| 摘要 |
PURPOSE:To prevent squelch malfunction in inspecting a repeater, by inserting or extracting a band-limiting circuit into or from a gain control loop according to the input level of a signal wave. CONSTITUTION:While a signal wave is inputted at a standard level, switch 14 is turned off and the signal wave is reflected and then inputted to level detection part 8 having an impedance matching circuit, so that gain control part 9 controls the gain of each amplification part. As the signal wave input level decreases below a threshold level, the output of switch control part 16 is inverted to turn on switch 14. Then, the signal wave is inputted to band-stopping filter 15 which reflects only the band components of the transmitted signal, and consequently a disturbing wave of an approximate reception frequency is absorbed by terminator 17 to input only the signal wave to detection part 8, performing gain control operation. When the output of gain control part 9 exceeds a certain threshold level, squelch discrimination part 12 operates to turn on amplification part 5. |
