It is unique to Raid Mode. Categories: Articles to be expanded from December 2018.
Other receivers (FrSky and FlySky for example) have a pretty simple procedure of pressing a button on the receiver whilst the radio is in 'bind mode'. Spektrum is a little more complicated however. In DragonSky, you can bind a Dragon to another Dragon to strengthen the power of the Master Dragon while not using any extra slot in the team.