Linksys SPA921-NA Administrator's Manual page 23

Chapter 1 Introducing Linksys 900 Series IP Phones
Table 1-4
Feature
Voice Activity
Detection with
Silence Suppression
and Comfort Noise
Generation
Configurable Dial
Plan with Interdigit
Timers
Report Generation
and Event Logging
Syslog and Debug
Server Records
Dynamic Payload
Call Statistics and
Reporting
Document Version 3.0
Linksys ATA Features (continued)
Description
Voice Activity Detection (VAD) with Silence Suppression is a means
of increasing the number of calls supported by the network by
reducing the required bidirectional bandwidth for a single call. VAD
uses a very sophisticated algorithm to distinguish between speech and
non-speech signals. Based on the current and past statistics, the VAD
algorithm decides whether or not speech is present. If the VAD
algorithm decides speech is not present, the silence suppression and
comfort noise generation is activated. This is accomplished by
removing and not transmitting the natural silence that occurs in
normal two-way connection. The IP bandwidth is used only when
someone is speaking. During the silent periods of a telephone call,
additional bandwidth is available for other voice calls or data traffic
because the silence packets are not being transmitted across the
network. Comfort Noise Generation provides artificially-generated
background white noise (sounds), designed to reassure callers that
their calls are still connected during silent periods. If Comfort Noise
Generation is not used, the caller may think the call has been
disconnected because of the "dead silence" periods created by the
VAD and Silence Suppression feature.
SPA900 Series IP phones have three configurable interdigit timers:
•
Initial timeout (T)—Handset off hook; no digit pressed yet.
•
Long timeout (L)—One or more digits pressed, more digits needed to
reach a valid number (as per the dial plan).
•
Short timeout (S)—Current dialed number is valid, but more digits
would also lead to a valid number.
SPA900 Series IP phones report a variety of status and error reports
to assist service providers in diagnosing problems and evaluating the
performance of their services. The information can be queried by an
authorized agent, using HTTP with digested authentication, for
instance. The information may be organized as an XML page or
HTML page.
SPA900 Series IP phones support detailed logging of all activities for
further debugging. The debug information may be sent to a
configured Syslog server. SPA900 Series IP phones provide
configuration settings that determine the type of activity/events that
should be logged, as for instance, a debug level setting.
When no static payload value is assigned per RFC 1890, SPA900
Series IP phones can support dynamic payloads for G.726.
The statistics collected by SPA900 Series IP phones during normal
operation statistics are available in the Info tab. Line status is reported
for each line (1 and 2). Each line maintains up to 2 calls: Call 1 and 2.
Linksys 900 Series IP Phone Administrator Guide
Feature Descriptions
1-9