Identification systems
US4691202A · kind A · utility
Inventors
Key dates
| Filing date | Apr 3, 1985 |
| Grant date | Sep 1, 1987 |
| Priority date | — |
| Expiry date | Apr 3, 2005 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG07C9/28
- WIPO fieldComputer technology
- WIPO sectorElectrical engineering
Abstract
An identification system comprises an interrogator which transmits an interrogation signal to a plurality of transponders, each of which is arranged automatically to reply by means of a first coded identification signal stored in the transponder and modulated onto a carrier wave transmitted by the transponder. The interrogator receives and checks the reply signal. In the event of there being a plurality of transponders within range and broadcasting reply signals simultaneously, the interrogator receives corrupted reply signals. The interrogator therefore retransmits the reply signals to the transponders and each transponder checks the retransmitted reply signal with its first coded identification signal. In the event of correspondence the transponder discontinues transmission and in the event of non-correspondence the transponder continues transmission. In a polling mode of operation, the interrogator initially transmits a second coded identification signal corresponding to a selected transponder, and each transponder within the range compares the second signal with the first signal stored therein. If correspondence is established, the transponder is adjusted to receive further ins…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.