A picture data memory device which can be used universally comprises a central picture data memory for storing picture data of a plurality of picture data input channels, in which case the stored picture data can additionally be read out via a plurality of picture data output channels for different kinds of further processing. The roofing shingles includes an overlay sheet including a headlap portion and a tab portion and an underlay sheet secured to the overlay sheet such that a region of the underlay sheet overlaps a region of the headlap portion of the overlay sheet. The monitoring unit is operable to monitor at least one physiological parameter of a patient. Complementary surfaces at the holding compartment and at the exterior of the external enclosure are in engagement with one another and provide surfaces along which the holding compartment travels when it is inserted into and withdrawn from the interior of the external enclosure.