The remote control switch bought directly replaces the ordinary household switch and does not connect the zero line. Why?

The switch itself does not need to be connected to the zero line (only the live wire enters and exits), but it can form a loop with the load (indirectly connected to the zero line). By using remote control switch and load, a small current (uA level in standby) loop can be realized. At the same time, the remote control switch adopts the principle of thyristor chopping, and uses the initial section after AC zero crossing to supply power to the circuit itself. After the voltage rises to the set value, the unidirectional thyristor is turned on and the circuit is bypassed. On the one hand, it ensures the stability of output voltage and solves the problem that the power supply of the circuit itself is affected by the change of load current; On the other hand, because the thyristor works in the switching state, its own voltage drop is small and power consumption is low. In addition, the output power supply voltage can be changed only by changing the adjustment value of the Zener diode.

I'm a vegetable, too. Hehe, I smiled.

This is the explanation given to me by the engineer who bought the remote control switch in Shanghai Pudong Company last year. Due to my limited level, I only made a general understanding. Please ask their engineers for more details if possible. Website: www.spdkj.com, please let me know if you can understand it more deeply.