A portable radio telephone handset operates as a data transfer terminal as
well as an analog cellular telephone subscriber station. Two modes of
operation, an analog cellular communication mode and a Cellular Digital
Packet Data (CDPD) mode, are available in the handset. The handset
distinguishes between paging signals indicating CDPD mode communications
and those indicating analog cellular communications. The handset also
automatically preempts CDPD communications in favor of analog cellular
communications such as those carried out in an AMPS configuration. The
handset maintains an active status on a CDPD communication channel during
a "sleep mode", when the handset can carry out AMPS activity.
