= TrueTime GPS/GOES Receivers
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== Synopsis

["verse",subs="normal"]
Name: truetime
Reference ID: TRUE
Serial Port: +/dev/true+'u'; 9600 bps 8N1
Features: +tty_clk+

== Deprecation warning

This refclock is deprecated and obsolete. The NTPsec maintainers plan
to remove it in a future release.  If you have a requirement for it,
please make this known to us.

This driver reports only two-digit years, and is thus reliant on the
system clock to be near correct before samples will be processed
properly. You will not be able to use it to run autonomously, nor will
it reliably recover from a trashed or zeroed system clock.

It is likely any surving instances of this hardware will have
era-rollover issues when reporting dates. One or more "g" suffixes
on your 'time1' option may be useful as a workaround.

== Description

This driver supports several models of Kinemetrics/TrueTime
timing receivers, including GPS- DC MK III and GPS/TM-TMD GPS
Synchronized Clock, XL-DC (a 151-602-210, reported by the driver as a
GPS/TM-TMD), GPS-800 TCU (an 805-957 with the RS232 Talker/Listener
module), and very likely others in the same model families that use
the same timecode formats.

Most of this code is originally from refclock_wwvb.c (now
refclock_spectracom.c) with thanks. It has been so mangled that wwvb is
not a recognizable ancestor.

[literal]
Timecode format: ADDD:HH:MM:SSQCL
A - control A (this is stripped before we see it)
Q - Quality indication (see below)
C - Carriage return
L - Line feed


Quality codes indicate possible error of:

--------------------------------------------------
GPS-TM/TMD Receiver
    ? +/- 500 milliseconds # +/- 50 milliseconds
    * +/- 5 milliseconds . +/- 1 millisecond
    space less than 1 millisecond
--------------------------------------------------

In general, an alarm condition is indicated by ? at A, which occurs during
initial synchronization and when received signal is lost for an
extended period; unlock condition is indicated by other than <SP>
in the quality field.

== Notes on the TL-3 receiver:

The mini-DIN RS-232 port uses the Apple pinout.

Send the clock ST1 to turn on continuous (1/s) timecodes. You can
also enable "mode C" via the front panel. ST0 turns off this mode.

QV will return the firmware revision (and is useful in identifying
this clock.)

QW will return its weekly signal log, useful if you're testing
antennas. You may wish to turn the loss interval down from 4 h (04) to 1 h
(01), so the receiver declares itself unlocked sooner. When in holdover,
drift can be on the order of 10 ms/hr since there is no high quality
reference oscillator.

== Monitor Data

When enabled by the +flag4+ option, every received timecode is
written as-is to the +clockstats+ file.

== Driver Options

+unit+ 'number'::
  The driver unit number, defaulting to 0. Used as a distinguishing
  suffix in the driver device name.
+time1+ 'time'::
   Specifies the time offset calibration factor, in seconds and fraction,
   to be used for the West satellite, with default 0.0.
+time2 time+::
   Specifies the time offset calibration factor, in seconds and fraction,
   to be used for the East satellite, with default 0.0.
+stratum+ 'number'::
   Specifies the driver stratum, in decimal from 0 to 15, with default 0.
+refid+ 'string'::
   Specifies the driver reference identifier, an ASCII string from one to
   four characters, with default +TRUE+.
+flag1 {0 | 1}+::
   Silence the clock side of ntpd, just reading the clock without trying to
   write to it.
+flag2 {0 | 1}+::
   Generate a debug file /tmp/true%d.
+flag3 {0 | 1}+::
   Not used by this driver.
+flag4 {0 | 1}+::
   Enable verbose +clockstats+ recording if set.
+subtype+::
   Not used by this driver.
+mode+::
   Not used by this driver.
+path+ 'filename'::
  Overrides the default device path.
+ppspath+ 'filename'::
  Not used by this driver.
+baud+ 'number'::
  Overrides the default baud rate.

== Configuration Example

----------------------------------------------------------------------------
refclock truetime
----------------------------------------------------------------------------

== Additional Information

link:refclock.html[Reference Clock Drivers]

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