Cisco 521SG - Unified IP Phone VoIP Administration Manual page 136

Configuring Security, Quality, and Network Features
Configuring Voice Codecs
Cisco Small Business SPA300 Series, SPA500 Series, and WIP310 IP Phone Administration Guide
Parameter
Silence Supp
Enable
DTMF Tx Method
DTMF Tx Volume
for AVT Packet
Description
To enable silence suppression so that silent audio frames
are not transmitted, select yes. Otherwise, select no.
Defaults to no.
The method for transmitting DTMF signals to the far end.
The options are: InBand, audio video transport (AVT), INFO,
Auto, InBand+INFO, or AVT+INFO.
• InBand sends DTMF by using the audio path.
• AVT sends DTMF as AVT events.
• INFO uses the SIP INFO method.
• Auto uses InBand or AVT based on the outcome of
codec negotiation.
Defaults to Auto.
Allows you to manually configure the AVT Tx volume. The
value of this parameter is inserted into the volume field of
the payload in the AVT packet.
Values are based on the AVT specification as described in
RFC-2833, RTP Payload for DTMF Digits, Telephony Tones
and Telephony Signals
volume field is represented by 6 bits, and describes the
power level of the tone, expressed in dBm0 after dropping
the sign.
Valid range for this parameter is 0 to 63. If the provisioned
value is negative, it is negated first. Thereafter, if the value
is beyond the high limit of 63, it is clipped to 63.
The default value is 0 and the recommended setting.
However, some gateways do not accept this volume
setting. If the gateway does not accept a value of 0, the
DTMF tone is not relayed to the remote end. As a
workaround for the phone to interoperate with those
gateways, you can change the value to a value greater
than 0.
. According to RFC-2833, the
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