Packet A chunk of data that is sent over a network, whether it's the Internet or wireless network. Packet data is the basis for packet-switched networks, which are under development in the United States as a faster, more reliable method of transferring wireless data than a circuit-switched network. Packet-switched networks eliminate the need to dial in to send or receive information because they are "always on," transferring data without the need to dial. The packets that hold data depend on the size of the data involved; "chunks" are broken down into an efficient size for routing. Each of these packets has a separate number and carries the Internet address for which it is destined.
Packet-switched network Networks that transfer packets of data (see Packet).
PCS (personal communications services) An alternative to cellular, PCS works like cellular technology because it sends calls from transmitter to transmitter as a caller moves. But PCS uses its own network, not a cellular network, and offers fewer "blind spots" -- areas in which access to calls is not available -- than cellular. PCS transmitters are generally closer together than their cellular counterparts.
PDA (personal digital assistant) Mobile, handheld devices -- such as the Palm series and Handspring Visors -- that give users access to text-based information. Users can synchronize their PDAs with a PC or network; some models support wireless communication to retrieve and send e-mail and get information from the Web.
Radio frequency devices These devices use radio frequencies to transmit data. One typical use: a bar code scanner gathers information about products in stock or ready for shipment in a warehouse or distribution center and sends them to a database or ERP system.
Satellite phone Phones that connect callers via satellite. The idea behind a satellite phone is to give users a worldwide alternative to sometimes unreliable digital and analog connections. So far, such services have proven very costly and have appealed to few users aside from, for example, the crews at deep-sea oil rigs with phones configured to connect to a satellite service.
Smart phone A combination of a mobile phone and a PDA, smart phones allow users to converse as well as perform tasks, such as accessing the Internet wirelessly and storing contacts in databases. Smart phones have a PDA-like screen. As smart phone technology matures, some analysts expect these devices to prevail among wireless users. A PDA equipped with an Internet connection could be considered a smart phone. Ericsson, Nokia and Motorola also make smart phones.