VTRs, both analog and digital, have audio tracks, but with the use of timecode, audio only recorders can be synchronized so that they operate at the same speed as a video recorder. Magnetic recording relies on the hysteresis of magnetically hard media. Analog magnetic recorders have to use bias to linearize the process, whereas digital recorders are not concerned with the non-linearity, and bias is unnecessary. The frequency response of a magnetic recorder is far from ideal, and both analog and digital recorders must use some form of equalization. As the record and replay equalizations are in series, then in theory it would be possible to make all of the corrections on, say, replay. In large broadcast systems, the edited work can be broadcast directly from the disk file. In smaller systems it will be necessary to output to some removable medium, since the Winchester drives in the editor have fixed media.