redesigned, mainly on the BMM chassis system.
Audio Jackfield
A new eight way jackfield has been designed as an interface with Post
Office
lines.
It provides
"lines"
and
"listen"
jack
sockets,
an
attenuator socket and a line repeating coil for each position.
Ceefax Measurements at Certain Transmitters
Measurements of Ceefax signals radiated from Sandy Heath, Hannington,
and Fremont Point have been carried out, in cooperation with Transmitter
Department. These tests, taken in conjunction with other evidence, have
indicated that at least those transmitters which obtain their input
signals by rebroadcast means will require Ceefax regenerators at their
inputs, and that a degree of pre-equalisation may also be desirable. A
demonstration of the results obtained on the tests has been given.
Proposals for Revising the Allocation of TV Distribution Limits
Transmitter Group proposals for the reallocation of limits on television
distribution chains have been tested on a chain involving four
transmitters between Blaen Plwyf and Llandrindod Wells. As a result
certain modifications to the proposals have been agreed and they are now
being generally implemented.
Tests on a V.G. Electronics Teletext Regenerator
An investigation has been carried out into the performance of a
synchronous Ceefax regenerator manufactured by V.G. Electronics Limited
to assess its suitability for use in the BBC. In general it was found
to work well but some changes have been suggested.
Investigation into Reflections on LDK5 Cameras
An investigation has been carried out into the problems involving
reflections, i.e. delayed images, which have been experienced on signals
sent
to
and
from
the
LDK5
camera used by Television
O.B.'s.
The
troubles have been shown to be due to mismatches in the terminating
impedances at both ends of the cable linking the camera and the control
unit.
Final Meeting_(Study_Period 1974-1978) of the CMTT
This joint CCIR/CCITT Study Group concerned with long distance
transmission of television and sound, held its Final Meeting in
September/October. The two members of the Section who attended this
meeting succeeded in getting two Recommendations accepted. The most
important of these deals with international television transmission, and
gives details of the test waveforms, measurements, and limits, which are
applicable. The second Recommendation covers the BBC Sound-In-Sync
system.
PROJECTS IN PROGRESS
Video Amplifiers and Equalisers
A series of low noise l5dB gain video amplifiers on the BMM chassis have
been designed, together with associated equaliser cards. In addition a
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