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D.B. Abbreviation
for "Direct Current." Decibel (dB). A unit to express
differences of power level. Used to express power gain
in amplifiers or or power loss in passive circuits or
cables.
Delay Line. A cable made to provide very
low velocity of propagation with long electrical delay
for transmitted signals.
Derating Factor. A factor used to reduce
the current carrying capacity of a wire when used in environments
other than that for which the value was established.
Dielectric. Any insulating material between
two conductors which permits electrostatic attraction
and repulsion to take place across it.
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). The ratio of
the capacitance of a condenser with dielectric between
the electrodes to the capacitance when air is between
the electrodes. Also called Permittivity and Specific
Inductive Capacity.
Dielectric Strength. The voltage which
an insulation can withstand before breakdown occurs. Usually
expressed as a voltage gradient (such as volts per mil).
Dielectric Test. A test in which a voltage
higher than the rated voltage is applied for a specified
time to determine the adequacy of the insulation under
normal conditions.
Direct Burial Cable. A cable installed
directly in the earth.
Direct Capacitance. The capacitance measured
directly from conductor to conductor through a single
insulating layer.
Direct Current (DC). An electric current
which flows in only one direction.
Direct Current Resistance. (D.C.R.).
The resistance offered by any circuit to the flow of direct
current.
Dissipation Factor. The tangent of the
loss angle of the insulating material. (Also referred
to as loss tangent, tan S. and approximate power factor.
Double Foot. Combined length of one linear
foot of paired material; i.e., one double foot is equal
to one foot of positive material plus one foot of negative
material. Usually used in determining thermocouple wire
loop resistance.
Drain Wire. In a cable, the uninsulated
wire in intimate contact with a shield to provide for
easier termination of such a shield to a ground point.
Multi/Cable can include a drain wire with shielded pairs,
overall shields or both.
Drawing. In wire manufacturing, pulling
the metal through a die or series of dies to reduce diameter
to a specified size.
Duct. An underground or overhead tube
for carrying electrical conductors.
Duplex Insulated. In the thermocouple
industry, a combination of dissimilar metal conductor
of a thermocouple or thermocouple extension wire.
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