| 摘要 |
The circuit for compensating the reduction of the conference call uses the side tone protection function. An OP amp (34a) acts as an amplifier for reception of the call with a side tone circuit comprising resistors (14a,15a,18a-20a,22a) and capacitors (29a,30a, 32a), and an OP amp (34b) acts as one for transmission of the call with a side tone circuit comprised resistors (14b,15b,18b-20b,22b) and capacitors (29b,30b,32b). The side tone characteristics like the frequency or level are controlled by variation of the element values of the resistors and capacitors.
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