There are some methods that are patent encumbered and the only source of ways to decode them are with tightly controlled modems/decoders. This is especially the

There are some methods that are patent encumbered and the only source of ways to decode them are with tightly controlled modems/decoders. This is especially the case with the advanced PACTOR modems and some of the digital voice encoders. The FCC considered patented methods to be open even if there are no available methods to decode them.