| 摘要 |
PROBLEM TO BE SOLVED: To prevent a malfunction by generating an infrared carrier wave modulation pulse having a pulse width longer than the maximum pulse width of the infrared carrier wave modulation pulse of a remote control device for a household electric appliance by an infrared transmitter and detecting only the infrared carrier wave modulation pulse of the infrared transmitter by an infrared receiver. SOLUTION: An infrared transmitter generates an infrared carrier wave modulation pulse having a pulse width longer than the maximum pulse width of the infrared carrier wave modulation pulse of a remote control device for a household electric appliance. A resistance R11 and a condenser C11 of the infrared receiver RE constitute an integral time constant circuit of a pulse detection circuit for detecting the infrared carrier wave modulation pulse and the time constant is expressed by R11×C11. When R11 and C11 are set to 47 kΩand 0.47μF respectively, the time constant=47×103×0.47×10-6=22.1 msec and a pulse of the pulse width 22.1 msec or less is not detected. This device thus detects no infrared carrier wave modulation pulse from the remote control device of the household electric appliance so as to prevent a malfunction.
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