other audio hardware than the PJB and replacements for the included accessories): 1600 mAh Li-Ion Battery Waterproof neoprene bag for use of the PJB at a beach or pool Audio-cassette adapter for playback on car/home stereos Swan-neck car-holder Magnetic mounts to attach the PJB within a car Power-supply-adapters for car cigarette-lighters Firmware Features and version history The latest firmware version, which surfaced in December 2003, is v2.3.3-alpha; the latest stable version is v2.3.2, introduced in mid-2001. Initially, the functions provided by the player were basic: when music was played back, selecting another track would immediately start this track and stop the current one; playlists had to be created on the computer; files could only be uploaded to the PJB, but not downloaded back to the computer. New firmware versions came out regularly, but were mostly bug fixes with very few new functions introduced. Later firmware versions added some of the most requested features: Files could be transferred from player to PC The ability to browse without interrupting playback Some (hidden) games were added File system and table of contents (TOC) The PJB's disk is not formatted as FAT or FAT32 as is the case with most of the players that were released later, and enables those to be mounted as another drive in an operating system. Instead, a unique file system is used, which, while losing the mounting ability, is optimized for the structure of MP3 files (having a cluster size of 128 kB, which equals about 8 seconds of 128-kBit-encoded MP3-music). Therefore, managing actions like defragging become unnecessary. The file system allows the linking of Tracks into various Discs/Sets. Therefore, each track is ideally only stored once on the disc and recurring occurrences of it (for example in playlists or samplers) are just links to the original file. This may help to preserve a good amount of disk space and allows for more tracks to be stored on the disk. All of this info is stored in the TOC (table of contents). The TOC is stored in a human-readable text-format and can be downloaded, changed with a text editor and re-uploaded to the PJB again. A copy of the TOC is always stored on the unit as well, so errors and damage to the original TOC can usually be fixed. Software Software development kit The original developers at Compaq Research designed an SDK (Software Development Kit) for the unit