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54 VoIP subscriber gateways
Fax transfer can be realized by using G. 711 voice codec or special codec to transmit T.38 facsimile
messages.
T.38 – is a standard for sending facsimile messages in real time over IP networks. Signals and data sent by
the fax unit are copied to T.38 protocol packets. Generated packets may feature redundancy data from previous
packets that allows you to perform reliable fax transmissions through unstable channels.
– Fax transfer Codec 1..3 – you may select a codec and the .and an order of their usage. The highest
priority codec should be specified in the 'Fax codec 1' field. For operation, you should specify at
least one codec:
off – codec is not used.
G.711a – use G.711A codec;
G.711u – use G.711U codec;
T.38 – use T.38 protocol.
All fax codecs should be different! Also, when G.711a or G.711u codec is selected, the
respective codec should be enabled in the device voice codec list.
– Take the transition to T.38 – when checked, incoming re-invite to T.38 from the opposite gateway
otherwise it will be enabled;
– Flash transfer –Flash transmission way:
off –flash transmission is disabled;
RFC2833 – flash transmission is provided in accordance with RFC2833
recommendation as a dedicated payload in RTP
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voice packets;
info – transfer ‘flash’ via SIP protocol. INFO messages are used for SIP protocol and
flash signal view will depend on MIME expansion type;
– Modem Transfer (V.152) – determine the transfer in the ‘Voice band data’ (V.152 is
recommended). Gateway disables voice activity detector (VAD) and generator comfort noise
(CNG). It is necessary when modem connection is established;
Off – modem signal is not detected;
G.711A VBD –use G.711A codec for data transmission via modem connection.
Switching to G.711A codec in the VBD mode is realized via CED tone detection;
G.711U VBD – use G.711U codec for data transmission via modem connection.
Switching to the G.711U codec in the VBD mode is realized via CED tone detection;
G.711A NSE –CISCO NSE support. If data is transmitted via modem connection,
G.711A codec is used;
G.711U NSE – CISCO NSE support. G.711U codec is used for data transmission via
modem connection.
Selected codec should be enabled in voice codec list.
– Payload type for RFC2833 packet transfer (Payload) – payload type for packet transmission via
RFC2833 (acceptable values for use are from 96 to 127);
– Use the same PT both for transmission and reception – when checked, use the same type of
payload for transmission and reception;
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Flash transmission via RFC2833 is not available for firmware version 1.1.
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