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A recent news article appeared, based on the attached PDF (which is a court decision regarding a bank robbery, in which 29 people were detained while police looked for the suspect who presumably had a tracking device).

I wrote the following to the reporter, as most reporters let technology non-sense slip through:

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There are things in the story that don't make sense, and I suspect they might have been deliberately introduced by police, prosecutors and the court.

Here's some of the language from the PDF:

"it sent a signal via satellite to the Aurora Police Department ("APD"), where it could be tracked on a map on an APD computer monitor"

This is a ridiculous concept. A transmitter in a stack of money would not have sufficient power to reach a satellite.

"Every 6-10 seconds the GPS tracking device sent a “ping” off the satellite, which would mark a dot on the map on the APD’s computer monitor."

Ping suggests a transmission to the object (satellite). More nonsense.

"Second, officers were on notice that devices called handheld “beacons” existed that could be brought to a particular scene to much more accurately identify the precise location of a GPS tracking device
embedded in a stack of stolen money, to within approximately five feet."

Beacon is something that would transmit. They are probably talking about receivers, not transmitters.

"Trooper Williams turned off the tracking device, and dispatch confirmed that the satellite signal of the tracking device that dispatch had been following had become deactivated."

Kind of vague: Presuming "satellite signal" means transmitting to satellite.

"When those events occurred, Trooper Patrick Williams, an expert in using the handheld beacon (which was reliable and accurate when used by an expert), had already gotten a “very strong” positive signal that the GPS tracking device was located in Defendant’s SUV."

Again, beacon is misleading. A beacon comes from a transmitter. This handheld device is a receiver, detecting the transmission of the device embedded in the cash.

More likely:

a) the device embedded in the cash (about the size of a credit card) transmitted a tone on 220Mhz. (Most likely activated by lack of magnet in the cash drawer; magnet keeps the circuit open. Removing magnet closes the circuit and turns on the transmitter.)

b) receiver sites around town would detect the signal and provide triangulation

c) handheld receivers provide ability to detect signals up close.

d) signals received by the stationary receiver sites are detected and a signal strength measurement is relayed to police dispatch, along with a direction (because the receiver sites have directional antennae)

Background:

1996, FCC authorizes 216-217Mhz spectrum for tracking:
http://transition.fcc.gov/Bureaus/Wirel ... c96315.txt

In the early 1990's the system described above was being deployed by ETS (Electronic Tracking Systems, dba Pronet) of Plano, TX. See for example:
http://articles.latimes.com/1990-02-27/ ... ing-system

See also:
http://img02.mar.cx/us/1985185.png

ETS was later bought by or merged into Metrocall about 1997:

http://www.bizjournals.com/dallas/stori ... aily2.html

Metrocall later sold the tracking system portion of the company to Spectrum Management, LLC:

http://online.wsj.com/article/SB9500268 ... 3.djm.html

Company site:
http://etstracking.com
http://etstracking.com/s3/bankrobbery.php

Now, assuming technology has been updated and there actually is a gps receiver embedded in the cash, the location data from the gps receiver would need to be transmitted and this is most likely done through cell systems or the 216Mhz band. It would not be transmitted to a satellite because a device that small would not have sufficient power to transmit to a satellite.

See also:
http://www.chemir.com/dye-pack-chemical-analysis.asp
If dye packs are also embedded with the cash, then anyone trying to turn off the tracking transmitter would want some insight into the dye packs.

Note that in this 2008 article "gps" is not used:

http://www.hendonpub.com/law_and_order/ ... ng_systems

And.....?

_________________
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