Very few Betas were equipped with linear stereo (recorded by two stationary heads located in the ACE head assembly). This added flexibility and was limited to the professional Betas models such as the GCS-50,SLO-383,SLO-420 and SLO-1800. The GCS-50 and SLO-1800 also recorded in Betahi-fi stereo but only the SuperBeta model GCS-50 allowed the operator to select the two linear tracks separate from the Betahi-fi stereo. The SLO-1800 studio duplicator had linear stereo audio tracks that were presumably there to accommodate the Marantz VR 200 (actually made by Sanyo) that was introduced just a few years prior to Betahi-fi. (See the Marantz VR 200 by clicking here.) Sony disabled the 1800 linear stereo in mid production, presumably because so few consumer machines could take advantage of it.