设计数字抢答器通过定时电路和译码电路将秒脉冲产生的信号在显示器上输出实现计时功能，构成扩展电路。-Through timing circuit and decipher second signal function while outputs and realizes counting on the displaying that pulse produce circuit, form and expand the circuit. Through connect up , weld , debug figure vie for answering device take shape after the work.