In this category are grouped : a) Transient Voltage Suppressors with non-linear current-voltage characteristics that sustain an almost constant voltage over a wide range of current. b) Gas Arresters that above their spark-over value act as gas discharge tubes with the known negative current-voltage characteristics. c) Inrush current NTC suppressors that due to their initial cold resistance-value absorbe the surge current, limiting that way the current across the circuit and sufficiently protecting it.

Varistors Metal Oxide Varistors are ideally suited to all transient voltage protection applications. Their high clamping efficiency and low steady power dissipation offer considerable circuit advantages of most existing protection methods.During operation idle at a low current level at the nominal voltage. When transient over voltage occurs, varistor current increases rapidly while its voltage remains virtually constant absorbing the transient energy content.Packages: Radial Leads & Blocks. Check the Suppression Portofolio Guide - Download the requested Littelfuse-Harris PDF files
Voltage RMS	Type	Dimentions	Miscellaneous
11V up to 420V	Disc type	Max. Diameter: 7.0 - 7.5mm	Radial leads
11V up to 420V	Disc type	Max. Diameter: 9.0 - 9.5mm	Radial leads
11V up to 620V	Disc type	Max. Diameter: 12.5 - 13.5mm	Radial leads
11V up to 1000V	Disc type	Max. Diameter: 16.5 - 17.0mm	Radial leads
11V up to 1000V	Disc type	Max. Diameter: 22.5 - 24.0mm	Radial leads
75V up to 750V	Block type
130V up to 600V	Block type	Check the Suppression Portofolio Guide
130V up to 660V	Block type	Download Littelfuse-Harris PDF files
130V up to 1000V	Block type

Zener Protectors Silicon PN junction Diodes designed, manufactured and specified as Transient Voltage Suppressors (Varistors).Available in an Axial lead package.
Stand-off Voltage	Type	Steady state Power Dissipation	Operating Temperature
12.10V up to 128V	Bi-polar & Uni-polar Axial leads	0.5 Watt	-40°C to 150°C
6.63V up to 185V	Bi-polar & Uni-polar Axial leads	1 Watt	-40°C to 150°C
6.63V up to 185V	Bi-polar & Uni-polar Axial leads	3 Watt	-40°C to 150°C

Gas Surge Arresters They consist of a mettallized ceramic(insulating) tube of aluminum oxide with two electrodes of a special alloy. The electrodes are vacuum-tide soldered to the ceramic tube which is filled with a rare gas. Above their spark over value they act as a gas discharge tube with the known negative current-voltage characteristics. Used as over voltage protectors for telecom-systems and remote-control equipments are excellent protection against any type of transient over voltages caused by interference of inductive and capacitive influences(Such as the atmospheric ones, etc).
Type	Shape	Uagn/V	Tolerance	Miscellaneous
Mini (5x 5mm)	Button	90/230/350V	± 20%	with or w/out 2 leads
Medium Duty(8x 6mm)	Button	90/230/350V	± 20%	with or w/out 2 leads
Heavy Duty(8x 6mm)	Button	90/230/350V	± 20%	with or w/out 2 leads
Heavy Duty(8x 8mm)	Button	90/230/350V	± 20%	with or w/out 2 leads
Heavy Duty(8x12mm)	Button	90/230/350V	± 20%	with or w/out 3 leads
Heavy Duty(9x15mm)	Button	90/230/350V	± 20%	with or w/out 3 leads & Fail-Safe Spring
Heavy Duty(5x20mm)	Fuse	90/230/350V	± 20%
Heavy Duty(9.5x50.6mm)	Fuse	90/230/350V	± 20%	Vertical adapted
Heavy Duty(5x41mm)	Fuse	90/230/350V	± 20%	Horizontal adapted
Gas Arrester Holders Available Upon Request

Inrush Current They provide a soft start-up of sensitive circuits due to their initial cold resistance. The absorbed energy heats their body thus decreasing their initial cold "protective" resistance and gradually applying most of the power back to the circuit. In circuits design care must be taken in order to select thermistors with thermal capacity higher than the surge absorbed energy and the fact that they are functioning as an inrush current protection only if they are in cold resistance mode.
Resistances @ 25°C	Type	I max.	Res. Tolerance	Miscellaneous
0,5 Ohms up to 220 Ohms	Disc	30A to 1.3A	± 15 to 25% @ 25°C	Radial leads