Where I can find an USB dongle to connect two devices with external power

usb

Can you please tell me where I can find an USB dongle which follows this diagram:

enter image description here

I have a tablet and a BobjGear USB to RJ45 Ethernet Adapter, but the battery will discharge while using the tablet connected to the network cable.

I want something as described in the diagram where A is the tablet, B is the Ethernet Adapter and C is the regular USB charger !

Does such a thing exists ?

What will happen to the tablet when I will try to provide the input power while it's supposed to be outputting power ? Is it even possible to connect the power in parallel – as the Tablet A is supposed to power the Adapter B ( A -> B )
Connecting the charger will force the current to flow in the opposite direction ( C -> A & C -> B ) ?

Best Answer

According to the USB specification, these things should NOT exist. They are illegal (re: USB) for precisely the reasons you are struggling with it.

Electrically, we describe this condition as "contention." You are causing two power sources to fight for control of a wire. It's a bad thing... ;-)

USB On-The-Go (OTG) uses a separate pin (not shown in your diagram) to solve the contention issue.