此十字路*通灯控制系统，分东西道和南北道，设南北道为A道，东西道为B道。规定：首先，东西路口红灯亮，南北路口绿灯亮，同时开始25s倒计时，以7段数码管显示时间。25s倒计时结束后开始5s倒计时，南北路口的绿灯闪烁，计时到最后2s时，南北路口黄灯亮。完成1次这样的循环需要30s。30s结束后，南北路口红灯亮，东西路口绿灯亮，并重新30s倒计时，依次循环。若有紧急车辆要求通过时，此系统应能禁止普通车辆，而让紧急车辆通过。-This intersection traffic light control system, and North-South Road West and East Road, located north-south road for the A Road, East Road to B Road. Requirements: First, what intersection red light, green light intersection north and south, and 25s countdown began with a 7-segment display time. 5s 25s countdown after the end of the countdown, the green light flashes north-south junction, to the last time 2s, the north-south crossing yellow light. Completion of this cycle requires 1 30s. After the 30s, north-south crossing the red light, green light thing intersection, and re-30s countdown, followed by cycle. If required by emergency vehicles, this system should be able to prohibit ordinary vehicles, and to allow emergency vehicles.