Summary:ASTERISK-05213: Getting the clocking right for E1 and T1 lines
Reporter:steveu (steveu)Labels:
Date Opened:2005-10-02 03:42:33Date Closed:2008-06-07 11:05:12
Versions:Frequency of
Environment:Attachments:( 0) zaptel.conf.sample.patch
Description:If the wording about setting clock sources in zaptel.conf.sample is changed to that below I think I will have a lot less support issues with spandsp. :-) This was discussed some time ago on the mailing list, but it looks like CVS was never changed. I think the *majority* of users currently have their clock sources set incorrectly, and the current wording makes the adamant they are right.

# 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.
# Chose 1 to make the equipment at the far end of the E1/T1 link the preferred
# source of the master clock. Chose 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). Chose 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 awlways 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.
Comments:By: Jared Smith (jsmith) 2005-10-02 08:54:20

Personally, I think this is a great idea.  I see people misinterpret the timing all the time, and the timing set to 0 on all their spans.

By: Olle Johansson (oej) 2005-10-02 15:08:35

Please provide a patch for the sample config file.

By: steveu (steveu) 2005-10-02 18:48:45

I have uploaded the same change as a patch file.

By: Russell Bryant (russell) 2005-10-04 15:03:23

Very nice.  I think it's very informative, and will probably reduce the number of problems Digium support has with these issues as well.

It looks like there might be a few typos, though.  In the second paragraph, did you mean for "Chose" to be "Choose" ?

By: Russell Bryant (russell) 2005-10-04 15:05:29

Oh, and in the 3rd paragraph, "awlways" --> "always".

By: Kevin P. Fleming (kpfleming) 2005-10-04 18:52:09

Committed to CVS HEAD, thanks!

By: Digium Subversion (svnbot) 2008-06-07 11:05:12

Repository: dahdi
Revision: 790

U   trunk/zaptel.conf.sample

r790 | kpfleming | 2008-06-07 11:05:08 -0500 (Sat, 07 Jun 2008) | 2 lines

make timing source configuration easier to understand (issue ASTERISK-5213)