Other examples include dbx, Inc.'s Model 700 system, which, similar to later Super Audio CDs, used a high sample-rate delta-sigma modulation rather than PCM; Decca's 1970s PCM system,[3] which used a videotape recorder manufactured by IVC for a transport; and Mitsubishi's X-80 digital recorder, a 6.4 mm (¼ in) open reel digital mastering format that used a very unusual sampling rate of 50.4 kHz.