Field Trial of Optical Fibre Cable-TV System Optical Fibre System for ...

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In planning the optical fibre network,
spare fibres have been allowed to cater
for future growth of the telephone and
data transmission systems or for other
communication systems such as the
new London Underground Ticketing
Communications network.
Preparation and testing for
cut-over
The new digital system could not work
directly into the old Strowger exchanges
unless expensive interface
equipment was designed. With such
equipment it would have allowed the
new exchanges to be commissioned individually,
but with a period of a mixture
of 4- and 5-digit telephone numbers
which was considered unacceptable. It
was therefore decided to cut over in one
operation, and careful planning was
needed to ensure a successful introduction
of the new system. Each of the 6000
telephones was wired to its new exchange
and temporarily back to the old,
fig. 7. This involved a number of miles of
extra tie cabling being added to some
telephone lines, thus causing an increased
fault liability and reducing
speech quality in the months prior to
cut-over. In the old exchanges cross
connections were made in order to route
telephones to the new exchange, and
connections were then arranged to be
isolated in both old and new by means of
break jacks on the MDFs. The cut-over
wiring where an exchange area was not
to be altered was fairly straight forward
but where a large existing area was
being divided up, complex teeing had to
be made at trackside location boxes.
In February 1984 exchange co-ordinators
were appointed for every exchange
to ensure that the cut-over connections
were correctly installed and to coordinate
all other work within their exchange
prior to cut-over. This included
both exchange and transmission equipment
and alarm panel. Regular meetings
were held with all exchange co-ordinators
and the project team to enable
overall progress of the project to be
monitored.
Once the cut-over MDF connections
were completed, each line in turn was
disconnected from the old exchange
equipment by placing wedges in the
break jacks. The associated connection
was then made in the new exchange and
the line was tested. The user was requested
to dial a test number and finally
the line was restored back to the old
exchange.
During one Sunday prior to the main
cut-over all telephone users connected
to Loughton old exchange were temporarily
transferred to Loughton new
exchange enabling the users at the east
end of the Central Line to try out the new
system. This provided the project team
with valuable feedback information
both technically and operationally.
A flood test of telephone calls was also
undertaken in January 1985 between
Acton Head Office, Lillie Bridge and
MDF for
new
exchange
F
i IT
MD110
Fig. 7
Exchange cutover jumpering
F
G
A
B
E
P
T
Fuse mounting
Gas discharge tube
Arrester
Tag block
Existing jumpering
Permanent jumpering
Temporary jumpering