Toshiba Strara CTX Series Installation And Maintenance Manual page 167

.
RBSU
NT Circuit
Insert 100-ohm
TR using RBSU
and RBSS
option switches.
5434
Figure 5-16 RBSU/RBSS NT Circuit Pinout on Passive Bus
As a parallel bus, the RBSU/RBSS BRI-NT passive bus will accept TE-1 and TA devices scattered on
the bus; however, the locations of the TE and TA devices on the S bus is limited by timing
considerations. Specifically, the round trip propagation delay of a signal from the RBSU/RBSS circuit
to one device must be within four microseconds of the delay from the other device on the bus. That is
to say, layer-1 frames from the RBSU/RBSS must be received within a two microsecond window. This
says nothing about how large the delay can be. In fact, it can be much larger, as long as the differences
remain small.
To control electrical characteristics, a 100-ohm terminating resistor (TR) is required at the end of the
passive bus. One resistor should be across the Tx pair and one across the Rx pair at either end of the
passive bus. Branch-type passive bus configurations, shown in
TR on the RBSU/RBSS NT circuit side and not on the TE or TA device side of the bus.
The RBSU and RBSS circuits provide an option switch that allows the 100-ohm TR to be switched
into the circuit on the Strata CTX side of the bus (see
5-16). Most TE-1 and TA devices also provide option switches to connect 100-ohm terminating
resistors as shown in
If the TE or TA devices do not provide TRs, they may be permanently wired in place on a RJ45 jack at
the far end of the bus. Only one terminating resistor on each pair should be on the far (TE) end of the
passive bus - do not switch in TRs on more than one TE-1 or TA device on the passive bus.
Important! The correct placement of TRs on the Passive Bus is critical to ISDN BRI circuit operation
(see the following RBSU/RBSS Passive Bus configurations section).
Strata CTX I&M September 2002
RJ45
Pinout
3
6
4
5
BRI (four-wire)
3
S-type, TE-1s or TAs without
100-ohm terminating resistors
(maximum eight TE-1s or TAs per
RBSU/RBSS circuit).
Figure 5-15.
RJ45
Pinout
3
6
S-type, TE-1 or TA with
100-ohm TR or just a
100-ohm terminating
4
resistor across each pair
on a RJ45 jack.
5
6 4 5
To local
AC Power
Figures
Table 5-3 on Page 5-12
ISDN Interfaces
To local
AC Power
5-17~5-19, may only require a
and Table 5-6 on Page
5-19