Galaxy Tab S stuck in "Downloading" mode

Galaxy Tab S stuck in "Downloading" mode:

Press: Power + Vol Down + Home for 20 seconds

Recovery Mode
Turn off the device
Press and hold Volume UP key + Home Key
then Press and hold Power key
Release all key when you see Android System Recovery
Use Volume UP key and Volume Down key to select Menu
Use Power key to Confirm or Execute Menu

Download Mode or ODIN Mode
Turn off the device
Press and hold Volume Down key + Home key
then Press and hold Power key
Release all key when you see ODIN Mode
Use Volume Up key to continue
Use Volume Down key to cancel ( Restart the device )

Odin is a tool for updating the firmware on Samsung devices.