PURPOSE: To beforehand prevent accidents, by projecting antennae to a dead angle portions of a car, and by informing a driver of the existence of men or obstacles by electric signals.

CONSTITUTION: A switch mechanism is formed which uses a contact needle 3 as one electrode at a nose portion of a main body 7 and employs an electrode bush 10 as the other electrode. When a contact needle 13 touches with a body and is bent, the electrode contacts and is in ON, an electric circuit is organized by terminals 4, 6 for drawing out a power source 5 and a switch 8, which is in ON when this antenna is perfectly set, and signals are sent to a driver by load 11. The antenna 13 is mounted to a dead angle portion of a driver's seat 14 in such a manner that it is usually built in a car body portion and is made up at the outside, which is permitted by regulations, at an oblique lower portion in the arrow head 17 direction as necessary so that a nose portion be located at a portion of approximate 20cm on the ground, and the antenna is operated through levers 1, 2 by working power.