Toshiba Strata CTX100, Installation And Maintenance Manual

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ISDN Interfaces
RPTU Interface Unit
Strata CTX I&M 10/02
5-3
ISDN Inte
rface
s
RPTU Interface Unit
Circuits per PCB:
24 channels
Interfaces with:
ISDN PRI
Older Version(s):
none
The RPTU provides 24 channels for ISDN PRI service. Network connection using RPTU PRI
interface requires installation of a customer-provided CSU in most locations of the U.S. Refer to
“CSU Requirements” on page 5-3 for CSU installation.
Testing procedures (local and remote loop back) are in “RPTU Loop-back Test” on page 5-31 .
The RPTU’s LEDs indicate a continuous status of its operation (see Figure 5-3 and Table 5-2 on
page 5-6 ).
Switches, jumpers, and interface connectors are described in Figure 5-1 .
RPTU Overview
The RPTU is a DS-1 divided into 24 TDM channels using standard T1 electrical signal format.
The RPTU’s D-channel is typically the 24th channel and can control the signaling of 23 of its own
B-channels and 24 B-channels of another designated RPTU. Each RPTU can also use its own
D-channel for control.
The RPTU’s in-service bit rate is 1.544 mbps (± 4.6 ppm), but during a maintenance session, the
rate may vary ± 32 ppm. The RPTU provides Binary 8-Zero Substitution (B8ZS) and ESF with
Framing Pattern Sequence (FPS) and Cyclical Redundancy Check (CRC) error checking in the
framing bits.
Extracting the Stratum-1 clock from the ISDN PRI, BRI, or T1 provider is the most common
method used to synchronize the RPTU PCB and the Strata CTX time switch to the public
telephone network. One RPTU, RBSU, RBUU, or RDTU T1 must extract the clock from the ISDN
or T1 provider. The selected unit is designated as the “Primary” timing source in Program 105. In
remote cabinet applications, the Primary clock source PCB must be installed in the Base Cabinet
(main location). For more information, refer to
“Timing and Synchronization” on page 5-32 .
A dealer-supplied CSU must be installed between the ISDN PRI network line and the RPTU PCB
as shown in
Figure 5-1 . Some telephone companies supply the CSU and call it the Network
Interface Unit (NIU).
CSU Requirements
In the U.S., the CSU must be UL listed and comply with Part 68 of the FCC rules. It must also
comply with the limits for a Class A digital device, pursuant to Part 15 of FCC Rules. In Canada,
the CSU must be CSA certified.
The CSU is transparent to data, clock, and framing. It acts as a repeater, not a controller, for
timing. The CSU also acts as a signal regenerator and must be able to perform loop-back tests and
maintenance to both the network and Strata CTX RPTU. The CSU is the same type as used for T1
circuits although it performs the function as NT1 for PRI ISDN in the ISDN reference model as
shown in
Figure 5-1 .