A communication system includes devices configured to communicate with each other through a temporal sequence of frames. The accessory includes a mounting plate for attaching the accessory to a skateboard truck, a rotatable kick plate assembly and a spring component coupled between the mounting plate and the rotatable kick plate. The directory includes authenticated registrant information comprising authenticated information for a payee, the directory identifying via a publicly available account identifier at least one linked account of said payee. The invention is also for a method for making arithmetical calculations. A significant reduction in analyzer dimensions is achieved through a redesign of the optical bench: single detectors of IR radiation are replaced by detector arrays. 5 kgf or more from the individual optical fibers cut from the parent optical fiber whose failure strength F1 and failure time T satisfy the inequality T>2.