I've just watched this 1968 episode of 'aircrash', it deals with the stockport air disaster of 1967 and subsequent investigation.
Although interesting in its own right, the documentary spends a little while at Royston Instruments, showing the 60's technology of the nacent flight data recorder. The ill-fated Canadair Argonaut that crashed was an early adopter of the Royston 'Midas' system.
Royston Industries of course is known in TV & Radio circles as being the parent of Vidor-Burndept (who were into aircraft locator beacons at the time) and Jennings / Vox when the group went into receivership, Vidor-Burndept being bought by Crompton Parkinson.
Worth a watch to see the technology of the day as narrated by the magic voice of Kenneth Baker
https://www.youtube.com/watch?v=Zz94kJRXWqA