Well then we need to agree to disagree then, as a user of the system (tracking) Towers only transmitted to the box and the Box only transmitted to the Cruisers/Airwing or the few areas that implemented RX Sites to be able to triangulate (rare and expensive)
No need to disagree. What you are saying was true
before 2002. What I am saying is true
after 2002. We are both correct!
After 2002, legacy LoJack devices, at least those which incorporated the early warning system, had the added/additional capability of transmitting "uplink" messages directly to the towers. This additional capability was requested by LoJack and approved by the FCC. The new "uplink" messages notified the tower if the vehicle was being moved without permission, was being hot wired and whether an activation or deactivation command was successful. The internal battery voltage could also be relayed by these new messages to the towers. This was all done using the 173.075 MHz frequency.
I receive uplink/acknowledgement messages on my scanner all the time on the 173.075 MHz LoJack frequency especially while driving around Denver. Typically, they just sound like someone keying up a dead mic, with a little clicking in the background, for several seconds. The clicking is the 100 bits being transmitted at 55.8 baud. Most of these transmissions are just early warning messages being issued to the towers due to people driving around without their LoJack key fobs with them.
Also, the towers have the capability of detecting reply codes being broadcast on the LoJack frequency. There is some indication LoJack experimented with technology in their towers which could roughly triangulate the location a specific reply code was being broadcast from. The towers also monitor each other to verify they are staying within their assigned time slots. There are even commands sent between towers to resynch them into the correct time slot and for other maintenance related work.
Have you ever studied into the early warning system rolled out in 2002 and how it works? I think you would find this very fascinating. How do you think customers receive e-mails/phone calls from LoJack within 15 minutes of their vehicle being moved without the key fob? The early warning system is another part of the LoJack system, running on 173.075 MHz, which many people are entirely unaware of. The early warning system runs alongside and in conjunction with the primary LoJack system so it's entirely possible for a person to miss this new system and never even realize a new capability was added to the primary LoJack system.
Here are a few quotes from an FCC document regarding the new capability in the legacy LoJack system:
"When activated, the EWD [early warning detector] will detect external movements of the vehicle or determine that the vehicle has been started without using a key (i.e., 'hot-wired'), and thereupon instruct the TU [transponder unit] to transmit an alert message.
The nearest base station will process and forward the message to the LoJack central control center, whereupon LoJack personnel will alert the car owner that the vehicle is possibly being stolen.
These TU 'uplink' transmissions, which must be limited to six messages per mobile unit in any thirty-minute period,
also can be used to acknowledge base station activation and deactivation messages."
"Under the proposed rule change, the
mobile-to-base 'uplink' transmissions are used to alert a control center whose personnel, in turn, alert the vehicle owner that his or her vehicle has been moved without consent. Thus, a vehicle theft is detected immediately, which gives the owner the ability to notify the police immediately. By comparison, under the old technology, the stolen vehicle is not tracked until the vehicle owner discovers the theft and reports it to the police. This may not occur for hours or days after the theft."
"While the 'uplink' transmission path incorporates the early warning feature, it
also serves to acknowledge base station activation and deactivation messages.
Specifically, mobile units using the 1800 milliseconds cycle are capable of transmitting acknowledgements to instructions received from a base station."
Manuals for LoJack units which have the early warning capability state, "
The LoJack Early Warning feature will not function if the Vehicle is not in range of a LoJack tower, or if the Vehicle’s battery is discharged or disconnected and the LoJack backup battery also is discharged."
User Manual IDIEW2VLU-05 Users Manual
If the LoJack box inside the vehicle cannot communicate with a tower (base station) then the customer will not be notified when their vehicle is moved without permission.
The early warning system is an interesting part of the legacy LoJack system however I believe it failed to deliver as most did not want to pay the extra expense for the early warning system and the towers had a difficult time receiving messages from vehicles. Anyway, there are a lot of documents online about the early warning system and the use of "uplink" messages to the base stations from the LoJack boxes installed in vehicles.
One of the best documents on how the early warning systems works is the following
FCC document beginning on page 3:
https://www.fcc.gov/ecfs/document/5006009662/1
Again, the early warning system technology works alongside the existing legacy LoJack technology;
it did not replace the old technology it was simply added in 2002 as another layer on top of the existing LoJack technology. They basically sandwiched two different LoJack systems together into one box. Each of the two systems runs on 173.075 however for different purposes. So, it's possible someone could have worked with tracking down LoJacks for decades and never have known this other part of the LoJack system even existed in which the vehicle communicates with the towers.
