To add to this, the Astros has basically installed cameras in their stadium that allowed the coaches and players in the dugout to know which sign the catcher ha

To add to this, the Astros has basically installed cameras in their stadium that allowed the coaches and players in the dugout to know which sign the catcher has signalled (the dugouts are behind the catcher, so you cannot normally see the catchers sign from there). The dugout then used the drum banging method to convey that information to the batter.