Oh yes. Patent rights has ended in 1998, if I remember, but "x10 powerhouse", producer of TW523, has not actualized TW523.pdf since 1997. In this document, on page 2 you see this words: "The X10 code format is patented" :smile:.
here is a good site, it has everything to build your own x-10 module, including the software an schematics, you can use it as reciver or as a two-way interfase to PC
here is a good site, it has everything to build your own x-10 module, including the software an schematics, you can use it as reciver or as a two-way interfase to PC