The adaptor is called a USB hub, and it has been around since USB 1.0.
If the hub itself is not powered, the power available to the hub has to be shared among all devices connected to the hub. How much that is, depends on the USB specification. Not all USB devices take power from the connection.
If the hub is powered, check the power specifications for the hub itself. These will vary quite a bit with product.
Hubs always have to share the USB bandwidth, whatever that is, among connected devices. USB port, device and hub specifications, connectors, cables can all impose limits on bandwidth.
Tom Test
Itasca Spirit 29B
