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ISDN Interfaces
RBSU/RBSS Interface Units
7-14 Strata CTX I&M 06/04
RBSU/RBSS Interface Units
Circuits per PCB:
2 circuits (2B + D each circuit)
Interfaces with:
ISDN BRI S/T when connected to the Public Network or a BRI S-type, TE-1, or TA devices
when connecting to ISDN station equipment
Older Version(s):
none
RBSU/RBSS switches, jumpers, and connectors are shown in Figures 7-11 and 7-12 on page 7-17
and described in Table 7-8.
LEDs on the RBSU/RBSS show a continuous status of BRI operation. Refer to Table 7-8 on page
7-17 for a list of each LED’s status.
Overview
The RBSU and RBSS PCBs provide the Basic Rate Interface (BRI) circuits. The RBSU is the
main plug-in PCB that plugs into the Strata CTX cabinet slots.
The RBSS is an optional PCB that plugs onto the RBSU. Each PCB provides two ISDN BRI
circuits. Each BRI circuit provides 2 B-channels + 1D channel for voice/data/video applications.
An REBU PCB is a piggy-back PCB that plugs onto the RBSU and provides basic functions for
RBSU/RBSS circuits so it must always be installed on the RBSU.
The RBSU circuits are four-wire S/T type circuits and connect to the Public Switched Telephone
Network (PSTN) BRI lines using an Network Terminator unit (NT1); or, on the station side, they
can connect to ISDN Terminal Equipment (TE) or Terminal Adapters (TA) as shown in Figure 7-9.
TE devices include any ISDN device (telephone, fax, computer) that connects directly to S/T
ISDN BRI circuits. TA devices match the protocol of non-ISDN devices (telephone, fax,
computer) to the protocol of S/T ISDN BRI circuits.
The TBSU and RBSU circuits can be configured as:
• BRI – TE circuits which connect to Telephone Network BRI lines using a NT1.
• BRI – NT circuits which connect to ISDN TEs or TAs. These devices must be S-type station
devices.
Important! The Strata CTX BRI circuits allocate line numbers and station ports differently.
Each BRI circuit consumes two line numbers and two station port when configured
as line-side or station side.
RBSU Connection Options
The RBSU connection options (BRI line or ISDN TE-1/TA devices) are selected in customer
database programming and option switches located on the RBSU.
The RBSU circuits that connect to the ISDN network side requires a dealer-supplied NTI interface
box to convert the two-wire, U-interface BRI line from the telephone network to the four-wire,
T-interface of the RBSU circuit. The NT1 must be UL listed (U.S.) or CSA certified (Canada). The
network BRI line connection is a point-to-point connection, which means that the network BRI
line can only be connected to one RBSU or TBSU circuit via the NT1 (T-reference point).
RBSS circuits connect directly to S-type TE-1 or TA ISDN devices only. They do not support BRI-
TE telephone network BRI line connections.