WWII Operation Plotting Clock
The dial of these Sector clocks, found in all RAF Ops Rooms of that era, had a very specific design intended to aid the complex efforts of RAF controllers.
Information received by the Group Operations Room concerning the altitude, bearing and strength of approaching hostile aircraft were plotted on large table maps like that shown in the above photo.
Group would then alert the most appropriate or its subordinate Sector Operations Rooms, who would take charge of the local response once their interceptor squadrons had been scrambled.
Work in the Group Ops Rooms must have been incredibly hectic.
Numerous incoming messages had to be sorted, prioritised, and disseminated at a breathtaking pace.
After all, late information could send a precious squadron of Hurricanes or Spitfires looking for hostile targets on bearings and at altitudes vacated by the enemy.
A quick and reliable method of sorting stale information from current and more urgent reports was devised by the RAF, and the Ops Room clock was at the heart of this method.
All incoming reports would be colour coded with flags of either red, yellow, or blue according to the time they were received.
These colour-indicated times were assigned according to the position of the minute hand on the special Operations Room Clock which had its dial painted with triangles in this trio of colors at a succession of five minute intervals around the dial.
The colour indicated by the minute hand at the time the report was received would be the colour given to the message and plotted on the Operations Room map.
Because of the speed of these enemy raiders crossing Britain's coastline the RAF's response had to be made in minutes.
This colour coding process and the elaborate communications network behind it created a highly effective and efficient system.
It was possible, according to reports from system veterans, to have fighters in the air and on their way to an intercept within five minutes of the initial contact.
Without the simple yet elegant time coding system devised by the RAF, the British might not have been so successful in holding control of the skies over Britain during the crucial Battle of Britain as well as later in the war.
Two basic Sector Clock designs emerged and where used in the same way.
Type A - (Biggin Hill) had outward pointing triangles whilst the:
Type B - (Uxbridge) had inward pointing triangles:
Both had 5 minute segments in the same colour sequence Red, Yellow and Blue, repeated each 15 minutes.
It should be noted that these Sector Clocks are not designed or sold as a replica. Original Sector Clocks were very large over 18" dials. Xarim Sector Clocks are produced only as a copy suitable for modern homes, for the memorable value of their historic existence and the very important roll they served in the RAF.