Geophone Based Intrusion Sensors

Brooke Clarke 2000 - 2015

Web Page Summarizing Intrusion Detectors and Related Equipment 
PEWS - Platoon early Warning Systems AN/TRS-2(V)
AN/USQ-42 Radio Frequency Monitor Set
Frequency Disconnect 
ID-1631A/GSQ Info Wanted
MOID Modular Outdoor Intrusion Detectors

Geophones have been developed for the oil exploration business. They have a "ground shaker" which could be a heavy vehicle with a "tamper" that pounds the ground or they set off explosions.  By using a number of geophones (earth microphones) and listening to the sub sonic sounds they can make a sub surface map of the rock formations that may help in locating oil.  Needless to say they have a lot of money to develop these geophones.
As of 10/19/98 the following three units are on the Stano Components Inc. Seismic page..  Note mine is a PSR-1 and they are showing a PSR-1A.

Vietnam film: Bugging the Battlefield (1969) -

TRC-3/3A Transmitter

TRC-3 Seismic Detector
            Set Cover Removed to show PCBThe PCB has about 2 dozen transistors, a single crystal, a couple of adjustable inductors and 3 variable caps.  The axial lead resistors are all standing up so that they take up less board space.  The switch is located near the sensor input and has a number of resistors connected in series between contacts, like a voltage divider.  The final transistor may be a TO-5 2N3866, all the other transistors look like Fairchild plastic units.  There is a panel on the face opposite the label about 2x3.5" that is the PCB cover.  It's been sealed by cementing the plastic together

The crystal oscillator is in the corner opposite the switch and feeds an RF chain ending with the antenna..

This is a single geophone combined with a radio transmitter.  The transmitter only turns on when there is a sub sonic signal above a selectable threshold.  I find that if I place it within 30' of my house at the least sensitive setting it goes off from my foot steps inside the house.  At 100' from my house at the least sensitive setting if I jump in the house it will go off, but not with foot steps.  So far I have not found a location where it will go off for a car coming into my drive way but not from me in the house.  The fidelity is not as good as the PSR-1 maybe because of the radio link and the use of squelch on the receiver.
TRC-3 Seismic Detector Set
TRC-3 Seismic Detector Set
Photo showing the "single bump" indicating that this one sends out a single "beep" others send out 2,3 or more "beeps"
TRC-3 Seismic Detector Set

The frequency on this one is 129.000 MHz which is below the 160 to 176 MHz range of the UQS-46 sensor receiver.
The modulation is probably AM.

RC-3A PSID Receiver

This receiver is housed in a case with the same outline as the TRC-3/3A transmitter and runs on 2 each 9 Volt batteries. It has a coaxial output connecter that is 0.243" in diameter and has two lugs for a bayonet sytle mating connector.  It has a male pin. This may be a "BN" connector, but I have not found a reference for it.  These may be part of the GSQ-151 PSID system.
Stock number 6350-179-1560 (6350-179 matches the TRC-3/3A transmitter). Freq. 126.6 MHz
DAAK02-70-C-0577 is the contract number.

Dorsett Electronics may now be part of LaBarge.

PEWS Ear phoneThis is a single earphone that has 3 straps with Velcro ends so you can install it under a helmet.  The coax connector looks like a miniature BNC plug.  

This headset mechanically plugs onto the URC-68 headphone jack, but does not function properly on that radio. 

Being sold on eBay as: Military Intrusion Alarm Receiver Headset by j5w23

I have been told that this is a TRC-3 headset.

PEWS - Platoon early Warning Systems AN/TRS-2(V)

PEWS Receiver
This set consists of one of the R-1808(V)x receivers and ten DT-577(V)x Detectors plus misc. other items. (the x is the version number and indicates the RF frequency as follows:
Frequency (MHz)
Note that all the frequencies are below the 160 to 176 MHz range of the UQS-46 sensor receiver.

The set can also be used in a wire line mode with the RF mode disabled.  The DT-577 Detectors have both seismic and magnetic sensors. The magnetic sensor has a sensitive axis the DT-577 has an arrow to be aligned parallel to the path or road.  You do not get to hear the sub sonic sounds with this unit, it only sends a digital byte of data with the area and sensor ID and  the type of detection, either seismic or magnetic.  If a deer sets it off the signal is the same as if a man set it off.  You can not select either magnetic or seismic, you must always have both.  I would like to have magnetic only - no deer would set it off.  There is NO sound from the receiver, only a digital byte or two is sent, so you can not "hear" what's happening.

