The Wikipedia article on the Telstar satellites from the early 1960s says that in order to facilitate transatlantic television signals (where the US had the 525-line (480 visible) NTSC system, and the UK's BBC had a 405-line system) the BBC had room-filling video signal conversion apparatus.

The standards 525/405 conversion equipment (filling a large room) was researched and developed by the BBC and located in the BBC Television Centre, London

I'm curious how this conversion equipment setup worked. I know that delay-lines are used in relatively modern analog television systems (such as PAL), but it's implied a delay-line system could really only buffer a single line - rather than multiple entire frames to cover a frame-rate mismatch.

Today, to convert video of one-frame-rate and resolution to another necessarily involves modern interpolation algorithms operating on multiple digital frame-buffers - but [Wikipedia implies that the capability for video framebuffers in the 1960s simply didn't exist. I know that but it wasn't feasible to bufferm

(I'm assuming that they had a fully electronic system and that they weren't employing tricks such as using a 525-line TV-signal projector to illuminate a screen that was being simultaneously filmed by a 405-line camera for onward distribution.)

My question is: how could an electronic television signal frame-rate-and-resolution conversion system be implemented using 1960s-era technology?


1 Answer 1


1960's standards convertors did involve CRTs and cameras, with quite a lot of tweaking to minimise artefacts. This description of the state of the art at the time, from BBC Engineering, goes into a lot of detail about the process.

Quartz crystals used as delay lines were just around the corner. By 1970 the BBC had built an entire field store based convertor that way. THe references in the linked report show that the design process was already under way in 1964.

enter image description here Quite a substantial piece of equipment. (picture from RD Report 1970/37 linked above)

  • \$\begingroup\$ Wow! Thank you :D \$\endgroup\$
    – Dai
    Dec 22, 2019 at 3:34
  • \$\begingroup\$ Substantial?? Heck, that's barely a minicomputer! \$\endgroup\$
    – Hot Licks
    Dec 22, 2019 at 13:50
  • \$\begingroup\$ @HotLicks It's very substantial by today's standards! \$\endgroup\$
    – Hearth
    Dec 22, 2019 at 16:20

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