Radar System Engineering

SEC. 7.51 RA DAR IN THE RAF FIGHTER COMMAND 227
information was displayed in lights to a “teller,” who passed the information
over a telephone line to Fighter Command Headquarters. At a
later stage, the plots were passed by teletype to save time. The whole
computation process was completed in a second or so.
The operator then pressed a button which connec Led the goniometer
to the height-finding antenna arrays. Again she turned the goniometer
until the signal disappeared, and pressed a button. The height of the
target was computed by the fruit machine and passed to headquarters.
Radar plots from all of the chain stations were sent to Fighter ~ommand
in Stanmore, north of I,ondon. Because of the shortcomings of the
early radar equipment, and the “blind spots” in the coverage of individual
sets! it was felt to be essential to combine the information from
all radar stations at a central point. This was done at a so-called
“filter center. ”
In a large underground bombproof room was mounted a central
table whose surface was a gridded map of England. A crew of plotters,
each with a telephone connection to one of the radar stations, stood
around the table at positions corresponding to the geographical locations
of the Chain stations. As a plotter received plots over the telephone,
she put colored disk markers in the grid positions indicated. It usually
happened that two m more stations were simultaneously plotting the
same aircraft, so that several girls might be putting down counters representing
the same formation. Owing to the errors in the system and the
variable delays in the plotting process, the interpretation of the piles of
disks in terms of aircraft was not easy. Special officers known as filterers
stood beside the girls and decided, for example, whether two adj scent
tracks were really separate, or represented the same aircraft, erroneously
plotted by one of the stations. After he had analyzed the data, the
filterer put on the map a little plaque that bore his best estimate of the
identity, position, height, speed, and number of aircraft in the formation.
This whole process was observed by filter ofice~s who sat on a balcony
overlooking the map. They were informed of the plans for the movements
of friendly aircraft. They were able to direct the operations of the
whole Chain and to decide which formations should be plotted by each
station. The work of the filter officer called for a considerable understanding
of the performance of CH stations, and an appreciation of the
good and bad qualities of each individual installation.
Established tracks on the filter-room board were telephoned by a
teller to a second plotting board maintained in an ‘‘ operations room. ”
Here the filtered radar tracks were combined with plots of the Observer
Corps (visual airplane spotters), and with fixes made by means of radio
direction finders, In this main control room, the aim was to display the
whole of the picture of the air \var; all operations were generally directed