What data format does LoJack use?

[ECPD279]

I already have the frequency, but does anyone have any idea what data format LoJack systems use? Also, is there software capable of decoding the data bursts. I am toying with the idea of building my own sort of LoJack locator, just for grins. Any info is appreciated.

 

[RolnCode3]

I can't add to the discussion, but if you build one, I'd be up for doing the same. Hell, I'd be willing to donate a few bucks if it would help get one set up. I'll be that if you emailed LoJack directly, they'd probably send you the LE press pack for it. They might even be willing to give you tech info if they thought it might help recover a car one day. Maybe, might be a long shot though.

 

[Pro-95]

There is a program called slurp that will read the discriminator tap information from your scanner. If you have the freq and an active LoJack device you could at least be getting to a start. I'd imagine that the information burst is relativly short and probably only contains the unit number and the coordinates. That way you could virtually track real time without delays of information not relavant to locating the car(device).

Radio Shack sells a device called Roadside Companion that with a monthly service fee you can even track the device(car/person/etc) via the Internet. I'll see what info I can get on that as they may be similar.

 

[N_Jay]

There is a program called slurp that will read the discriminator tap information from your scanner. If you have the freq and an active LoJack device you could at least be getting to a start. I'd imagine that the information burst is relativly short and probably only contains the unit number and the coordinates. That way you could virtually track real time without delays of information not relavant to locating the car(device).

Radio Shack sells a device called Roadside Companion that with a monthly service fee you can even track the device(car/person/etc) via the Internet. I'll see what info I can get on that as they may be similar.

LoJack does not send the coordinates. It is not a "location" system, it is a "Tracking" system. It sends out a data burst (I think all it does is identify the unit). The unit is tracked through a combination of triangulation from fixed radio sites and RDF (Radio Direction Finding) from equipped mobile units.

The fixed sites also trasmit the signal required to activate the in-car transmitter.

I don't know anything about the data structure of either the fixed site transmissions or the vehical transmissions.

I would guess it is probably fairly simplistic due to when the system was first designed. (Late 1980's)

 

[Pro-95]

Ok I'm probably confused. I thought I saw a blurb on one of the car or technology shows where they used Lo-Jack and showed the device(car) moving on a rolling map.

:? Oh well. They say the mind goes first.

 

[Thayne]

Somewhere on my computer I have a PDF of how Lojack works, including calibrating the transmitter. If I remember right, Moto designed it. If I can find it I will post it.

I do know its not like gps, it works by the diversity of the four antennas on the police cars; ie by direction and signal strength. It gets you close, then you must use your eyes. Usually when one goes off, all the various jurisdictions pick it up and communicate as to where it is coming from.

A lot of the time they end up breaking into garages where they find the vehicle--

 

[loumaag]

Ok I'm probably confused. I thought I saw a blurb on one of the car or technology shows where they used Lo-Jack and showed the device(car) moving on a rolling map.

You may very well have seen that. As N_Jay points out, there are places where there are fixed receiver sites that can pretty well pinpoint where the active transmitter is; although obviously the mobile units can get a better read as they close in on the vehicle. You will not find these fixed sites in the country of course, they are located where they can be most cost effective, large metro areas.

Mike, take a look in that new antenna book you have at RDF. I expect to see posted pictures of a 4 antenna setup on your vehicle shortly. :lol:

 

[RolnCode3]

I know that the guys in the field have the units installed. It's the little box that has a light that can spin 360 degrees, around about a dozen lights. The box has a small screen for the output of the device, which is just a few letters/numbers.

You'll hear a Deputy call out a Lo-Jack hit, and give that code. They'll run the code thru the Lo-Jack system, and get the description of the vehicle. THEN, everyone floods the area looking for it. They just triangulate/drive around aimlessly till they find it. Usually doesn't take more than about 10-15 minutes.

This is a major metro area (1-1/2 to 2 million people), but as far as I know, there aren't any towers with Lo-Jack receivers. We have RAT packs and you'll hear those go hot/cold all the time, but I've never heard dispatch call out a "hot" Lo-Jack tower receiver anywhere.

 

[ECPD279]

There are other tracking systems that do give Lat/Lon info, such as Teletrac, but these systems are more expensive and are generally used only on large fleets, like trucking companies. These systems generally have a GPS receiver and are satellite based, so they are not much use to law enforcement.

LoJack is intended to be tracked by RDF'ing (That'd be Radio Direction Finding to the uninitiated) by properly equipped patrol cars, and supposedly by LoJack fixed sites as well. One of our officers got the info packet, and the receiving equipment is free to law enforcement, they will come out and install it in the patrol cars for free too. Our department doesn't want to get it though, and for the record I don't plan on using it in the patrol car, but I want to play around with it anyway and see how it works. Just to satisfy my natural curiosity.

My reason for wanting the data format, is so I can decode the data bursts and see the ID number. I hear the bursts all the time around Richmond. The data bursts are only maybe .1 - .25 second long, and I think it only sends the unit ID number. Once you have the number, a dispatcher can trip it and it will come back with complete vehicle info including color and license plate. It's mostly just a personal project to fiddle with something else radio oriented.

 

[scanfan03]

What's the freq., do you have it as 173.075? That's what I have it as.

 

[Mick]

Coordinates

The signal does not send out coordinates. PD receivers have 4 antennas that allow the officer to tell what direction the signal is coming from.
Mick

>There is a program called slurp that will read the discriminator tap information from your scanner. If you have the freq and an active LoJack device you could at least be getting to a start. I'd imagine that the information burst is relativly short and probably only contains the unit number and the coordinates. That way you could virtually track real time without delays of information not relavant to locating the car(device).<

 

[ECPD279]

What's the freq., do you have it as 173.075? That's what I have it as.

That's what I have.

 

[ECPD279]

There is a program called slurp that will read the discriminator tap information from your scanner.....

Where would one find this program. When I do a web search for "slurp" all I get is a bunch of porn sites.......... go figure huh?

 

[RolnCode3]

How about this one? First is a link to a webpage, second is directly to the file:
http://members.cox.net/kplotkin/scanner.htm

SLURP file:
http://members.cox.net/kplotkin/SLURP.ZIP

By title, the "Serial Line Universal Reading Program".

Located this thru Strong Signals:
http://www.strongsignals.net/access/content/software.html

 

[PJH]

LoJack will only send you free equipment if you are within certain area's. My old dept looked into it, and since it wasn't in a high traffic area, they would have had to pay for it.

In my town of 50k (and abundance of traffic), there are only 4 or 5 vehicles with it. The new control heads are nice and really small.

The format is close to the Motorola MDC1200 format, so I am told. Most likely MDC1200 with a couple of extra commands.

 

[PJH]

Almost forgot to add...the system (when I was in the car all the time) usually sent out a test data packet every 10 or 15 min I think. Could have been every 30.

 

[ECPD279]

Almost forgot to add...the system (when I was in the car all the time) usually sent out a test data packet every 10 or 15 min I think. Could have been every 30.

That could explain why I hear bursts all the time around Richmond. RPD has several LoJack equipped cars.

 

[PJH]

Just to clarify, the road units (crusiers) do not transmit, just the towers with the LoJack transmitters.