Alarm System Diagnostic Apparatus.

摘要

A diagnostic status indicating apparatus is used with an alarm system having a plurality of normally-closed switch contacts (32) which are opened upon occurrence of an alarm condition. Light-emitting diodes (34) are connected across the normally-closed switch contacts at an opposite polarity to that of the current normally passing through the contacts in the operating mode. In order to diagnose the alarm-generating condition of the electrical contacts, a switch (20) removes the operating voltage and connects a test voltage (60) at a reverse polarity, whereupon the LED (34) for any open circuited electrical contact is activated. The device is preferably based upon a double-pole-double-throw switch and includes indicators for a test condition (62) and for a ground fault (64).