The magnetic charge, which is generated on the recording and playback heads during recording and playback is removed by this cartridge in electronic manner. Then the sound will be clear.
Demagnetising takes only 2 to 3 seconds. As a check a little red lamp lights up during the process of demagnetising.
Most tape recorders sent in for repair have nothing wrong with them other than needing a cleaning.
As to how often the machine should be cleaned and demagnetized, it depends entirely on the quality of tape run through it. Cheap or poorly made tape can shed so much oxide and binder on the tape heads, guides, and pinch roller, that the machine would require cleaning between every tape played or duplicating run
Important! This product is only suitable to demagnetise equipment using compact-cassettes.