RAF Fighter Command beat radar noise with a central filter room

Britain's earlier air-defense doctrine, dating to Edward Ashmore's WWI-era defense of London, had already tried centralizing spotter reports into one plotting room, but it was built for slow, low-flying aircraft tracked visually and by sound.

The reflexive way to use a fast new sensor is to get its output to the people who have to act on it as fast as possible, and let each of them interpret their own slice of it — which is roughly how the pre-radar reporting chain already worked, feeding raw sightings outward to local units to judge for themselves. Against 1940's volume of overlapping, sometimes contradictory contacts, that would have meant scrambling squadrons against duplicate sightings and false tracks as readily as against real ones.

Dowding's central filter room deduplicated raw radar and observer reports into one confirmed track per raid, so squadrons scrambled only against real threats, not noise.

Each station's report had errors and lag, so raw feeds were contradictory.

A single Filter Room cross-checked reports and merged duplicates into one track.

Only confirmed tracks reached squadrons, so they scrambled against real raids.

False alarms collapsed, conserving scarce fighters and pilots.

When raw signals are noisy and overlapping, don't push them to every responder; centralize interpretation into one confirmed picture first.

During the Battle of Britain the interception rate reached roughly 90 percent, against a pre-integration peacetime estimate of 30 to 50 percent for locally-interpreted defense. Outnumbered roughly four to one, Fighter Command was able to husband its limited pilots and aircraft by committing them only against confirmed raids, and the system — commonly called simply "the system" at the time — is credited by military historians as central to Britain's ability to hold off the Luftwaffe in 1940.