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Types of faults, measures and
subscriber reactions
Of the fault types and subscriber reactions given
below, only type 1 represents a real fault. The
other types are to be considered as mishaps
and are difficult to foresee. Moreover, experience
has shown that they usually do not appear
until an SPC exchange operates in its proper
environment.
1. Traffic to certains PABXs did not function
satisfactorily because of faulty system adaption,
which in its turn was caused by ambiguities
in the specifications. The fault was
cleared immediately by means of a hardware
correction.
2. Unforeseen variations in different AGF equipments
caused such faults as failure to establish
speech connection, prematurely disconnected
calls and holding. The faults were
cleared by changing the time-dependent signals
to and from AXE 10.
3. Certain number series to other trunk code
areas were erroneously barred and were
opened by means of a correction of the exchange
data.
4. Missing data for a number of subscribers
were included.
5. A number of faulty subscriber connections
in the main distribution frame were corrected.
6. The built-in line test function was set to the
prescribed limits, but these proved to be too
narrow in view of the condition of the network.
Many subscribers were temporarily
blocked and the values for the line test function
were adjusted to suit the actual network
conditions.
7. Because of the very short setting-up time in
AXE 10 unwarranted fault complaints concerning
"permanent dialling tone" were received,
since this tone is sent out immediately
the subscriber lifts the receiver or dials
a trunk code.
8. An individual supervisory function indicated
that for 24 hours no call had been initiated
from a three-coin instrument situated
in a lonely place. Since the telephone turned
out to be in working order it is likely that it
had not been used during that period. The
supervisory interval was therefore extended
to 48 hours, and since then there has been
no more indications.
Plans for the future
The experience gained from the Sodertalje
exchange has helped to make possible
the realization of previously prepared
plans for the future earlier than
expected.
Extension rate
The Telecommunications Administration's
network now contains about 5
million installed local lines, of which
just over half are served by modern
crossbar exchanges. The remainder are
connected to AGF exchanges, the oldest
of which have been in service for
over 50 years. Problems concerning the
realization of new functions, wear,
spares and maintenance have led to the
Administration preparing a modernisation
plan. It comprises a long-term program
for the replacement of AGF by
AXE 10, with the aim that all AGF exchanges
shall be replaced before the
year 2000.
Centrally stationed staff
It is already clear that a changeover to
AXE 10 will mean a radical improvement
in the operation and maintenance activities.
Thus the system permits authorized
departments within the Administration
to send commands via terminals
(I/O devices) direct to the exchanges
concerned, in order to carry out any desired
changes. For example, the sales
department will be able to connect in or
disconnect subscribers direct by means
of a command, instead of having to
make out a work order and sending it
to the exchange for manual action. This
applies for most other operational activities
that can be remotely controlled,
for example
— connecting in and disconnecting different
subscriber facilities
— traffic recording
- traffic observation
- reading of call meters
— changing the charging and traffic
routing
- collecting statistics
It is the aim of the Telecommunications
Administration to successively transfer
all operational and maintenance work
within a geographical area to staff stationed
at a centrally placed maintenance
centre. From there the maintenance
staff will be sent out to the exchanges
when the need for manual intervention
arises.
Conclusion
The operational experience obtained
from the Sodertalje exchange has
proved that the modular structure of
both the system software and hardware
makes the system easy to handle.
Furthermore owing to the fact that the
operational reliability already from the
beginning has proved to be good it has
been possible to introduce push-button
dialling and abbreviated dialling six
months earlier than was originally planned.
If regard is also paid to the wide range
of possibilities and facilities offered by
AXE 10 —not least concerning rationalization
and reducing the cost of the operation
and maintenance activities —it is
clear that this new generation of SPC
exchanges meets the requirements of
today and tomorrow and has thus come
to stay.
7
References
LSundblad, A.: Operating Experience
from AKE 120, Tumba. Ericsson
Rev. 47 (1970):2, pp. 42-49.
2. Ericsson, L. G. and Persson, A.:
Operation and Maintenance Characteristics
of AKE 13. Ericsson
Rev. 54 (1977):3, pp.125-135.
3. Ericsson, L. G. and Persson, A.:
Operational Experience of AKE 13.
Ericsson Rev. 54 (1977):4, pp.168
-173.
4. Meurling, J.: Sodertalje-the First
AXE Exchange. Ericsson Rev. 54
(1977):1,pp. 2-6.