4人抢答器，计时器和抢答器综合，开始抢答时，计时器从20s开始倒计时，如果无人抢答，计时器到0时报警器响3s，有人抢答，数码管会显示第几人抢答。-4 hours of answering device, timer and answer device synthesis, began to answer, the timer 20s countdown, if no one answer, the timer to 0 when the alarm ring 3s, some people a