ISDN Interfaces
RBSU/RBSS Interface Units
5-18 Strata CTX I&M 10/02
BRI Wire Type Recommendations
CAT3 or CAT5 wire is recommended for ISDN BRI customer-premises wiring. While the ISDN
BRI signal works for some distance over almost any wire that is suitable for analog voice service,
better wire enables longer runs. CAT5 provides better 100-ohm impedance matching (at little extra
cost) between the RBSU/RBSS circuit and the station Terminal Equipment (TE-1).
Normally the CAT3 or CAT5 wiring does not have to be shielded when used for ISDN BRI
premises wiring. However, the RJ45 jacks on the RBSU/RBSS BRI circuits are shielded and
provide a ground shield in the event that shielded modular plugs and cable are used.
Note If using shielded cable and plugs, cable runs should only be grounded at the Strata CTX
RBSU/RBSS, RJ45 jacks. To prevent ground loops, do not ground both ends of shielded
cable runs.
Figure 5-12 RBSU/RBSS Location of LEDs and Connector Locations
RBSU/RBSS BRI Cable Jacks and Connectors
In the U.S., the standard connector for ISDN equipment is the eight-pin RJ jack. Patch cables have
eight-pole plugs at both ends. The same pinout applies to both ends of an ISDN cable, which is the
practice of the data world. This means that a flat untwisted cable with an RJ modular plug at both
ends will have the locking tab of the plug on one end, “up;” and on the other end, “down,” as
shown in Figure 5-13.
Note This is the opposite of telephony “silver satin” cables which have locking tabs on both ends
facing the same direction. Telephony cables cause the pins at either end to crossover while
data cables provide a straight through pin-to-pin connection between modular jacks.
RBSU
Reset Switch
(resets RBSU Firmware)
RS-232C Connector
for Call-Data Monitor
RJ-45 8-pin (shielded)
Modular Connector
BSY
TS
LOS
FS
BSY
TS
LOS
FS
2795
RBSS
3rd Circuit
2nd Circuit
1st Circuit
4th Circuit
BSY
TS
LOS
FS
BSY
TS
LOS
FS
CKT2
CKT1
CKT4
CKT3
TB3 (FG)
TB1 and TB2 (PFT)
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