"A",
"B",
"C",
"D",
"E",
"F",
"G",
"H",
"I",
"J",
"K",
"L",
"M",
"N",
"O",
"P",
"Q",
"R",
"S",
"T",
"U",
"V",
"W",
"X",
"Y",
"Z"
The previous portion of the D listing;
"D" Terms and definitions
DOMAIN NAME SERVER. A server that retains the
addresses and routing information for TCP/IP LAN users.
DOMAIN THEORY. A theory of magnetism based upon the electron-spin principle. Spinning electrons
have a magnetic field. If more electrons spin in one direction than another, the atom is magnetized.
DOMINANT MODE. The easiest mode to produce in a waveguide, and the most efficient mode in terms
of energy transfer.
DONOR. An impurity that can make a semiconductor material an N-type by donating extra "free" electrons to the conduction band.
DOORKNOB TUBE. An electron tube that is similar to the acorn tube but larger. The doorknob tube is
designed to operate, at high power, in the uhf frequencies.
DOPING. The process of adding impurities to semiconductor crystals to increase the number of free
charges that can be moved by an external, applied voltage. Doping produces N-type or P-type material.
DOPPLER EFFECT. The apparent change in frequency or pitch when a sound source moves either
toward or away from a listener. In radar, the change in frequency of a received signal caused by
the relative motion between the radar and the target.
DOPPLER FREQUENCY. The difference between transmitted and reflected frequencies; caused by the
Doppler effect.
DOPPLER SHIFT. The apparent change of frequency caused by the motion of the frequency source (transmitter) relative to the destination (receiver).
DOUBLE-MODING. In a transmitter output tube, the abrupt and random change from one frequency to
another.
DOUBLE NEGATIVE LAW. In Boolean algebra, the law which states that the complement of a
complement is the equivalent of the original term.
DOUBLE RECEIVER. A fine and coarse synchro receiver enclosed in a common housing with a two-shaft
output (one shaft inside the other).
DOUBLET. Another name for the dipole antenna. Also refer to a separate dictionary of Antenna Terms.
DOUBLING UP. This is a type of two-equipment installation where one unit can be substituted for
another in the event of failure. Also Hot-Swap.
DOWN LINK. The frequency used to transmit an amplified signal from a satellite or other craft back to
earth.
DRAIN WIRE. An uninsulated wire in contact with a cable shield
throughout its length, used for terminating the shield. A Drain Wire may form part of a cable bundle or cable assembly. A wire that runs linearly along a foil shield wire or cable and is used to make
contact with the shield. Grounding of foil shields is done with drain wires.
DRAM. A type of RAM that maintains its content as long as the data stored in the device is refreshed at regular intervals. DRAM requires a refresh cycle every few milliseconds in order to retain its data. The data is stored in a capacitor which slowly leaks, the refresh cycle re-charges the capacitor. DRAM is cheaper and slower than SRAM because of the longer access times. [DRAM Manufacturers]
DRIFT SPACE. In an electron, a region free of external fields in which relative electron position depends
on velocity.
DRIVE-BY-WIRE. A control system that replaces traditional mechanical or hydraulic linkages with electronic connections between control units that drive electro-mechanical actuators. Automotive by-wire includes three categories: throttle by-wire, steer by-wire, and brake by-wire. Related data; Automotive Bus Descriptions.
DRIVER. An IC used to switch on a heavily loaded net, as in bus driver [74244]. The final stage of amplification.
DRUM-TYPE ARMATURE. An efficient, popular type of armature designed so that the entire length of
the winding is cutting the field at all times. Most wound armatures are of this type.
Next set of "D" Terms and definitions
