The DS9490R# is a USB bridge with a 1-Wire RJ12 interface to accommodate iButton touch-and-hold probes. One such probe, the DS1402D-DR8+ ("Blue Dot" probe) can readily be plugged into the DS9490R# to create a complete communication pathway between multiple iButton devices and the PC.
The DS9490B# is a USB bridge and holder for a single F5-size iButton. The iButton is securely held behind a latched door.