The USWF-RCHO4.12 is a replacement controller for the USWF-4C101, 4C151, & 4CR2 systems. USWF replacement controllers feature a splash proof case, a fully potted ballast to protect from possible water damage and to improve heat dissipation, and are backed by a three-year, no-hassle warranty. The controller has an LED display with a 4-digit lamp change reminder, along with an audible lamp out indicator. Failure to replace the UV lamp on schedule will put additional stress on the controller ballast, always change your lamp after the reminder alert for optimal system performance.