它由主体电路和扩展电路两部分组成。主体电路完成基本的抢答功能，即开始抢答后，当选手按动抢答键时，能显示选手的编号，同时能封锁输入电路，禁止其它选手抢答。扩展电路完成定时抢答的功能。 -it from the main circuit and the circuit extended two components. The main circuit completed basic Responder function, which is to begin Responder, when activ