Monitoring arrangement for monitoring a change from a normal condition of any one of a plurality of condition sensing devices

摘要

A monitoring arrangement for monitoring a change from a normal condition of any one of a plurality of condition sensing devices. It includes a common two conductor circuit connecting the condition sensing devices. A central monitoring apparatus is connected to the common two conductor circuit and supplies current to the circuit. Each of the condition sensing devices includes a device for limiting the amount of current flowing therethrough from the common two conductor circuit; a mechanism to detect and to react to any change from a normal condition being sensed; and a mechanism to interrupt the current to at least all following condition sensing devices in the circuit upon reaction of the condition sensing device to a change in a condition being sensed. An apparatus is formed as part of the central monitoring apparatus for measuring and indicating a magnitude of current being supplied to the common two conductor circuit at any given time.