EP 0628937 A1 19941214 - Theft detection system.
Title (en)
Theft detection system.
Title (de)
Diebstahldetektorsystem.
Title (fr)
Système de détection de vol.
Publication
Application
Priority
NL 9300991 A 19930609
Abstract (en)
A theft detection system comprising an interrogation unit and a detection unit for generating an electromagnetic interrogation field with a predetermined frequency and detecting the presence of electronic labels belonging to the system in the interrogation field. The electronic labels generate a reply signal in the interrogation field by means of a resonant circuit which comprises at least a coil and a capacitor and which also functions as receiving circuit for the interrogation field. The labels comprise means which provide a frequency-switched signal with the aid of which the signal generated by the interrogation field in the resonance circuit is modulated via a first switching element in such a manner that at least two high-frequency signal components arise which are located within the resonance curve of the resonance circuit, in such a manner that these signal components are strongly present in the secondary magnetic field formed by the coil. <IMAGE>
IPC 1-7
IPC 8 full level
G08B 13/24 (2006.01)
CPC (source: EP)
G08B 13/2417 (2013.01); G08B 13/2422 (2013.01); G08B 13/2431 (2013.01)
Citation (search report)
- [XY] EP 0441237 A1 19910814 - STOBBE ANATOLI [DE]
- [Y] US 3984835 A 19761005 - KAPLAN GERALD STANLEY, et al
- [YD] EP 0084400 A2 19830727 - NEDAP NV [NL]
- [X] FR 2598006 A1 19871030 - SIGNALISATION [FR]
- [A] FR 2371128 A7 19780609 - NEDAP NV [NL]
Designated contracting state (EPC)
DE FR GB NL
DOCDB simple family (publication)
DOCDB simple family (application)
EP 94201631 A 19940608; NL 9300991 A 19930609