The selecting frequency network usually located in the amplifying circuit, or located in the positive feedback network.
其中的选频网络一般可以设置在放大电路中，也可以设置在正反馈网络中。
2
If you want to send a no-hard-feelings signal for the sake of future conference-circuit encounters, put in some vaguely positive statement: you've enjoyed "aspects of the job" or "learned a lot."