PURPOSE: To inform automatically the set of swings by providing a counter generating the output when receiving an output from a detector responsive to at least a predetermined acceleration to count set values and a pronouncing device for receiving the output from the counter to pronounce an informing sound on sports outfits swung.

CONSTITUTION: A desired swing circuit is preset in a down-counter 6 by a preset device 7. By swinging a racket with at least a predetermined acceleration is displaced at least predetermined amount a magnetic body core 3a of a differential transformer so that an output of at least a predetermined level from a converting circuit 4 is generated to generate an output from a clipper circuit 5. This output is counted by a down-counter 6 and the remaining number of swings is indicated by an indicator 10. When the desired number of practice swings are carried out, the content of the down-counter 6 becomes zero so that a circuit 15 for judging zero generates an output to produce an informing sound from an announcing device 16. Thus, when the number of swings reaches a desired one, it is automatically informed, so that the number of swings does not need to be counted and thereby one's mind can be concentrated into the practice swing training.