Editing Chain crew (section)

==History==
All levels of organized football have used the chain crew.  The "box" (down marker) has evolved over time. In the pre-television era, it was a rod (shorter than the height of the operator) with a triangular pointer that rotated to show the official the down number. It was replaced with a much larger, two-sided flipper system when television became widespread; flipper-style down markers are still in use in scholastic and amateur football. A more modern model is the ''Dial-a-Down'', in which compact levers display a new down number over the entire face of the "box"; this model is used at most college and professional games.<ref name=chaininterview/> Electronic down markers using [[Light-emitting diode|LEDs]] are emerging as the next advance.<ref>{{Cite web
|url=https://www.anthem-sports.com/fisher-electronic-football-down-marker-5004.html
|title=Fisher Electronic Football Down Marker
|publisher=Anthem Sports
|access-date=January 8, 2019}}</ref>