When the user specifies a transfer function to FA, FA will generate a filter network that realizes this transfer function. There is an infinite number of filter networks that realize the same transfer function. In stead of specifying the transfer function, the user may also specify the filter network. FA stores filter network as a state-space representation. The user may specify or request the state-space representation of the network.
FA can also transform a network into a different network which realizes the same transfer function. This is useful for network optimization.