The disclosed invention addresses a very unique problem and provides a format of interaction to assist people to effectively interact in any situation through an embodiment of a mark, which is situated in any type of location or event where people assemble, with strangers. Then, an AC pulse voltage is applied to the gap between a wire electrode and a workpiece by alternately turning on and off a switching element present in a secondary power supply. The toner discharge outlet is formed on the case main body. The process involves the steps of: preparing a flexible printed circuit substrate and making a window at a predetermined bent part; coating the substrate with a metal layer so that the substrate become conductive; etching the metal layer through a photolithography process to produce a conductive circuit on the flexible printed circuit; and forming a cover layer at the window.