Technicolor DTMF sequences

Many SP-mode videotapes duplicated at Technicolor in Livonia and New York City beginning in mid-1989 and ending in circa-2004 included a sequence of DTMF tones at the start and/or end of the tape. On certain tapes with this sequence, a faint sound of extra tones precedes it. It is not yet known exactly what each tone in the sequence indicates, except there's usually a pause between the first and second tones, the second tone is always 1, the third tone is always #, and the fourth tone is always D. This sequence was used to encode audio and video on the master tape by providing information on settings such as format, running time, audio level balance, volume control, etc. to automatic videotape duplication machines, allowing better replication. On most tapes, the tones are heard on the left channel of the hi-fi audio track. However, on some tapes, the tones are heard either on the right channel of the hi-fi track or exclusively on the linear audio track.

The only other videotape duplicator that used the DTMF sequences was AstralTech, a division of Canadian conglomerate Astral Media. AstralTech began using them in 1996 and was later acquired by Technicolor in 2000.