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

Fig. 5
2 Mbit/s line system ZAD 2-6. The different parts
are identified with the aid of addresses. Alarms
are connected to ZAN101 and identified by the
physical position in the alarm collection magazine
Fig. 4
Maintenance Entities, ME, in accordance with the
CCITT recommendation
Fig. 7
The alarm display in AOM 101 is divided up so
that each sector represents the transmission
equipment either in a station or on a route
between two stations
The grouping of the supervised equipment
is in accordance with the maintenance
entity concept recommended by
CCITT, i.e. the equipment is divided into
independent maintenance entities, ME,
fig. 4, which can consist of:
- a line system consisting of two line
terminals and intermediate repeaters
- a multiplexer.
Other equipment, which is not included
in the CCITT recommendation, for example
analog transmission equipment,
pressure protection systems, security
systems and fire detectors, are divided
into similar MEs.
Digital equipment is designed so that a
fault that disturbs the traffic will normally
only initiate an alarm in the faulty
or the adjacent equipment.
Each ME is identified with the aid of
- its geographical position, i.e. a station
or a route between two stations
- the type of device
- a numerical index within the type of
device.
Fig. 5 shows a 2 Mbit/s line system comprising
two line terminals and three intermediate
repeaters. Fig. 6 shows a
printout of the network data. The examples
in figs. 7-10 show what happens
when a fault occurs in an intermediate
repeater.
Alarm processing
ZAN 101 continuously scans the alarm
status of all connected devices and initiates
printouts of all alarms. For each ME
the network data includes the seriousness
of each alarm condition, the alarm
class and the category for routing of
alarms to the desired work station.
Alarms from a device which has already
been identified as faulty and alarms that
are generated in connection with fault
tracing can be suppressed.
WhenZAN101 is connected to AOM 101
the alarm display in AOM 101 receives
an initial alarm report, which provides
information as to which station or route
is initiating the alarm and how serious
the fault is, fig. 7.
By acknowledging the alarm the operator
can then receive information regarding
the faulty system, fig. 8, and various
traffic activities can be initiated. Depending
on the circumstances the operator
can then either try to locate the fault
immediately or leave it until later. More
detailed alarm information can be obtained
by means of commands, and will
simplify the tracing of the fault. The alarm
information then received is of the
type "loss of power", "loss of signal",
etc.
Locating faults in line systems
The purpose of the fault location is to
indicate the position and type of faulty
devices in order to enable the maintenance
personnel to be directed to the
right place, equipped with the right
spares.
When an alarm occurs a fault location
command is given either automatically
or manually by the operator. The operator
requests fault location by giving the