For many years, some Manufacturers have incorporated discrete devices into their circuit and board designs in an attempt to mitigate the effects of electrical power disturbances of various kinds. Some of those devices include:

• Zener diodes – A semi-conductor that becomes conductive and begins to act like shunt resistor when circuit voltage approaches a design threshold. Zener diodes are often applied at a value around twice the nominal circuit operating voltage. They typically fail when operated above their design current, which can be quite small or quite large. They may fail open or shorted.

As we all know by now, or will find out, microprocessor-based systems\devices and other sensitive [CMOS, etc.] electronics have a great aversion to voltages, currents, and frequencies they are neither designed nor intended to handle. Historically, a number of different schemes have been applied to the problems of lightning and surge protection, with varying degrees of success. In the case of Life Safety Systems [Fire Alarm, Mass Notification, Security, CCTV, Surveillance, Access Control, etc.], our main concern is preservation of specific systems, sub-systems, and devices in fully operational condition, and that is what we will focus on in this series.