| 摘要 |
PURPOSE:To allow a practicing person to clock practice time individually by attaching a detachable stopwatch constituted indeendently of an abacus to the edge frame 1 of the abacus, and displaying calculation time with a switch botton. CONSTITUTION:An electric stopwatch 3 is equipped detachably to one side end of the edge frame 1 of an abacus, and an electric circuit 5 led out of the power source of a timer is connected to a switch provided to the edge frame 1 of the abacus; and its operation button 6 is projected at a proper position on the edge frame. Therefore, the switch botton 6 is only operated to clock time during abacus practice, so a practicing person has effective practice in abacus individually without any instructor. |
