A portable hand-held bandage dispenser includes a cartridge containing a multiplicity of self-adhesive bandages, and a dispenser with an end slot housing the bandages. With the above structure, the radial gap between the first sealing surface and the second sealing surface is varied when at least one of the two domed doors is moved. Therefore for a highly effective method for is provided for determining the availability of a page, having a block address and page address, to be identified, in one instance, as being an erased page that is available to be written to. When a measurement is in neither zone, both first and second etalon signals are employed to determine the wavelength.