Electronic article security system employing variable time shifts

US6249229A · kind A · utility

Assignee

• Checkpoint Systems, Inc., a Corp. of Pennsylvania · US

Inventors

• Eric Eckstein · Yeadon, US
• John Edwin Davies, Jr. · Sewell, US
• Edwin H. Hopton, Jr. · Philadelphia, US
• Nimesh Shah · Marlton, US
• Bent Svendsen · Roskilde, DK

Key dates

• Filing date: Aug 16, 1999
• Grant date: Jun 19, 2001
• Expiry date: Aug 16, 2019

Classification

• Technology area (CPC G): Physics
• CPC primary: G08B13/2488
• WIPO field: Control
• WIPO sector: Instruments

Abstract

A pulse-listen electronic article security (EAS) system for detecting the presence of a security tag within a detection zone is disclosed. The EAS system includes a transmitter for radiating a first electromagnetic signal into the detection zone. The first electromagnetic signal is a time sequence of RF bursts emitted during each of a plurality of contiguous frame intervals in which the duration of each of the frame intervals is one of a plurality of different values. The EAS system also includes a receiver synchronized with the transmitter for receiving a second electromagnetic signal re-radiated from a security tag in the detection zone in response to the first electromagnetic signal. The receiver provides an output signal if a security tag is detected. The values of the plurality of the frame interval durations are selected to be different from the values of frame interval durations of other EAS systems thereby rendering the EAS system substantially free of false alarms or blockages caused by the operation of other EAS systems.