| 摘要 |
An athletic ball comprising (a) a ball having an airtight bladder with an air injecting valve, (b) a housing provided with the ball on the opposite side of the valve without interfering the airtightness of the bladder, a detector for detecting an application of external force to the ball, an operation converter for converting the detected impact signal to a numerical information signal, a display for displaying the numerical information and/or for generating a sound according to the numerical information, and a battery power source; the converter, display and battery power source being accommodated in the housing, and the sum of the weights of all of the above elements being adjusted to the weight which does not substantially interfere the impact resilience of the bladder and is substantially the same as that of the valve.
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