Cisco 7975G Troubleshooting And Maintenance

Listening quality scores (MOS LQK) relate to the clarity or sound of the received voice signal. Conversational
quality scores (MOS CQ such as G.107) include impairment factors, such as delay, that degrade the natural
flow of conversation.
You can access voice quality metrics from the Cisco Unified IP Phone by using the Call Statistics screen (see
Call Statistics Screen) or remotely by using Streaming Statistics (see Remote Monitoring).
Voice Quality Metric Interpretation
To use the metrics for monitoring voice quality, note the typical scores under normal conditions of zero packet
loss and use the metrics as a baseline for comparison.
It is important to distinguish significant changes from random changes in metrics. Significant changes are
scores that change about 0.2 MOS or greater and persist in calls that last longer than 30 seconds. Conceal
Ratio changes should indicate greater than 3 percent frame loss.
MOS LQK scores can vary based on the codec that the Cisco Unified IP Phone uses. The following codecs
provide these maximum MOS LQK scores under normal conditions with zero frame loss:
• For Cisco Unified Phone 7975G, 7965G, and 7945G:
• G.711 gives 4.5 score.
• G.722 gives 4.5.
• G.728/iLBC gives 3.9.
• G.729A/AB gives 3.8.
• For Cisco Unified Phone 7971G-GE and 7970G:
• G.711 codec gives 4.5 score.
• G.729A/AB gives 3.7.
• CVTQ does not support wideband (7 kHz) speech codecs, as ITU has not defined the extension of the
technique to wideband. Therefore, MOS scores that correspond to G.711 performance are reported for
G.722 calls to allow basic quality monitoring, rather than not reporting an MOS score.
• Reporting G.711-scale MOS scores for wideband calls through the use of CVTQ allows basic quality
classifications to be indicated as good/normal or bad/abnormal. Calls with high scores (approximately
4.5) indicate high quality/low packet loss, and lower scores (approximately 3.5) indicate low quality/high
packet loss.
• Unlike MOS, the Conceal Ratio and Concealed Seconds metrics remain valid and useful for both wideband
and narrowband calls.
Note
A Conceal Ratio of zero indicates that the IP network is delivering frames and packets on time with no loss.
Voice Quality Troubleshooting Tips
When you observe significant and persistent changes to metrics, use the following table for general
troubleshooting information:
Troubleshooting and Maintenance
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Troubleshooting and Maintenance
Voice Quality Metric Interpretation

Cisco 7975G Specifications

General

Handset type	Wired handset
Product type	IP Phone
Product color	Grey, Silver
Speakerphone	Yes
Voice codecs	G.711Mu, G.711a, G.722, G.729A, iLBC
Number of melodies	24
Aspect ratio	4:3
Display diagonal	5.6 \
Display resolution	320 x 240 pixels
Lines quantity	8 lines
Phonebook capacity	- entries
Number of VoIP accounts	-
Front camera	No
Security algorithms	128-bit AES
Networking standards	IEEE 802.1Q, IEEE 802.1p, IEEE 802.1x, IEEE 802.3af
Ethernet LAN data rates	10, 100, 1000 Mbit/s
Ethernet LAN interface type	Gigabit Ethernet
Supported network protocols	DHCP, TFTP
Volume control	Digital
Headphone outputs	1
Ethernet LAN (RJ-45) ports	2
Number of handles included	1 pc(s)
AC adapter output voltage	48 V
Storage temperature (T-T)	-10 - 60 °C
Operating temperature (T-T)	0 - 40 °C
Operating relative humidity (H-H)	10 - 95 %
Certification	FCC

Weight and Dimensions

Depth	152.4 mm
Width	266.7 mm
Height	203.2 mm
Weight	1600 g