By the late 1970s, 3M introduced the first digital multi-track recorder. It used 1-inch wide tape and recorded 32 tracks. Unlike analog tape, edits could not be accomplished with a grease pencil, razor blades and splicing tape. So a secondary 4 track editing & mix down recorder was also created with an electronically-controlled edit controller to make effective digital edits. This early system used a 16-bit digital "word". The only converters of the day were 12 bit & 4 bit. So two were cascaded/daisy-chained to create the necessary 16-bit "word" for 96 DB of dynamic range. The signal was then sampled faster than any other digital recordings made up until that time at 50,000 times per second (50 kHz). It was known to be the best sounding of all the later digital multi-track recorders because their use of 50 kHz sampling did not become the industry standards later established as 44.1 kHz for CD's & 48 kHz for digital video.