| 摘要 |
PURPOSE:To attain long service life and low current consumption of a transmission section by starting transmission LEDs grouped corresponding to each photodetection level in the talking direction. CONSTITUTION:When a mobile station makes transmission from a direction A of a fixed light receiving and emitting section, its stimulated output is received simultaneously by photodetectors(PD) 27, 28, 35, 36, the light is photoelectric-converted by light reception buffer circuits 41, 43 and amplified by light receiving amplifier circuits 42, 44. The amplified carrier levels are compared by a comparator 45 and since a mobile station makes transmission from the direction A, the level of a light emission amplifier circuit 49 in the direction A in the comparison output gets higher. Then an LED group 37 is lighted up for a talking carrier while being driven by an LED transmission drive circuit 47 in the same direction A. Thus, the entire current consumption of the light emission circuit is less and number of LEDs lighted simultaneously is less, then a voltage driving the LEDs is suppressed small and the LEDs are lighted by directions and not always lighted, then long service life is attained. |
