A USB plug socket is ideal for charging portable devices such as a smartphone or tablet whilst still being able to utilise socket outlets. They are easy to retrofit into existing systems without the need for additional wiring. The socket with usb is available with two USB connections. It is important to choose the correct rating of a usb wall socket to match the devices that you wish to connect otherwise the device may not connect or charge properly. A mains usb socket will typically split the amp rating by the number of usb connections, this means that if you plug in only one device at a time then all of the power will be sent to that device but if you intend to plug in more than one device at a time the current will be shared you should look for a higher amp rating so that more power will be sent to each connection.