My program works like this :

a detection for RBx cause a different display to FIS Tachometer and for input isolator (output RC5,6,7) cause a +5V and +12V on output isolator .
BUT it is dangerous because a +12V on output isolator cause a failure on FIS tacho input voltage .
I would like only a No intrusive +12V but GROUND ONLY (action with ground input RBx) .
FIS give +12V in normal operation :

Name: opto-level-shift Sol.JPG Views: 2070 Size: 7.7 KB