The key Technical Manuals are:
TM 11-5895-1047-10 Operators Manual
TM 11-5895-1047-23 Organization and Direct Support Maintenance Manual
TS-3565/TRS-2 can generate the digital messages like the sensor, but has no capability to receive data.
TM 11-6625-2784-14 Test Set, Receiver TS-3565/TRS-2(V) (NSN 6625-01-075-0046)
TM 11-6625-2784-24P Test Set, Receiver TS-3565
TM 11-6625-2784-14HR Test Set, Receiver TS-3565
The test set has capabilities similar to the TS-2963/USQ-46 Test Set except that the 3565 has only wire line outputs (an RF generator is needed for RF testing) and the data format is different. The PEWS equipment works with: Area: 3 bits, ID: 4 bits, Parity: 1 bit, Class (Seismic or Magnetic).

TRS-2 was offered by Stano Components Inc. 1998

Frequency Disconnect

The TRC-3 and PEWS sensors transmit in the 129 to 150 MHz range BUT the USQ-42 and USQ-46 receivers tune in the 161 to 175 MHz range. Note that sonobouys operate in the 162 to 174 MHz range and the air dropped sensors were modified sonobouys.
The modern sensors like the GSQ-154, -160 that use the "common components" match the newer USQ-42, -46 receivers.  What receivers were meant to be used with the TRC-3? answer follows:

Igloo White (Wiki) -

Acoubuoy, Spikebuoy, Muscle Shoals and Igloo White by Chris Jeppeson - a lot of info on how the electronic battlefield worked in Viet Nam.  The early air dropped seismic sensors were based on sonobuoys with the hydrophone replaced by a geophone.  They transmitted to AN/ARC-??(V) aircraft transceivers in the 100 to 156 MHz range.  There were constantly aircraft flying, acting as relay stations to pickup the sensor signals.  Since the sensor transmitters were low power (2 Watts typical) they were hard to detect on the ground, but had a long range to aircraft.

There is still a problem because the airborne sonobuoy receivers will not receive the 129 to 150 MHz sensor transmissions.  But the AN/ARQ-52 maybe does. It was a FM Sonobuoy Signal Receiver; used in P-2, P-3A, S-2, SH-2D, EC-121R "IGLOO WHITE"

10 April 2001 - the GSQ-187 and R-2016/GSQ receivers for the REMBRASS II program cover a frequency range of 138 to 153 MHz.  There probably were earlier versions of these units.

5 Apr 2002, (after 9/11) A thought.  It would be good to have a system of satellites to receive these transmissions.  Much more effective than aircraft circling on a 24/7 basis and you would have world wide coverage.  The technology could be similar to the SARSAT system.

Crash of EC-121R - Bat Cat aircraft
EC-121R Bat Cat  - photo -


This is a Vietnam era fake turd that has mercury batteries a vibration sensor (not a geophone) and a VHF transmitter.  I need to take a photo and do some reverse engineering.  X-Ray of dog turd, lump of clay and tree branch. You can see 3 coin batteries, transistors and coils in these.
X-ray courtesy of  Dr. Christof Hasse.
Vietnam era Dog Turd X-Ray

The tree branch sensor is shown on the fifth page after pg 54 in the book "The Electronic Battlefield" by Paul Dickson, Indiana University Press, 1976, ISBN 0-253-12158-2, extensive bibliography.  On the next page -

"WATCH YOUR STEP. One of the many new sensor set-ups that are part of the current electronic battlefield.  Here noiseless button bomblets (NBB), which are disguised as such things as twigs and animal droppings, are activated when a human walks close by.  The NBB sends a signal to an ARFBOUY transmitter, which passes the signal along to those in charge of the action. (U.S. Navy/MITRE)"
Watch Your Step
            Noiseless button bomblets
New Turd with wrapper still on
Vietnam era Turd
          Seismic transmitter

I've heard of small disks, maybe 1" diameter by 0.4" tall related to this and now have found a patent for them.
3706867 Electronic anti-intrusion device, U.S. Army, Feb 18, 1971, 200/61.52, 102/424, 340/541, 200/61.11
This unit uses two switches.  S1 when in the safe position shorts out the noise maker (detonator or transmitter) and when in the arm or operate position starts an RC time constant where the capacitor is the main power source.  R would be a medium value resistor and C would be a fairly high capacitance that's also very low loss.  After that RC time constant has passed (allowing time for an air drop and bouncing around and settling) then switch S2 comes into play.  S2 is a ball in cage switch that may be either shorted or open after the RC time goes by, but in either case the SCR will not trigger.  S2 must change state then the SCR will trigger.  The patent mentioned the size of 1" dia. by 0.4" high.  Maybe this is the NBB?

Note the patent talks about a noise maker as the output and also mentions the idea that the noise maker might be a detonator, but it also could be a radio transmitter.


