and other vehicles. SFIM is today part of the Safran group and is still present in the flight recorder market. The advantage of the film technology was that it could be easily developed afterwards and provides a durable, visual feedback of the flight parameters without needing any playback device. On the other hand, unlike magnetic tapes or later flash memory-based technology, a photographic film cannot be erased and reused, and so must be changed periodically. The technology was reserved for one-shot uses, mostly during planned test flights: it was not mounted aboard civilian aircraft during routine commercial flights. Also, cockpit conversation was not recorded. Another form of flight data recorder was developed in the UK during World War II. Len Harrison and Vic Husband developed a unit that could withstand a crash and fire to keep the flight data intact. The unit was the forerunner of today's recorders, in being able to withstand conditions that aircrew could not. It used copper foil as the recording medium, with various styli, corresponding to various instruments or aircraft controls, indenting the foil. The foil was periodically advanced at set time intervals, giving a history of the aircraft's instrument readings and control settings. The unit was developed at Farnborough for the Ministry of Aircraft Production. At the war's end the Ministry got Harrison and Husband to sign over their invention to it and the Ministry patented it under British patent 19330/45. The first modern flight data recorder, called "Mata Hari", was created in 1942 by Finnish aviation engineer Veijo Hietala. This black high-tech mechanical box was able to record all important details during test flights of fighter aircraft that the Finnish army repaired or built in its main aviation factory in Tampere, Finland. During World War II both British and American air forces successfully experimented with aircraft voice recorders. In August 1943 the USAAF conducted an experiment with a magnetic wire recorder to capture the inter-phone conversations of a B-17 bomber flight crew on a combat mission over Nazi-occupied France. The recording was broadcast back to the United States by radio two days afterwards. Australian designs In 1953, while working at the Aeronautical Research Laboratories (ARL) of the Defence Science and Technology Organisation, in Melbourne, Australian research scientist David Warren conceived a device that would record not only the instrument readings, but also the voices in the cockpit. In 1954 he published a report