Changing input gain and output attenuation on Voice Port

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Aug 13th, 2008
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one of our customers in Germany has a VoIP network consisting of a CUCM cluster and 2 Voice Gateways (Cisco 2811, IOS c2800nm-ipvoicek9-mz.124-15.T6.bin).

As the title already indicates, PSTN users are complaining about low volume on calls with users on this VoIP network.

Cisco suggests the following solution (adjusting input gain and output ettenuation):

Since my experience is limited in the VoIP field, my question is if this solution has any side-effects which one should be concerned about. If its relevant, we also have fax calls across these Voice Gateways. No other PBX is connected.

Here is some of the cofiguration that might be relevant:


interface Serial0/0/0:15

no ip address

encapsulation hdlc

isdn switch-type primary-net5

isdn timer T310 10000

isdn overlap-receiving T302 6000

isdn incoming-voice voice

isdn number called enbloc 1

isdn outgoing-voice info-transfer-capability 3.1kHz-audio

no cdp enable



controller E1 0/0/0

pri-group timeslots 1-31



voice service voip

no supplementary-service h225-notify cid-update


h225 timeout t302 6

h225 signal overlap

no h225 alt-ep hunt user-busy

call start slow



voice-port 0/0/0:15

cptone DE



dial-peer voice 1 pots

tone ringback alert-no-PI

description --------- main dial-peer in+out

destination-pattern 0

progress_ind setup enable 3

progress_ind alert enable 8

incoming called-number .


port 0/0/0:15


Would be grateful if anybody has any advice!

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Brandon Buffin Wed, 08/13/2008 - 05:09
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Can you post the output of "show controllers e1"?


ivarnhagen Wed, 08/13/2008 - 08:34
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thanks for the quick reply! The "show controllers e1" displays:

XXXXXXXXX#sh controllers E1

E1 0/0/0 is up.

Applique type is Channelized E1 - balanced

No alarms detected.

alarm-trigger is not set

Version info Firmware: 20071011, FPGA: 13, spm_count = 0

Framing is CRC4, Line Code is HDB3, Clock Source is Line.

CRC Threshold is 320. Reported from firmware is 320.

Data in current interval (403 seconds elapsed):

0 Line Code Violations, 0 Path Code Violations

0 Slip Secs, 0 Fr Loss Secs, 0 Line Err Secs, 0 Degraded Mins

0 Errored Secs, 0 Bursty Err Secs, 0 Severely Err Secs, 0 Unavail Secs

Total Data (last 24 hours)

0 Line Code Violations, 0 Path Code Violations,

0 Slip Secs, 0 Fr Loss Secs, 0 Line Err Secs, 0 Degraded Mins,

0 Errored Secs, 0 Bursty Err Secs, 0 Severely Err Secs, 0 Unavail Secs


let me know if more info, or output of any other commands is needed.


Brandon Buffin Wed, 08/13/2008 - 09:12
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I thought you might have a problem with the E1 config that was causing the problem, but it looks good. Adjusting the ouput attenuation as described in the link in your original post should not present any other problems. Start with the value indicated in the link and adjust as needed.


ivarnhagen Wed, 08/13/2008 - 09:34
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Thanks for taking a look at it! I will give it a try then! :)



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