Doorbells can be wired to flash a light, or a door knocker can be placed which flashes a light when someone knocks.
(Doorbells; can be wired; to flash a light) (Doorbells; to flash; a light) (a door knocker; can be placed; ) (someone; knocks; )
Doorbells Doorbells a door knocker someone
can be wired to flash can be placed knocks
to flash a light
a light