A retractable and extendable medical needle protective shield which provides opportunity for accessing and reaccessing a medical needle and associated sharpened needle tip and recovering the needle and tip for safety between accesses. At least one of LPC devices requiring to perform DMA transmission or bus master request includes a LDRQ controller serving as a LDRQ control device. The PED transmits a signal A transponder or micro-transponder that is tagged to an object is arranged to reply to a transmission received from the PED.