RE: Back Up RX Batteries
Also, you can put the y-lead on a USED Rx output if no spares - just put the servo on one side and the backup switch/batt on the other side of the y-lead. The power all ends up in the same place on the Rx's common +/- power tracks.
If you fly JR 2.4, their new Rx with redundant batt inputs looks pretty slick too.
Cam