Cisco MC3810-APM-FXO= Datasheet download pdf (Page 62)

Configuring Voice Ports

Configuring Digital Voice Ports

VC-96

Cisco IOS Voice, Video, and Fax Configuration Guide

Voice Level Adjustment

As much as possible, it is desirable to achieve a uniform input decibel level to the packet voice network

in order to limit or eliminate any voice distortion due to incorrect input and output decibel levels.

Adjustments to levels may be required by the type of equipment connected to the network or by local

country-specific conditions.

Incorrect input or output levels can cause echo, as can an impedance mismatch. Too much input gain can

cause clipped or fuzzy voice quality. If the output level is too high at the remote router’s voice port, the

local caller will hear echo. If the local router’s voice port input decibel level is too high, the remote side

will hear clipping. If the local router’s voice port input decibel level is too low, or the remote router’s

output level is too low, the remote side voice can be distorted at a very low volume and DTMF may be

missed.

Use the input gain and output attenuation commands to adjust voice levels, and the impedance

command to set the impedance value to match that of the voice circuit to which the voice port connects.

To change parameters related to voice levels, use the following commands as appropriate, in voice-port

configuration mode:

Command Purpose

Step 1

Router(config-voiceport)# input gain

value

Specifies, in decibels, the amount of gain to be

inserted at the receiver side of the interface,

increasing or decreasing the signal. After an input

gain setting is changed, the voice call must be

disconnected and reestablished before the changes

take effect. The value argument is any integer

from –6 to 14. The default is 0.

Step 2

Router(config-voiceport)# output attenuation

value

Specifies the amount of attenuation in decibels at

the transmit side of the interface, decreasing the

signal. A system-wide loss plan can be

implemented using the input gain and output

attenuation commands.

The default value for this command assumes that

a standard transmission loss plan is in effect,

meaning that normally there must be –6 dB

attenuation between phones.

The value argument is any integer from –6 to 14.

The default is 0.

Step 3

Router(config-voiceport)# impedance {600c | 600r |

900c | complex1 | complex2}

Specifies the terminating impedance of a voice

port interface, which needs to match the

specifications from the specific telephony system

to which it is connected.

• 600c—Specifies 600 ohms complex.

• 600r—Specifies 600 ohms real.

• 900c—Specifies 900 ohms complex.

• complex1—Specifies Complex 1.

• complex2—Specifies Complex 2.

The default is 600r.

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Cisco MC3810-APM-FXO= Datasheet Page 62

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