The system includes a modem unit with a standardized form factor and
standardized connector. The modem unit can be connected to a phone shell
personal digital assistant and for other data units. Connected to the
phone shell, the modem unit transmits voice data. Connected to the
personal digital assistant or other data device, the modem unit transfers
data. By having a modem unit that can usable both for voice and data, a
single cellular transceiver can be used for both voice and data without
requiring a wired connector. Additionally the standardized form factor
and connector allows a second modem unit, having a second type of
cellular connection, to be used in place of the first modem unit. The
other type of cellular connection can be a different communication
standard.