In analog magnetic tape recording, saturation is the maximum magnetization that a tape can attain. Actual recorded levels are less than saturation because saturation distortion is introduced if saturation is approached, especially at low frequencies. At high frequencies, it is not possible to reach tape saturation because the signal itself acts to partially erase itself as it is being recorded because the high-frequency signal causes the record head to act like a tape degausser. This is called self-erasure, and limits the maximum level attainable in a tape recorder at high frequencies. Distortion occurs in an analog tape recording caused by input levels set in excess of 0VU. Setting a record input level too high on an analog medium is more forgiving than on a digital medium, and levels up to +3VU can sometimes be tolerated, but with a corresponding loss of high frequencies. See overs, headroom, retentivity.