This is a challenge on many different levels because machines are subject to mechanical failure and need repair on a semi-frequent basis. Many machines require frequent maintenance like cleaning and degaussing in order to remain functional. Occasionally, especially in more recent devices, certain parts may need to be replaced regularly in order to function optimally, even if the part in question is still intact. In addition to maintaining machines like phonographs and VCRs, organizations must maintain stocks of replacement parts for their machines. Unfortunately, once a particular technology becomes obsolete companies generally stop making machines and replacement parts, turning instead to making equipment to support whatever new technology is now dominant. In doing this, many machines that were once commonplace become rare as there are only limited supplies of replacement machines or parts, with no new replacements forthcoming. This has actually become more of a challenge as the technology in question has become more sophisticated; while it is possible for a skilled technician to create a phonograph which works at least as well as one from 1905, it is extremely difficult if not impossible to maintain a tape recorder or digital video recorder without prefabricated parts from the original manufacturing company.