Modern Intelligent Electronic Devices, encountered at a substation, conform to a common architecture: A processor directs Analog and Binary Input subsystems to acquire data from the power system; a Binary Output provides system control and Communication Subsystem interfaces to Substation Automation, SCADA and Energy Management Systems. The rigid, real time performance demands placed on Protective Relays, Remote Terminal Units, Communication links, SCADA and EMS systems, coupled with harsh operating environment, make these systems complex to design, install and operate. This article describes real life episodes as seen through the eye of equipment provider. More