ORIGINAL: Steve Steinbring
The slave radio does not have to be turned on as mentioned above, with the slave set on a vacant airplane model memory. Set the master radio your DX7 in P-Link mode, plug in the slave box and you should be good to go!
Not true for Spectrum and JR, is true for Futaba. On Futaba, and I think Hitec, you do not have to have a battery in the slave but in JR and Spectrum, you do.