A collection of digital media is stored at a source device and transferred to a target device. In one embodiment a quadrupole mass filter 3 upstream of a collision cell 4 is arranged to operate in a highpass mode. The memory can thus maintain high performances in terms of random access speed but shows a high erasing speed typical of memory architectures of the NAND type. The exhaust pipes are communicated together upstream of the upstream three-way catalysts and the control valves by a communicating pipe. The system and apparatus also exchanges device status information using USSD messages. The trellis system also includes accent bands.