Electronic Engineering Glossary Terms

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.

Dongle. A hardware component used as a security device, or key to unlock a software feature or program. When required the software programs reads the port that should contain the dongle and expects a certain reply, to unlock the software. An example is shown in the right side-bar as a parallel port connected dongle, the red device is the dongle. These days if a hardware dongle is required it would be a USB device, as many computers and peripherals no longer have a parallel ports. Note that this particular dongle still allows another device with a parallel cable to connect to it.

Donor. An impurity that can make a semiconductor material an N-type by donating extra "free" electrons to the conduction band.

Don't Care. 'X'. Irrelevant. A variable may take any logic state without effecting circuit operation, logical operation.

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. The change in the observed frequency (or wavelength) of a wave, caused by a time rate of change in the effective path length between the source and the point of observation.

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). Refer to Doppler Frequency Shift. The degree of observed change in frequency (or wavelength) of a wave due to the doppler effect.

Dropout. A momentary loss of signal in a communications system.

DOS. [Disk Operating System]. A text oriented program that operates between the computer and the user.

Dot-Matrix Printer. An obsolete style of printer that printed dots in a pattern to form letters. Largly replaced by the Laser printer in the early 1990's. A related list of PC Printer Manufacturers.

Double-Moding. The abrupt and random change from one frequency to another in a transmitter output tube.

Double Negative Law. In Boolean algebra, the law which states that the complement of a complement is the equivalent of the original term.

Double Pole Switch. A switch that control two independent circuits simultaneously.

Double Receiver. A fine and coarse synchro receiver enclosed in a common housing with a two-shaft output (one shaft inside the other).

Double Sideband Transmission. The transmission of both the upper and lower sideband generated in amplitude modulation but not the carrier.

Doublet. Another name for the dipole antenna. Also refer to a separate dictionary of Antenna Terms.

Double-Tuned Circuit. An LC circuit that is resonant to two closely spaced frequencies so that the over-all bandwidth of the circuit is increased, covering both frequencies. A circuit that is resonant to two different frequencies.

Double-Word. An eight byte quantity, aligned on eight byte boundaries.

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-Converter. A device that translates a given frequency band to a frequency band with a lower center frequency.

Down Link. The frequency used to transmit an amplified signal from a satellite or other craft back to earth.

Drain. A region of a FET into which majority carriers flow from the channel. One of three terminals on a Field Effect Transistor.

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]

Drive. In a chopper, the power supplied to a coil to cause action, usually measured in terms of voltage and frequency also called coil voltage.

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]. A component used to switch a high voltage or high current load [40107 right side-bar]. The final stage of amplification. An IC or circuit used to supply an input to another circuit. A software routine which receives Input/Output request from higher levels within the operating system and converts those requests to the protocol required by a specific hardware device.

Droop Rate. A circuits ability to hold a stored voltage over a defined period of time. The reduction in amplitude of a pulse over time. Also see Pulse Droop.

Dropout Voltage. The input-output voltage differential at which a regulator ceases to regulate against further reduction in input voltage. Dropout voltage is dependent upon load current and junction temperature. Related topics include Voltage Regulator Manufacturers, and Low Dropout Voltage Regulators.

Drum-Type Armature. A 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.