asterisk users - Oct 2005 - zap group channels

Hi,

Am having a problem with Zap group channels.  Wondering if anyone has 
seen the same and if there is a quick solution.

I have  bonded multiple zap channels to a group for outbound calling, 
e.g. channels 3 and 4 are in Zap/g2.

We have an intermittent problem with our PSTN provider in that from time 
to time the POTS line on channel 3 is not operative i.e. no dial tone.  
The problem resolves itself after a few hours usually and we're back to 
normal.

The problem is that during the outage, Asterisk doesn't recognize that 
there is no dial tone on channel 3 and still passes the call to that 
channel.  Obviously the call is never completed and the caller has no 
idea why.  I have tried to alter the order that Asterisk chooses 
outbound channels but haven't had any success.  So, my questions are:

1) How to force asterisk to choose the order of lines in a channel 
group, and
2) If there is a conf variable that will effect asterisk in a way so 
that it recognizes there is no dial tone on a line.

Am using the basic zapata.conf for asterisk example config, with 
following channel specific settings

; FXO lines (incoming from PSTN)
context=pstn-in
group=2
signalling=fxs_ks
channel=4,3
busydetect=yes

Thanks,

Rob

> Am having a problem with Zap group channels.  Wondering if anyone has 
> seen the same and if there is a quick solution.
> 
> I have  bonded multiple zap channels to a group for outbound calling, 
> e.g. channels 3 and 4 are in Zap/g2.
> 
> We have an intermittent problem with our PSTN provider in that from time 
> to time the POTS line on channel 3 is not operative i.e. no dial tone.  
> The problem resolves itself after a few hours usually and we're back to
> normal.
> 
> The problem is that during the outage, Asterisk doesn't recognize that 
> there is no dial tone on channel 3 and still passes the call to that 
> channel.  Obviously the call is never completed and the caller has no 
> idea why.  I have tried to alter the order that Asterisk chooses 
> outbound channels but haven't had any success.  So, my questions are:
> 
> 1) How to force asterisk to choose the order of lines in a channel 
> group, and
> 2) If there is a conf variable that will effect asterisk in a way so 
> that it recognizes there is no dial tone on a line.
Assuming you are using the TDM card, there is no code in asterisk to 
detect whether a pstn line is connected/disconnected, nor does it listen
for dialtone before dialing.