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.

SMS (short messaging service) A service through which users can send text-based messages from one device to another (see BlackBerry). The message--up to 160 characters--appears on the screen of the receiving device. SMS works with GSM networks.

TDMA (time division multiple access) This protocol allows large numbers of users to access one radio frequency by allocating time slots for use to multiple voice or data calls. TDMA breaks down data transmission, such as a phone conversation, into fragments and transmits each fragment in a short burst, assigning each fragment a time slot. With a cell phone, the caller would not detect this fragmentation. Whereas CDMA (which is used more frequently in the United States) breaks down calls on a signal by codes, TDMA breaks them down by time. The result in both cases: increased network capacity for the wireless carrier and a lack of interference for the caller. TDMA works with GSM and digital cellular services.

WAP (wireless application protocol) WAP is a set of protocols that lets users of mobile phones and other digital wireless devices access Internet content, check voice mail and e-mail, receive text of faxes and conduct transactions. WAP works with multiple standards, including CDMA and GSM. Not all mobile devices support WAP, but IDC (a sister company to CIO’s publisher, CXO Media) projects that more than 1.3 billion wireless Internet users will have WAP-capable devices in their hands by 2004.