| 摘要 |
PURPOSE:To prevent an electric appliance from mulfunction by staggering a carrier frequency between a first command signal and a second and a third command signal. CONSTITUTION:Both the first command signal which is sent out from a transmitter 11 and the second command signal from a remote control transmitter 5 or 8 are received at a photodetecting part 41 to which detecting circuits 42a and 42b are connected. The detecting circuit 42a extracts a data signal from an output signal of the photodetecting part 41 after eliminating a carrier part of a fixed first frequency. The detecting circuit 42b extracts a data signal from an output signal of the photodetecting part 41 after eliminating a carrier part of a fixed second frequency. A modulation circuit 47 which modulates a carrier signal of the fixed frequency according to an output of the data signal is connected to an output terminal of a data generation circuit 46 and then the output signal of the modulation circuit 47 is made as the third command signal. The detecting circuit 42b does not extract any data signal from signals including carrier part of the fixed first frequency, therefore, no output is produced from the detecting circuit 42b.
|
