User guide

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T1 Line Configuration
1. Framing Format : D4 Superframe
2. Line Coding : Alternate Mark Inversion (AMI)
3. Line Type and Length : CSU (0db) or DSX-1 (0-133ft)
Enter Selection (-(previous), q(uit), <1>): _
Framing Format
The MultiDSU supports two types of framing formats: D4 Superframe
(D4) and Extended Superframe (ESF).
The D4 Superframe option (option 1) is a 193-bit frame format in which
the 193rd bit has framing and signaling information. A D4 superframe
consists of 12 frames.
The Extended Superframe (ESF) option (option 2) is similar to D4
except that it consists of 24 frames instead of 12 frames and provides
CRC error detection and a 4 kHz Facility Data Link (FDL).
Line Coding
The MultiDSU supports two types of line coding: AMI and B8ZS.
The Alternate Mark Inversion (AMI) option (option 1) is a bipolar coding
scheme in which successive ones alternate in polarity to prevent a
Bipolar Violation (BPV). A BPV occurs when two consecutive ones are
the same polarity. When AMI is selected, the digital data stream from the
user equipment on the data port is converted into this bipolar format to
be transmitted over the T1 line.
The B8ZS option (option 2) is a coding technique used to satisfy the
ones density requirements of the T1 carrier facilities while also allowing
clear channel data. Since the system timing is recovered from the pulse
width of the ones, it is important to ensure that there is an adequate
proportion of ones in the data stream. If the data stream contains more
than 8 consecutive zeroes - a condition that could disrupt system timing
- B8ZS substitutes a predetermined pattern for the zeroes. This substitu-
tion intentionally causes a BPV to occur, alerting the unit on the receiv-
ing end that a substitution has taken place.