AT&T MERLIN LEGEND Release 4.0 Feature Reference page 421

Feature Reference
Line Compensation
Line compensation adjusts for the amount of cable loss in decibels (dBs),
based on the length of cable between the 100D module and the CSU or other
far-end connection point. The factory setting is a value of 1, which allows a
maximum loss of 0.6 dB. The possible settings are shown in Table 29.
Table 29. Line Compensation Settings
Setting
1
2
3
4
5
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 is important only for T1 service; PRI always uses
CCS (23 B-channels and 1 D-channel). The signaling types are as follows:
Robbed-Bit Signaling. 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 same channel that carries the user's
voice or data in a call. Robbed Bit Signaling must be used if T1 Switched
56 service is to be used on the T1 connection.
Robbed-bit signaling is appropriate for voice and voice-grade data, and
digital data in Release 4.0 systems on channels programmed for
Switched 56 service.
Common-Channel Signaling. Common-channel signaling (CCS) is an
out-of-band signaling format that places the signaling bits for channels 1
through 23 into the 8-bit word of the twenty-fourth channel. This restricts
DS1 from using the twenty-fourth channel for voice or data transmissions.
D4 framing does not preclude the use of CCS, but CCS is not compatible
with D4 channel banks, because the D4 channel banks only recognize
RBS. Common Channel Signaling is used when PRI service is desired on
the DS1 facility.
dB Loss Cable Length (22-Gauge Wire)
0.6 0–133 feet (0–40.5 meters)
1.2 133–266 feet (40.5–81 meters)
1.8 266–399 feet (80–121.5 meters)
2.4 399–533 feet (121.5–162 meters)
3.0 533–655 feet (162–199.5 meters)
Primary Rate Interface (PRI) and T1
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