Technical data

22
Connection of ISDN Devices to the internal S
0
Port
The connection of the internal S
0
bus happens at the internal S
0
port on
the four clamps
1
b2, b1, a1 and a2. This labelling of the clamps is
printed in front of the clamp on the circuit board. The clamp blocs can
be detached from the module to simplify the installation.
Normally you use an unshielded twisted pair cable for wiring installation
(J-YY 2x2x0,6 St III Bd). Under certain circumstances (e.g. near a
strong radio/television station or a power cable), you have to use a
shielded twisted pair cable.
In any case it should be twisted pair cable with four wire positioning like
in Pic. 17. Here both sending data wires (a1 and b1) as well as both
receiving data wires (a2 and b2) are positioned vis-a-vis. This cable
configuration will help to compensate interferences considerably.
You can buy many different types of wall jacks. They are sometimes
called IAE (ISDN-Anschluss-Einheit), UAE (Universal-Anschluss-Ein-
heit), RJ-45, Western modular, wall jacks with integrated termination
resistors as well as shielded wall jacks belong to them.
In order to make the setting as simple as possible, please pay attention
to the following points: Use only wall jacks of one type for one S
0
bus
and check the wall jacks before installation. The pin assignment may be
different compared to the usually used products or the termination resis-
tors are integrated into the ISDN wall jacks.
The maximum length of the total bus wiring should be 150 m. As at any
rewiring position (ISDN wall jack etc.) reflections occur, the maximum
quantity of allowed clamp positions (12) has to be respected. This and
the cable quality as well as the proper adjustment of the termination
resistors can be the key factor for a proper function of the S
0
bus.
If you use western modular wall jacks with the clamp labelling 1a, 1b,
2a and 2b, you connect the clamp b2 of the PBX with the clamp 2b of
the first wall jack socket, b1 with 1b and so on (see Pic. 19). Then the
clamps of the first wall jack socket are connected with the correspond-
ing same marked clamp of the second wall jack socket.
In the last wall jack socket a resistor of 100 ⏲ (power rating min. 0,25 W)
must be inserted between the clamps 1a and 1b and also 2a and 2b
each. The so-called termination resistors are avoiding unwanted reflec-
tions.
If you use wall jacks with eight clamps you only use the middle four
clamps that are marked with 3, 4, 5, 6, instead of all eight existing
clamps. How to connect them to the PBX is shown in Pic. 20.
1. Technical modifications in the layout may lead to a change in the position of the
ISDN jacks and clamps.
a1
b1
a2 b2
a1
b1
a2 b2
Pic. 17: Wire position
red
black
white yellow
2b 1b 1a 2a
Pic. 18:
Layout of the Western
modular jack
b2 b1 a1 a2
1a 1b 2a 2b
1a 1b 2a 2b
1a 1b 2a 2b
100 ⏲ 100 ⏲
letzte
IAE
2. IAE
1. IAE
Pic. 19: Clamp connection of ISDN wall jack (IAE)
b2 b1 a1 a2
letzte
UAE8
2. UAE8
1. UAE8
654378 2 1654378 2 1
654378 2 1
654378 2 1654378 2 1
100 ⏲
100 ⏲
Pic. 20: Connection of ISDN wall jack (UAE)