17(48)
Date
Rev
Documentnumber
Prepared
Doc respons/Approved
Checked
Reference
1999-07-15
A
1531-BDV BS 101 05 Uen
INSTALLATION INSTRUCTION
Subject responsible
6.9.2
DIP-switches in positions 198 and 199
Selection of ground strapping for the coax 75
Ω
or se-
lection of the 120
Ω
twisted pair interface.
On factory delivery the switches are set to OFF-posi-
tion = no ground thus enabling 120
Ω
interface with a
twisted pair cable. These DIP-switches connect the
75
Ω
interface coax screen to ground, either directly to
0V or via a 1 nF capacitor. DIP-switch 198 switches the
receiver and 199 the transmitter side. The screen shall
normally be grounded on the transmitter side. Normal-
ly, the screen on the reception side is not connected to
ground. Refer to local market requirements
Ranges on the interface of the BTU-D
This interface covers the short distance to the next NT
or Line Terminating Unit as the end point of a public or
private network. The range is only defined in terms of
the covered attenuation by the interface that is 6 dB. If
required choose cables with low attenuation to achieve
a maximum distance.
For ranges exceeding 6 dB attenuation additional digit-
al data transmission equipment is required. Line Ter-
minating Unit (LTU) ASB 501 04 is available for such
purposes.
There are specific requirements for the digital interface
wiring to meet the demands of EMC.
If a twisted pair connection should be installed and the
requirements of EN 55022, class B have to be fulfilled,
a ferrite is available with the ERICSSON ordering
number STF 82 601. Taking the cable and making
three turns around the ferrite core meets the demand
of sufficient noise reduction. The ferrite should be
situated close to the slot where the cables are led out
of the cabinet. In most cases this cable is supplied by
the PTT and should not be fed via the MDF.
Some markets (e.g. Austrian PTT) require the use of a
double-shielded interface cable. The outer shield
should be connected to frame earth and the inner
shield should be connected to 0V on the board. A 20 m
long standard cable is available with the ERICSSON
ordering number TSR 901 0481/20000.
197/1
197/2
FUNCTION
OFF
OFF
ON
digital trunk MFC
digital trunk MFE
only
BTU-D
ON
OFF
ON
Register MFC
Register MFE
BTU-D
or
REG.
198/1
199/1
198/2
199/2
FUNCTION
OFF
OFF
120
Ω
connection
1)
1) Factory setting
OFF
ON
screen connected to ground
ON
OFF
screen connected to ground
via 1nF capacitor
d1
d1 - The line length depends on the cable type used. The board
Line terminating unit
BTU-D
Coax 75
Ω
and twisted pair 120
Ω
interface
attenuation at 1,024 MHz per 100m.
allows 6 dB cable attenuation at 1.024 MHz. Check cable
26
28
30
32
C
18
20
22
24
A
RING_OUT
RING_IN
TIP_OUT
TIP_IN
19
23
LA1
LB1
LA2
LB2
0 V
Outgoing
Incoming
Connection field 6
wires
wires
Connection for 75
Ω
coaxial cable
Connection for
120
Ω
twisted pairs