In [5] John Tucker and I defined a general concept of a network of analog processing units or modules connected by analog channels, processing data from a metric space A, and operating with respect to a global continuous clock T, modelled by the set of non-negative reals. The inputs and output of a network are continuous streams u : T → A, and the input-output behaviour of a network with system parameters from A is modelled by a function of the form Φ:C[T,A]~p ×A~r → C[T,A]~q, where C[T, A] is the set of all continuous streams equipped with the compact-open topology. We give an equational specification of the network, and a semantics when some physically motivated conditions on the modules, and a stability condition on the behaviour of the network, are satisfied. This involves solving a fixed point equation over C[T, A] using a contraction principle based on the fact that C[T, A] can be approximated by metric spaces. We analysed in detail a case study of analogue computation, using a mechanical system involving a mass, spring and damper, in which data are represented by displacements. The curious thing about this solution is that it worked only for certain ranges in the values of the parameters M (mass), K (spring constant) and D (damping constant), namely M > max(K, 2D), www which has no obvious physical interpretation. (More on this below.)
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