Radio signalling systems

• US 4,162,448 A
• Filed: 03/16/1977
• Issued: 07/24/1979
• Est. Priority Date: 03/16/1977
• Status: Expired due to Term

• Current Assignee: Lewis Security Systems Limited
• Original Assignee: Lewis Security Systems Limited
• Inventors: Gilmour, deceased, William D.
• Primary Examiner(s): Bookbinder, Marc E.
• Application Number:
  US05/778,150
• Time in Patent Office: 860 Days
• Field of Search: 325/64, 325/111, 325/118, 325/37, 325/466, 325/51, 325/53, 325/119, 325/161, 325/164, 325/166, 325/338, 325/66, 325/158, 325/364, 325/142, 325/143, 325/157, 178/66 A, 343/225, 340/171 A, 340/311, 340/224, 340/258 D, 340/277, 340/280, 340/283, 340/539, 328/136, 328/140, 324/78 D, 179/15 AW, 179/15 BA
• US Class Current: 340/539.11
• CPC Class Codes: G06K 19/0723 the record carrier comprising an arrangement for non-contact communication, e.g. wireless communication circuits on transponder cards, non-contact smart cards or RFIDs
• CPC Class Codes: G07C 9/28 the pass enabling tracking or indicating presence
• CPC Class Codes: G08B 13/00 Burglar, theft or intruder alarms

Abstract

This invention is a radio frequency identity system in which each user has a token containing a low power transmitter. If he wants to enter a security area, a receiver operates to let him enter if it recognizes that the transmission is correct. A correct transmission is one having a set number of R.F. carrier cycles between successive modulation pulses.

In an alarm system a user can identify himself in a similar manner.

Claims

1. A radio signalling system including a number of portable tokens each capable of transmitting signals in the form of a carrier radio frequency which is common to the tokens, with spaced modulation pulses superimposed on the carrier and defining a carrier burst between successive of said pulses, the number of carrier frequency cycles in a carrier burst between successive modulation pulses being different for different tokens, and a receiver capable of distinguishing between received signals from tokens with different characteristic numbers of cycles in their bursts, said receiver comprising a counter of clock pulses derived from the cycles in the burst of received carrier frequency and a comparator of the count achieved by the counter which comparator is arranged to compare the achieved count with a pre-set count identifying tokens to which access is to be given to a security area, wherein said comparator is arranged to compare the achieved count with the count achieved in the preceding burst of carrier frequency received.

2. A radio signalling system including a number of portable tokens each capable of transmitting signals in the form of a carrier frequency which is common to the tokens, with spaced modulation pulses superimposed on the carrier and defining a carrier burst between successive of said pulses, the number of carrier frequency cycles in a carrier burst between successive modulation pulses being different for different tokens, and a receiver capable of distinguishing between received signals from tokens with different characteristic numbers of cycles in their bursts, said receiver comprising a display of a symbol identifying the number of cycles in a received burst of carrier frequency.

3. A radio signalling system including a number of portable tokens each capable of transmitting signals in the form of a carrier radio frequency which is common to the tokens, with spaced modulation pulses superimposed on the carrier and defining a carrier burst between successive of said pulses, the number of carrier frequency cycles in a carrier burst between successive modulation pulses being different for different tokens, and a receiver capable of distinguishing between received signals from tokens with different characteritic numbers of cycles in their bursts, said receiver comprising a counter of clock pulses derived from the cycles in the burst of received carrier frequency and a comparator of the count achieved by the counter which comparator is arranged to compare the achieved count with a pre-set count identifying tokens to which access is to be given to a security area, wherein said receiver is arranged in response to a successful comparison to operate a release mechanism to a security area, and said comparator operates on successive received bursts of carrier frequency and only operates an alarm or operating circuit when a certain number of correct comparisons have been made.