Patents
The 9-pin ADAT sync port used by the HD24 recorder is covered by U.S. Patent 5,541,781 (filed on Apr 12, 1994, issued on Jul 30, 1996) and its European counterpart, Patent EP0621976B1. Measuring the signals on the pins of the recorder however reveals that the pinout of the actual implementation of the sync port differs from the patent description.
The HD24 recorder has triple ADAT Lightpipe interfaces, each of which permit 8 channel, 24-bit digital audio transfer over fiber-optic cable. This is covered by U.S. Patent 5,297,181 (filed on Jan 17, 1992, issued on Mar 22, 1994).
The FST file system used by the HD24 recorder was previously described as "Patent pending" in Alesis marketing material. However, no patent appears to be issued in relation to the file system and current HD24 marketing material no longer makes any mention of patents on the file system.
Read more about this topic: Alesis ADAT HD24