As aircraft increased in size it became necessary to get a remote indication of the angular position of flaps, ailerons, retractable under-carriages, petrol float mechanisms etc. to the pilot's or/and flight engineer's instrument panels.
The Desynn type of system, and the repeater motor were developed in 1937 and were the only devices capable of catering for the transmission of unrestricted rotation
Smiths Aviation Division made remote instruments which operated on the "Desynn" principle. It is electrically operated, being available for 12 or 24 volts, and gives readings which are independent of voltage fluctuations and a clear indication of supply failure, should this occur. The equipment consists of two units joined by five core cable which can be of considerable length.
There does not seem to have been a registered company called Smiths Desynn, but the ‘Desynn’ name was a Trademark and the system was patented presumably by Smiths Aircraft Instruments.