On 2008-06-17, Al Patrick wrote:

[ ... ]

You can use many different triggers. The beam works fine but leaves a visible trail in
dusty or smoky conditions. You may want to install one to give them something to dance
around while they activate another one. :-)

Note that you can get infrared LEDs and sensors, so nobody can
see it -- without optical enhancement like night vison scopes. :-)

And yes -- also put in a visible one to give them something to
try to work around. :-)

Enjoy,
DoN.

--
Email: | Voice (all times): (703) 938-4564
(too) near Washington D.C. | http://www.d-and-d.com/dnichols/DoN.html
--- Black Holes are where God is dividing by zero ---