Smart sockets with USB port
— the presence of a USB port (one or more) in the design of a smart socket / extension cord.
The main (and usually the only) purpose of such outlets is to charge various gadgets like smartphones and tablets, as well as power some accessories (for example, miniature desktop fans). The number of USB ports — and, accordingly, the number of simultaneously connected devices — can be different, usually from 1 to 4.