ericsson review - ericssonhistory.com

18
Fig. 9
Typewriter terminal for communication with the
exchange
Operation and maintenance
The principle for the operation and
maintenance of ASB 100 can be summarized
as follows:
— the operation of the exchange is continuously
supervised by a built-in
supervisory system
— if disturbances occur, measures to
limit the effect of these are carried out
automatically
— all preventive maintenance and all
routine testing during the operation
of the exchange is avoided
— it is possible to carry out fault localization
down to the printed board assembly
level with the aid of simple
tools.
Operational supervision
In the case of an exchange of this size
the program volume must be kept as
small as possible for reasons of
economy and reliability.
Since the number of components is
small and the reliability is high, ASB 100
requires only a few supervisory functions,
primarily for the supervision of the
control system.
The system contains the following
supervisory functions that can give
alarms:
— a hardware circuit that supervises the
progress of the program handling
— a disturbance ratio supervision function
that counts the number of connections
and disturbances
— supervision of the power supply unit
when the exchange is fed from both
the mains and batteries.
Alarms from the supervisory functions
of the exchange are obtained both in the
exchange and on a lamp in the
operator's console as follows:
— time supervision alarm gives steady
light
— disturbance ratio alarm gives slowly
flashing light
— voltage alarm gives rapidly flashing
light.
It is also possible to have these alarms
indicated on a separate panel. The exchange
itself also contains an observation
alarm function that indicates if any
units are blocked or any printed board
assemblies have been removed.
The function "disturbance marking of
devices and data areas" has been introduced
in order to limit the number of
traffic disturbances caused by technical
faults as far as possible.
This means that after devices or data
areas have caused a disturbance marking
they will not be selected until all devices
or areas without faults are engaged.
If a connection attempt with a
marked device or area is then successful,
the disturbance marking will be
cancelled.
Disturbance marking can be initiated
for, for example, the devices and store
areas included in a disturbed connection.
Disturbance marking is also
obtained for breaks or shortcircuits on
external lines in those cases where
supervision is possible. This supervision
is normally in the form of supervision of
the current feeding and then only when
it is a question of closed circuit current.
Aids
ASB 100 is designed to permit a certain
amount of communication with the
system from the units that are always