the use of high contrast patterns.

Here in these hills, a storm can hop over a ridge and kill without any visual warning.

They'd have visual warning of an attack by fringes.

Humans build physical impediments and visual warnings to mark defended territories.