PCS digital cellular technologies are only one kind of wireless data technology in use today. Here's information about some others.

• Click here for an illustration of wireless data radio frequency ranges in the US.

• Packet data - Wireless packet-switching technologies such as AT&T's CDPD provide data-only capability. Currently they are used primarily to transmit short messages to "smart phones" and PDA's (personal digital assistants).

• Mobile radio technologies - Mobile radio is used primarily for dispatch applications by the emergency services, transport sector and utilities.

• Satellite technologies - Satellite services will not compete directly with terrestrial systems, but will instead complement them by offering service in areas without terrestrial coverage.