| 摘要 |
PURPOSE:To make an output level constant regardless of channels by automatically offsetting the difference of the levels between output channels even when it is generated by the frequency characteristics of a frequency converter, an amplifier and a filter circuit. CONSTITUTION:The output levels of the respective channels of the output of the filter circuit 5 are measured and the lowest level of the channel is defined as a reference value. Then, at the other channels, the difference of the level with the reference value is calculated and stored in a memory 10 as a correction value. Then, at the time of controlling a variable attenuator 8, a CPU 9 reads the correction value corresponding to the output channel from the memory 10, turns it to a fixed value, supplies it to the attenuator 8 and controls attenuation amount. Thus, the difference of the levels between the output channels is offset and the output level at an output terminal 7 is fixed at all times.
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