Instruction manual

Features
Table 28. Line Compensation Settings
Cable Length
Setting
dB Loss
(22-Gauge Wire)
1 0.6 0—133 feet (0—40.5 meters)
2
1.2 133—266 feet (40.5—81 meters)
3
1.8
266—399 feet (80—121.5 meters)
4 2.4 399—533 feet (121.5—162 meters)
5 3.0 533—655 feet (162—199.5 meters)
Clock Synchronization
Clock synchronization is an arrangement in which digital facilities operate from
a common clock. Whenever digital signals are transmitted over a
communications link, the receiving end must be synchronized with the
transmitting end to receive the digital signals without errors.
The system synchronizes itself by extracting the timing signal from the incoming
digital stream. If the system has more than one 100D module, the module that
provides the primary synchronization for the other 100D modules and for the
time-division multiplexing (TDM) bus must be identified during system
programming. The factory setting is the first 100D module in the carrier. This
can be changed to the second or third module.
In the event of a maintenance failure, backup synchronization can be provided
by programming in the second and third installed modules as secondary and
tertiary synchronization.
In addition, the source of synchronization can be factory set to “loop clock
reference source” (the clock is synchronized to the external endpoint—the
factory setting) or to “local clock reference source” (the clock is free-running).
This setting must be made for the primary, secondary, and tertiary
synchronization modules.
Signaling Mode
Signaling is the process of communicating channel-state information, such as
dialing, from endpoint to endpoint. Two types of signaling can be used in T1
transmission: robbed-bit signaling (RBS) and common-channel signaling (CCS).
Choosing a signaling mode pertains only to T1 service; PRI always uses CCS
(23 B-channels and 1 D-channel). The signaling types areas follows:
■ Robbed-Bit Signaling
RBS replaces the least significant bit of every sixth frame of each DS0
channel with signaling information. RBS is also called in-band signaling,
since signaling information is embedded in the least significant bit of
every sixth 8-bit word.
356 Primary Rate Interface (PRI)