Cisco MC3810-APM-FXO= Datasheet download pdf (Page 75)

Configuring Voice Ports

Troubleshooting Analog and Digital Voice Port Configurations

VC-109

Cisco IOS Voice, Video, and Fax Configuration Guide

Distorted speech Use the show voice port command to confirm the cptone

keyword setting (also called region tone) is US.

Setting a wrong cptone could result in faulty voice reproduction

during analog-to-digital or digital-to-analog conversions.

Music on hold is not heard Reduce the music-threshold level.

Background noise is not heard Enable the comfort-noise command.

Long pauses occur in

conversation; like speaking on a

walkie-talkie

Overall delay is probably excessive; the standard for adequate

voice quality is 150 ms one-way transit delay. Measure delay by

using ping tests at various times of the day with different network

traffic loads. If delay must be reduced, areas to examine include

propagation delay of signals between the sending and receiving

endpoints, voice encoding delay, and the voice packetization time

for various VoIP codecs.

Jerky or choppy speech Variable delay, or jitter, is being introduced by congestion in the

packet network. Two possible remedies are to:

• Reduce the amount of congestion in your packet network.

Pings between VoIP endpoints will give an idea of the

round-trip delay of a link, which should never exceed 300 ms.

Network queuing and dropped packets should also be

examined.

• Increase the size of the jitter buffer with the playout-delay

command. (See the “Jitter Adjustment” section on page 92.)

Clipped or fuzzy speech Reduce input gain. (See the “Voice Level Adjustment” section on

page 96.)

Clipped speech Reduce the input level at the listener’s router. (See the “Voice

Level Adjustment” section on page 96.)

Volume too low or missed DTMF Increase speaker’s output level or listener’s input level. (See the

“Voice Level Adjustment” section on page 96.)

Echo interval is greater than 25 ms

(sounds like a separate voice)

Configure the echo-cancel enable command and increase the

value for the echo-cancel coverage keyword. (See the “Echo

Adjustment” section on page 94.)

Too much echo Reduce the output level at the speaker’s voice port. (See the

“Voice Level Adjustment” section on page 96.)

Table 10 Troubleshooting Voice Port Conﬁgurations (continued)

Problem Suggested Action

1 ... 74 75 76 77 78 79 80 81 82

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