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Fig. 4
The structure of the program system
The cabinet on the left is
for up to 100 extensions
The cabinet on the right is
for up to 40 extensions
Fig. 5
Cabinets for the exchange
equipment
ories (PROM) were chosen for storing
the programs — program stores - whereas
the parameters that can vary from
one installation to another are stored in
electrically changeable memories
(RAM)-data stores. The latter also provide
the storage capacity required for
storing temporary data in connection
with the traffic in progress in the PABX.
The data store boards are equipped with
chargeable miniature batteries that can
keep the voltage intact for at least 100
hours, so that the semi-permanent data
stored in the data store will not be lost
in case of a power failure.
When designing the program system in
ABS 100 the demands that can be made
on a modern PABX have been met as far
as possible. In addition to the abovementioned
division into program and
data stores it has been the aim to facilitate
the introduction of new functions
and make market adaptions. The
structure of the program system is
shown in fig. 4.
The program system can be divided into
three parts: traffic programs that handle
the actual telephony functions, monitor
programs that supervise the program
handling and common functions in the
exchange, and finally operation and
maintenance programs.
The traffic programs in their turn can be
divided into two parts: one procedure
block and one line signal block. The
program modules of the procedure
block each cover different traffic cases
in the exchange, whereas the line signal
block modules constitute the interface
between the procedure programs and
the different hardware units in the exchange.
In this way small program modules with
well defined interfaces have been
obtained. The procedure program modules
are affected when new facilities are
introduced and existing ones are modified,
and the line signal program modules
are affected, for example, when the
PABX is adapted to new types of signalling.
Cabinets
ASB 100 can be supplied with two different
cabinet heights depending on the
final capacity required, fig. 5. The smaller
cabinet, which accommodates one
magazine containing three shelves,
permits extension up to 40 extensions, 5
local junctors, 12 trunk lines and 3 tone
senders. The larger cabinet, which accommodates
two magazines with three
shelves each, permits extension up to
100 extensions, 10 local junctors, 24
trunk lines and 6 tone senders. At the
manufacturing stage space is prepared
in the cabinets not only for the control
unit and the required traffic-carrying
devices and switches but also for the
extra printed board assemblies that are
required for additional facilities.
There is also space in the cabinets for a
built-in power unit.
Switching network
The switching network in ASB 100 is
built up of thyristor crosspoint matrices
for symmetrical two-wire through-connection.
The matrix capacity gives
optimum utilization with 40 and 100
lines. A matrix, which is accommodated
on one printed board assembly, can
connect 12 inputs to 28 outputs. Thus