Draytek Vigor2820 Series User Manual page 199

MISC
DTMF
Dial Tone Power Level - This setting is used to adjust the
loudness of the dial tone. The smaller the number is, the louder
the dial tone is. It is recommended for you to use the default
setting.
Ring Frequency - This setting is used to drive the frequency
of the ring tone. It is recommended for you to use the default
setting. Notice that such setting is not available for DECT
phone port.
DTMF Mode – There are four DTMF modes for you to
choose.
InBand - Choose this one then the Vigor will send the DTMF
tone as audio directly when you press the keypad on the
phone.
OutBand - Choose this one then the Vigor will capture the
keypad number you pressed and transform it to digital form
then send to the other side; the receiver will generate the tone
according to the digital form it receive. This function is very
useful when the network traffic congestion occurs and it still
can remain the accuracy of DTMF tone.
SIP INFO- Choose this one then the Vigor will capture the
DTMF tone and transfer it into SIP form. Then it will be sent
to the remote end with SIP message.
Payload Type (rfc2833) - Choose a number from 96 to 127,
the default value was 101. This setting is available for the
OutBand (RFC2833) mode.
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Vigor2820 Series User's Guide