Intellectual Property Due Diligence
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Modems and voice coding are heavily patented area. Implementing these without serious
consideration of IP issues would be foolish. This document describes the basis on which
the software has been implemented.

The FAX facilities
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A check of the intellectual property information at the ITU web site showa a number of patent claims against the current FAX standards. It is important to realise, however, that some of these patents have long since expired (group III fax dates back to the 1970s). Also, many are related to recent additions to the FAX standard, such as colour FAX handling, which few people ever use.

The V.21 standard dates from the 1950s. There is no possibility that any patents related to it are still in force. However, the implementation also needs to be free of patented techniques. The implementation only uses very mature numerical oscillator and quadrature correlation techniques, so there should be no patent issues.

Only one patent is listed as relevant to the V.29 standard. This dates from the 1970s, and must have expired. The modem has been implemented using only very mature techniques, none of which can be less than 20 years old. There seem no possibility, therefore, that any patents are still in force related to the techniques used.

Many patents are listed as relevant to the T.30 standard. However, they all appear to relate to newer features, such as colour FAX, added in recent years. The current implementation only covers the original features from the late 1970s, where there appear to be to patent issues.

The original T.4 standard defines the image compression and decompression techniques. The current implementation actually uses the freely available libtiff library to perform these functions. This has existed for a number of years without IP issues, and is believed to be a safe choice.
