| 摘要 |
PURPOSE:To attain the miniaturization of a telephone set and the light weight of said set and to realize an accurate switch operation by providing a light emitting element and a light receiving element to constitute a circuit in which the light receiving element switches a hook switch contact and using a transmitter-receiuer placed on a cradle so as to shut a light projected from the light emitting element to the light receiving element. CONSTITUTION:When the transmitter-receiuer 3 is place on the cradle 2, an infrared ray projected from an infrared-ray LED 6 through a window 4a is shut by the transmitter-receiver 3 and does not reach an infrared-ray phototransistor (TR) 7, which is turned off, a TR is turned off and no current is conducted to a relay coil 12. Thus, contacts 13,14 open a channel 15. When the transmitter-receiuer 3 is lifted up, the infrared-ray projected from the infrared-ray LED 6 is projected onto the TR 7 through a window 5 a from the window 4a, the TR 7 is turned on, then the TR is turned on to cause a current to be conducted to the relay coil 12. Thus, the contacts 13,14 are closed to close the channel 15.
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