| 摘要 |
PURPOSE:To enable wide gain switching while maintaining broad-band characteristics, by using a board-band amplifier and alternative circuit selectively through switching. CONSTITUTION:Light signal beam 204 inputted via optical fiber, etc., it photoelectrically converted by light signal input device 203 and inputted to gain switching device 300 via coaxial cable 220B. When the input signal to gain switching device 300 is small and a high gain is required, broad-band signal switches 301A, 302A, 301B, and 302B are so changed over that the input signal may be amplified by board-band amplifiers 304A and 304B. This operation is performed corresponding to the operation of a sensitivity change-over switch. As amplifiers 304A and 304B, noninvertive amplifiers are used so that the signal polarity will not be inverted in the switching of the number of stages. |
