The cadmium sulfide (CdS) or light dependent resistor (LDR) whose resistance is inversly dependent on the amount of light falling on it, is known by many names including the photo resistor, photoresistor, photoconductor, photoconductive cell, or simply the photocell.
Anti-surge resistor RCR series are made by metal glaze coating on the surface of a cylindrical substrate with excellent characteristics and stable at even high resistance range.
Carbon film CF series are the earliest and a still popular type made by breaking down hydrocarbon gases at high temperature in a vacuum to form a carbonic deposit on the surface of a cylindrical substrate.