A firmware model is provided for a shared port membership table that is partitioned for different needs of a distributed network switch, such as broadcast groups, multicast groups, ACL rules, and other port membership groupings. This object is achieved by the following construction: A resonator 15 that resonates with the electromagnetic wave having the predetermined frequency is located between an input waveguide 13 and an output waveguide 14 and close to the two waveguides. A pair of grooves is defined in two opposite sides of the rear portion of the main body, and a front end of each groove is bounded by an inclined wall. The envelope is initially configured in a retracted configuration. The alignment groove slippingly receives the femoral alignment member.