突然想解释下这个，是因为看到世界头部企业的项目技术规范出现了中国人犯下不可饶恕的错误。
I suddenly want to explain this because I see that some Chinese have made unforgivable mistakes in the project technical specifications of the world's leading enterprises.从图片可知，一些工程师对双联开关、双控开关、两极开关的区别模糊不清。
It can be seen from the picture that some engineers are confused about the difference between the two-gang switch, the two-way switch and the two-pole switch.简单的说，双联开关就是采用了同一相序，去控制两个灯控回路。
在平面图上，灯具的联开线有两条。
显然，N线并不接进开关盒。
In short, the two-gang switch uses the same phase to control two lamp control circuits. In the plan layout, there are two connecting lines of lamps. Obviously, the neutral wire is not connected into the switch box.再看双控开关。
它的功能就是对同一个控制对象在两地实现控制。
比如，卧室灯可以在门口和床头两地控制。
显然，电源还是来自同一相序，且N线不必进开关。
Look at the two-way switch. Its function is to control the same control object in two places. For example, bedroom lights can be controlled at the door and at the head of the bed. Obviously, the power supply still comes from the same phase sequence, and the neutral wire does not need to be switched.最后，我们看双极开关。
DP来自英文douplex poles的简写。
一极代表相导体，一极代表N线，可见此时需要同时切断两根带电导体。
此种情形用于FCU、电热水器供电插座等。
Finally, let's look at the DP switch. DP is short for Douplex poles. One pole represents the phase conductor, and the other pole represents the neutral wire. It can be seen that two live conductors need to be cut off at the same time. This case is used for FCU, electric water heater power socket, etc.