Electrical surges can be in the form of a sudden steep rise in the line voltage, which probably lasts for not more a fraction of a second. However the sudden induction of a high voltage might force your precious electronic gadget to "gulp" a huge amount of current, causing an instant damage or burning of the involved electronics.
Surge protectors are basically designed to stop and neutralize the entry of these sudden voltage peaks.
Opening a typical surge buster unit may reveal a circuit, consisting of some copper coils wound over ferrite drums and a few subsequent MOVs or varistors.
The coils are introduced over both the input lines so as to provide better control and blockage of the transients.
As we all know inductors oppose a sudden change in the flowing voltage, the copper inductors here restrict sudden voltage rise or fall thereby fulfilling conditions. The MOVs are positioned to ground or neutralize any voltage that may pass through the inductor bank, thus confirming a sound protection to your sound systems.