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I have an Asterisk/Dahdi server that serves as a PSTN software PBX running on Debian with a Digium 1TE134F card. The setup has been up and running for sometime but we noticed that one of our lines is bad because the third caller into the system ( anyone who calls when two previous inbound calls are still active ) gets a connection that is so poor that they can barely hear us at all. Until it can be fixed I am trying to find a way to omit the line in our trunk -- we have seven others which is plenty.

I have tried changing channel => 1-8 to channel => 1,2,4,5,6,7,8 in chan_dahdi.conf and fxsks=1-8 to fxsks=1,2,4,5,6,7,8 /etc/dahdi/system.conf but doing so only makes it so that the third active incoming call does not get recognized at all by the Asterisk server so that the call cannot be answered at all instead of the desired affect of the call coming in on the next channel which would be Dahdi/4-1.

Does anyone know how I might be able to omit this channel? Below are my two config files mentioned above. Another solution would be for the bad line to be the last channel assigned ( assigned only for the 8th active inbound call ) but I have no idea how to do that either.

/etc/dahdi/system.conf

span=1,0,0,esf,b8zs
fxsks=1-8
fxoks=9-24

loadzone = us
defaultzone=us

/etc/asterisk/chan_dahdi.conf

[trunkgroups]
[channels]
context=default
usecallerid=yes
hidecallerid=no
;callwaiting=yes
callwaiting=no
usecallingpres=yes
callwaitingcallerid=yes
pickupgroup=1
callgroup=1
threewaycalling=yes
transfer=yes
cancallforward=yes
callreturn=yes
echocancel=yes
echocancelwhenbridged=yes
;rxgain=2.0
;txgain=1.0
immediate=no
;busydetect=no
busydetect=yes
busycount=6
musiconhold=native           

; for the POTS lines
signaling=fxs_ks
context=incoming
group=1
channel => 1-8

group=2
; for the internal phones
signaling=fxo_ks
context=internal
channel => 9-24

1 Answer 1

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I'm actually quite confused...

1TE134F is a T1/E1 card, which would use bchan/dchan. Do you have some sort of channel-bank in the middle?

fxsks and fxoks are for POTS... which don't work in T1/E1. Your problem definitely sounds like an issue related to a POTS line, but you're going to have problems when you come to know that it is up to your telco to do channel selection for incoming calls. Simply eliminating a channel from a group will not prevent your telco from passing a call down that horrible line. You'll have to call them. You can exclude it so you don't make a call on that line... but if a call comes in, it will just ring & ring, and won't signal anything in the PBX to do something with that channel.

You would need to call the telco, and exclude that line from their ring-group... then you could simply exclude the line from the group declaration:

----------------------snip----------------

; for the POTS lines
signaling=fxs_ks
context=incoming
group=1
channel => 1-2
channel => 4-8

----------------------snip----------------

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  • Sorry, the asterisk server is connected to a Adit channel bank which has one FXO and two FXS cards. The channel bank is connected to a punchdown box via an amphenol connector. The punchdown is connected via an amphenol to an Adtran 624 T1 router.
    – gatorreina
    Dec 16, 2019 at 23:20
  • Is there any way for me to see the phone numbers in my truck so I can try do determine which one to tell my telco to deactivate?
    – gatorreina
    Dec 16, 2019 at 23:22
  • That makes a bit more sense. Unfortunately POTS lines don't send DID info. So, you're out-of-luck as to getting the phone number that way. You would probably need to trace lines back to the punch-down block of your telco... and figure out which one is the bad one that way. At most, you could see channel number in the logs. You could also plug a butt-set into the punch-block and find the offending channel that way. It's possible that your channel-bank might have a bad channel on it as well.
    – TheCompWiz
    Dec 16, 2019 at 23:29
  • Thank you very much for your insights. I suspected the channel bank but all eight lights on the FXO card are green.
    – gatorreina
    Dec 16, 2019 at 23:44
  • If it is the channel-bank, you could physically move lines around the bad channel, and then adjust the dahdi config to omit the bad channel. (you'd end up with one line that is unused until you replace the channel bank, but at least it would work)
    – TheCompWiz
    Dec 17, 2019 at 15:35

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