Time synchronization in North America
Telephone time sources
Several different organizations provide publicly accessible recorded voice time sources, including the NIST Telephone Time of Day Service,

Time synchronization in North America

Section Title: Telephone time sources
Table Section Text: Several different organizations provide publicly accessible recorded voice time sources, including the NIST Telephone Time of Day Service,

Time Signal	Time Provided	Accuracy	Source	Signal Format	Hardware Requirements	Linux/Unix Software	Windows Software

GPS	UTC(USNO)	1575.42 MHz	NMEA 0183 sentences, 1PPS signal.	Minimum: GPS receiver that works with one's chosen software; this requires some combination of GPGGA, GPRMC, GPZDA, GPGSA, and GPGSV, sentences.	Gpsd plus ntpd with the GPSD NG client driver	NMEATime2 COAA's GPSTime F6CTE's CLOCK ToyNTP BktTimeSync by IZ2BKT

WWVB	UTC(NIST)	60 kHz AM	IRIG "H" PWM time code with PM BPSK signal overlaid.	Radio-controlled clock: NIST list of receivers AC-100-WWVB Time Receiver AC-500-MSF Time Receiver	ClockWatch Radio Sync F6CTE's CLOCK

WWV	2.5, 5, 10, 15, and 20 MHz AM	Voice with modified IRIG-Hformat time code on 100 Hz sub-carrier (CCIR code)	HF radio and antenna (plus software if automatic updating of computer time is desired) TrueTime TL-3 WWV Receiver	ntpd with Radio WWV Audio Demodulator/Decoder (driver can tune ICOM HF radios via C-IV)	COAA's Radio Clock F6CTE's CLOCK

WWVH	5, 10, and 15 MHz AM	Voice with modified IRIG-Hformat time code on 100 Hz sub-carrier (CCIR code)	HF radio and antenna (plus software if automatic updating of computer time is desired) TrueTime TL-3 WWV Receiver

CHU	3.33 MHz, 7.85 MHz, 14.67 MHz	Bell 103 modem tones, decodable by most computer modems	ntpd with Radio CHU Audio Demodulator/Decoder driver (driver can tune ICOM HF radios via C-IV)

Daytime Protocol	UTC (variant depends on server's time source)	ClockWatch Pro for Windows

Time Protocol

Network Time Protocol	pool.ntp.org	Computer with NTP client that syncs at least once an hour.	Meinberg NTP NetTime ToyNTP BktTimeSync by IZ2BKT

NTPSec

Precision Time Protocol	Domain Time II

eBay protocol	San Jose, CA local time	HTTP	Computer with Web browser and TCP port 80 open for HTTP traffic and able to reach the eBay Time page	ClockWatch Pro for Windows

NIST Telephone Time of Day Service	UTC(NIST)	+1-303-499-7111 +1-808-335-4363	Voice announcement with sync pips.	Telephone connection	n/a	Manual sync only.

NIST Automated Computer Time Service (ACTS)	+1-303-494-4774 +1-808-335-4721	Windows computer with dialup modem.	ntpd with NIST/USNO/PTB Modem Time Services driver	ClockWatch Pro for Windows

USNO Master Clock modem time	+1-202-762-1594	Computer with Bell 212A or CCITT V.22 compatible modem

US Naval Observatory time service	UTC(USNO)	+1-202-762-1401 +1-202-762-1069 (Washington, D.C.) +1-719-567-6742 (Colorado Springs)	n/a

Sentence(s)

GPS receiver with the NMEA 0183 GPZDA sentence a 1PPS signal.

final_sentence: GPS receiver with the NMEA 0183 GPZDA sentence a 1PPS signal.