| 摘要 |
PURPOSE:To obtain a receiver which reduces background noises by comparing the output of a background noise photodetector with a predetermined value, and driving a burst transmitter by the comparison output. CONSTITUTION:Transmit data applied to a terminal 101 is stored temporarily in a buffer memory 102, whose output is applied to a modulator 103, the output of which drives a light emitting device 104. The background noise photodetector 105 receives and converts background noise light into an electric signal. When the output of the photodetector 105 decreases below the predetermined value, a decision device 106 sends a transmission ready signal to the burst transmitter consisting of the memory 102, modulator 103, and light emitting device 104 to perform transmission. The background light noise originates mainly from a fluorescent lamp and turns on and off repeatedly at a frequency twice as high as the frequency of its power source, so the decision device 106 detects a section T wherein the similar time variation of the output current of the photodetector 105 decreases below the specific value Ith and sends the transmission ready signal to the transmitter. |
