make timing source configuration easier to understand (issue #5356)

git-svn-id: http://svn.digium.com/svn/zaptel/trunk@790 5390a7c7-147a-4af0-8ec9-7488f05a26cb

1 files changed, 23 insertions, 6 deletions

diff --git a/zaptel.conf.sample b/zaptel.conf.sample
index ac98114..e6cf6c5 100755
--- a/zaptel.conf.sample
+++ b/zaptel.conf.sample
@@ -5,12 +5,29 @@
 #
 #
 # First come the span definitions, in the format
-# span=<span num>,<timing>,<line build out (LBO)>,<framing>,<coding>[,yellow]
-# 
-# The timing parameter determines the selection of primary, secondary, and
-# so on sync sources.  If this span should be considered a primary sync
-# source, then give it a value of "1".  For a secondary, use "2", and so on.
-# To not use this as a sync source, just use "0"
+# span=<span num>,<timing source>,<line build out (LBO)>,<framing>,<coding>[,yellow]
+#
+# All T1/E1 spans generate a clock signal on their transmit side. The
+# <timing source> parameter determines whether the clock signal from the far
+# end of the T1/E1 is used as the master source of clock timing. If it is, our
+# own clock will synchronise to it. T1/E1's connected directly or indirectly to
+# a PSTN provider (telco) should generally be the first choice to sync to. The
+# PSTN will never be a slave to you. You must be a slave to it.
+#
+# Choose 1 to make the equipment at the far end of the E1/T1 link the preferred
+# source of the master clock. Choose 2 to make it the second choice for the master
+# clock, if the first choice port fails (the far end dies, a cable breaks, or
+# whatever). Choose 3 to make a port the third choice, and so on. If you have, say,
+# 2 ports connected to the PSTN, mark those as 1 and 2. The number used for each
+# port should be different.
+#
+# If you choose 0, the port will never be used as a source of timing. This is
+# appropriate when you know the far end should always be a slave to you. If the
+# port is connected to a channel bank, for example, you should always be its
+# master. Any number of ports can be marked as 0.
+#
+# Incorrect timing sync may cause clicks/noise in the audio, poor quality or failed
+# faxes, unreliable modem operation, and is a general all round bad thing.
 #
 # The line build-out (or LBO) is an integer, from the following table:
 # 0: 0 db (CSU) / 0-133 feet (DSX-1)