For connecting up to 4 USB (Universal Serial Bus) devices (eg a mouse keyboard printer USB (Universal Serial Bus) memory stick) to a USB (Universal Serial Bus) port Topside socket means that you can plug USB (Universal Serial Bus) devices in on the top for added simplicity & convenience Bus powered ie power supply via the USB (Universal Serial Bus) socket of a PCnotebook Integrated USB (Universal Serial Bus) cable for connection with a PCnotebook Suitable & tested for USB (Universal Serial Bus) 20 downward compatible with USB (Universal Serial Bus) 11 System Requirements Operating system Windows 1087 Vista XP & Mac OS 10x