| 摘要 |
PURPOSE: A surveillance camera selecting the least noises and a broadcasting device are provided to select and output a frequency band having the least noises. CONSTITUTION: A hand wireless receiver includes a microphone, a transmission antenna, an amplifier and a modulator. The amplifier amplifies a voice signal, and the modulator modulates a 200MHZ band, 700MHZ band and 900MHA band. A wireless receiver includes a reception antenna, an amplifier, a decoder, a phase shifter and a level meter. The amplifier amplifies the modulated signal voice signal to 200MHZ band, 700MHZ band and 900MHA band. The decoder decodes the amplified voice signal. |
