A device for removing magnetism from the heads and metal tape path components of tape machines. When magnetic (magnetized) tape passes across these metal parts it tends to magnetize them as well. In general, this is not a good thing! When these parts become magnetized they tend to degrade the signals recorded and played on subsequent tape passes through the transport. Notably, high end may be compromised, signal levels can be reduced, and so on. Opinions vary as to how often a machine should be demagged; some fanatical engineers have been known to demag after each pass of tape – we don’t recommend getting quite THAT carried away! Check your tape machine’s documentation for its manufacturer’s recommended maintenance schedule. In most cases if the machine is being used fairly heavily, we recommend demagnetizing once a month or so.