serial interface for CM-REX

[lev arris]

hi !

i've been constructing a serial cable
( wiring diagram original FMS )
and - no chance, no reactions at the COM1 interface !
does anyone have the correct wiring diagram of
the trainer socket for the transmitter ROBBE CM-REX ?!
on which pin where is the right signal ?
and what voltage level does it have ?!
i have NO IDEA !

thanks,
lev