half-duplex signaling - A bidirectional signaling method in which data transfer can take place in either direction, but in only one direction at a time. Contrast with dualduplex signaling, full-duplex signaling, and simplex signaling.

half-tap - Splicing of a cable or individual pairs where the through cable/conductor is not cut until the cutover takes place. This is a "hot cut" penetration step.

hand geometry - A biometric reader that verifies a person's identity using the variations in hand size, finger length, and finger thickness.

hand trace - The act of physically hand tracing a cable, patch cord, jumper, or crossconnect from one known point to another known point to determine its path.

handhole (HH) - A structure similar to a small maintenance hole in which cable can be pulled, but not large ertough for a person to fully enter to perform work.

handoff - The process that occurs when a mobile user moves from one cell (thereby terminating communications) to another cell (thereby initiating communications) in a cellular network. The handoff is accomplished without disruption of the exiting connection.

handover - See handoff.

handshaking - A connection-oriented protocol. The process whereby verification is established before controlled data is sent to a remote system. When handshaking is successful, the systems establish connection.

hardened equipment - Outdoor housed equipment or apparatus designed to withstand varying temperature, dust, and seismic conditions.

hard-line trunk - A rigid coaxial cable, typically used for backbone cabling. (TIA)

hard-sheath cable - A cable or wire contained within a continuous inner or outer metallic sheath. (TIA)

hardware address - See device address and medium access control address.

hard-wire system - A connection in which a device is either connected directly to the wires within a cable by screw lugs or a splice.

harmonic - A frequency that is a whole number multiple of the fundamental frequency.

harmonic coupling - Used to describe the transfer of electrical energy from one signal into another signal in a different media through an indirect connection (usually electromagnetic interference). For the transfer to work, it must be a divisible multiple of the original signal's fundamental frequency. Any other energy transfer would be noise surrounding the signal. For differences, see electrical-magnetic coupling.

harmonic distortion - The presence of additional undesirable sinusoidal components at frequencies that are integer multiples of an original sinusoidal frequency.

headend - The equipment located at the start of a coaxial cable distribution system where the signals are processed and combined prior to distribution.

headend equipment - The main active components of a distributed antenna system (DAS). Headend equipment provides the interfaces for the donor services (i.e., those to be retransmitted by the DAS) and the interfaces to the backend equipment to facilitate distribution of radio frequency signals to the coverage areas on other floors or in other buildings on a campus.

header - The initial part of a message, typically containing identification and control information.

header duct (trench duct, feeder duct) - A raceway of rectangular cross-section placed within the floor to tie distribution duct(s) or cell(s) to the telecommunications room. (TIA)

heartbeat - The signals issued periodically by a clustered device to indicate that it is functioning normally.

heat coil - A device that grounds a conductor when the conductor's current time limits are exceeded.

heat shrink tubing - Rubber (or similar material) tubing that shrinks upon the application of heat. Used to insulate splices, connectors, or to create weather or environmental protection to a connection.

henry (H) - The unit used to measure inductance of magnetic fields.

hermaphroditic connector - A connector that is neither male nor female.

hertz (Hz) - A unit of frequency equal to one cycle per second.

heterodyning - The technology used to generate new frequencies by mixing two or more signals in a nonlinear device (e.g., a vacuum tube, transistor, diode mixer).

hidden node (HN) - An instance where two or more nodes in a wireless LAN are within transmission range of the same access point, but not within transmission range of each other.

hierarchical star topology - An extension of the star topology using a central hub connecting two or more middle layer hubs.

hierarchical topology - A topology that links devices or networks using a series of levels, similar to an organizational chart.

high pair-count cable - A cable where balanced twisted-pair conductors are bundled into sets of 25 pairs.

high-rate direct sequence spread spectrum (HRIDSSS) - A form of wireless signaling similar to DSSS, but employing a more advanced coding scheme to enable higher data rates.

high-speed downlink packet access (HSDPA) - A third generation mobile telephony digital cellular standard based on the evolution of wideband code division multiple access technologies.

home automation - The interoperation of devices and subsystems in the home.

home run - A pathway or cable between two locations without a splice or intermediate termination points in between.

horizontal cable - Distribution media that connect the telecommunications outlet/ connector at the work area and the first piece of connecting hardware in the horizontal cross-connect (floor distributor).

horizontal connection point - A location for connections between horizontal cables that extend from building pathways and horizontal cables that extend to building automation systems devices and equipment. (TIA)

horizontal consolidation point/telecommunications outlet cable - A segment of horizontal cable between the consolidation point connector and the telecommunications outlet/connector. This cable is intended to be easily moved for modular office rearrangement. Also known as horizontal CP-TO cable.

horizontal cross-connect (HC) [floor distributor (FD)]) - A group of connectors (e.g., patch panel, punch-down block) that allows equipment and backbone cabling to be cross-connected with patch cords or jumpers. Floor distributor is the international equivalent term for horizontal cross-connect.

horizontal directional drilling - A method for placing underground facilities that uses a directed horizontal auger or drill to establish the path, place casings or cables, and minimize restoration costs associated with plowing or trenching.

horizontal HC-CP cable - The segment of horizontal cable permanently installed between the horizontal cross-connect (HC) and the consolidation point (CP) connector.

host - 1. In the Internet environment, the term used to describe any network-attached device that provides application-level services. 2. A generic term used to describe mainframes and minicomputers.

host computer - The central controlling computer on which access control software runs.

host identification (hostid) - Part of an IP network address. It identifies a device within a broadcast domain. See also network identification (netid).

hot cut - A cutover where the active cables are unplugged from the old system and plugged into the new system. See also cutover and flash cut.

hot red light - A low-intensity laser.

hub - A network device that provides a centralized point for LAN communications, media connections, and management activities of a physical star topology cabling system.

hybrid cable - An assembly of two or more cables, of the same or different types or categories, covered by one overall sheath. (TIA) Contrast with bundled cable.

hybrid coupler - A component used to combine two wireless bands to a single antenna feed or distribution cable.

hybrid optical fiber cable - An optical fiber cable containing two or more fiber types (e.g., multimode and singlemode). (TIA)