Sergei Bezrukov writes:
It is not a rare phenomenon that some USB devices attached to a computer during power-up remain invisible to the OS after booting. This concerns home-made devices during experiments and also some commercial ones. To make them visible again one has to disconnect the USB plug and reconnect it again. This leads to excessive contact wear of the USB connector. It would be nice to have a way to reconnect the device without mechanically unplugging it. A trivial solution based on buttons/switches or relays won’t work because of their contact bouncing, which might confuse as device as well as the OS.
USB switch - [Link]