PAL Colour Recovery from black-and-white ‘telerecordings’ (2008)
In Australia before the official introduction&#x2F;launch date of PAL colour television in 1975 it was a requirement of the then, now defunct, broadcasting regulator, the ABCB - Australian Broadcasting Control Board for television stations to remove any colour content from their TV broadcasts. (During the conversion period leading up to the launch stations would run a mixture of B&amp;W and colour material within their stations).<p>To comply, stations would strip the colour burst from the TV 
video sync block before it was broadcast. This infuriated many propeller-head techies and nerds, myself included.<p>To overcome the problem, the 4.43 MHz colour subcarrier in the broadcast video which wasn&#x27;t deliberately stripped out was used to reconstitute the colour burst. This was achieved by modifying standard PAL colour TV sets (which weren&#x27;t that difficult to obtain) with the addition of some subcarrier-extracting filters and appropriate phase-locking&#x2F;modifying circuitry. This was a bit tricky, as the reference phase was no longer there and the fact that it was a PAL signal (PAL - Phase Alternating Line encoding).<p>In fact, I recall at the station I was working for at the time we had a modified TV set in the engineering department working in colour from off-air signals (one of my colleagues was a past master at tweaking up sets this way).<p>Perhaps a bit of broadcasting history trivia but it sure shows the colour recovery technique in this story wasn&#x27;t the first effort.<p><i>Edit: Incidentally, the same trick was used on source material such as quadruplex videotape that already had the burst stripped at other locations.</i>