input gain and output attenuation on Cisco Voice Gateway Router

Posted on 2013-10-28
Last Modified: 2013-11-21
The lovely world of VOIP and analog phone lines has been making my brain hurt:)  So I have a customer who has 9 analog phone lines plugged into FXO ports on a Cisco router.  I've been getting complaints about call volume for some time now.  The number one complaint I am getting is when a user calls the office from their cell phone, they have a hard time hearing each other.  I've tested every phone line by plugging it directly into an analog phone line, and all 9 lines tested fine.  Then then tested each port on the FXO cards and they tested fine as well.  I did notice that calls coming in from cell phones do have lower volume, which is weird, and I noticed this while testing the analog phone lines completely bypassing the Voice gateway router, so I know if not the router.  Will changing the input gains or output attenuation help increase volume?  Here is what a FXO port currently looks like:

Voice_Gateway_Router1#show voice port

Foreign Exchange Office (FXO4-M1/M2/M3) 2/0 Slot is 0, Sub-unit is 2, Port is 0
 Type of VoicePort is FXO
 Operation State is DORMANT
 Administrative State is UP
 No Interface Down Failure
 Description is not set
 Noise Regeneration is enabled
 Non Linear Processing is enabled
 Non Linear Mute is disabled
 Non Linear Threshold is -21 dB
 Music On Hold Threshold is Set to -38 dBm
 In Gain is Set to 8 dB
 Out Attenuation is Set to 3 dB
 Echo Cancellation is enabled
 Echo Cancellation NLP mute is disabled
 Echo Cancellation NLP threshold is -21 dB
 Echo Cancel Coverage is set to 64 ms
 Echo Cancel worst case ERL is set to 6 dB
 Playout-delay Mode is set to adaptive
 Playout-delay Nominal is set to 60 ms
 Playout-delay Maximum is set to 250 ms
 Playout-delay Minimum mode is set to default, value 40 ms
 Playout-delay Fax is set to 300 ms
 Connection Mode is plar
 Connection Number is 2001
 Initial Time Out is set to 10 s
 Interdigit Time Out is set to 10 s
 Call Disconnect Time Out is set to 60 s
 Ringing Time Out is set to 180 s
 Wait Release Time Out is set to 30 s
 Companding Type is u-law
 Region Tone is set for US

 Analog Info Follows:
 Currently processing none
 Maintenance Mode Set to None (not in mtc mode)
 Number of signaling protocol errors are 0
 Impedance is set to 600r Ohm
 Station name None, Station number None

 Caller ID Info Follows:
 Standard BELLCORE
 Caller ID is received after 2 ring(s)
 Translation profile (Incoming):
 Translation profile (Outgoing):

I never have problems with customers phone lines that come in on a digital circuit, it seems to always be customers who have analog phone lines.
Question by:denver218
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Accepted Solution

Robert Sutton Jr earned 500 total points
ID: 39605733
Have you tried a THL tone sweep to determine the best match impedance setting? I see you are set to 600 Real which is standard for N. America. Have a look over here...

Let us know.

Author Closing Comment

ID: 39667181

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