Some commercial H-520 operators are purchasing a Typhoon H Plus to use as a backup or second system. With the recently added Team Mode function, a TH Plus ST16S Controller may be used as a Slave to the H-520 system. The Slave ST16S controls the E90 camera and the Master ST16S pilots the craft. Very useful for the team operating close to dangerous towers or electrical devices.
This video shows exactly how to set it up.