Chapter 6 – Alarm Wiring

Publisher Summary This chapter presents schematic diagrams showing alarm wiring in controllers. Most controller and I/O power supplies include an alarm relay connector for output to alarm systems. The contacts may be either daisy chained so that any controller and I/O power supply in a group triggers an alarm or individually connected to an alarm system to know exactly which supply generated an alarm condition. Usually, contacts are open when the supply is not powered. One diagram shows a typical wiring arrangement for power supplies in a group, while the other one shows contacts connected from a single power supply to the input terminals for a typical discrete input card.