A microwave generator, which includes a housing having two mutually opposite electrodes which are separated via an electrode intermediate space which is filled with a dielectric, and with the electrodes having a spark gap between them, which breaks down in order to emit microwaves when a high voltage is applied. The tuning device has a meter having a graduated display and a movable needle, one or both of which are provided with a fluorescent substance. The switching power converter controller is configured to assert a reset command for the host microprocessor if the watchdog timer expires and to not de-assert the reset command until the plurality of switching power converters are operating as desired. If a trigger, such as time elapsed, occurs for the first-attempted device and the PoC preferences permit, the PoC server sends an invitation message to the second server. Likewise, the eyeglass retainer can be secured to a pair of eyeglasses by securing the opposing ends of the eyeglass retainer together and using a loop formed by the eyeglass retainer to retain the eyeglasses in a closed configuration.