The PSR-1A is a Vietnam era seismic sensor designed to detect ground vibrations. It uses wires between the geophones and the box. There are 4 separate inputs and each of these can have a number of sensors. You can tell which of the 4 circuits is active, thereby you know where there is action. It translates the sub sonic signals into the audio spectrum so that you can "hear" them. It is very easy to distinguish a women walking, a man walking or children playing. Deer, cars, trucks, and helicopters all have their own unique sounds which you can recognize without any training. It runs on 6 each D batteries.
I used to live in a house where there was no view of the street from any of the commonly used rooms. By connecting an outside microphone to an inside speaker you could hear "out front" and/or using the PSR-1 you knew what was happening even though you could not see. . . Of all the outdoor intrusion detectors this is my favorite because it's the only one that allows you to hear what's going on. -- Brooke Clarke
Just finished, in order, an extended, contentious argument with Alan Colmes on his radio show and then a long interview with a Washington Post reporter. I'm beat. Fed the dogs tonight only the minimum so they will sleep lightly. If the PSR1A's begin to crackle, I'll let you know after I call the body retrieval and documentation service (9-1-1).