“NBC Tape Central. These are the four RCA TRT-1A color prototypes. Primary use for these and the Ampex machines below were for Time Zone Delay. From “RCA Broadcast News,” March, 1959″
A history of developments in videotape technology and broadcasting. Not specifically about sitcoms, but it provides some background on how sitcoms must have been recorded over the years.
Richard Wirth, “Technical and Engineering Advancements Made at NBC,” March 16, 2014.
http://provideocoalition.com/pvcexclusive/story/the-demise-of-nbc-burbank-part-2