Abstract
Two quantum systems, each described as a random-matrix ensemble. are coupled to each other via a number of transition states. Each system is strongly coupled to a large number of channels. The average transmission probability is the product of three factors describing, respectively, formation of the first system from the entrance channel, decay of the second system through the exit channel, and transport through the transition states. Each of the transition states contributes a Breit-Wigner resonance. In general, the resonances overlap.