Toshiba strata CT Installation & Maintenance Manual page 346

ISDN Interfaces
RBSU
NT Circuit
Insert 100-ohm
TR using RBSU
and RBSS
option switches.
3344
H
Figure 10-13 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
C
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
10-14~10-16, may only require a 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 CT side of the bus (see
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!
10-20
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 10-12.
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).
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 RJ-45 jack.
5
6 4 5
To local
AC Power
Table 10-5 on Page
Strata CT I&M Manual October 2000
To local
AC Power
Figures
10-13). Most TE-