Science: SARAH

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During the Battle of Britain, when airmen parachuted by the dozens and scores into the choppy waters of the English Channel, the R.A.F. was never quite satisfied with its, search & rescue gear. The keenest eyes and the most sensitive radars often missed the tiny, bobbing targets made by helmeted heads and yellow Mae Wests.

Last week, more than a dozen years after the R.A.F.'s heroic tangle with the Luftwaffe, Ultra Electric Ltd.. a London television manufacturer, announced that its engineers have finally built a reliable gadget for finding lost flyers. For more than 200 NATO delegates at the Royal Aircraft Establishment at Farnborough.

Ultra demonstrated "SARAH" (search and rescue and homing), a tiny (42-oz.) transmitter-receiver, small enough to be hung on a Mae West.

Downed pilots need only pull a ring to release a coiled, 31-in. antenna, and the little, battery-powered transceiver automatically transmits distress signals. Search planes as high as 10,000 ft. and as far away as 66 miles can pick up the signals on a pair of antennas. Matched like radar pips on the face of a cathode-ray tube, the signal from each antenna is the same length when the plane is headed directly toward the target. Directly over the target, both pips disappear. Then the downed pilot switches to voice communication for final instructions to his rescuers.