PSR-1 Seismic Intrusion Detector

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 traning.  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. 

I'm guessing that prior to the Vietnam era Texas Instruments was doing some work with geophones in support of the Oil Business that's a big thing in Texas.  When a need arose for an outdoor intrusion detector they were the company that had the needed experience.

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.

The geophones have a reasonant frequency around 5 to 20 Hz which for practrical use is below human hearing.  They pickup the sound of the earth shaking as caused by people walking, vehicles with engines, and most of all helicopters nearby.  Inside the PSR-1 a circuit translates the subaudibal frequencies into a range that can easily be heard.

The geophones can easily be hidden and the simplest way is to bury them underground along with the WD-1 phone wire that connects them to the main unit.  Attaching a sensor under a suspended floor or bridge provides mechanical amplification of the sound.  The poorest place to put a geophone is on concrete.  Vertical orientation seems to work best for most things.

Unlike all the other systems that use geophones this one lets you hear the sounds.  In the other systems there is an alarm, but when it goes off you don't know if it was an animal, one person, or a division.  The benefit is that those systems can be set and left alone.

The label says:
AN/PSR-1
DETECTOR, SEISMIC INTRUSION
MODEL X-150A
STOCK NO. 6655-903-0932
PT NO. 87990-5133-000-0001-2
CONTR NOm-73280    SER. NO. T-17
MFR: 18667

The geophone consists of a permanent magnet surrounded with a coil of wire.   One of those is connected firmly to the housing and the other is held by springs.  When the earth moves a voltage is generated.  The operation is very similar to that of a dynamic microphone only the frequency response goes much lower.

Geophones are very similar to seismometers.  As far as I can tell seismometers are more precise and typically calibrated.  Also seismometers are made so that they can be used not only vertically but also horizontally.  A typical seismometer setup would have vertical, North-South and East-West sensors.  Some seismometers are optimized for weak signals and others for strong motion.  Geophones are designed for detecting local events, not weak distant events.

The newest geophones use MEMS integrated circuits that act as an accelerometer instead of the coil and magnet approach.  For most applications the results are about the same.  The IC type cost a lot less.

A lookup on CAGE code 18667 yeilds: HALLIBURTON GEOPHYSICAL SERVICES INC, 6909 Southwest FWY, PO Box 36306, Huston, TX 77236-6306.
Inside the cover is a stick on label that says "Texas Instruments Incorporated, Science Services Division, Dallas, Texas.   Below this label a plate with the operating instructions riveted to the cover.

Manual

Marine Corps (TM-04704B-15) dated January 1968 

Patent

3296587 Intrusion Detector System, Buford M. Baker (TI), Jan 3 1967, 367/136 ; 340/384.7; 340/566; 367/93 -
3508238 Intrusion Detector System, Buford M. Baker (TI), Apr 21 1970, 340/551 - loop magnetic field sensor

3806907 Premiter Intrusion Detection System with Comon Mode Rejection, Bound et al.(TI), Apr 23 1974, 340/566 ; 340/525 - buried piezoelectric sensors

3806908 Premiter Intrusion Detection System with Comon Mode Rejection, Bound et al.(TI), Apr 23 1974, 340/525 ; 340/566 -

3806909 Stress Sensor for a Peirmeter Intrusion Detector System, Lloyd R. Bound (TI), Apr 23 1974, - 310/367 ; 310/330; 310/338; 340/566; D25/46