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The National Institute of Standards and Technology (NIST) maintain the standards for time and frequency for most users in the United States. It provides a variety of services designed to deliver time and frequency signals to the people who need them. The signals are broadcast via several mediums, including high and low frequency radio, the Internet, and telephone lines. These signals are used to synchronize millions of clocks every day, throughout the United States and around the world. NIST Time and Frequency Services Special Publication 432 Table of Contents Chapter 1 How NIST Provides Time and Frequency Standards for the United States Who Needs Time and Frequency Standards? NIST and the Primary Standards of Measurement Atomic Time and the Definition of the Second Coordinated Universal Time (UTC) Leap Seconds Traceability Time and Frequency Services Offered by NIST Chapter 2 Synchronizing the Nation’s Clocks: NIST Radio Station WWVB History of WWVB WWVB Station Description WWVB Signal Description WWVB Coverage Area WWVB Receiving Equipment and Applications WWVB Performance Chapter 3 Time Signals You Can Hear: NIST Radio Stations WWV and WWVH History and Site Description of WWV History and Site Description of WWVH Station Specifications Antennas Transmitters Information Transmitted Time Announcements Standard Time Intervals Standard Audio Frequencies and Silent Periods UT1 Corrections Time & Freq Sp Publication A 2/13/02 5:24 PM Page 5 Official Announcements Geophysical Alerts Marine Storm Warnings Global Positioning System (GPS) Status Announcements WWV/WWVH Time Code Receiving Equipment Listening to the Signals by Telephone HF Propagation Applications and Measurement Results Chapter 4 Keeping Computers on Time: NIST Computer Time Synchronization Services Internet Time Service (ITS) ITS Servers ITS Time Code Formats Daytime Protocol (RFC-867) Time Protocol (RFC-868) Network Time Protocol (RFC-1305) ITS Performance Automated Computer Time Service (ACTS) ACTS Time Code Chapter 5 Remote Calibration Services NIST Frequency Measurement and Analysis Service NIST Time and Frequency Services Special Publication 432 ![]() ![]() ![]() ![]() |
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