Electronic Engineering Glossary Terms

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.

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.

DOUBLING UP. This is a type of two-equipment installation where one unit can be substituted for another in the event of failure.

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 shield throughout its length, used for terminating the shield.

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.

DRIVEN ARRAY. An array in which all of the elements are driven.

DRIVEN ELEMENT. The element of an antenna connected directly to the transmission line.

DRIVER. 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.

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