A B C D E F G H I J K L M N O P Q R S T U V W X Y Z
Hardwire - To directly attach or dedicate a cable or line between units of equipment.
Hertz (Hz) - International standard unit of frequency, measuring the number of cycles per second in a waveform. One Hz is one cycle per second (CPS). Cycles per second and Hz measure analog signals, bits per second measure "square wave' clock sample signals in a digital transmission.
Head End - Where cable-TV signal processing occurs; where the array of satellite dishes that cable TV companies use, picks up their programming transmissions before being sent down its coax cables for distribution.
Header - Binary signaling and address information, added to the front of a data packet. Instructs network components how and where to send the packet.
High Bit Rate Digital Subscriber Line (HDSL) - Clear channel hysical layer carrier, delivering networking up to 1.544 Mbps over two copper pairs, and 2.048 Mbps (E1) over two or three pairs at a base transmission range of 20,000 feet from a central office (but can be extended over 30,000 feet using repeaters, and beyond using fiber optic).
High Level Data Link Control (HDLC) - Communications protocol; the frame layer protocol in X.25, and the data-link layer protocol by OSI standards.
High-speed Serial Interface (HSSI) - Network standard for high speed (up to 52Mbps) serial communications over wide area network (WAN) links.
Hub - (1) Device that serves as the center of a star-topology network. (2) In Ethernet/IEEE 802.3, a multiport repeater, sometimes referred to as a concentrator. (3) Hardware/software device that contains multiple independent but connected modules of network and internetwork equipment.
Hubbing - Converting analog lines to a digital T1 facility.
Hunt - Where several telephone lines work together, so that a call rotates from line to line until it finds a line that is not busy.
Hunt Group - Number of telephone lines that are grouped together by a PBX system or central office.
Hybrid Key System - Switching system, allowing telephone users to choose which lines appear/don't appear under the keys of electronic telephones; typical of PBX systems, but hybrid keys require the user to select a line to dial out.
Hypertext - Software feature; linking one file or address to another. For example, in a document, hypertext is text that when clicked on, transfers the user to another address or file.
Hyper Text Markup Language - Text and graphics formatting software, that uses coding for indicating how a document should be presented by a viewing application such as a web browser.
HyperText Transfer Protocol (HTTP) - Control software used by web servers and browsers on the Internet to provide support to lower level OSI protocols when transferring HTML files containing both text and graphics.
In-Band Signaling - Unlike data transfer and PBX applications (which are out of band), where digits you dial and the ringing are carried within the channel you talk on (like your home hone line).
Independent Telephone Company (ITC) - Local carrier other than the seven Regional Bell Operating Companies (RBOCs) and GTE.
Information Technology - Study of how best to use newer/better devices & machines to improve data and information processing.
Input/Output (I/O) - User interface devices such as keyboards, monitors, terminals, printers - devices that interface people with computers.
Inside Plant - Electronic equipment, such as central office switches, PBX switches, distribution frame, broadband transmission equipment, etc., that reside inside a central office.
Inside Wiring (IW) - Telephone wire on the customer side of the Telephone Network Interface, including jacks.
Internet Assigned Numbers Authority (IANA) - Organization operated under the support of the Internet Society (ISOC); part of the Internet Architecture Board that delegates authority for IP address allocation and domain name assignment to the InterNIC.
Institute of Electrical and Electronic Engineers (IEEE) - (1) International society of professionals that its own standards. (2) Member of ANSI and ISO. (3) Active setting local area network (LAN) standards.
Integrated Services Digital Network (ISDN) - Switched network providing end-to-end digital connectivity for the simultaneous transmission of voice, data, video, imaging and fax over several multiplexed communications channels. Employees high-speed, out-of-band signaling protocols that conform to international standards. Signaling and communications are separate, therefore, reduces network blockage and provides faster connectivity for users.
Interactive Voice Response (IVR) - Data processing / telecommunications technology, which uses a phone line to interface a person to information in a computer. In other words, where a computerized voice reads back information, based on what a person has keyed into a phone.
Interconnect Agreement - Aka co-location agreement.
Interexchange (IX) - Services or channels furnished between one or more rate centers or local and long-distance carriers.
Interexchange Carrier (IXC) - Provider of long-distance service.
Interior Gateway Routing Protocol (IGRP) - Traffic control program for networks, used by routers, developed by Cisco in the early 1980's. Determines the best path through an internet by looking at the delay and bandwidth of the networks between routers.
Inter Local Access Transport Area (Inter LATA) - Services that originate and terminate within the same area code.
International Dialing - Dial 011-county code-city code-number to dial international phone numbers from within the United States.
International Gate Ways - Where international telecommunications get connected from the gateway central office to other countries, translating T1 to E1, T3 to E3, and back.
International Organization for Standardization (ISO) - Organization that promotes the development of standards to facilitate the international exchange of goods and services; develops mutual cooperation in areas of intellectual, scientific, technological and economic activity.
International Record Carrier (IRC) - Exchange companies that offer telex and teletypewriter interconnect services.
Internet - (1) International network infrastructure supporting research, engineering, education and commercial services using primarily transmission control protocol/internet protocol (TCP/IP); established by the US Department of Defense, now available commercially. (2) Any interconnected set of sub networks running an internetwork protocol such as TCP/IP
Internet Address - a 32 bit code assigned to hosts using TCP/IP, written as four octets separated with periods (dotted decimal format) that are made up of a network section, an optional subnet section and a host section. Synonym: IP Address.
Internet Control Message Protocol (ICMP) - Used by hosts and routers to send feedback between each other, regarding routing, retransmission & other controls / notifications - used for routers to sense each other and share diagnostic information about the network.
Internet Group Management Protocol (IGMP) - Rules and procedures, existing as software in a networks operational memory, used by IP devices to report multicast group membership to adjacent multicast routers - automatically identifying the devices they are routing data between.
Internet Message Access Protocol (IMAP) - Provides email users a way to retrieve their messages, providing expanded POP functions using simple mail-transfer protocol (SMTP) to transfer messages to the mail server from the user.
Internet Protocol (IP) - OSI Layer 3, the network layer protocol, that contains addressing information and some control information that allows packets to be routed.
Internet Protocol Multicast (IP Multicast) - Where IP packets are sent to multiple destinations via an IP destination group address in a multicast group, instead of sending one packet to each destination.
Internet Service Provider (ISP) - Company that purchases direct access to the internet and resells the services to smaller subscribers.
Interoffice - Phone connection that starts in one central office, and ends in another central office, within the same area code.
Interoffice Trunk (IOT) - Direct link between local exchange offices.
Interstate Long Distance - Service or call that starts in one state, and ends in another state.
Intranet - Inter-company network based on TCP/IP protocols. Accessible from the internet, but only through passwords or decryption keys.
Intrastate Long Distance - A call or service that starts and ends in the same central office.
IP Address - In TCP/IP message transmissions, packets/datagrams are routed within a network via the IP address; consists of a network identifier and host identifier.
ISDN Subscriber Line (IDSL) - Physical layer transport method for symmetric download/upload speeds, ranging from 64 to 144 Kbps on single pair copper wire. Maximum range from the central office is 18,000 feet (36,000 feet with a repeater). Used for transporting ISDN.