US 5,218,367 · Granted 1993-06-08
The 1993 Patent That Turned Your Car Into a Trackable Device
Imagine a hidden box in your car that talks to cell towers to pinpoint where you are—even if it gets stolen. This patent describes that exact system: sensors detect break-ins, send distress signals through the cellular network, and a control center figures out your location based on which towers heard the signal loudest.
The plain-English version
What it protects
The claim covers a vehicle tracking system that combines sensors (like break-in detectors) with a cellular modem hidden in a car, plus the method of using cell tower signal strength and cell site identification to triangulate vehicle position and send emergency alerts to a remote monitoring station. What's protected here is the specific integration of in-vehicle sensors, cellular transmission logic, and location computation at the receiving station.
Why it matters
This patent arrived right as cellular networks were expanding in the early 1990s, opening the door to car theft recovery and fleet management without requiring dedicated satellite or radio infrastructure. It's a foundational patent for the stolen-vehicle tracking industry, which became a major insurance and law-enforcement tool. The elegance of reusing existing cellular infrastructure meant the system could scale nationally without massive new hardware investment.
Real-world use
When a car alarm goes off and your insurer receives an alert with the car's location pinpointed to a few city blocks, you're benefiting from this patent's core logic—sensors plus cellular triangulation.
Original USPTO abstract
A vehicle tracking system makes use of a conventional cellular telephone network including a plurality of fixed cellular transmitter sites each covering a predetermined area. The system includes a plurality of cellular signal processing units for installation at hidden locations in vehicles to be monitored. Each unit is connected to one or more different sensors in the vehicle, at least one of the sensors being a break-in detector for detecting tampering with the vehicle, and to a cellular antenna, and includes a controller for monitoring the sensor outputs and initiating an emergency message transmission to a remote monitoring station in the event of actuation of a sensor. The car processing unit monitors site identifying signals and signal strengths of transmissions from adjacent cellular transmitter sites in an emergency, and the emergency message includes vehicle identifying information, cell site identifying information, and signal strength information which will be dependent on distance from the cell site. The monitoring station includes a computer for determining and displaying an approximate vehicle location from the incoming cell site identifying and signal strength information.
Patent details
- Publication number
- US 5,218,367
- Filing date
- 1992-06-01
- Grant date
- 1993-06-08
- Assignee
- Trackmobile
- Inventor(s)
- SHEFFER; ELIEZER A., THOMPSON; MARCO J.
- CPC class
- H04W64/00
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