CCIR System F
CCIR System F was an adaptation of System E used in Belgium and Luxembourg. With only half the vision bandwidth and approximately half the sound carrier offset, it allowed French 819-line programming to squeeze into the 7 MHz VHF broadcast channels used in those neighboring countries, albeit with a substantial loss of horizontal resolution. Use of System F was discontinued in Belgium in February 1968, and in Luxembourg in September 1971.
Between 1976 and 1981 when French channel TF1 was switching area by area to the new analog 625-lines UHF network with SECAM colour, some transmitters and gapfillers broadcast the 819-line signal in UHF. When switching to 625-lines, most gapfillers did not change UHF channel. They were switched to 625-lines in June 1981.