[ntpsec commit] Update refclocks page reflecting ubiquity of GPSes.

Eric S. Raymond esr at ntpsec.org
Tue Oct 6 04:13:12 UTC 2015


Module:    ntpsec
Branch:    master
Commit:    d4b8bc5a7a3b54e0a088304f8775bf6fe78b0113
Changeset: http://git.ntpsec.org/ntpsec/commit/?id=d4b8bc5a7a3b54e0a088304f8775bf6fe78b0113

Author:    Eric S. Raymond <esr at thyrsus.com>
Date:      Mon Oct  5 22:25:33 2015 -0400

Update refclocks page reflecting ubiquity of GPSes.

---

 docs/refclock.txt | 22 ++++++++++++----------
 1 file changed, 12 insertions(+), 10 deletions(-)

diff --git a/docs/refclock.txt b/docs/refclock.txt
index ec1e19e..7665548 100644
--- a/docs/refclock.txt
+++ b/docs/refclock.txt
@@ -4,9 +4,6 @@ image:pic/stack1a.jpg[gif]Master Time Facility at the
 http://www.eecis.udel.edu/%7emills/lab.html[UDel Internet Research
 Laboratory]
 
-Last update: 10-Mar-2014 05:20 UTC
-
-
 == Related Links ==
 
 include::includes/hand.txt[]
@@ -24,7 +21,7 @@ include::includes/audio.txt[]
 [[intro]]
 == Introduction ==
 
-NTP Version 4 supports almost four dozen satellite, radio and telephone
+{project-shortname} supports almost four dozen satellite, radio and telephone
 modem reference clocks plus several audio devices for instrumentation
 signals. A general description of the reference clock support is on this
 page. Additional information about each reference clock driver can be
@@ -38,13 +35,18 @@ reference clock use only Coordinated Universal Time (UTC). Timezone and
 standard/daylight adjustments are performed by the operating system
 kernel.
 
-A reference clock will generally (though not always) be a radio timecode
+Nowadays a reference clock will generally (though not always) be a GPS or GPSDO
+(GPS-conditioned oscillator). In former times it was often a radio timecode
 receiver synchronized to standard time as provided by NIST and USNO in
-the US, NRC in Canada and their counterparts elsewhere in the world. A
-device driver specific to each reference clock must be compiled in the
-distribution; however, most common radio, satellite and telephone modem
-clocks are included by default and are activated by configuration
-commands.
+the US, NRC in Canada and their counterparts elsewhere in the world.
+Precision time radios have been extinct in the U.S. since NIST changed their
+signal modulation in 2013; elsewhere they still exist but usage is
+declining under pressure from GPS technology.
+
+A device driver specific to each reference clock must be compiled in
+the distribution; however, most common GPS, radio, satellite and
+telephone modem clocks are included by default and are activated by
+configuration commands.
 
 Reference clocks are supported in the same way as ordinary NTP clients
 and use the same filter, select, cluster and combine algorithms. Drivers



More information about the vc mailing list