 However, extensive archival research within the ABC following the recent closure of the old Gore Hill studios in Sydney has revealed that, although some early videotape-only content was erased, much of the primary footage had (fortunately) been shot on film and most of this was retained.It is believed that approximately 80% of "GTK" has survived.In the early years of television, the ABC had been using Lissajous figures as fillers in-between programs.