It seems there is a bit of confusion between activation and transfer function. From Wikipedia ANN:
It seems that the transfer function calculates the net while the activation function the output of the neuron. But on Matlab documentation of an activation function I quote:
satlin(N, FP) is a neural transfer function. Transfer functions calculate a layer's output from its net input.
So who is right? And can you use the term activation function or transfer function interchangeably?
No, they are the same. I also quote from wikipedia: "Usually the sums of each node are weighted, and the sum is passed through a non-linear function known as an activation function or transfer function. Don't take the matlab documentation too literally, it's thousand of pages long so some words might not be used in their strict sense.
In machine learning at least, they are used interchangeably by all books I've read.
So, to sum up