19c2daa00SOllivier Robert<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"> 29c2daa00SOllivier Robert<html> 39c2daa00SOllivier Robert<head> 49c2daa00SOllivier Robert<meta http-equiv="Content-Type" content="text/html;charset=iso-8859-1"> 59c2daa00SOllivier Robert<meta name="GENERATOR" content="Mozilla/4.01 [en] (Win95; I) [Netscape]"> 69c2daa00SOllivier Robert<title>NIST/USNO/PTB Modem Time Services</title> 79c2daa00SOllivier Robert<link href="scripts/style.css" type="text/css" rel="stylesheet"> 89c2daa00SOllivier Robert</head> 99c2daa00SOllivier Robert<body> 109c2daa00SOllivier Robert<h3>NIST/USNO/PTB Modem Time Services</h3> 119c2daa00SOllivier Robert<p>Author: David L. Mills (mills@udel.edu)<br> 129c2daa00SOllivier Robert Last update: 139c2daa00SOllivier Robert <!-- #BeginDate format:En2m -->12-Oct-2017 08:13<!-- #EndDate --> 149c2daa00SOllivier Robert UTC</p> 159c2daa00SOllivier Robert<hr> 169c2daa00SOllivier Robert<h4>Synopsis</h4> 179c2daa00SOllivier Robert<p>Address: 127.127.18.<i>u</i><br> 189c2daa00SOllivier Robert Reference ID: <tt>NIST | USNO | PTB | WWVB</tt><br> 199c2daa00SOllivier Robert Driver ID: <tt>ACTS_MODEM</tt><br> 209c2daa00SOllivier Robert Serial Port: <tt>/dev/acts<i>u</i></tt>; 9600 baud, 8-bits, no parity<br> 219c2daa00SOllivier Robert Features: <tt>tty_clk</tt><br> 229c2daa00SOllivier Robert Requires: <tt>/usr/include/sys/termios.h</tt> header file with modem control and a dial-out (cua) device.</p> 239c2daa00SOllivier Robert<h4>Description</h4> 249c2daa00SOllivier Robert<p>This driver supports the US (NIST and USNO) and European (PTB (Germany), NPL (UK), etc.) modem time services, as well as Spectracom GPS and WWVB receivers connected via a modem. The driver periodically dials a number from a telephone list, receives the timecode data and calculates the local clock correction. It is designed primarily for backup when neither a radio clock nor connectivity to Internet time servers are available. It can also be configured to operate full period.</p> 259c2daa00SOllivier Robert<p>For best results the indicated time must be corrected for the modem and telephone circuit propagation delays, which can reach 200 ms or more. For the NIST service, corrections are determined automatically by measuring the roundtrip delay of echoed characters. With this service the absolute accuracy is typically a millisecond or two. Corrections for the other services must be determined by other means. With these services variations from call to call and between messages during a call are typically a few milliseconds, occasionally higher.</p> 269c2daa00SOllivier Robert<p>This driver requires a 9600-bps modem with a Hayes-compatible command set and control over the modem data terminal ready (DTR) control line. The actual line speed ranges from 1200 bps with USNO to 14,400 bps with NIST. The modem setup string is hard-coded in the driver and may require changes for nonstandard modems or special circumstances.</p> 279c2daa00SOllivier Robert<p>There are three modes of operation selected by the <tt>mode</tt> keyword in the <tt>server</tt> configuration command. In manual mode (2) the calling program is initiated by setting fudge <tt>flag1</tt>. This can be done manually using <tt>ntpq</tt>, or by a cron job. In auto mode (0) <tt>flag1</tt> is set at each poll event. In backup mode (1) <tt>flag1</tt> is set at each poll event, but only if no other synchronization sources are available.</p> 289c2daa00SOllivier Robert<p>When <tt>flag1</tt> is set, the calling program dials the first number in the list specified by the <tt>phone</tt> command. If the call fails for any reason, the program dials the second number and so on. The phone number is specified by the Hayes ATDT prefix followed by the number itself, including the prefix and long-distance digits and delay code, if necessary. The <tt>flag1</tt> is reset and the calling program terminated if (a) valid clock update has been determined, (b) no more numbers remain in the list, (c) a device fault or timeout occurs or (d) fudge <tt>flag1</tt> is reset manually using <tt>ntpq</tt>.</p> 299c2daa00SOllivier Robert<p>The driver automatically recognizes the message format of each modem time service. It selects the parsing algorithm depending on the message length. There is some hazard should the message be corrupted. However, the data format is checked carefully and only if all checks succeed is the message accepted. Corrupted lines are discarded without complaint. Once the service is known, the reference identifier for the driver is set to NIST, USNO, PTB or WWVB as appropriate.</p> 309c2daa00SOllivier Robert<p>The Spectracom radio can be connected via a modem if the radio is configured to send time codes continuously at 1-s intervals. In principle, fudge <tt>flag2</tt> enables port locking, allowing the modem to be shared when not in use by this driver. At least on Solaris with the current NTP I/O routines, this results in lots of ugly error messages.