The concept of a Variable Structure System (VSS) ,in which the structure is determined by the dynamical response, is described and measurements and simulations on VSSs comprising electronic systems which display bursty chaotic or "intermittent" behaviour, and also on a network traffic transfer protocol, which is demonstrated to be a VSS in the same sense, are used to support the thesis that such bursty behaviour is common in such systems. An example of trapping in a two-centre system is given to show that the ideas can be extended to continuous-variable dynamical systems having piecewise-linear properties. The studies of these simple electronic systems provide insight for cases where similar behaviour of a time series is observed in other complex systems; some other VSSs are listed and their properties are considered.