ATE60682T1 - EMERGENCY ALERT SYSTEM. - Google Patents

Abstract

A danger-signalling system with a central station with an evaluating device exhibits several signal lines having in each case one two-wire line (a,b). To this, a multiplicity of individually identifiable detectors (Mi) having in each case one switching transistor (S1,S2...) are connected in a chain in one of the two wire lines (b). The detectors (Mi) of each signalling line (ML) are cyclically interrogated from the central station (Z) for their respective analog detector measurement values. In the evaluating device, the respective line current (IL) is measured, the detector address and the detector measurement value being determined from the respective time when the line current increases and an alarm or fault message being derived from this. Each signalling line (ML) is constructed as signalling loop and connected with its line end (E) to the central station (Z), in which arrangement the evaluating device can be switched from the line start (A) to the line end (E) of the respective signalling line (ML). In each detector (Mi), a semi- conductor diode (Di) is connected in parallel with the switching transistor (Si) in the reversely polarised direction. In the case of a fault on a signalling line, the evaluating device is connected to the line end (E) and an alarm is detected on the basis of the line current determined and is indicated as line alarm. At the same time, the time from the application (TS) of an interrogating voltage until the occurrence (TR or, respectively, TA) of the line current increase is measured, the time (tA) being shorter with an alarm condition compared with the time (tR) of an idle signalling line. <IMAGE>