ZyXEL Communications NVG2053, Руководство пользователя

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Chapter 17 Voice
NVG2053 User’s Guide
175
Primary
Compression
Type
Secondary
Compression
Type
Third
Compression
Type
Select the type of voice coder/decoder (codec) that you want the
NVG2053 to use.
G.711 provides high voice quality but requires more bandwidth (64
kbps). G.711 is the default codec used by phone companies and digital
handsets.
• G.711a is typically used in Europe.
• G.711u is typically used in North America and Japan.
G.722 is a 7 KHz wideband voice codec that operates at 48, 56 and 64
kbps. By using a sample rate of 16 kHz, G.722 can provide higher
fidelity and better audio quality than narrowband codecs like G.711, in
which the voice signal is sampled at 8 KHz.
G.723.1 is an ITU (International Telecommunication Union) standard
for voice coding. The G.723.1 codec compresses voice audio in 30 ms
frames. The G.723.1 operates at two bitrates: 6.3 kbps when sampling
at 24 bytes or 5.3 kbps when sampling at 20 bytes per 30 ms frame.
G.726 is an Adaptive Differential Pulse Code Modulation (ADPCM)
waveform codec that uses a lower bitrate than standard PCM
conversion. Differential (or Delta) PCM is similar to PCM, but encodes
the audio signal based on the difference between one sample and a
prediction based on previous samples, rather than encoding the
sample’s actual quantized value. G.726 operates at 16, 24, 32 or 40
kbps.
G.729 is an Analysis-by-Synthesis (AbS) hybrid waveform codec. It
uses a filter based on information about how the human vocal tract
produces sounds. G.729 provides good sound quality and reduces the
required bandwidth to 8kbps.
The NVG2053 must use the same codec as the peer. When two SIP
devices start a SIP session, they must agree on a codec.
Select the NVG2053’s first choice for voice coder/decoder.
Select the NVG2053’s second choice for voice coder/decoder. Select
None if you only want the NVG2053 to accept the first choice.
Select the NVG2053’s third choice for voice coder/decoder. Select None
if you only want the NVG2053 to accept the first or second choice.
Call Features
Send Caller ID
Select this if you want to send identification when you make VoIP phone
calls. Clear this if you do not want to send identification.
Enable Call
Transfer Select this to enable call transfer on the NVG2053. This allows you to
transfer an incoming call (that you have answered) to another phone.
Enable Call
Waiting Select this to enable call waiting on the NVG2053. This allows you to
place a call on hold while you answer another incoming call on the same
telephone number.
Call Waiting
Reject Timer Specify a time of seconds that the NVG2053 waits before rejecting the
second call if you do not answer it.
Table 57 VoIP > SIP > SIP Account: Add (continued)
LABEL DESCRIPTION