Test trained NARX neural network with new external input

Hi,

I used the nn toolbox to train a NARX neural network. I want my network to predict the output at the next time interval. Lets take the well know example of the magnetic leviation from matlab. For this example we have one input (magnetic current) and one output (leviated magnetic position). I want to deploy the trained network such that when I give in the input (magnetic current) and the delayed input and output states, it should give me the output (leviated magnetic position) at the next time interval.

But when I deploy my network using the toolbox, it generates a function with different input arguments like,

x1 input 1: from my understanding this is the input to our system (magnetic current in our case)

x2 input 2: from my understanding this is the output to our system (we only have one input, so what is this???)

xi1 delayed input state

xi2 delayed output state

What I don't understand is, what exactly is x2? Why should I give the output? I don't have this output, that is why I am using the network to predict the output.

Thank you!