The base construction of the AC, AC-AT series is a ceramic substrate, also known as ceramic rod. Metal caps are pressed over the ends of the rod. The resistor element is a resistive wire which is wound in a single layer on a ceramic rod. The ends of the resistive wire and the leads are connected to the caps by welding. Tinned copper clad iron leads with low heat conductivity are employed, permitting the use of relatively short leads to obtain stable mounting without overheating. The resistor is coated with a green silicon cement which is non-flammable, will not drip even at high overloads, and is resistant to cleaning solvents specified as per IEC 60115-1.