EP 0032135 A2 19810715 - Monitoring apparatus.
Title (en)
Monitoring apparatus.
Title (de)
Überwachungsanlage.
Title (fr)
Installation de surveillance.
Publication
Application
Priority
GB 8000544 A 19800108
Abstract (en)
Where monitoring apparatus includes remote units intended to maintain surveillance of an area for an event such as unauthorised entry into the area, a remote unit fails to convey to a master unit any information if the remote unit ceases to function. A master transmitter (11) therefore transmits, over mains electricity supply lines, frequency-modulated bursts which stimulate the or each remote unit to reply with a characteristic frequency-modulated burst for each burst from the master transmitter (11). The master frequency-modulated burst resets a counter (38) in the remote unit. If a remote unit fails, or detects an alarm situation, the remote unit does not reply, the counter (38) being frozen. A master receiver and indicator (12) demodulates the characteristic bursts from the remote unit or units and prevents an alarm (65) from sounding provided that the characteristic bursts are received at the expected intervals. Failure of a characteristic burst to arrive results in the alarm (65) being sounded and a red LED (64, 76, 77 or 78) being energised to indicate which of four remote units has failed to reply.
IPC 1-7
IPC 8 full level
G08B 25/06 (2006.01); G08B 29/04 (2006.01); G08B 29/08 (2006.01)
CPC (source: EP)
G08B 25/06 (2013.01); G08B 29/04 (2013.01); G08B 29/08 (2013.01)
Designated contracting state (EPC)
AT CH DE FR IT LI NL SE
DOCDB simple family (publication)
EP 0032135 A2 19810715; EP 0032135 A3 19820210; GB 2067321 A 19810722; GB 2067321 B 19830706; ZA 81120 B 19820127
DOCDB simple family (application)
EP 81300065 A 19810108; GB 8000544 A 19800108; ZA 81120 A 19810108