A neural network comprising interconnected neuron means that are arranged in two layers, referred to as an upper layer and a lower layer, in which each neuron means of said upper layer performs a weighted sum of all its inputs, the result being a first summed signal, and then performs a neural threshold operation on said first summed signal, and in which each neuron means of said lower layer performs a weighted sum of all its inputs, the result being a second summed signal, and then performs a neural threshold operation on said second summed signal, wherein said neural threshold operation on said first summed signal is performed according to a constraint function so defined that ##EQU11## where H(z) is Heaviside's step function, a>0, and F(z)=-2a, and wherein said neural threshold operation on said second summed signal is performed according to another constraint function
- f.sub.2 (z)=0 if z.ltoreq.0, otherwise f.sub.2 (z)=z,
- and wherein each output of the neuron means of said lower layer is being fed back, with a time delay, as a local input to the respective neuron means of said lower layer.