Reliance Automax. In stock ships today. 45C40. 4540. Input/Output. Optically Isolated Inputs. All input logic level circuits are optically isolated from field signals. These high threshold circuits will not energize until a pre-determined voltage is reached, to prevent triggering by false signals from external interference. Input module voltage ratings for the 45C40 are 115 VAC/DC. This module compares two analog voltage signals and sends the logical results to the processor. It can also compare an external voltage to a preset reference voltage determined by the user. Both greater-than and less-than comparisons are made.