Path: utzoo!utgpu!news-server.csri.toronto.edu!rpi!zaphod.mps.ohio-state.edu!wuarchive!udel!rochester!uhura.cc.rochester.edu!fval_ltd
From: fval_ltd@uhura.cc.rochester.edu (Trey Valenta)
Newsgroups: sci.electronics
Subject: Re: IR receiver on traffic lights ?
Message-ID: <13337@ur-cc.UUCP>
Date: 11 Apr 91 22:57:07 GMT
References: <1991Apr11.211957.7309@lynx.CS.ORST.EDU>
Distribution: na
Organization: University of Rochester - Rochester, New York
Lines: 15

In <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 ?

I don't know about how the lights are changed, (I'd think radio) but as for
the sun's inteference, what one can do is put a filter that allows only IR
to pass through, and the light from a transmitter is many times more
powerful that what's put out by the sun.

trey valenta
fval_ltd@uhura.cc.rochester.edu