TELE-X - a Satellite System for TV and Data Communication ...

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Fig. 1
The figure shows three of the most common
types of circuits: point-to-point (A), multiplexer
(B) and multipoint (C). The diagnostic channel,
which connects the supervised units to the central
equipment, is in the form of a secondary
channel
Diagnostic unit (DU)
Data transmission channel
Diagnostic channel
Diagnostic channel arranged as a secondary
channel
either secondary channels between the
modems or separate transmission lines
for supervision and control signals. The
same degree of freedom cannot be obtained
with systems that use the supervised
data channel for the transmission
of signals.
The need for network supervision systems
varies greatly for different countriesand
applications, depending on the
industrial structure and the conditions
laid down for the use of the public network.
In cases where the telecommunications
administrations own and lease the data
networks they are also responsible for
fault location and repairs. The customer's
part in the supervision is to ascertain,
before the fault is reported to the
administration, that the fault is located
in the equipment owned by the administration.
In markets where the users
also own the transmission equipment
they are also responsible for the supervision
of the network.
The way that EDNET is used depends on
the network structure. Fig. 1 shows a
network containing the three most common
elements: point-to-point links, multipoint
links and multiplexing links.
It has been found that the network structure
varies with the type of business. For
example, multipoint networks are predominant
in the bank and transport sectors,
whereas manufacturing industry,
insurance companies and administrations
usually have point-to-point and
multiplexer networks.
Public and large private switching networks
are particularly attractive applications
for such data transmission networks.
In Ericsson's ERIPAX system the
subscriber connections can be built up
using primarily point-to-point and multipoint
circuits 1 . The supervisory functions
for transmission and nodes are
brought together in a centre using a uniform
interactive method for the input of
commands and processing of alarms.
Previously developed components from
the product family ASK 101 and from
other Ericsson products have been used
in the development of EDNET. It has
therefore been possible to design
EDNET so that it fits in with integrated
communication systems, where the
products interact to give the optimum
result.
EDNET consists of diagnostic units and
central control equipment. The diag-