Do you know how many kinds of home use USB socket?
USB socket is a safe and power-saving universal socket with USB interface, including the socket body. Belongs to the weak current electronic product, the output voltage is about 5V.
Current market category
1. Direct USB socket (Features: no button, no indicator light or USB socket with indicator light, low cost), Because the USB socket market is still in the early indicators to the security of USB socket standard haven't perfect, that makes the market a lot of cheap USB socket in mostly belong to the direct USB socket, the inside of the USB socket always keep contact with family voltage directly, kept running, is quite similar to the TV on standby, makes life greatly reduced, there is a big security hidden danger. 
2. USB socket with button (Features: USB socket with or without buttons, high safety performance), USB socket with a button outside, USB circuit on and off integrated into a button, when the button is pressed, USB power, so that USB does not have to keep contact with the family voltage, security risks are greatly reduced.
3. Automatically turn on and off the USB socket (features: with or without indicator light, built-in switch, that is, switch on if inserted, switch off if pulled out)
Because the button USB socket is not humanized enough, most people will forget to turn off the button when unplugging the USB cable, some buttons are too old-fashioned, are to press for on and off, people do not know whether the USB on and off, so that the button is useless, so there is an automatic USB socket