Traceable® Digital Clock has 2-1/4 inch-high big digits for visibility from 20 feet. Accuracy is 1/10,000 of a second. Radio signal from NIST in Colorado automatically adjusts clock to precise time, daylight savings, leap year, and leap seconds (earth rotation wobble corrections). Display shows AM/PM or 24-hour time, month, date, day-of-the-week, and ambient temperature (32 to 122 °F and 0 to 50°C with 0.1° resolution). Large digits are 2-1/4 inches high for viewing from 20 feet. To assure accuracy an individually serial-numbered Traceable® Certificate is provided from the manufacturer’s ISO 17025 calibration laboratory accredited by A2LA. It indicates traceability to standards provided by NIST (National Institute of Standards and Technology). Complete with wall mount, screw, and 2 AA batteries. Size is 8-3/4 x 9-1/4 x 3/4 inches. Weight is 1-1/8 pounds. Replacement battery Cat. No. CON1111.