| 摘要 |
PROBLEM TO BE SOLVED: To secure the communication at its least level by reducing the transmission bit rate in such a case where the speech channel length is increased or the speech channel is temporarily cut and the communication is impossible at a prescribed transmission power level. SOLUTION: The signals received via a reflector are condensed on the surface of a light receiving element 1A2 of a photoelectric conversion part consisting of a photodiode, etc., via a lens 1A1. The condensed signals of the element 1A2 undergo the photoelectric conversion and are amplified by a front-end amplifier 1A3 to undergo the phase control via a phase control circuit 1A4. The circuit 1A4 sends a transmission bit rate switch control signal (d) to a terminal equipment 2 to instruct the transmitter side to change the transmission bit rate according to the change of intensity of the electric power received at a receiver 1A. The equipment 2 sends the signal (d) to the communication device of the opposite party via a transmitter 1B. When a communication circuit is defective due to an obstacle, etc., the transmission bit rate is changed to a low level to control the quantity of main beam leaking outside. Thus the communication is secured at a low bit rate. |
