Thanks Melanie,

The device I'm making is to ensure that the customer pays, we have instances when we installed the system after they pay 2 thirds of the price and then never complete the payment, continuously making up new problems to avoid paying. This is a cruel way but only way to stay above water.
I think your way makes good sense but the PLC programmers there are not "so thick", they will see the LEDs showing the digital inputs and note them and then replace my unit with direct connections. I thought maybe analog values using a voltage to 4-20mA generator. Do you think this will be reliable enough. I cannot have this thing stopping without reason or I am toast!

Regards

Chris