Recently I saw that certain Sonoff and Xiaomi smart Wifi/Zigbee switches can be wired without neutral wire, like shown in this schematic: http://dl.itead.cc/sonoff-t4eu1c/T4EU1C_02.jpg

Some examples of no-neutral smart switches:

I understand that, if the switch is ON, the live wire will be connected with the neutral wire across the lamp. But, how can these devices be powered if the switch is OFF?


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