Using the Optic 6 as the prime transmitter or alone, it works the airborne system well. However, when trying to use either a Futaba or Hitec transmitter as a slave, when the trainer switch is thrown on the Optic 6 it powers up the slave but will not respond to any of the slaves stick inputs. Yes, we are using the Hitec trainer cord with Master and Slave ends appropriately plugged in. Is there some special thing that must be done or is there a possible defect in the Optic 6 trainer switch? Yes, both Optic 6 and slaves were in PPM mode, not PCM. The receiver is a Futaba PPM.