</p> 319c2daa00SOllivier Robert<p>The <tt>minpoll</tt> and <tt>maxpoll</tt> keywords of the server configuration command can be used to limit the intervals between calls. The recommended settings are 12 (1.1 hours) for <tt>minpoll</tt> and 17 (36 hours) for <tt>maxpoll</tt>. Ordinarily, the poll interval will start at <tt>minpoll</tt> and ramp up to <tt>maxpoll</tt> in a day or two.</p> 329c2daa00SOllivier Robert<h4>US Phone Numbers and Formats</h4> 339c2daa00SOllivier Robert<p>Note: Phone numbers include the entire Hayes modem command, including the <tt>ATDT</tt> and other control codes as may be necessary. For most cases only the <tt>ATDT</tt> may be necessary.</p> 349c2daa00SOllivier Robert<p><a href="http://www.boulder.nist.gov/timefreq">National Institute of Science and Technology (NIST)</a></p> 359c2daa00SOllivier Robert<p>Phone: (303) 494-4774 (Boulder, CO); (808) 335-4721 (Hawaii)</p> 369c2daa00SOllivier Robert<p><a href="http://www.boulder.nist.gov/timefreq/service/acts.htm">Data Format</a></p> 379c2daa00SOllivier Robert<p><tt>National Institute of Standards and Technology<br> 389c2daa00SOllivier Robert Telephone Time Service, Generator 3B<br> 399c2daa00SOllivier Robert Enter question mark "?" for HELP<br> 409c2daa00SOllivier Robert MJD YR MO DA H M S ST S UT1 msADV <OTM><br> 419c2daa00SOllivier Robert 47999 90-04-18 21:39:15 50 0 +.1 045.0 UTC(NIST) *<br> 429c2daa00SOllivier Robert 47999 90-04-18 21:39:16 50 0 +.1 045.0 UTC(NIST) #<br> 439c2daa00SOllivier Robert ...</tt></p> 449c2daa00SOllivier Robert<p><tt>MJD</tt>, <tt>YR</tt>, <tt>ST</tt>, <tt>UT1</tt> and <tt>UTC(NIST)</tt> are not used by this driver. The <tt><OTM></tt> on-time character "<tt>*</tt>" changes to "<tt>#</tt>" when the delay correction is valid.</p> 459c2daa00SOllivier Robert<p><a href="http://tycho.usno.navy.mil">US Naval Observatory (USNO)</a></p> 469c2daa00SOllivier Robert<p>Phone: (202) 762-1594 (Washington, DC); (719) 567-6743 (Colorado Springs, CO)</p> 479c2daa00SOllivier Robert<p><a href="http://tycho.usno.navy.mil/modem_time.html">Data Format</a> (two lines, repeating at one-second intervals)</p> 489c2daa00SOllivier Robert<p><tt>jjjjj nnn hhmmss UTC</tt></p> 499c2daa00SOllivier Robert<p>* on-time character for previous timecode message<br> 509c2daa00SOllivier Robert jjjjj modified Julian day number (not used)<br> 519c2daa00SOllivier Robert nnn day of year<br> 529c2daa00SOllivier Robert hhmmss second of day</p> 539c2daa00SOllivier Robert<p><a href="tf582_4.html">European Phone Numbers and Formats</a></p> 549c2daa00SOllivier Robert<p><a href="http://www.spectracomcorp.com">Spectracom GPS and WWVB Receivers</a></p> 559c2daa00SOllivier Robert<p>If a modem is connected to a Spectracom receiver, this driver will call it and retrieve the time in one of two formats, 0 and 2. Ordinarily, the receiver requires a <tt>T</tt> in order to return the timecode. As this driver does not send data via the modem, it must either be configured in continuous mode or be polled by another local driver.</p> 569c2daa00SOllivier Robert<h4>Monitor Data</h4> 579c2daa00SOllivier Robert<p>The received timecode is written as-is to the <tt>clockstats</tt> file along with the Hayes connection and hang-up commands and result codes.</p> 589c2daa00SOllivier Robert<h4>Fudge Factors</h4> 599c2daa00SOllivier Robert<dl> 609c2daa00SOllivier Robert <dt><tt>time1 <i>time</i></tt></dt> 619c2daa00SOllivier Robert <dd>Specifies the time offset calibration factor, in seconds and fraction, with default 0.0.</dd> 629c2daa00SOllivier Robert <dt><tt>time2 <i>time</i></tt></dt> 639c2daa00SOllivier Robert <dd>Not used by this driver.</dd> 649c2daa00SOllivier Robert <dt><tt>stratum <i>number</i></tt></dt> 659c2daa00SOllivier Robert <dd>Specifies the driver stratum, in decimal from 0 to 15, with default 0.</dd> 669c2daa00SOllivier Robert <dt><tt>refid <i>string</i></tt></dt> 679c2daa00SOllivier Robert <dd>Set by the driver to (one of) <tt>NIST</tt>, <tt>USNO</tt>, <tt>PTB</tt> or <tt>WWVB</tt>.</dd> 689c2daa00SOllivier Robert <dt><tt>flag1 0 | 1</tt></dt> 699c2daa00SOllivier Robert <dd>Initiate a call if 1. Automatically reset by program.</dd> 709c2daa00SOllivier Robert <dt><tt>flag2 0 | 1</tt></dt> 719c2daa00SOllivier Robert <dd>Enables port locking if 1, disables if 0 (default).</dd> 729c2daa00SOllivier Robert <dt><tt>flag3 0 | 1</tt></dt> 739c2daa00SOllivier Robert <dd>Not used by this driver.</dd> 749c2daa00SOllivier Robert <dt><tt>flag4 0 | 1</tt></dt> 759c2daa00SOllivier Robert <dd>Not used by this driver.</dd> 769c2daa00SOllivier Robert</dl> 779c2daa00SOllivier Robert<h4>Additional Information</h4> 789c2daa00SOllivier Robert<p><a href="../refclock.html">Reference Clock Drivers</a> </p> 799c2daa00SOllivier Robert<hr> 809c2daa00SOllivier Robert<script type="text/javascript" language="javascript" src="scripts/footer.txt"></script> 819c2daa00SOllivier Robert</body> 829c2daa00SOllivier Robert</html> 839c2daa00SOllivier Robert