Toshiba CTX28 manual BPTU/RPTU Overview, CSU Requirements, Slot Assignments

ISDN Interfaces

BPTU/RPTU Overview

BPTU/RPTU Overview

Both the BPTU and RPTU provides 24 channels for ISDN PRI service. The BPTU is fully compatible with RDTU2 and will replace the RPTU. Network connection using BPTU or RPTU PRI interface requires installation of a customer-provided CSU in most locations of the U.S. Refer to “CSU Requirements” on page 7-3for CSU installation.

The BPTU or RPTU is a DS-1 divided into 24 TDM channels using standard T1 electrical signal format. The BPTU or 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 BPTU or RPTU. Each BPTU or RPTU can also use its own D-channel for control.

The BPTU or 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 BPTU or 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 BPTU or RPTU PCB and the Strata CTX time switch to the public telephone network. One BPTU, 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 7-35.

A dealer-supplied CSU must be installed between the ISDN PRI network line and the BPTU or RPTU PCB as shown in Figure 7-1. 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 BPTU or 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 7-1.

Slot Assignments

Up to eleven BPTU or RPTU PCBs can be installed in a Strata CTX system providing up to 264 PRI lines (B-channels). If BPTU or RPTU (PRI) and RDTU (T1) PCBs are installed, the maximum combined PCBs cannot exceed eleven. The PCBs must be placed in designated slots in each of the cabinets. Refer to Chapter 2 – Strata CTX Configuration, “ISDN PRI Digital Line PCBs” on page 2-40, for the guidelines regarding BPTU or RPTU PCB slot assignments.

ISDN Interfaces

Strata CTX I&M 06/04 7-3