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The previous portion of ;
"D" Terms and definitions
DIGITIZE. Conversion of an analog signal into a digital
signal carrying equivalent information.
Diode Schematic Symbols
DIODE. A two element, solid-state device made of either germanium or silicon; it is primarily used as a switching device. [Diode Manufacturers]. An electron tube containing two electrodes: a cathode and a plate. Description of different Diode Types and definitions.
DIODE DETECTOR. A demodulator that uses one or more diodes to provide a rectified output with an average value that is proportional to the original modulation.
| DIODE TRANSISTOR LOGIC. [DTL] A style of digital logic that used both diodes and transistors to preform the logic function. Diode Transistor Logic was used up to the early to mid seventies when it was replaced by TTL logic. Diode Transistor Logic is obsolete and should not be used in new designs, it's doubtful any DTL devices could be procured in any event. |
 Diode Transistor Logic |
| DIP IC. Dual Inline Package IC. A style of Integrated Circuit that has its pins on either side of a rectangular shaped package. Normally a DIP IC refers to a through-hole component, while a surface mound device would be called an SOIC [for example]. |
 DIP ICs |
DIPOLE. A common type of half-wave antenna made from a straight piece of wire cut in half. Each half operates at a quarter wavelength of the output. [Antenna Terms.]
DIRECT CURRENT. [DC] An electric current that flows in one direction only.
DIRECTIONAL COUPLER. A device that samples the energy traveling in a waveguide in one direction only.
DIRECTIVITY. The ability of an antenna to radiate or receive more energy in some directions than in others. The degree of sharpness of the antenna beam.
DIRECTLY HEATED CATHODE. A wire, or filament, designed to emit the electrons that flow from cathode to plate. The filament is designed so that a current is passed through it; the current heats the filament to the point where electrons are emitted.
DIRECTOR. The parasitic element of an array that reinforces energy coming from the driver element.
DIRECT MEMORY ACCESS. [DMA] a means of data transfer directly between a peripheral and the system memory without passing through the CPU. A transfer of multiple bytes of data in a system, but supervisory over-head only occurs on the first byte or the start of the transfer [all other bytes are transferred directly with system control] as in a Block Transfer.
DIRECT SHORT. Same as Short Circuit.
DISCIPLINED OSCILLATOR. [DO] An oscillator whose output frequency is continuously steered [often via a phase locked loop] to agree with an external reference.
DISCRETE COMPONENTS. Individual transistors, diodes, resistors, capacitors, and inductors.
DISCRIMINATOR. A circuit in which amplitude variations are derived in response to phase or frequency variations. The part of an FM receiver that extracts the desired signal from an incoming FM wave by changing frequency variations into amplitude variations.
DISH. A microwave antenna shaped like a dish. For more detail refer to the Antenna Dictionary.
DISKETTE. The same as a Floppy Disk, or just Floppy. A removable disk cartridge. The Diskette is out-dated and obsolete.
DISPERSION. The refraction of light waves that causes the different frequencies to bend at slightly different angles.
DISPLACEMENT CURRENT. The current that appears to flow through a capacitor.
DISTILLED WATER. Water that has been purified through a process of evaporation and condensation.
DISTORTION. Any unwanted change between an input signal and output signal. An undesired change between a transmitted signal and the received signal.
DISTRIBUTED CONSTANTS. The constants of inductance, capacitance, and resistance in a transmission line. They are spread along the entire length of the line and cannot be distinguished separately.
DISTRIBUTIVE LAW. In Boolean algebra the law which states that if a group of terms connected by like operators contains the same variable, the variable may be removed from the terms and associated with them by the appropriate sign of operation (for example, A(B + C) = AB + AC).
Next set of "D" definitions and terms.
