实现楼道间照明灯的方便控制，一个照明灯，在楼上和楼下各有一个（闭合式）开关控制。

　　　　　　开关的闭合并不直接决定灯的亮灭，而开关状态的改变才是决定灯亮灭的关键。即不管两个开关当前的状态

　　　　　　如何，只要有一个开关状态发声变化，都会使照明灯在打亮或者熄灭两种状态间切换。

　　　　　　比如当有人要上楼，若之前灯是灭的，在按下楼下开关后（此后开关为闭合状态），灯会打亮；当到楼上后，

　　　　　　再按楼上开关，灯会熄灭。而当后来又有人上楼时，再按次楼下开关（此后开关为打开状态），灯同样会打亮；

　　　　　　此试验中，用P1口相连的第一个led来模拟照明灯，而用s2和s3来模拟两个开关。注意，因为实际楼道中的

　　　　　　开关为闭合式的，而板上的开关为反弹式的，所以实验时，请用手一直按着按键演示开关的闭合。-Realize the corridor between the convenient control of light, a light, upstairs and downstairs there is a switch control (closed).

Not directly decided to destroy the light of lamp switch is closed, and the change of the switch state is the key to decide the light put out. Regardless of the current state of the two switches

How, as long as there is a voice switch state change, can make playing bright lights or go out to switch between two states.

When someone going upstairs, for example, if the lamp is destroyed before, after pressing the switch downstairs (after the switch is closed), light up　When upstairs,

According to the upstairs again switch, will go out. When later someone upstairs, downstairs again　time to time switch (after the switch is open), the lamp will also play