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PER FURU
Subscriber Equipment Division
Telefonaktiebolaget LM Ericsson
Fig. 2
Block diagram for the stored program controlled
PABX, ASB100
rotary dial and push-button telephone
instruments.
The use of push-button telephone sets,
which in addition to the ten digit buttons
have buttons with the star and square
symbols, makes it possible to provide
such facilities as
- individual abbreviated dialling
- automatic call diversion
- bypassing of automatic call diversion
- direct switching to a loudspeaking
telephone.
The push-button telephone sets also
have another button, the register button,
for calling in a register, for example
when making an inquiry call.
Special importance has been attached
to the utilization of the possibilities offered
by a stored program controlled
system as regards operation and maintenance
and also administration. As regards
operation and maintenance the
aim has been to reduce the need for
qualified staff and training to a minimum.
This has been achieved through
a well designed functional system structure
in combination with advanced test
programs and easily understood documentation.
The administration of the
system has been made more efficient
and flexible since certain tasks can now
be allocated to the operator, and because
it is possible to arrange central
administration of several PABXs via the
public telephone network.
System design
ASB 100 can be divided into a switching
equipment and a control system. The
exchange of information between these
two takes place via a bus system. Fig. 2
shows a block diagram of the system.
The units shown in unbroken lines constitute
the standard equipment in the
exchange and the units shown in broken
lines are supplementary equipments,
which can be supplied if required.
Switching equipment
ASB 100 is equipped with an electronic
switching network that is built up of
thyristor crosspoints. This means that
redirection in the switching network can
be carried out very quickly and that the
network can be used not only for speech
communication but also for the connection
of different signalling units. Such
units include the tone sender, which
gives different types of tone information
to the extension, or the dialling tone receiver,
for receiving the dialling tone
from the public network when this occurs.
The use of a single-stage thyristor
crosspoint switching network makes it
possible to order the setting up of different
connections direct from the units
concerned, for example extension line
circuit and tone sender, when initiating
a call. Thus special circuits for setting
up the switching network are not required.