I am writing a post about this device because I was positively surprised by it
I have a TV connected to an android TV box, neither the TV nor the android box have bluetooth, So i have tried quite a few bluetooth transmitters, where you connect the AUX jack from the TV out to the transmitter, and the transmitter automatically pairs with the bluetooth speakers, never went well, either the voice is really bad, or it does not work, this is all until i found this little cool guy
So, how those transmitters usually work is you power the thing from USB, then connect the auxiliary jack, to my surprise, even though this did have a 3.5MM aux jack, it was detected by my android box as a USB sound card, and it worked without me doing anything
It doubles as a BT receiver too, but those are all over the place, and not exactly why i like this, So now it is clear what they mean by 3IN1, it has a jack for input, output and also works as USB sound ! Amazing stuff