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case REP sends an order to SCS for reading in part 2. From a number of lists
the logic unit of SCS hunts for the particular subscriber's number; each such
number exists only on one list. Each list contains subscribers with identical
category combination and starts with a heading of three 8-bit words which
indicate the subscriber combination in question.
Reliability
Apart from the reliability guaranteed by careful selection of components,
advanced modular structure, duplication of units where required etc., ANA 30
offers the following features.
In the case of a fault in a processor the first processor in the group can interrupt
its work and take over the entire function of the faulty processor. In regular
operation the first register processor will then serve as many registers as, without
essential disturbance, can be inoperative during the period required for repair.
Should a fault arise in the first processor, the second processor blocks new calls
to it and releases any subscribers in register position.
In each unit there are circuits for time supervision, parity check, etc. In the
case of a fault in duplicated memories, multiplexors or central interface units,
the processors are automatically switched over to an intact unit.
All faults and measures associated with them can on command be printed on
an electric typewriter or shown on a display terminal at a suitable point in the
Operational and Maintenance Centre.
Programming Aids
As programming aids special programs have been written for the loading of
the program, translation and subscriber stores. A clear line writer printout is also
obtained, which is of assistance for operation and maintenance. The printout
can be supplemented, if desired, by the designer's explanatory comments. These
programs are run on commercial computers.
Operation and Maintenance
One of the great advantages of ARE is that die operation and maintenance
functions can be remote-controlled from an Operation and Maintenance Centre
and from a Central Subscriber's Office. These functions are available in the
operation and maintenance processor OMP in the exchange.
Operational Functions
Changes of subscriber data, for example connection and disconnection of a
subscriber category, are remote-controlled through write-in to the subscriber
store of the corresponding order on the electrical typewriter at the Central
Subscribers' Office.
Changes of exchange data, for example rerouting, introduction of a new
signalling plan and change of numbering schemes, are effected equally simply
from a data terminal in the Operation and Maintenance Centre.
Traffic measurement adapted to the alternative routing networks, with measurement
of traffic dispersion and several other detailed measurements the results
of which can be transferred by remote control to the Operation and Maintenance
Centre.
Maintenance
L M Ericsson's maintenance method, CCM (Controlled Corrective Maintenance),
has been successfully adopted by a number of telephone administrations,
among which the Rotterdam administration, as described in an article in Ericsson
Review 3 . The article reveals that only 0.075 man-hour per line and year is required
for maintenance of the Dordrecht 20,000-line ARF exchange. System
ERICSSON REVIEW No. 4, 1973