PA system having zone isolator circuits

(19)

(11)

EP 0 967 833 A3

(12)	EUROPEAN PATENT APPLICATION

(88)	Date of publication A3:
	17.03.2004 Bulletin 2004/12

(43)	Date of publication A2:
	29.12.1999 Bulletin 1999/52

(21)	Application number: 99305005.3

(22)	Date of filing: 25.06.1999

(51)	International Patent Classification (IPC)⁷: H04R 27/00

(84)	Designated Contracting States:
	AT BE CH CY DE DK ES FI FR GB GR IE IT LI LU MC NL PT SE
	Designated Extension States:
	AL LT LV MK RO SI

(30)

Priority:

27.06.1998 GB 9813882

(71)	Applicant: PROTEC FIRE DETECTION PLC
	Nelson, Lancashire BB9 6RT (GB)

(72)	Inventor:
	Priest, Eric, c/o Protec Fire Detection Plc Nelson, Lancashire BB9 6RT (GB)

(74)	Representative: Robinson, Ian Michael
	Appleyard Lees, 15 Clare Road Halifax HX1 2HY Halifax HX1 2HY (GB)

(54)	PA system having zone isolator circuits

(57) A public address network using a single pair of signal wires (12) split in to sections using isolator circuits (20) which detect short circuit faults and open circuit faults and isolate if a fault is detected. In a fault tolerant mode an audio signal (14) and a pilot signal (15) for powering the isolators (20) are supplied from both ends of the signal wires (12).

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