One of the important parameters used for choosing a photorelay is the CxR product. The "C" in the CxR product refers to the capacitance across the output terminals, Coff, when the photorelay is turned off; and the "R" in the CxR refers to the resistance across the output terminals, Ron, when the photorelay is turned on. In general, if the Coff is high, a high-frequency signal will not be able to turn the photorelay off as quickly. Whereas a high Ron will cause excessive signal loss. Therefore, high-frequency signals require photorelays with low CxR values. Automated Test Equipment is one of the applications that benefits the most from low CxR values.