The sector play system is useless in online casinos, so we won't go into in-depth description here.
The general idea of the sector play system is akin to shuffle tracking methods in Blackjack. Using perceptive skills, the player would learn the way the dealer throws the ball, and, with some measurements, predict into which sector it would fall. Combined with some statistical mechanisms, this system can be a very powerful weapon in land casinos. Essentially it is pointless to try it in online casino simply because there's no mechanical process and human instinct involved in throwing the ball.