Shielding field method and apparatus
First Claim
1. A method for selective communication between a stationary transmitting device and at least a selected one of a plurality of mobile responding device, the method comprising the steps ofgenerating from said stationary transmitting device a first field of radiated electromagnetic energy, said generating step including the step of encoding said first field with a first signal intelligible to said responding devices, said first signal being representative of a request to execute a selected operation,directing said first field at said at least one selected responding device,generating from said stationary transmitter a second field of radiated electromagnetic energy, said second field being effective at any responding device within said second field to blank out said first signal, and directing said second field at others of said plurality of responding devices, whereby said others of said plurality of responding devices are prevented from receiving said first instruction.
21 Assignments
0 Petitions
Accused Products
Abstract
A system for automatic collection of tolls includes a toll facility, an in-vehicle toll processor having memory for storing a toll-money-available quantity purchased by the user, and a toll-facility-identification site that transmits a toll-facility-identifier signal indicating the identity of the upcoming toll facility and the toll to be collected. As the vehicle approaches the identification site, the in-vehicle processor receives the identifier signal and calculates the toll to be debited. When the vehicle passes through the toll facility, the facility transmits a toll-collect signal instructing the in-vehicle toll processor to debit the calculated toll from memory. The in-vehicle processor debits the calculated amount and transmits an acknowledgement signal to the toll facility.
This application is related to the subject matter of application Ser. No. 525,103 filed May 17, 1990 now U.S. Pat. No. 5,144,553, issued Sep. 1, 1992, and application Ser. No. 524,654 filed May 17, 1990 now U.S. Pat. No. 5,086,389, issued Feb. 4, 1992, having as common inventors John J. Hassett and John M. Harrison.
-
Citations
12 Claims
-
1. A method for selective communication between a stationary transmitting device and at least a selected one of a plurality of mobile responding device, the method comprising the steps of
generating from said stationary transmitting device a first field of radiated electromagnetic energy, said generating step including the step of encoding said first field with a first signal intelligible to said responding devices, said first signal being representative of a request to execute a selected operation, directing said first field at said at least one selected responding device, generating from said stationary transmitter a second field of radiated electromagnetic energy, said second field being effective at any responding device within said second field to blank out said first signal, and directing said second field at others of said plurality of responding devices, whereby said others of said plurality of responding devices are prevented from receiving said first instruction.
-
9. A position determining system, comprising
first radiating means for rad electromagnetic energy field encoded with a first electromagnetic energy signal having a selected frequency and a first selected amplitude, second radiating means, oriented at a selected angle to said first radiating means, for radiating a second electromagnetic energy field encoded with a second electromagnetic energy signal having said selected frequency and a second selected amplitude, such that said first and second fields overlap, so that predictable variations in signal amplitude occur at selected positions relative to said first and second radiating means, whereby the amplitude of signals received by a receiver placed within said first and second fields and receptive to said first and second signals is representative of the position of said receiver relative to said first and second radiating means.
Specification