The Battle of Britain Five Months That Changed History, May—October 1940 by James Holland (z-lib.org).epub

GPO also created a separate network, authorized by the Treasury, called the
Defence Teleprinter Network (DTN), as a back-up and an extra means of
confirming signals. This linked and served all three home RAF commands,
but was still run by the GPO, and maintained by its specially created War
Group.
Clever science, ingenuity, common sense and the dedication of
thousands of volunteers ensured that Fighter Command could call on a
series of invaluable cogs in its defensive system. However, bringing all
these together effectively and efficiently into a smooth and reliable machine
was of vital importance were Fighter Command to reap the maximum
benefit from what each of these strands had to offer. Fortunately, Dowding
had managed exactly that.
Centralization and standardization were the key. Fighter Command was
divided into operational groups, each of which had its own headquarters
and Operations Room. The Groups were then divided into sectors, which
were given a code letter. Each sector contained a principal fighter station
and sector headquarters with its own Operations Room. Linked to this were
the sector’s direction-finding stations. Also within each sector were other
satellite airfields. For example, Duxford was a sector station, and nearby
Fowlmere was a satellite. All Operations Rooms, whether sector, Group,
Fighter HQ, or Observer Corps centre, looked the same. In the centre of the
room was a large plotting table with a map of Britain, on which were all the
sectors and Observer Corps zones. It was large enough for anyone looking
at it to see at a glance precisely what was going on. Around the table were
the plotters, each equipped with telephone headsets and a croupier’s rake.
As a call came through, the information would be plotted on the map, with
the marker pointing in the direction the aircraft were heading. Rectangular
coloured counters were added to show height, size and whether they were
bombers or fighters. RAF plotters were WAAFs, from the Women’s
Auxiliary Air Force, and were popularly known as the ‘Beauty Chorus’.
Overlooking the plotting table on a raised dais were the men who would
use the information being collated in front of them. At a sector station, there
were usually about eight such people, with the Senior Controller at the
centre, controlling the squadrons in his sector. Next to him were the
Assistant Controller, and then the two Deputy Controllers. Either side of
them was ‘Ops A’, who was in permanent contact with Group, and ‘Ops B’,
whose job it was to ring through to the squadron dispersal and scramble the