Low CR Photorelays Toshiba Low CR Photorelays are available as Solid State Relays (SSR) or MOSFET Output Optocouplers and are typically used as signal relay replacements. Photorelays are semiconductor relays made up of an LED optically coupled to a MOSFET. Low capacitance resistance (CR) photorelays are designed to switch high-frequency signals across output terminals. These Toshiba photorelays are available in through-hole or SMT/SMD mounting styles. In addition, they're offered in several package types, including S-VSON-4, VSON-4, USOP-4, SON-4, and SMD-4. The operating temperature range is -20°C to +110°C.