What is the usb splitter? Can all mouths be used at the same time?
A USB splitter, also called a USB hub, is a very common peripheral device because it extends a limited USB interface from one USB interface to multiple USB interfaces.
The multiple USB interfaces provided by the USB splitter can all be used at the same time, but due to the limited power supply of the upper USB interface, it may not be able to meet the needs of multiple devices that require large power supplies. The cable is normally used by external power supply.
The attached figure is a typical passive USB splitter: