Glossary - H
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
Half Duplex - Two-way transmission, one way at a time.
Halo - Most commonly, a dark area surrounding an unusually bright object, caused by overloading of the camera tube. Reflection of studio lights from a piece of jewelry, for example, might cause this effect. With certain camera tube operating adjustments, a white area may surround dark objects.
Hardware - The equipment involved in production, storage, distribution or reception of electronic signals. In cable television it means the headend, the coaxial cable network, amplifiers, the television receiver and production equipment like cameras and videotape recorders.
Headend - The control center of a cable television system, where incoming signals are amplified, converted, processed and combined into a common cable along with any original cablecasting, for transmission to subscribers. The system usually includes antennas, preamplifiers, frequency converters, demodulators, modulators, processors and other related equipment.
Headend Router - The computer, at the cable headend, responsible for gateway operations between the headend and the internet.
Header - Protocol control information located at the beginning of a protocol data unit.
Hertz (Hz) - A unit of frequency equivalent to one cycle per second.
High Band - TV channels 7 through 13.
High Definition Television (HDTV) - A television signal with greater detail and fidelity than the current TV systems used. The USA currently uses a system called NTSC. HDTV provides a picture with twice the visual resolution as NTSC as well as CD-quality audio.
High Q - A fiber circuit with a great deal of selectivity.
High Return - A frequency division scheme that allows bi-directional traffic on a single coaxial cable. Reverse channel signals propagate to the headend above the downstream passband.
High VHF Band - Part of the frequency band which the FCC allocates to VHF broadcasting, including channels 7 through 13, or 174 through 216 MHz.
Home Page - The default web page that is displayed when you open your browser. The browser may be configured to automatically load this page on startup, or not until the HOME button is pressed. It also refers to the main page of a web site.
Homes Passed - Total number of homes which have the potential for being hooked up to the cable system.
Horizontal (Hum) Bars - Relatively broad horizontal bars, alternately black and white, which extend over the entire picture. They may be stationary, or may move up or down. Sometimes referred to as a "venetian blind" effect. Caused by approximate 60-cycle interfering frequency, or one of its harmonic frequencies.
House Drop - The coaxial cable that connects each building or home to the nearest feeder line of the cable network.
Hub - A signal distribution point for part of an overall system. Larger cable systems are often served by multiple hub sites, with each hub in turn linked to the main headend with a transportation link such as fiber optics, coaxial supertrunk, or microwave. A hardware device that interconnects computers on a Local Area Network and acts as a central distribution point for the communications lines.
Hue - Corresponds to "color" in everyday use; i.e., red, blue, etc. Black, white and gray do not have hue.
Hum Modulation - Undesired modulation of the television visual carrier by the fundamental or low-order harmonics of the power supply frequency, or other low-frequency disturbances.
Hybrid Fiber/Coax(ial [cable]) (HFC) - HFC system is a broadband bi-directional shared media transmission system using fiber trunks between the headend and the fiber nodes, and coaxial distribution from the fiber nodes to the customer locations.
HyperText Markup Language (HTML) - The language used to create and display web documents. It uses "tags" to identify the components of a document (text, graphics, multimedia) and how those components should behave.
HyperText Transfer Protocol (HTTP) - The standard for exchanging files (text, graphics, and multimedia) on the World Wide Web.
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