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.

You do not mention which model Futaba or Hitec TX are being used as the slaves. Provided the receiver is on the same frequency as the master, there should be no problem unless the "slave" is one which requires a battery be installed to power up the board when the trainer plug is inserted. Non computerised slaves do not require a battery. When the master's trainer switch is sctivated, the signals from the slave should then be put out through the master TX. The slave (mode does not matter) must be set up the same as the master as any reverse or mixes held by the master are not transferred to the slave. For full details, refer to
Hitec Buddy - Trainer Box compatibility & battery requirements
Hitec Trainer (Buddy) System Update - New "Stereo Plug" system and how to use
and more under sub section "Buddy Boxes & Flight Simulator & Interface." at
Alan's Hobby, Model & RC FAQ Web Links
Regards
Alan T.