Xerox WorkCentre Pro 423 Service Manual page 134

WorkCentre Pro 423/428
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S/T point
An S/T point is a connection point between devices connected to an ISDN line.
connection points are named U, T, S, and R sequentially from the network side. The names
represent mere connection points but not physical things.
Connection
example 1
T point
point
U
NT1
Network side
Connection
point
T
point
U
example 2
Network side NT1
Connection
U point
example 3
S/T point
Network side NT1
Device Description
NT1 Network terminating device (when viewed from the office
side) realizing power feed and other functions
NT2 Device with line switching and concentration functions
TE1 ISDN terminal with I interface
TA Adapter to connect a non-ISDN terminal to ISDN
TE2 Conventional terminal with no I interface (Non-ISDN
terminal)
NT1 (DSU) is an essential device but the other devices are combined depending on the
status as follows:
l NT1+NT2+TE1 (above connection example 1)
l NT1+NT2+TA+TE2 (Connection example 2)
l NT1+TA+TE2 (Connection example 3)
l NT1+TE1
An S/T point indicates a connection point between NT1 (DSU) and TE1 or TA when there is
no NT2 (PBX). In NET64, T and S indicate the same connection point because NT2 is
usually not used. Then the point is expressed as S/T.
The U, T, S, and R points indicate the demarcation points of responsibility about each
terminal. They also define the ranges of responsibility for maintenance.
The U point is the demarcation point between the class-1 carrier and user. NET64 uses a
two-core cable (NET1500: optical cable) from the network to NT1 (DSU) and a four-core
cable of RJ45 from NT1 to TE1 or TA.
A TA/router with built-in DSU has NT1 and TA in one cabinet but allows TE1 (ISDN terminal)
connection by taking the S/T point outside. A model with no S/T point allows only TE2
connection. A router supporting an S/T point may have a built-in DSU.
point
S
4-core cable
NT2 TE1
2-core cable
point
point R
S
NT2 TA
TE2
point
R
TA
TE2
Actual example
DSU
PBX, etc.
G4 Fax, etc.
TA/router, etc.
G3 Fax, etc.
2-102
03/02
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The Bus wiring
Bus wiring is used to connect several terminals to an ISDN line. The figure below shows this
wiring. Two pairs of twisted-pair wires are used to make the polarities (TA, TB, RA, and RB)
common between DSU and all connection blocks.
Since the polarities of wiring screws in a connection block may be different, check the pin
numbers of RJ45 before wiring.
TB
TA
D
S
RB
U RA
RJ45 Connection
block pin No.
Pin8 ... 1
6
For bus wiring, note the distance from DSU to the farthest terminal.
Short-distance bus connection (terminals at random intervals on a bus): 150 m max.
Long-distance bus connection (all terminals centralized within 50 m on a bus): 550 m max.
Since the ISDN cable between a connection block and a terminal is not stranded (paired-
wire), do not use a long cable beyond 4 meters.
CHAPTER 2 TROUBLESHOOTING
Level 2 Troubleshooting
RB
RB RA
Use twisted-pair
TB
TB TA
Terminator
RA
TA