0-9  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 handheld device markup language (HDML) A specialized version of hypertext markup language (HTML) designed to enable wireless pagers, cell phones, and other handheld devices to obtain information from Web pages. HDML was developed before the wireless application protocol (WAP) specification was standardized. Due to the graphics limitations of wireless devices, a website must be HDML-enabled in order to allow access by such devices. hard-coded The practice of specifying the way an application works in the computer code rather than in tables that are easily modified. hard-optics The hardware technologies that create and transport light, such as DWDM, FEC, Raman amplification, tunable dispersion compensators, Variable Optical Attenuators (VOAs), dynamic spectral gain compensators, Micro-Electro-Mechanical Systems (MEMS), and Optical Spectrum Analyzers (OSAs). hertz (Hz) A unit of frequency equal to one cycle per second. hetero-bipolar transistors (HBT)   hierarchical A structure made up of different levels like a company organization chart. The higher levels have control or precedence over the lower levels. Hierarchical structures are a one to many relationship; each item having one or more items below it. high electron mobility transistors (HEMT)   high-speed circuit switched data (HSCSD) An enhancement to the GSM mobile communications system that enables up to four 14.4 Kbps channels to be combined to provide 57.6 Kbps data transfer. Part of GSM Phase 2, HSCSD enables users to access two time slots instead of one, thus doubling the data capability. HSCSD is suited for videoconferencing and multimedia transmission. high-yield debt Represents a bond that has is rated BB or lower by rating agencies. These bonds are issued to companies without a long track record of revenue or earnings, and whose credit strength is weaker. High-yield debt, also referred to as "junk bonds," pays a higher yield to compensate for its greater risk. There are a number of investment professionals who specialize in analyzing these risks in order to benefit from the higher yield. horizontal marketplace Sells materials or services that companies need such as MRO, procurement management and benefits management. Does not include those materials or services specific to manufacturing or production. hub In data communications, a hub is a place of convergence where data arrives from one or more directions and is forwarded out in one or more directions. A hub usually includes a switch of some kind. hybrid fiber coaxial (HFC) network A network (usually a cable TV network) consisting of (1) fiber links from the head-end to the distribution node and (2) coaxial cable from the node to individual dwellings. hybrid microwave integrated circuits (HMIC) A circuit manufacturing technology consisting of multiple gallium arsenide devices bonded to ceramic substrates and interconnected with hundreds of bond wires. hypertext markup language (HTML) A markup language used to structure text and multimedia documents and to set up hyperlinks between documents, used extensively on the World Wide Web. hypertext transfer protocol (HTTP) A protocol used to request and transmit files, especially Web pages and Web page components, over the Internet or other computer network.