| 摘要 |
PURPOSE:To send a message immediately anywhere in a building by sending a high frequency signal from a transmitter to an AC distribution line wired for lighting in a building premises, using a light sensor so as to receive an intensity change due to a high frequency signal in addition to the lighting and decoding a photoelectric conversion output signal. CONSTITUTION:In calling a specific individual, a call code registered for the individual is sent to an AC wire 11. A fluorescent light 7 is lighted by a voltage in 50Hz including harmonics. In irradiating the light of the fluorescent light 7 to a light sensor 9 provided to the surface of a wrist watch 8, an output waveform is obtained at an output terminal of the light sensor 9. This is amplified by an amplifier 12 and only the harmonics is extracted from a band pass filter 13. The call number data carried by the harmonics and a number data in a call code memory 19 at the reception side are compared and when they are coincident, an alarm section 21 of the wrist watch 8 starts ringing and the concerned person recognizes the own callout. |
