Abstract: A computerized device for propelling tennis balls by pneumatic pressure. The device contains a support pad to protect the tennis court. There is a by-pass valve which, when open, allows the blower for the pneumatic system to blow continuously, thereby avoiding carbon deposits. There is a pressure tank for the build-up of pressure for the pneumatic system when the by-pass valve is closed. Course and fine pressure valves are used to control the pressure in the pressure tank within narrow limits. A hopper contains pushers which prohibit balls accumulating in areas of little motion. A carousel advances only when a ball can drop freely into the ball outlet tube. A cover over the feeder point prevents balls in the hopper from interfering with the ball in the feeder point. The ball is held in an injection area until forced through a flap door into the pressure tank and a guide channel. The injection area contains a solenoid-controlled sweep arm which controls a injector which forces the ball through the flap door.