PURPOSE: To ensure the safety and assured start with a timer for a tone arm, by detecting the position of the tone arm with the pulses of a pair of light emitting and reserving elements.
CONSTITUTION: A power supply reset capacitor 25 is connected to a reset terminal of a microcomputer 1 which functions as a logical control circuit, and the output of a detection switch 2 for position of an arm rest is connected to an input terminal of the computer 1. An arm position detector 3 is constituted by setting a light emitting diode 16 and a phototransistor 17 with a specified space secured between them along with a light shielding plate 18 put between the diode 16 and the transistor 17. The slits 18a are provided to the plate 18 with fixed intervals. The plate 18 is turned, and thus the light beams crossing to the slits 18a shine the transistor 17 to be turned into light pulses. These pulses are fed to the computer 1 and processed by the soft counting within the computer 1.
WATANABE MASAYOSHI
UMEMURA SHIYOUICHI
