Configuring Basic Features
383
X ranges from 1 to 12 (for SIP-T42G)
X ranges from 1 to 6 (for SIP-T41P/T27P)
X ranges from 1 to 3 (for SIP-T40P/T23P/T23G)
X ranges from 1 to 2 (for SIP-T21(P) E2)
X is equal to 1 (for SIP-T19(P) E2/CP860)
Web User Interface:
None
Phone User Interface:
None
DTMF (Dual Tone Multi-frequency), better known as touch-tone, is used for
telecommunication signaling over analog telephone lines in the voice-frequency band.
DTMF is the signal sent from the IP phone to the network, which is generated when
pressing the IP phone’s keypad during a call. Each key pressed on the IP phone
generates one sinusoidal tone of two frequencies. One is generated from a high
frequency group and the other from a low frequency group.
The DTMF keypad is laid out in a 4× 4 matrix, with each row representing a low
frequency, and each column representing a high frequency. Pressing a digit key (such
as '1') will generate a sinusoidal tone for each of two frequencies (697 and 1209 hertz
(Hz)).
DTMF Keypad Frequencies:
Three methods of transmitting DTMF digits on SIP calls:
RFC 2833 -- DTMF digits are transmitted by RTP Events compliant to RFC 2833.
INBAND -- DTMF digits are transmitted in the voice band.
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