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Output attenuation and input gain for PRI circuits


Not sure if this is the right place to ask this question.

Cisco IOS voice command reference for "output attenuation" and "input gain" mentions that a default attenuation and gain plan is in effect (-6DB).

Is there a way to disable the output attenuation and input gain, basically I would like the router not to interfere with the audio at all.

The option 'no output attenuation' and "no input gain" on the pri voice port, do not seem to update the configuration, so essentially running that command sets the default, which again based on documentation leads me to believe a default gain plan will be in effect.

voice-port 0/0/0:23

playout-delay nominal 40

no comfort-noise

description PRI1

no echo-cancel enable


3 Replies 3

Daniele Giordano
Rising star
Rising star

There are no specific commands to disable input and output attenuation.
You can use output attenuation -6 and input gain 6.

In this case the gateway doesn't change original volume values.

If you have volume issue you can use also voicecaps commands.

You can set IP gain, PSTN gain and dynamic attenuation.
See this link:

P.S. Voice port changing takes effect  only after shutdown and no shutdown.



Thanks for the quick reply.

I am a little confused

Referring to this paragraph from the configuration guide,

"A system-wide loss plan must be implemented using both the input gain and output attenuation commands. You must consider other equipment (including PBXs) in the system when creating a loss plan. The default value for this command assumes that a standard transmission loss plan is in effect, meaning that there must be an attenuation of –6 dB between phones. Connections are implemented to provide –6 dB of attenuation when the input gain and output attenuation commands are configured with the default value of 0 dB."

But If in the above description, attenuation of -6DB means a corresponding configuration of "output attentionation 6" in that case setting output attenuation to -6 fits well, after some thought this seems like the right thing, but wanted to get it clarified.

Also the platform we are using is a 2811 which does not have the nextport stuff, is there anything specific to the ISR platforms for fine tuning gain/echo-cancellation issues?

Thanks again.

In case someone else runs into this and finds this thread.

The "output attenuation -6" is the right setting to avoid altering the audio and this would be the loudest setting, anything numerically higher (i.e. -5 through 14) would lower the volume.

(you cannot increase the volume that goes to PSTN, at least not using the "output attenuation" command)

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