Patent Class Numbers

253 MAGNETIC.Magnetometers..Saturable core magnetometers
147 WITH MEANS TO CHANGE COIL LENGTH OR CONNECTIONS. Plural coils (e.g., transformers)..Plural coils or coil portions connected in parallel or in series and parallel
522 CONDITION RESPONSIVE INDICATING SYSTEM.With particular system function (e.g., temperature compensation, calibration)..Selection from a plurality of sensed conditions...Combined for response
541 CONDITION RESPONSIVE INDICATING SYSTEM.Specific condition..Intrusion detection
541 to 579 are all under ..Intrusion detection
542 ... Lock
543 .... Permutation
544 ...Disturbance of fluid pressure
545.1 ...Door or window movement
546 ....Portable
545.2 ....Specified sensor
547 .....Magnetic sensor
548 .....Plug or cord tension sensor
549 .....Rotatable sensor
545.3 ....Sensing of electromagnetic energy (e.g., light, infrared, or microwave)
545.4 ....Sensing of electrical parameter (e.g., piezoelectricity or capacitance)
545.5 ....Inertia-type sensor (e.g., mercury or pendulum switch)
545.6 ....Door, cover, or lid for self-contained article (e.g., refrigerator, mailbox, drawer, cabinet, or box)
545.7 ....Specified door or window portion (e.g., doorknob)
545.8 ....Specified door or window attachment (e.g., shade or blind)
545.9 ....Plural doors or windows
550 ...Partition penetration
551 ...Disturbance of magnetic field
552 ...Disturbance of electromagnetic waves
553 ....Standing waves
554 ....Doppler effect
555 ....Light
556 .....Beam
557 .....Laser
561 ...Disturbance of electric field
562 ....Capacitance
563 .....With bridge
564 .....Fence
565 ...Responsive to intruder energy
566 ....Vibration
567 ....Electromagnetic energy
568.1 ..Article placement or removal (e.g., anti-theft)
568.2 ...Signal-carrying conduit between sensor and article (e.g., cable, power cord, or data link)
568.3 ....Power cord
568.4 ....Specified connector (e.g., phone jack-type plug)
568.5 ...Shopping cart or item thereon
568.6 ...Sporting equipment (e.g., golfbag, club, cart, or skis)
568.7 ...Currency, credit card, or container therefor (e.g., wallet or handbag)
568.8 ...Article on pedestal, in display case, or mounted on wall (e.g., work of art)
569 ...Mailbox
570 ...Drawer
571 ...Alarm on protected article
572.1 ...Detectable device on protected article (e.g., "tag")
572.2 ...Specified relationship between field and detection frequencies (e.g., nth order harmonics)
572.3 ...Deactivatable by means other than mere removal
572.4 ...Specified processing arrangement for detected signal
572.5 ...aving tuned resonant circuit
572.6 ...Having "soft" magnetic element (e.g., Permalloy)
572.7 ...Specified antenna structure
572.8 ...Specified device housing or attachment means
572.9 ....Having means locking device to article

3706867 Electronic anti-intrusion device, Bianchi John, Bohacz Maxine, Lyon Jerry, Pitman Robert L, Rand Henry T, Shaw Donald N (US Army), Dec 19, 1972, 200/61.52, 102/424, 340/541, 200/61.11

4001745 Intrusion detection transducer, Roger John Goodman (Honeywell Inc), Jan 4, 1977, 336/20 ; 336/147; 336/180; 340/566; 340/941 -
buried cable detects both seismic and magnetic disturbances
3634843 CIRCUIT AND METHOD FOR DETECTING LOCALIZED NOISE LEVEL CHANGES AND ESPECIALLY ELECTROMAGNETIC NOISE, C Corris, Jan 11 1972, 340/659 ; 340/661; 340/941 - automobile ignition noise
3736502 SERIES STRING FLUX GATE MAGNETIC SENSOR APPARATUS WITH ADDITIVE RESPONSE, Erick O. Schonstedt (Schonstedt Inst Co), May 29 1973, 324/253 ; 340/568.1
door gate gun detector
3846790 INTRUSION DETECTION SYSTEMS, Erdman (Honeywell), Nov 5 1974, 340/522 ; 324/345; 340/551; 340/566 - seismic & magnetic
3747036 MAGNETIC LINE SENSOR, David P. Erdmann (Honeywell), Jul 17 1973, 336/84R ; 324/234; 336/181; 336/234 -
3754223 Intruder detection system, Shmuel Shtrikman (Yeda R&D),Aug 21 1973,  340/551 -  magnetic cable
RE29019 Intruder detection system, Shmuel Shtrikman (Yeda R&D), Oct 26, 1976, 340/258C; 340/381 -


Looking for info on this unit.  Let me know and/or let N1TLK know, he send in the photo.
The left terminals are marked PHONE (Geophone) and the right terminals are marked RELAY.
The function switch has positions: OFF, Light Only, Soft, Med, Loud, Very Loud.
The green boot covered TEST buttom is also marked Hold for 4 Seconds.
If the output has a relay then the RESET button must reset it.
Not sure what the window is for next to the RESET button.
Might run on a common 9 V battery.

Brooke's, Military InformationHome Page
page created 3 Aug 2000.