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Field store converters
FS1, FS3 and FS2
CPS Field converter
DD IO converter 625->405
Standards converters
Standards converters FS3 (Pye)
ACE converter

Charles Hope, Supervisor in Standards Converters from 1964 to 1970 adds the following information:-
FS1, 2 & 3. Field store (solid state) field rate converters developed by BBC Research, FS1 525 > 625; FS2 625 > 525; both built as prototypes by RD.
FS3 could work either way, built by Pye TVT as their pre-production machine (they had bought manufacturing rights) FS1 appeared just in time for the
Mexico Olympics in 1968) Colour system was converted as well as line/filed rate.
CPS Field Converter. Not quite an accurate caption, inputs were 405/50, 525/60, 625/50 and 819/50. Came into service in 1961. Optical conversion,
CPSE camera pointing at a high quality monitor. Complex anti-flicker circuitry (all valves) to remove 10Hz beat when doing a field rate conversion. Not obvious from photo, but their floor space was taken over by FS 1, 2 & 3. The rack system on which the camera/monitor set-up is sitting was originally part of VERA.
DD IO converter. Worked 405<> 625. Very high quality monitor and Pye MkV camera. Was produced to cope with BBC1 & 2 being on different standards in case solid state ones didn't work.
"Standards conveters" Miscaptioned, its actually FS1, The separate unit at the RHS is doing the final line length change. It was the original 625 > 405 RD converter and was re-used here.
ACE was produced by the IBA as a 4 field 60/50 HZ converter. It appeared before Pye had time to sell only a couple of the BBC RD machine.
That 625/405 converter looks partly optical, but I'm sure I saw a solid state one on tv once.
The original RD one (bi-directional) is shown above, There was also a production Designs Dept one - 2 racks wide. There were, at one point, 4 of
these at TVC (625 > 405) and one 405 > 625, but eventually BBC 1 distribution went 625 and the converters were moved to the 405 transmitters, except for one to deal with archive tapes.