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D.C. - abbreviation of "Direct Current"

Datalene - Belden trademark for foam polyolefin.

Decibel (dB) - A unit to express differenced of power level. Used to express power gain in amplifiers or power loss in passive circuits or cables.

Delay Line - A transmission line or equivalent device designed to delay a wave or signal for a specific length of time.

DEPIC - Dual Expanded Plastic Insulated Conductor (Foam Skin).  Decreases outside diameter of cable.

Derating Factor - A multiplier used to reduce the current carrying capacity of conductors in more adverse environments, such as higher temperature, or where multiple conductors are together in one conduit.

Dielectric - An insulating (non-conducting) medium. It is the insulating material between conductors carrying a signal in a cable. In coaxial cables it is between the center conductor and the outer conductor. In twisted pair cables it is the insulation between conductors plus any surrounding air or other material.

Dielectric Absorption - That property of an imperfect dielectric whereby there is an accumulation of electric charges within the body of the material when it is placed in an electric field.

Dielectric Breakdown - The voltage at which a dielectric material is punctured, which is divisible by thickness to give dielectric strength.

Dielectric Constant (K) - Also called relative permittivity. That property of a dielectric which determines the amount of electrostatic energy that can be stored by the material when a given voltage is applied to it. Actually, the ratio of the capacitance of a capacitor using the dielectric to the capacitance of an identical capacitor using a vacuum (which has a dielectric constant of 1) as a dielectric. A number which indicates the quality of a material to resist holding an electrical charge when placed between two conductors.

Dielectric Strength - The voltage an insulation can withstand before it breaks down. Usually expressed as "volts per mil".

Dielectric Test - a test in which a voltage higher than the rated voltage is applied for a specific time to determine the adequacy of the insulation under normal conditions.