While the term USB modem refers to any type of data/fax/voice
modem device
which can be connected to a computer using
USB, the term more commonly describes
a specific portable USB device that looks similar to a
USB flash drive and can
be as small as 100 x 35 x 23mm in physical size and weigh only around 25grams . These
small portable USB fax modems do not require a power source and can be plugged
into any USB port on your
PC,
notebook, or
Macintosh computer and can also be disconnected
from the computer without turning off the system. One end of the portable USB
modem will have a USB
interface, while the other end will have an
RJ-11 port for
connecting your phone line.