资 源 简 介
1) 东西方向车辆放行20秒钟。即东西方向的绿灯和南北方向的红灯同时点亮20秒钟；
2) 20秒钟后，东西方向的黄灯闪烁2秒钟，以警示车辆将切换红绿灯。此时南北方向仍维持红灯点亮。在南北方向亮红灯期间，在2位数码管上显示计数值（每秒减1），从20减至01。
3) 东西方向的黄灯闪烁2秒钟后，转为南北方向放行20秒钟。即东西方向的红灯和南北方向的绿灯同时点亮20秒钟；
4) 南北方向放行20秒钟后，转为南北方向的黄灯闪烁2秒钟，以警示将切换红绿灯。此时东西方向仍维持红灯点亮。
5) 南北方向的黄灯闪烁2秒钟后，再转为东西方向车辆放行20秒钟。如此循环重复。
-1) direction vehicle release 20 seconds. What is the direction of red and green light at 20 seconds,
2) 20 seconds later, the yellow lights flashing warning vehicles with 2 seconds, switch to the traffic lights. This is still remain red light north-south direction. In the south during the red light, in the direction of the digital display tube of 2 per plan (minus 1), from 20 to 2001.
3) the yellow lights flashing direction to 2 seconds later, the south direction release 20 seconds. What is the direction of the north-south direction of red and green and light 20 seconds,
4) north-south direction after 20 seconds to release the north-south direction, yellow lights flashing warning, with 2 secon
