The paper explores the system of quantum waveguides and resonators. It suggests a solvable model of zero-width coupling windows based on the operator extensions theory in the Pontryagin space with indefinite metrics. The model self-adjoint operator is constructed explicitly. and it is similar (in some sense) to that of a physical system. https://www.ealisboa.com/top-offer-Telemarkskongen-SH-best-find/