Technicolor DTMF sequences

Many SP-mode videotapes duplicated at Technicolor Video Services' Livonia facilities beginning in the summer of 1989 and ending in circa 2004 included a sequence of DTMF phone-dial 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. The sequence was used to encode 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. This allowed better replication of the master tapes recorded on the formats the videotapes were released in.