TELE-X - a Satellite System for TV and Data Communication ...

Fig. 7
The structure of system 2AN201
Fig. 8
Part of a local network
ET
FLM
WS
PCM
FLP
Exchange terminal
Fault location magazine
Work station
PCM terminal
Fault location pair
R. Regenerator housing
regenerator section ZAN 101 printouts
specify the faulty maintenance entity.
ZAN 101 has the hierarchic structure
shown in fig.6, with the units:
- Transmission maintenance terminal,
TMT, (central terminal), for processing
alarm messages and alarm lists,
and for communication control
- Transmission maintenance control
terminal, TCT, (regional terminal), for
collecting and interpreting alarms
and locating faults
- Transmission maintenance sub-terminal,
TST, for sensing test points
and operating control points
- Fault detector unit, FDU, for bit error
rate measurements.
Separate fault location channels are required
for the data links used for the
communication between TCT, TST and
FDU. The channels used are either included
in the transmission medium
used for the supervised system (e.g. optical
fibre or coaxial cable) or are separate
transmission channels (e.g. fault location
pairs, FLP, on physical pairs).
ZAN 201
Command-controlled location of faults
on digital line systems is initiated by the
operator when a fault is detected in the
supervised system. The fault can give
rise to an alarm, which is reported from
an AXE 10 work station or is collected by
ZAN 201 over a special alarm report
channel. During the actual fault location
the bit error rate values from the regenerator
sections are compared with
preset threshold values. After an iterative
process the address of the faulty
regenerator is obtained. The network
data enable the operator to determine
which maintenance entity contains the
regenerator fault.
In the case of a cable cut that affects the
remote power feeding, a fault indication
is obtained from every regenerator that
has lost its power. However, the faulty
cable section can be located by means
of analysis of test signals generated at
each regenerator site.
ZAN 201 consists of a fault locating magazine
(circuit pack), FLM, fault detector
units, FDU, and alarm collection units,
ACU, fig. 7. All units are connected to a
fault location pair, FLP, or other types of
fault location channels.
Variants of FDU have been developed
for different line systems using different
transmission media and speeds. A variety
of transmission systems (over cables
and radio relay links) can be supervised
via one and the same fault location
channel.