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Strata CTX I&M 06/04 7-1
ISDN Interfaces
ISDN Interfaces 7
This chapter covers information on the ISDN Primary Rate Interface (PRI) and Basic Rate
Interfaces (BRI).
PRI Overview
For PRI services, the Strata CTX uses a BPTU or RPTU PCB to connect to a Public Switched
Telephone Network (PSTN) PRI line using a UL listed (or CSA certified in Canada) Channel
Service Unit (CSU) in most locations in the U.S. Each BPTU or RPTU provides 23B + D channels.
The B-channels support CO speech and data connections on the PSTN side only.
The Strata CTX also uses a BPTU or RPTU2 PCB to connect Strata Net QSIG network nodes
using DS-1. A DS-1 may be obtained in several ways, most commonly, leasing it from a carrier.
BRI S/T Overview
BRI S/T is available with the RBSU PCB. The RBSU provides two BRI S/T circuits to connect to
the PSTN BRI line using an external UL listed NT1; or, on the station-side, connect to:
• S-type ISDN telephones and Terminal Equipment (TE-1-S)
• S-type Terminal Adapters (TA-S) with non-ISDN devices
Each TE-1-S and TA1-S device can support voice and/or RS-232 switched-circuit data as shown in
Figure 7-1. The station-side BRI S/T circuits are point-to-multipoint.
A subassembly (RBSS) can be attached to the RBSU for two additional BRIs for S-type station-
side connections only. The RBSU PCB and the RBSS subassembly are shown in Figures 7-11 and
Figure 7-12 on page 7-17. The combination of RBSU and RBSS uses only one slot to provide up
to four BRI S/T circuits.
Note Each installed RBSU or RBSS circuit provides a 2B + D connection and uses a system
capacity of two station ports and two CO lines regardless of the circuit application, even if
the circuit is not actually connected.
BRI U Overview
For BRI U services, the RBUU provides two BRI U circuits that connect directly to PSTN BRI
lines; or, on the station side, connect to:
• U-type ISDN telephones and Terminal Equipment (TE-1-U)
• U-type Terminal Adapters (TA-U) with non-ISDN devices
Each TE-1-U and TA-U device can support voice and/or RS-232 switched-circuit data
depending on the device (see Figure 7-1). The station-side BRI U circuits are point-to-point.