Newsgroups: sci.electronics
Path: utzoo!utgpu!news-server.csri.toronto.edu!rpi!batcomputer!cornell!uw-beaver!milton!serval!yoda.eecs.wsu.edu!ckinsman
From: ckinsman@yoda.eecs.wsu.edu (Chris Kinsman)
Subject: Re: IR receiver on traffic lights ?
Message-ID: <1991Apr12.232038.22438@serval.net.wsu.edu>
Sender: news@serval.net.wsu.edu (USENET News System)
Organization: Washington State University
References: <1991Apr11.211957.7309@lynx.CS.ORST.EDU>
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Date: Fri, 12 Apr 91 23:20:38 GMT

In article <1991Apr11.211957.7309@lynx.CS.ORST.EDU> youngqd@jacobs.cs.orst.edu (Dean Youngquist) writes:
>The fire trucks in my town seem to trip traffic lights to green in
>their direction as they are approaching the intersection.  Does anyone
>know how they do this?  I thought they might have a system using
>infra-red light ?  If it is infra-red how can they work in the day-time?
>Doesn't the sun put out infra-red that would interfere ?
> 
>Dean Youngquist                 youngqd@jacobs.cs.orst.edu
>Corvallis, Oregon 97330         Tel. (503) 757-0335

I have been on departments in the past that use a system like that.  The
most common is one called Opticom.  This system uses basically strobe
lights to trip the signals.  It is usually a single strobe mounted on the
centerline of the vehicle although it is sometimes integrated into the
light bar.  The strobe flashes a pattern at a specified frequency to trip
the lights.

Chris  

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Chris Kinsman  					KINSMAN@WSUVM1
Washington State University			22487863@WSUVM1
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