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Line Type
Three selections are available, T1-RBS, T1-PRI and E1-PRI. Units leave the factory set to E1-PRI. Line
Interfaces that are activated in the field (when an MA30EXP port expansion module is installed) will default to
T1-RBS. Whenever the line type setting is changed form E1-PRI to a T1 choice (or from a T1 choice to E1-
PRI), after saving and sending the configuration change, the unit MUST be restarted. However, changing from
T1-RBS to T1-PRI or changing any other parameter (for example the Framing Format or the Line Build Out)
does NOT require a system reboot.
Framing Format
The Framing Format parameter is a layer 1 parameter used to construct & identify the basic signal transmitted
and received. The Line Type selection dictates the available formats.
When the line type is T1, your choices are:
•
Extended Super Frame (ESF),
•
Extended Super Frame (ESF) with Error Correction,
•
12 Frame MultiFrame (F12), - same as industry D4 Super Frame( SF)
•
4 Frame MultiFrame (F4),
•
72 Frame MultiFrame - Remote Switch Mode (F72)
The majority of T1 lines in North America now implement ESF framing with Error Correction (CRC4\6
Note:
on), however commonly referred to as just "ESF".
Line Code
The Line Code parameter is a layer 1 technique used to identify and control the ones and zeros of the data
pattern. T1 line codes are derived from the AMI (Alternate Mark Inversion) bi-polar technique. A voltage
(pulse) on the digital line represents a binary one. No voltage represents a binary zero. The line code says
each binary one must be of the opposite polarity with respect to the previous one (voltage alternating in polarity
- the essence of a bipolar signal). The Line Type selection dictates the available Line Code choices.
When the line type is T1, your choices are:
Alternate Mark Inversion (AMI)
Line code is a bipolar coding scheme in which successive ones alternate in polarity. Successive ones of the
same polarity are bipolar violations (BPV errors). BPVs and too many consecutive zeros are conditions that
cause signal degradation. AMI line code requires user data to contain enough binary ones to maintain 1s
density (signal integrity). The 1s Density rule is, in every 24 bits of information to be transmitted, there must be
at least 3 ones (pulses) and that no more than 15 zeros can be transmitted consecutively.
Binary 8 Zero Substitution (B8ZS)
B8ZS (Binary 8 Zero Substitution). This line code is the same as AMI, except for when user data does not
contain enough binary ones to maintain the "1s Density" rule). A "user" data stream of 16 consecutive
zeros (to be transmitted) will be replaced with a B8ZS pattern (a pattern that contains a specific sequence of
bipolar violations). The receiving end of this transmission will also be set to B8ZS line code and so when it
recovers the specific pattern of violations, it will replace it with a string of zeros (transparently passing the
data up to the receiving user as originally intended).
Receive Sensitivity
This layer 1 parameter configures (tunes) the interface's receiver circuit. There are two choices to select from,
Short Haul Mode (-10db) and Long Haul Mode (-36 dB).
T1 signals are full duplex. A T1 digital interface generates and transmits a signal onto the line, while at the
same time it receives and recovers a signal from the line.
Short Haul Mode (-10db)
Setting the receive sensitivity to Short Haul Mode means the MultiAccess receiver expects the size of the
incoming signal to be between 0db and -10db. If the incoming signal is greater than 0db or if it's smaller than
-10 dB, the interface will indicate a Red Alarm condition.
MultiAccess Communications Server MA30120 User Guide
Chapter 3 – Software
Line Interfaces > Line x
Setup>
T1RBS
120
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