Glossary G-H

Global System for Mobile Communications: Having such a standard ensures compatibility, so one can use the same cell phone for travel between countries. Today more than 105 countries, including the United States and Japan, have existing or planned GSM networks. These networks account for a large percentage of the world's cellular market.

GSM (Global System for Mobile Communication) - GSM is the most widely used mobile telecommunications standard in the world. A form of Time Division Multiple Access (TDMA) multiplexing, GSM is the standard in Europe and Asia.

Gateway Hardware, software or a combination of the two that acts as an entry point to a network. Gateway servers are also commonly used as firewall servers that guard against the entry of unauthorized users to a private network. In the client/server model, there is a gateway at the entry to both end points.

Gigabit (Gb) - 1) In terms of data transfer, one gigabit per second (Gbps) refers to 1,000,000,000 bits of information transferred per second. 2) In relation to data storage, one gigabit is exactly equal to 1,073,741,824 bits of stored data.

Gigahertz (GHz): 1) In radio frequency (RF) transmissions, GHz is used to describe 1,000,000,000 cycles per second, or Hertz. 2) In computing contexts, GHz describes 1,000,000,000 oscillations per second of the computer’s processor.

H.323 A standard approved by the International Telecommunications Union (ITU), the H.323 communications standard supports videoconferencing and Voice over Internet Protocol (VoIP). Theoretically, all devices using the H.323 standard can communicate with each other.

HPNA (Home Phoneline Network Alliance) - A standard for the creation of Local Area Networks (LANs) in residential or home-office environments. HPNA uses modified Ethernet technology to simultaneously transmit voice and data applications using a home’s existing copper wiring and jacks.

HTML (HyperText Markup Language) - A set of markup symbols (or tags) that are used to describe the appearance of a page on the worldwide web when displayed on a web browser. The current version of HTML is 4.0, (a.k.a. dynamic HTML). HTML is constantly evolving to increase flexibility for web presentations. The next version is a marriage of Extensible Markup Language (XML) and HTML called Extensible Hypertext Markup Language (XHTML) that will provide greater flexibility for new web applications.

HTTP (HyperText Transfer Protocol) - A set of rules for sharing files on the worldwide web. The most direct use of HTTP is the request for a web page by selecting a hypertext link. This HTTP request is sent to the selected Internet Protocol (IP) address. After it has been processed and authorized, the HTTP request is sent back to the client with the requested data.

Half Duplex: A form of 2-way communication that allows users to receive and communicate by voice, but not at the same time. Half duplex is common in speakerphones, intercoms, and 2-way radios.

Handset: The handheld part of a telephone that is used for transmitting and receiving voice signals. Also referred to as a telephone receiver.

Headset: An alternative device to a telephone handset. Headsets require a connection to a telephone, usually through the handset jack (RJ-9) on a corded phone, or via a built-in jack on a cordless or wireless phone.

Hertz (Hz) - The measure of the number of cycles per second of a waveform or system. It is used to 1) measure the frequency of a radio signal; 2) measure the frequency of sonic waves; or 3) measure the clock speed of a microprocessor by the number of oscillations the processor completes per second.

Home Run Wiring (also Star or Parallel Wiring) - A wiring topology that connects all phones or network devices directly to a central hub. Each device has a direct line (or "run") back to the central location (or "home").

Home RF (Home Radio Frequency) A standard created specifically for wireless networking in the home. Home RF is a competing standard with 802.11b (or Wi-Fi), though the applications do not necessarily overlap. 802.11 standards were developed with enterprise networking in mind.

Hookswitch: The mechanism that opens and closes the phone line to a phone. It is typically located at the top of the phone’s base (and therefore beneath the phone’s receiver) and is released by the act of removing the handset from the cradle, hence the term "off-hook." Host 1) A computer system that provides service features to other computers. Used in this context, any computer that acts as a server can be considered a host, whether on the Internet or a Local Area Network (LAN). 2) The provision of a computer to house a web server for one or several web sites.

Hub: A common connection point for computers or other devices in a network, usually a Local Area Network (LAN). There are several different types of hubs, many of which also perform switching and routing functions.

Hunting Service see Rollover Service.

Hypertext: A method for organizing and referencing information by associations and links. The creation of hypertext with its ability to instantaneously reference additional documents by "pointing and clicking" on a hypertext link ultimately made the worldwide web a viable enterprise.

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