[Asterisk-Users] Channel bank timing

[Rich Adamson]

> Can anyone help me understand channel bank timing? I have a server with 
> a Sangoma A104 T1 card connected to two channel banks and I am having 
> audio problems that is clearly timing errors. I thought I understood how 
> to configure it but clearly I don't.
> All my incoming lines are PSTN, I do not have access to PRI. All my 
> extension phones are SIP. My asterisk version is 1.2.1.
> 
> Channel bank 1: Adtran 600 with 12 FXO:
> Timing set to Network on CB
> /etc/zapata.conf: span=1,0,0,esf,b8zs
> 
> 
> Channel Bank 2: Adtran 750 with 12 FXO
> Timing set to loop on channel bank controller
> span=2,0,0,esf,b8zs
> 
> With this configuration I am getting choppy sound. What should they be 
> set to?

I don't believe the above config is correct.

Pick one of the channel banks and declare it as your source for timing.
I'll pick CB1 so as to follow through the words below.

Both channel banks will be generating timing/clock signals within their
transmit leg towards the asterisk box. That is part of T1/E1 low level
protocol design and you can't change it even if you wanted to.

On the asterisk T1 port connected to CB1, use:
 span=1,1,0,esf,b8zs
where the second "1" tells your asterisk T1 card to use this port for
syncing the onboard T1 clock (on the Sangoma card).

On the asterisk T1 port connected to CB2, use:
 span=2,2,0,esf,b8zs
where the second "2" tells your asterisk T1 card to use this port for
sync "if" the first port does dead, fails, cable is disconnected, or for
any other reason that would essentially represent a failure of CB1.

On CB2, configure it to obtain "its" clock sync from the T1. (I don't
have any Adtrans around, so can't tell you exactly what the setting
words are.)

On CB1, configure it to use internal T1 clocking (whatever words those
happen to be for an Adtran).

If you just want to play around without changing the CB at all, just
change the second digit in "span=1,0,0,esf,b8zs" to indicate that its
your source for timing. Only one span= statement can have a "1".

I'm not 100% sure on this next statement, but would guess you'll need to
stop asterisk and reload the T1 card drivers (or simply reboot).