ELTEX TAU-4.IP - Page 67

67 VoIP Subscriber Gateways
- DTMF transfer – DTMF signal transmission method:
 Inband – inband transmission;
 RFC2833–according to RFC2833 recommendation, as a dedicated payload in RTP
voice packets;
 SIP Info - transmission of the messages via SIP in INFO queries.
 Application/ dtmf–DTMF is sent in application/dtmf extension ('*' and '#'
are sent as digits 10 and 11);
 Application/ dtmf-relay–DTMF is sent in application/dtmf-relay extension
('*' and '#' are sent as symbols '*' and '#');
 Audio/telephone-event–DTMF is sent in audio/telephone-event extension
('*' and '#' are sent as digits 10 and 11).
- Fax Detect Direction – defines the call direction for fax tone detection and subsequent
switching to fax codec:
 No detect fax–disables fax tone detection, but will not affect fax transmission
(switching to fax codec will not be initiated, but such operation still may be
performed by the opposite gateway);
 Caller–tones are detected only during fax transmission. During fax transmission,
CNG FAX signal is detected from the subscriber's line;
 Caller–tones are detected only during fax receiving. During fax receiving, V.21
signal is detected from the subscriber's line;
 Caller and Callee–tones are detected during both fax transmission and receiving.
During fax transmission, CNG FAX signal is detected from the subscriber's line.
During fax receiving, V.21 signal is detected from the subscriber's line;
Fax transmission may be implemented using voice codec 711 or special codec for facsimile
codec t/38 messages transmission.
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 to perform reliable fax transmissions through unstable
channels.
- Fax transfer codec 1...3 - allows you to select codecs and an order of their usage. Codec
with the highest priority should be placed in 'Fax codec 1' field. For processing it is
necessary to point at least one codec:
 Off - codec is not using.