US 4,891,650 · Granted 1990-01-02
The 1990 Patent That Invented Vehicle Tracking
Imagine your car has an alarm that screams when something's wrong. This patent describes a system that listens to that alarm from multiple radio towers spread across a city, measures how loud the signal is at each tower, and uses that information to figure out exactly where your car is located. It's basically triangulation using cellular networks.
The plain-English version
What it protects
What's protected here is a method and system for locating a vehicle by receiving alarm signals at multiple fixed cellular sites, measuring the signal strength at each site, and using those strength measurements to calculate the vehicle's position. The claim covers the combination of the wireless detection units at different locations, the signal strength analysis, and the central control unit that processes all that data to pinpoint the vehicle's approximate location.
Why it matters
This patent represents one of the earliest applications of cellular-based vehicle location technology, filed in 1988 and granted in 1990. It pioneered the concept of using signal strength triangulation across a network of fixed receivers to track vehicle position without GPS (which wasn't widely available then). The patent laid groundwork for what would eventually become theft recovery systems, fleet management, and later navigation services—foundational technologies that the automotive and telecommunications industries would build upon.
Real-world use
When a car alarm goes off and a security company needs to dispatch help, they're using descendants of this technology to pinpoint the vehicle's location across a cellular network.
Original USPTO abstract
A system for determining a location of a selected vehicle from which an alarm signal is generated which includes a fixed array of cellular sites each site having a wireless signal detecting and generating units each of which is capable of receiving an input alarm signal having a signal strength which is a function of the distance between the position of the vehicle generating the alarm signal and the position of each of the wireless signal detecting units. Each unit also is capable of transmitting an output signal which is a function of the strength of the input alarm signal. The system also includes a main wireless signal detecting apparatus for receiving an output signal from each of the wireless signal detecting and generating units and a control monitoring unit which is coupled to the main wireless signal detecting apparatus, for receiving output signals there from, each of the output signals being a function of the strength of the received input alarm signal, for determining the approximate location of the selected vehicle from which the alarm signal is generated.
Patent details
- Publication number
- US 4,891,650
- Filing date
- 1988-05-16
- Grant date
- 1990-01-02
- Assignee
- Trackmobile Inc.
- Inventor(s)
- SHEFFER; ELIEZER A.
- CPC class
- B60R25/102
Want to file your own patent?
If you're designing an automotive safety or tracking gadget, our free patent scanner can help you spot whether similar location-tracking ideas are already locked down.
Free patentability scan