Designed to measure and display AC mains frequencies from 45–65 Hz, DMR20-1-FM-R-C features 4-digit LED display with out-of-range indication and 0.01 Hz resolution. This round, self-powered, 2-wire, digital panel frequency monitor operates from 85–264 Vac and employs quartz crystal-controlled, MCU-based timing circuitry. With seamless construction on all sides, housing provides protection to IP67/NEMA 6 and supports mounting in industry-standard, oiltight, 1.2 in. round panel cutout.