Thanks for the info.

I went ahead and measured a few more leads to check for voltages. I made a sketch of the lead arrangement in the multi-pin plug. The purple and blue leads go directly to the switch and are powered up when the Tx is off - these are the battery charge leads with the blue being Vcc+ and purple being ground. The Grey/white and black leads go to the encoder and are powered up when the Tx is on - these also have Vcc+ (grey/white) and ground (black) and are presumably to power up the slave Tx when the cable is plugged between two Kraft Tx's.

If the Kraft system works like all other trainer systems I'm familiar with, the master Tx is turned out in order to provide voltage to the RF deck and the slave Tx receives power from the master via the trainer cable. Since the grey/white lead has battery voltage when the Tx is powered up and goes to the encoder, it makes sense for it to provide power to the slave encoder.

I had assumed that I would measure PPM voltages at the yellow/red lead to send the signal to the master Tx when in slave mode and would "see" PPM voltages on the orange/black lead to receive PPM signals when in master mode. Until two Tx's are connected together, it will be difficult to assess whether the orange/black lead is for this purpose. I didn't however measure PPM at the yellow/red lead whether the trainer switch was enabled or not. One way or another though, these leads need to pass PPM in some configuration as they are the only two leads that can send encoder signals when in slave trainer mode. I suspect that the cable needs to be connected in order for the respective encoders to output or receive PPM signals.

A scan of the service manual of this particular area would help to sort this out. Pages concerning the wiring for the switch reversing, dual rate and snap/roll buttons would also help.

David.

P.S. I'LL HAVE TO REVISE THIS POST SINCE IT IS NOW CLEARER THAT IT CONTAINS WRONG "GUESSES" !!