NTC thermistor devices are made of a specially formulated metal oxide ceramic material which is capable of suppressing high inrush current surges.

Inrush current limiter devices, being of relatively high resistance, shall limit the inrush current for 1~2 seconds during which time the device decreases in resistance substantially to a point where its voltage drop is negligible. The devices are specially useful for power suppliers because of the extremely low impedance of the capacitor being charged, of which the bridge is usually subjected to an exceedingly high current surge at turn-on point.