Linksys VOICE SYSTEM SPA 900 SERIES - Manual (Page 15)

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Linksys IP Phone Administrator Guide
Firmware Version 5.1
Chapter 1 Introducing Linksys IP Phones
Linksys IP Phone Features
SPA92x, SPA94x, SPA962
The SPA921, SPA922, SPA941, SPA942, and SPA962 provide an LCD display and additional features
that are not provided with the SPA901, including the following:
• Line Status Indicators: Active Line, Name, and Number
• Menu-Driven User Interface
• Digits Dialed with Number Auto-Completion
• Caller ID Name and Number and Outbound Caller ID Blocking
• On-Hook Dialing
• Redial from Call Logs
• Personal Directory with Auto-dial (100 entries)
• On Hook Default Audio Configuration (Speakerphone and Headset)
• Called Number with Directory Name Matching
• Call Number using Name - Directory Matching or via Caller ID
• Subsequent Incoming Calls with Calling Name and Number
• Name and Identity (Text) Displayed at Start Up
• Distinctive Ringing Based on Calling and Called Number
Ensuring Voice Quality
Voice quality perceived by the subscribers of the IP Telephony service should be indistinguishable from
that of the PSTN. Voice quality can be measured with such methods as Perceptual Speech Quality
Measurement (PSQM), with a scale of 1–5, in which lower is better; and Mean Opinion Score (MOS),
with a scale of 1–5, in which higher is better.
Table 1-2 displays speech quality metrics associated with various audio compression algorithms. For
information about bandwidth requirements for each supported codec, refer to Table 2-1 on page 2-10 .
Note Linksys IP phones support all the above voice coding algorithms.
Table 1-2 Speech Quality Metrics
Algorithm Complexity MOS Score
G.711 Very low 4.5
G.726 Low 4.1 (32 kbps)
G.729a Low–medium 4
G.729 Medium 4
G.723.1 High 3.8