The DS9104 Digital Decoder Ring brings jewelry into the information age. In its custom-designed setting it holds a Memory iButton with a unique, 64-bit serial number permanently engraved into the silicon chip inside plus 64 kbits of nonvolatile SRAM for virtually unlimited read and write cycles. For technical details on iButtons please refer to www.iButton.com. Applications of the Digital Decoder Ring include access control to buildings, personal information such as medical records, business card data, private address, telephone list and access control to computers. Under iButton TMEX, files for all applications can reside in the same device without disturbing each other. The memory chip is formatted like a floppy disk and maintains a directory of files for random access.