Switching circuits have variable structural topologies. In every topology, they have different dynamics and time constants. Resistances of switching elements vary between a very small value and a very large value during conduction mode and disconnection mode. Therefore, equivalent circuit modelling of switching circuits requires averaging the on-state and off-state resistances of switching elements over one switching period. Determining averaged switch models allows to determine unified time constants of variable structural switching circuits. In this paper, analytically, it is shown how to calculate the equivalent average resistance and to derive unified time constants. The formulation method is based on nodal equations, very suitable for the analysis of switching circuits.