headlight auto mode
THE ULTI-MOD
Joined: Jan 2007
Posts: 19,797
Likes: 36
From: Union NJ
LOL!!! Shrps! Ya gotta get your eyes checked! That LED is too small to warn anyone of anything unless it's for an alarm. I operate an emergency vehicle and I can tell you the LEDs that are used are way bigger and brighter than that. At least you said it was part of an alarm first! 
re-read please, signal emitters for the traffic light changing devices is what i said it might have been.
Hall Of Fame
Joined: Jun 2005
Posts: 14,228
Likes: 19
From: Riverton, UT
The device emits a radio wave to a receiver on the stop lights. Then the receiver changes the lights you are coming up on to green so the emergency vehicle doesn't have a red light and can get through the light faster.