Varistors

Varistors are voltage-dependent resistors that protect electronic systems from over voltages. Their resistance value decreases with increasing voltage, thus limiting a further increase in voltage.

Varistors have established themselves as a reliable and low cost method of protecting both high and low voltage AC and DC systems from transients.
Surge current ratings can be as high as 100 kA.

New types have been developed especially for telecommunications applications. Available in surface mount, thru-hole and mechanically fixed versions to cover most applications from design - in to retrofit.