We will develop a neural network that can classify a 7x5 rectangular matrix representation of alphabetic characters. As a typical programmer can see, conventional algorithmic solution methods would not be easy to apply to this situation. Connections exist between selected pairs of the PEs. These connections carry the output in the form of a real number from one element to all of the elements to which it is connected. Each connection is also assigned a numeric weight.
PEs operate in discrete time steps t .
The operation of a PE is best thought of as a two-stage function. The first stage calculates what is called the net input, which is the weighted sum of its input elements and the weights assigned to the corresponding input connections. The second stage is the application of some output function, called the activation, to the weighted sum. This function can be one of any number of functions, and the choice of which one to use is dependent on the application. In order to help the reader make sense out of the above discussion, the illustration in Figure 3 shows an example network.