| ICEA | Insulated Cable Engineers Association (formerly IPCEA) |
| IEC | International Electrotechnical Commission, similar to the ISO in structure and scope |
| IEEE | Institute of Electrical and Electronic Engineers |
| Impact Strength | A test for determining the mechanical punishment a cable can withstand without physical or electrical breakdown by impacting with a given weight, dropped a given distance, in a controlled environment |
| Impedance | The total opposition that a circuit offers to the flow of alternating current or any other varying current at a particular frequency. It is a combination of resistance R and resistance X, measures in ohms. |
| IMSA | International Municipal Signal Association Specifications for Fire Alarm Cable |
| Induced Current | An electrical current set up in a circuit by cutting lines of force; a current caused by electromagnetic induction |
| Inductance | The property of a circuit or circuit element that opposes a change in current flow, thus causing current changes to lag behind voltage changes. It is measured in henrys |
| Inductive Coupling | Crosstalk resulting from the action of the electromagnetic field of one conductor on the other |
| Insulation | A material having high resistance to the flow of electric current. Often called the dielectric in radio frequency cable. |
| Insulation Resistance (I.R.) | That resistance offered by an insulation to an impressed DC voltage, tending to produce a leakage current through the insulation |
| Insulation Thickness | The wall thickness of the applied insulation |
| Interaxial Spacing | 1) Center-to-center conductor spacing in paired wire or 2) Center-to-center spacing between conductors in flat cable |
| Interconnecting Cable | The wiring between modules, between units, or the larger portions of a system |
| Interference | Any undesired electrical signal induced into a conductor by electrical or electromagnetic means |
| Interstices | Voids or valleys between individual strands in a conductor or between insulated conductors in a multi-conductor cable |
| Ionization | Generally, the dissociation of an atom or molecule into positive or negative ions or electrons. Restrictively the state of an insulator whereby it facilitates the passage of current due to the presence of charged particle usually induced artificially. |
| IP (Intelligent Peripheral Interface) | An ANSI standard that defines the mechanical and electrical interface requirements for peripheral devices attached to and between computers |
| Irradiation | In insulations, the exposure of the material to high energy emissions for the purpose of favorably altering the molecular structure by crosslinking |
| ISA | Instrument Society of America |
| ISO | International Standards Organization |
