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Fundamental Operating Principles This chapter describes the basic interaction between transponder and reader, in particular the power supply to the transponder and the data transfer between transponder and reader (Figure 3.1). For a more in-depth description of the physical interactions and mathematical models relating to inductive coupling or backscatter systems please refer to Chapter 4. | RFID Handbook Fundamentals and Applications in Contactless Smart Cards and Identification Second Edition Klaus Finkenzeller 3 Copyright 2003 John Wiley Sons Ltd. ISBN 0-470-84402-7 Fundamental Operating Principles This chapter describes the basic interaction between transponder and reader in particular the power supply to the transponder and the data transfer between transponder and reader Figure 3.1 . For a more in-depth description of the physical interactions and mathematical models relating to inductive coupling or backscatter systems please refer to Chapter 4. 3.1 1-Bit Transponder A bit is the smallest unit of information that can be represented and has only two states 1 and 0. This means that only two states can be represented by systems based upon a 1-bit transponder transponder in interrogation zone and no transponder in interrogation zone . Despite this limitation 1-bit transponders are very widespread their main field of application is in electronic anti-theft devices in shops EAS electronic article surveillance . An EAS system is made up of the following components the antenna of a reader or interrogator the security element or tag and an optional deactivation device for deactivating the tag after payment. In modern systems deactivation takes place when the price code is registered at the till. Some systems also incorporate an activator which is used to reactivate the security element after deactivation Gillert 1997 . The main performance characteristic for all systems is the recognition or detection rate in relation to the gate width maximum distance between transponder and interrogator antenna . The procedure for the inspection and testing of installed article surveillance systems is specified in the guideline VDI 4470 entitled Anti-theft systems for goods detection gates. Inspection guidelines for customers . This guideline contains definitions and testing procedures for the calculation of the detection rate and false alarm ratio. It can be used by .