| 摘要 |
PURPOSE:To perform the operation of a tone arm smoothly and properly and to make the titled device compact by arranging four pieces of photodetecting elements on vertical and horizontal positions of the inside of one vertical wall of a recessed body and also arranging one light emitting element on proper position of the other vertical wall. CONSTITUTION:Phototransistors 1, 2, which are photodetecting elements, are arranged on a straight line l3 separated by a proper distance from the vertical center line l1 of a tone arm rotary shaft to the back in a plane Z including the vertical center line l1 and the horizontal center line l2 and parallel with the center line l1. If it is defined that the intermediate point between the phototransistors 1, 2 is 0, phototransistors 3, 4 are arranged on a straight line l4 passing the intermediate point 0 and perpendicular to the plane Z at equal intervals from the intermediate point 0. On the other hand, the light emitting diode 5 is arranged on a straight line l5 perpendicular to the straight lines l3, l4 and passing the intermediate point 0 in the vertical wall 7. Since a shutter plate 9 performs the same operation in accordance with the operation of the tone arm 8, the quantity of light made incident to the phototransistors 1-4 is changed, so that the position of the tone arm 8 can be detected precisely and easily. |
