Comfort Noise Generation (CNG) is used to generate background noise for voice communications
during periods of silence in a conversation.
Halo series phones support fixed type of jitter buffers. A fixed jitter buffer adds the fixed delay to
voice packets.
DTMF (Dual Tone Multi-frequency) tone, better known as touch tone. 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.
Five methods of transmitting DTMF digits on SIP calls:
➢ RFC 2833 - DTMF digits are transmitted by RTP Events compliant with RFC 2833. You can
configure the payload type and sending times of the end RTP Event packet. The RTP
Event packet contains 4 bytes. The 4 bytes are distributed over several fields denoted as
Event, End bit, R-bit, Volume and Duration. If the End bit is phone to 1, the packet contains
the end of the DTMF event. You can configure the sending times of the end RTP Event
packet.
➢ RFC 4733 – It obsoletes RFC 2833.
➢ INBAND - DTMF digits are transmitted in the voice band. It uses the same codec as your
voice and is audible to conversation partners.
➢ SIP INFO - DTMF digits are transmitted by SIP INFO messages. DTMF digits are
transmitted by the SIP INFO messages when the voice stream is established after a
successful SIP 200 OK-ACK message sequence. The SIP INFO message can transmit
DTMF digits in three ways: DTMF, DTMF-Relay and Telephone-Event.
➢ SIP INFO + RFC 2833
Topic
Transmitting DTMF Digit Configuration
The following table lists the parameters you can use to configure the transmitting DTMF digit.
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