Trip Wires The Fiendish Burglar alarm device before Motion Sensors

Before there where Photo Electric break beams and Motion Sensors there was a fiendish device known as the Trip wire. Which took some science and skill to place to trap burglars .
At left are some trap wires as shown in an old Ademco catalog in 1981  they could be wired Open Circuit where pulling the wire across a door way caused the clip to pull loose causing contact and an alarm trip or Closed Circuit where the wire going across the door way could cause an alarm by either pulling wire and clip fell out breaking the circuit or cutting the wire. The far left unit was a pressure sensitive unit  cutting the wire and pushing or pulling on wire tripped it in case a burglar bumped the wire and then stepped away it would still trip unlike  the simple open or closed model .

You could put these units all over a business to trap a burglar  such as across a window AC unit if they tried to remove it or attach the wire to an item on a shelf and when it was removed wire was pulled or across a door way or a foot up from floor across a garage door, across an aisle way etc etc. when I worked for Holmes Protection they had this big old warehouse in the south side of Pittsburgh  that was a Rexall plumbing supply it was always a pain responding there for an alarm  they  had 42 of these trap wires and after the alarm went off usually false from a raccoon getting in the warehouse and gnawing on things  police  would walk thru and it took an hour to walk around and reset them all. But as simple as they where they caught burglars all the time. Once beams and motion sensors became widely available and cheap trip wires went away like foil but there are still some out there being used. I have not seen them lately in any catalogs But USP- United Security Products  and GRI -George Risk Industries  still makes something like it.  They even used this special thin trap wire thru duct work to keep thieves from crawling thru duct work they would put 1/4 inch hollow  wooden tubes thru the duct then pull the wire thru them. and wire walls and anything else you could think of that could move to keep burglars out. Any cut to the thin wire the alarm which in Holmes case was silent and you did not know the armed   Holmes armed  responder guard  or police where on the way
Old technology but a very devious one like floor mats which I will talk about in a future article .