Littelfuse FS491 is a compact and encapsulated circuit protection device. With a maximum load rating of 0.5A, it provides surge protection according to IEEE C62.41 - 1991 Level A standards. It offers steady state operation, input tolerance of ±15%, and works with LED or resistive load types. It has a low output voltage drop of 2V and an open state leakage current of 250A. It can handle a wide range of AC line frequencies (50/60Hz) and operates reliably in 95% non-condensing humidity. The on/off ratio is approximately 50%, and the flash rate is fixed at 75 ±20% fpm.