a second neural network is used to filter the predicted structure of the first network. this network is also fed with a window of 15 positions. the indicator on the possible position of the window at a chain terminus is also forwarded. this results in 60 input units, divided into 15 groups of four. the network has one hidden layer of 60 units and results in three output nodes (one for each secondary structure element: helix, sheet, coil).