| 摘要 |
PURPOSE:To obtain a stable output signal in a short time, by transmitting a switch signal to switch a switch when the signal level has a fault and at the same time transmitting a time constant switch signal to an automatic gain control circuit to shorten the time constant of the automatic gain control circuit by a fixed time. CONSTITUTION:The signal delivered from a transmitting circuit 1 is fed to a switch circuit 9 through transmission lines 2 and 3. An automatic gain control circuit 10 controls the level of the signal which is selected by a switch and passed through the line 2 or 3. Then this level is led to an output terminal. A monitor circuit 11 monitors the output level. When the line 2 or 3 is cut off, the circuit 11 detects a fault and sends a switch signal to the circuit 9 to switch the line 2 to the line 3 or vice versa. At the same time, the circuit 11 transmits a time constant switch signal to the circuit 10. The circuit 10 shorten the time constant by a certain time to perform the gain control in a short time and then resets the time constant to prevent a malfunction due to the impulsive noises, etc. |
