Yngve Rapp - The history of Ericsson

ERIC STRINDLUND
LARS-AKE ANDERSSON
LENNART BRENNICK
Data Communication Department
Telefonaktiebolaget LM Ericsson
Fig. 2
LM Ericsson is today one of the world's largest
suppliers of equipment for telex and data
switching exchanges. Of LM Ericsson's crossbar
system ARB/ARM for telex, which was introduced
in the early sixties, there are in 1977 more than
250,000 multiple positions for subscriber and
trunk lines in operation oron order in more than 20
countries
Fig. 3
Modernization of telex network with system AXB
20 for both national and international circuits
Existing national exchange
National/international exchange
National telex exchange
Terminal exchange
Multiplexor/Concentrator
Asynchronous data networks
For asynchronous data networks a
separate switching system, APT 603,
has been designed, based on the same
technique as switching system APT 601
and, like the latter, regenerating. The
switching system can handle the codes
and speeds laid down by CCITT in Recommendation
X 1, User Classes 1 and
2.
Switching systems APT 601 and APT
603 can be combined in one exchange
and controlled by one pair of processors
APZ 210 (fig. 4).
System properties
As mentioned in the introduction,
system AXB 20 has a number of new
properties, which can be broadly listed
under three headings: flexibility, ease of
handling, and reliability.
The properties presented in this context
relate primarily to telex applications of
the system, since telex is the entirely
predominant service in terms of traffic
volume.
Flexibility
— In transmission
owing to optional line adapters for
high or low level signalling for adaptation
to different methods of trans­
mission, and owing to integrated
connection of division multiplex
transmission equipment. The regeneration,
furthermore, permits teleprinters
and lines to work higher
distortion than was previously possible.
In signalling
owing to the structuring of the software
system into separate function
blocks, which can be altered, extended
or exchanged, for example for
compliance with new international
recommendations.
In new subscriber facilities
which are programmed in independent
function blocks. These new
facilities will be described below.
In traffic routing
owing to unlimited number of possibilities
offered for the forming of
routes, alternative routes, one- and
two-way circuits, the establishment
of closed user groups, etc.
In charging
owing the various possibilities that
exist, e.g. multimetering, toll ticketing,
and a combination of the two.
The calculation of charge for a set-up
connection can be based on several
different criteria, e.g. destination,