Yes, im terrible at theory, but i built entire mixing desks, microphones and other studio gear from schematics. im very confident with the soldering iron. And i really enjoy building

 

Okay, If you want to do that, I will generate a complete circuit schematic which may take a day or two.

Questions:
Can you configure the fault switches to form a SPDT configuration so they output is either the supply voltage or ground?
If so, that will eliminate 16 resistors.

Can you provide 12Vdc power for the circuit and the SMS module?
The circuit can't operate on 24Vdc.

 

That should work. The fault switches are 1N/O 1N/C. Shorting the outputs while feeding supply voltage to the N/C and ground to N/C. Please correct me if im wrong

Atm i only have 24V supplies. Maybe i could just use on of those tiny Dc/Dc converters for your circuit? Otherwise ill have to buy a 12V supply.