Hard Drawn Copper Wire -- Copper wire that has been drawn to size and not annealed.

Hardness -- Resistance of material to plastic deformation, usually by indentation. However, the term may also refer to stiffness or temper, or to resistance to scratching, abrasion, or cutting. Indentation hardness may be measured by various hardness tests, such as Brinell, Rockwell and Vickers.

Hardwired -- Applied to a telephone set, it is the connection of the telephone set line (mounting) cord to a connecting block with screw terminations. Under the FCC's Registration Program for terminal equipment, only those telephone sets which were connected to the telecommunications network in a "hardwired" manner prior to July 1, 1979, may remain connected in such a fashion.

Harness -- A group of conductors laid parallel or twisted by hand, usually with many breakouts, laced or bundled together, or pulled into a rubber or plastic sheath, used to interconnect electrical circuits.

Hash Mark Stripe -- A non-continuous, helical stripe applied to a conductor for circuit identification.

Hazardous Locations -- Article 500-503 in the NEC covers hazardous (classified) locations and the requirements for electrical equipment and wiring in locations where fire or explosive hazards may exist due to flammable gases or vapors, flammable liquids, combustible dust, or ignitable fibers or flyings. Locations are defined by Class and Division depending upon properties and/or mixture of the hazardous elements. Acceptable wiring methods, including types of cables, are mentioned in the NEC articles for the specific Class and Division locations.

Head -- The end section of an extruder in which the plastic melt is transferred to the cable.

Heat Distortion -- Distortion or flow of a material or configuration due to the application of heat.

Heat Endurance -- The time of heat aging that a material can withstand before failing a specific physical test.

Heat Seal -- In cabling, a method of sealing a tape wrap jacket by means of thermal fusion.

Heat Shock -- A test to determine stability of a material by sudden exposure to a high temperature for a short period of time.

Heater Cord -- Flexible stranded copper conductor, cotton wrap, rubber insulation, asbestos roving, for indoor use on household appliances.

Helical -- Spiral.

Helical Stripe -- A continuous, colored, spiral stripe applied to a conductor for circuit identification.

Henry (H) -- A practical unit of inductance that will produce a voltage drop of one volt when the current changes at a rate of one ampere per second.

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

Hi-Pot -- A test designed to determine the highest potential that can be applied to a conductor without breaking through the insulation.

High Frequency -- The band from 3 to 30 mHz in the radio spectrum, as designated by the Federal Communications Commission.

High Voltage -- Generally considered to be a wire or cable with an operating voltage of over 600 volts.

Holding Strength -- Ability of a connector to remain assembled to a cable when under tension.

Hook Up Wire -- Insulated wire used for low current (low voltage under 1000 volts) applications internally within enclosed electronic equipment.

Horizontal Stripe -- A colored stripe running horizontally with the axis of a conductor, sometimes called longitudinal stripe, used as a means of circuit identification.

Hospital Wiring -- The NEC, in its section on hospital anesthetizing locations, requires wiring with a dielectric constant of 3.5 or less. This is to minimize capacitive coupling, thereby lowering the capacitive leakage current for patient safety reasons. Rome's Type XHHW has an SIC below 3.5 so it is deemed suitable for this type of hospital wiring.

Hot Tin Dip -- A process of passing bare wire through a bath of molten tin to provide a coating.

Hot-Rolled Rod -- The as-rolled section, normally round, produced by hot-rolling in a rod mill from a billet or wire bar.

Hum -- A term used to describe the 60 or 120-hps sound present in the sound of some communications equipment. Usually hum is the result of undesired coupling to a 60-hps source or to the defective filtering of 120-hps ripple output of a rectifier.

Hybrid Cable -- A multi-conductor cable containing two or more types of components.

Hygroscopic -- Having the tendency to absorb moisture and retain moisture.