A microwave delivery system for a cooking appliance having a cooking chamber includes a toroidal-shaped waveguide, a magnetron, a tubular feed member interconnecting the magnetron with the toroidal-shaped wave guide and a field flux generator positioned about the tubular feed member. The amplifier is arranged facing the waveguide only in the region of a first section of the waveguide. Each edge in the graph is assigned a binary edge mask, each bit of which indicates whether it is reachable from a source or destination type relevant to user specified timing constraints. Connection resistance is employed as a Key code by subjecting the capacitance between the electrodes to AD conversion. The video screen may provide an image of the remote participant that is reflected by the projection screen.