ビデオ判定
Instant replay has been credited as a primary factor in the rise of televised American football, although it was popular on television even before then. While one camera was set up to show the overall "live" action, other cameras, which were linked to a separate videotape machine, framed close-ups of key players. Within a few seconds of a crucial play, the videotape machine would replay the action from various, close-up angles, in slow motion.