Path: utzoo!mnetor!ghp!jim
From: jim@ghp.UUCP (Jim Stewart)
Newsgroups: sci.electronics
Subject: Re: Car Detectors for Traffic Lights
Message-ID: <289@ghp.UUCP>
Date: 31 May 89 13:06:23 GMT
References: <18811@cup.portal.com>
Reply-To: jim@.UUCP (Jim Stewart)
Organization: Gellman Hayward & Partners Ltd., Toronto, Ontario, Canada.
Lines: 22

In article <18811@cup.portal.com> Mark Robert Thorson writes:
>Does anybody know how the car detectors for traffic lights work?  Are
>they tuned circuits?  If so, what frequency?

From university days...we used to open the exit gates in the parking lots
with the right sized closed loop of wire.  It would obviously detune
the car detector and open the gate.

In case you are wondering, it started out as a practical joke on the
old lady who was the cashier for one of the lots.  People would ride
their bicycles past the in-gate and a ticket would come out.  Of course
the machine would buzz until she got annoyed and came out of her kiosk
to remove the ticket.  The poor dear must have had to put down her
knitting at least 5 times a morning for this, and in the winter it was
cold outside.  (University of Waterloo '79)

We tried to do the same thing with a loop of wire in your shoe, but found
we needed a loop diameter of about 2 feet even if we used multiple turns.
-- 
Jim Stewart, VE3SRJ
UUCP:  jim%ghp@mnetor.uucp
BELL:  (416)862-0430