Cisco SPA303 Administration Manual page 141

Configuring Security, Quality, and Network Features
Configuring Voice Codecs
Cisco Small Business SPA300 Series, SPA500 Series, and WIP310 IP Phone Administration Guide
Parameter
Release Unused
Codec
DTMF Process AVT
Silence Supp Enable
DTMF Tx Method
DTMF Tx Volume
for AVT Packet
Description
Allows the release of codecs not used after codec negotiation
on the first call so that other codecs can be used for the
second line. To use this feature, select yes.
Defaults to yes.
Select yes to process RTP DTMF events. Otherwise, select no.
If this parameter is set to no, the AVT payload type is not
included in outbound SDP.
Defaults to yes.
To enable silence suppression so that silent audio frames are
not transmitted, select yes. Otherwise, select no. See
"Ensuring Voice Quality" section on page
Defaults to no.
Select the method to transmit DTMF signals to the far end:
InBand, audio video transport (AVT), INFO, Auto, InBand+INFO,
or AVT+INFO. InBand sends DTMF 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
. According to RFC 2833, the 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 will be negated first. Thereafter, if the value
is beyond the high limit of 63, it will be clipped to 63.
The default value is 0, and is the recommended setting.
However, some gateways do not accept this volume setting. If
the gateway does not accept the 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.
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