H3C Technologies H3C MSR 50 - Manual (Page 726)

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Features of E1 and T1
E1 and T1 are characterized by the following:
• Signaling modes
• Fax function
• Protocols and standards
Signaling modes
E1/T1 interfaces support these types of signaling:
• DSS1/QSIG user signaling, adopted on the D channel between ISDN user and network interface
(UNI). It has a data link layer protocol and a Layer 3 protocol used for basic call control.
• ITU-T R2 signaling, which includes digital line signaling and interregister signaling. Digital line
signaling is transmitted in TS16 (ABCD bits) of E1 trunk. It conveys status information about E1
trunks to describe whether the trunks are occupied, released, or blocked. Interregister signaling
conveys information about address, language and discriminating digits for internal calls, echo
suppressor, caller properties and callee properties in multi-frequency compelled approach (forward
and backward) in each timeslot.
• Digital E&M signaling, similar to R2 signaling. It transmits E (recEive) and M (transMit) call control
signals similar to analog E&M signaling in TS16, alignment signals in TS0, and voice signals in
other timeslots. In digital E&M signaling, when an E1 trunk detects and sends connection signaling,
it looks at the signal in TS16. Digital E&M signaling provides three start modes, immediate, wink,
and delay, to adapt to different devices for more reliable connection.
• Digital LGS. Digital loop start signaling is used between telephones and switches to identify the
off-hook/on-hook state, while ground-start signaling is used between switches. They differ in that
the two parties in conversation must check grounding state before closing the line in the ground-start
approach.
Fax function
The fax function is available on E1/T1 voice interfaces to set up fax channels and transmit/receive fax
data.
Protocols and standards
E1/T1 voice supports SIP and recommendations in ITU-T H.323 framework, and G.711, G.729, and
G.723.1 Annex A (5.3 K and 6.3 K) in ITU standards.
Table 267 Protocols supported by E1/T1
Item E1 voice T1 voice
Framing format CRC4, non-CRC4 SF, ESF
Line coding
format
HDB3, AMI B8ZS, AMI
Introduction to BSV interface
The BRI S/T voice (BSV) interface supports simultaneous transmission of voice and data, can receive,
send, compress, de-compress digital PCM voice traffic, and realizes VoIP function through other WAN
interfaces of the router.