| 摘要 |
PURPOSE:To eliminate a manual adjustment and to decrease a trouble by adjusting the attenuation extention of a variable attenuation oscillator automatically based on the result of comparison between a reception voltage level and a setting voltage. CONSTITUTION:The output level of the oscillator 7 is adjusted by a variable attenuation oscillator 8 so as to obtain a prescribed value E at the point B of a line 3. A reception level at the output side of a variable attenuation oscillator 9 of a reception side terminal equipment is rectified by a rectifier circuit 17 and becomes a DC voltage, inputted to comparators 15, 16, and they are compared with reference voltages V1, V2 respectively. When the output voltage of the circuit 17 is V1 or below, the output of an AND circuit 12 is at 0 level, a variable attenuation oscillator control section 13 adjusts to reduce the attenuation extention of the oscillator 9 and when V2 or above, the output of the circuit 12 is 1, and the control section 13 is adjusted to increase the attenuation extention of the attenuator 9. When the output voltage of the circuit 17 is between voltages V1 and V2, the output of the AND circuit 11 is 1, a display device 10 is lighted and when a switch SW is turned on, the control section 13 stops the control. |
