Hello David,
There was in fact a clever switch that did just that. It was a
pendulum that hung 1" inside the door, with a contact on one side
so as the door opened, but not closed, it closed. I have not seen
one in 30+ years.
There still is a type of switch that sits above the door and has an oval
spring. This spring closes a switch above it while the door is between
just a crack and 10 degrees maybe. Many stores have that but the
downside is that is also alerts when closing the door.
Did I mention this is an office? The FedEx and UPS folks are our FRIENDS...
This is also an office. The dogs alert the same way when anyone pulls up
and sometimes that's a good thing. It keeps not so well meaning folks
away. When the meter reader comes they make a racket, too, but then sit
there next to the meter drooling because he always has dog biscuits.
Dogs have an amazing sense of good and bad. When they sense trouble they
show some teeth with the growl.
And as for
http://www.yoursecurity.us/dchime.htm; the only one I
see there that's close is the air pressure one. Err, no thanks. This is
an interior door, from the elevator lobby...
I have heard a Dog bark type electronic alert before. It was pathetic.
The bark stopped in the middle of a woof. Intruders aren't that stupid.
I want a simple mechanical or magnetic sensor on the door; not
photobeams, air pressure, or backscatter radar....
Should be no problem. Some electronic "bong" chimes from the hardware
stores react to a door bell button the same way whether it is
momentarily pressed or held down long. So if you'd get one of these and
an "open when released" switch you should be in business. Hardware
stores often also have those switches as kits, with brackets, screws and
all. They used to be popular to illuminate a walk-in closet or pantry
the instant its door was opened. If they don't have them you could look
at garage door opener end switches since it's a low voltage application.
Regards, Joerg
