| 摘要 |
<P>PROBLEM TO BE SOLVED: To obtain an optical terminal device which is capable of receiving a specific channel, such as notice broadcast etc, for a certain time or more by a simple backup mechanism even if the power failure of a commercial power supply takes place. <P>SOLUTION: A second high-frequency amplifying circuit 102 is equipped with two-stage amplifiers 11a and 11b connected in series, and a power is fed to the circuit 102 from a capacitor 14 of a large capacity through a current limiting circuit 26 when a commercial power source fails. The sinal output terminal b2 of the second high-frequency amplifying circuit 102 is connected to the isolation terminal of a directional coupler 13 through the intermediary of an attenuator 12. The second high-frequency amplifying circuit 102 is designed so as to efficiently amplify high-frequency signals of 70 to 80 MHz band with small electric power, and a low-pass filter 10 which is equipped with a built-in buffer resistor at its pre-stage and serves as an FM band filter whose pass band is 70 to 80 MHz is arranged at the signal input stage of the amplifying circuit 102. The input terminal a2 of the low-pass filter 10 is connected to the cathode of a PIN photodiode 6. <P>COPYRIGHT: (C)2006,JPO&NCIPI |
