A security system and a signal-carrying member therefor

(19)

(11)

EP 0 317 101 A3

(12)	EUROPEAN PATENT APPLICATION

(88)	Date of publication A3:
	27.09.1989 Bulletin 1989/39

(43)	Date of publication A2:
	24.05.1989 Bulletin 1989/21

(21)	Application number: 88310110.7

(22)	Date of filing: 27.10.1988

(51)	International Patent Classification (IPC)⁴: H01B 7/32, G01R 31/02

(84)	Designated Contracting States:
	AT BE CH DE ES FR GB GR IT LI LU NL SE

(30)

Priority:

19.11.1987 GB 8727092

(71)	Applicant: W.L. GORE & ASSOCIATES, INC.
	Newark, Delaware 19714-9206 (US)

(72)	Inventor:
	MacPherson, Hugh Kinross-shire Scotland (GB)

(74)	Representative: McCallum, William Potter et al
	Cruikshank & Fairweather 19 Royal Exchange Square Glasgow G1 3AE Scotland Glasgow G1 3AE Scotland (GB)

(56)

References cited: :

(54)	A security system and a signal-carrying member therefor

(57) A security system comprises a signal-carrying member and a detector for detecting a change in the resistance of a conductive path surrounding a core of the signal-carrying member. The conductive path comprises inner and outer layers (11,13) of semi-conductive tape separated by an insulating layer (12) but interconnected at one end. The semi-conductive tape of at least the outer layer is made of fibrous material such as carbon-loaded PTFE such that when a sharp object pierces the outer layer (13) and the insulating layer (12), semi-conductive fibres are dragged from the outer layer into contact with the inner layer (11) and form a conductive bridge between the layers.

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