The majority of tennis ball launcher machines on the market operate using counter-rotating wheels. When the machine is turned on an electric fan draws in outside air which is then pushed into the canister. To protect the fan motor from debris the air passes through a slab of foam as well as a screen barrier. An electric motor powered hopper is used to channel balls into the landing area. During this process the wheels squeeze the balls and put them under intense pressure, thus forcing them into a circular tube which leads to a small opening. This soft, rubbery circular area is called a detent. When the ball is lodged in the detent it creates an airtight seal at the end of the tube. Simultaneously, a plastic flap falls over the entrance which causes pressure to mount. Under pressure method, Eventually air pressure pushing on the ball overpowers resistance from the detent. This causes the ball to shoot down the barrel and onto the court. When the pressure has been released the entrance flap is released and another ball is able to enter the tube. The process is repeated until all balls are depleted.