The invention relates to glass-ceramic plates, hotplates incorporating them and their fabrication process. One of the base plate and fin unit includes a protruding member, and the other one of the base plate and the fin unit defines a groove corresponding to the protruding member. The method also includes initiating verification of the value token. Each communicator has a processor for controlling a security routine with the tag. For example, emergency locators and outdoor lighting displays will benefit from this invention.