| 摘要 |
In order to better exploit the training possibilities of a program-controlled ball throwing machine (1) which throws on the playing ground particularly tennis balls with different speeds, under variable angles and optionally with different spins and according variable sequencies, there is arranged essentially in the plane of at least one outlet opening (2) of a ball throwing machine (1) a projection screen (3) leaving free the outlet opening (2), and on which screen there is projected a series of film images related with the throwing program and the different throws. The motions of the tennis player which may be viewed on the screen (3) correspond to the programming mode of the ball throws.
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