Line Framing Options:
D4/Superframe: The D4 framing format, as specified in AT&T
TR62411 is the standard in which twelve frames make up a
superframe. All signaling and synchronization are done in-
band.
Extended Superframe (ESF): Extended Superframe, as speci-
fied in AT&T TR 54016, consists of twenty-four (24) T1
frames. The framing bits are now used for framing, CRC and
the Facility Data Link (FDL). The FDL allows maintenance
messages and information to be passed between the 2720
and the Central Office.
Line Coding Options:
Alternate Mark Inversion (AMI): This mode does not inherently
account for ones density. To meet this requirement, each time
slot can be reduced to 56 kbps and the Least Significant Bit
(LSB) of each time slot set to one.
Bipolar 8 Zero Substitution (B8ZS): This mode assures proper
bit density in the data stream. In this mode any data pattern
can be transmitted without causing ones density errors. This
mode allows for 64 kbps clear channel timeslots.
Switch S2-5: DS0 Channel Rate
Use Switch S2-5 to set the DS0 rate.
SW2-5
Setting
Off
56 kbps
On
64 kbps
3.1.1 Switch S2
The table below shows the default configurations for Switch S2. A
description of all S2 options follows this table.
Switches S2-1, S2-2, and S2-3
Use Switches S2-1, S2-2 and S2-3 to set the DTE data rate.
Each setting represents an nx56/nx64 setting. Individual channel set-
tings can be configured through the software control port.
S2-1
S2-2
S2-3
Speed
Off
Off
Off
Clear Channel (Unframed)
On
Off
Off
112kbps/128kbps
Off
On
Off
224kbps/256kbps
On
On
Off
336kbps/384kbps
Off
Off
On
448kbps/512kbps
On
Off
On
672kbps/768kbps
Off
On
On
896kbps/1024kbps
On
On
On
1344kbps/1536kbps
Switch S2-4: Line Framing and Coding
Use Switch S2-4 to control the Network Line Framing and Coding
Options. Set these options to be the same as the Line Framing and
Coding Options given to you by your Service Provider. If you are using
two Model 2720s together as short range modems, set both units iden-
tically.
S2-4
Line Framing & Coding
Off
ESF/B8ZS
On
D4/AMI
9
10
S2 SUMMARY TABLE
Position
Function
Factory Default
Selected Option
S2-1
Data Rate
On
S2-2
Data Rate
On
S2-3
Data Rate
On
S2-4
Framing & Coding
Off
S2-5
DS0 Rate
On
S2-6
Clock Mode
Off
S2-7
Clock Mode
Off
S2-8
Reserved
Off
1.536 Mbps
(DTE Rate)
ESF/B8ZS
64 kbps
Network
Reserved
Network
