Complex sentence: KWFT sold the TV station in 1956 to Sydney Grayson at which time channel 6 became KSYD-TV and then KAUZ-TV in July, 1963 following a subsequent transfer of ownership.
Split into simpler sentences: KWFT sold the television station in 1956 to Sydney Grayson, at which time channel 6's call letters were changed to KSYD-TV. The station's calls then changed to KAUZ-TV in July 1963, following a subsequent transfer of ownership.