Data Matrix is a high Density two dimensional (area) matrix style Barcode Symbology that can encode up to 3116 characters from the entire 256 byte ASCII character set. The symbol is built on a square grid arranged with a finder pattern around the perimeter of the barcode symbol.
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See Symbologies (List)for a list of common symbologies.
A database is a collection of data that is organized so that its contents can easily be accessed, managed, and updated. The most prevalent type of database is the
Relational Database, a tabular database in which data is defined so that it can be reorganized and accessed in a number of different ways. A distributed database is one that can be dispersed or replicated among different points in a network. An object-oriented programming database is one that is congruent with the data defined in object classes and subclasses.
Structured Query Language (
SQL) is a standard language for making interactive queries from and updating a database such as IBM's DB2, Microsoft's Access, and database products from
Oracle, Sybase, and Computer Associates.
In communications, the decibel (abbreviated as dB, and also as db and DB) is an expression of the ratio between two signal power levels. An increase of 3dB is a doubling of power, an increase of 6dB is a quadrupling of power. Conversly, a 3db decrease is a half of the power and a 6dB decrease is a quarter of the power.
dB is used to express gain in output power of radios and
Antennas used in data collection equipment such as
Access Points. Radio output power is denoted with the suffix dBm and antenna gain is denoted with the suffix dBior
dBd.
In
RF communications, transmit power and receive sensitivity are specified in "dBm," where "m" means 1 milliWatt (
mW). So, 0dBm is equal to 1mW; 3dBm is equal to 2mW; 6dBm is equal to 4mW, and so on. For example, an Access Pointat 100mW transmit power is equal to 20dBm. Related terms:
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Direct Current (DC) is the unidirectional flow or movement of electric charge
Carriers, usually electron. The intensity of the current can vary with time, but the general direction of movement stays the same at all times. As an adjective, the term DC is used in reference to voltage whose polarity never reverses. Most data collection equipment takes DC power. The power supplies that are ordered with the equipment converts
AC power into the appropriate DC power level.
Distribution Center–generally refers to a primary location with a receiving, shipping and warehouse facility. For an enterprise, it is the location where all product is accumulated from multiple manufacturing and warehouse locations and then distributed to customers nation wide or world wide.
DEC –Digital Equipment Corporation
DEC, now part of Compaq, has long occupied a leading position in the mid-range computer, traditionally known as the minicomputer, the business computer
Platform that fits between the
Mainframe and the personal computer and serves small and medium-sized businesses with its VMS operating system. Today, DEC is focusing strongly on Internet systems and software.
Usually refers to a decoded or decoding
Barcode scanner. In the old days, scanners transmitted data called raw count data which is simply a list of the amounts of time spent on each bar and space in a barcode. It was then up to another device called a reader or decoder to translate the raw count data into something meaningful such as
ASCII data. The decoder would then transmit the data to a host computer.
Today, we have scanners that decode the raw count data into ASCII or
Keycode data and transmit it straight to the host computer.
The penalty for exceeding free time allowed for loading/unloading under the terms of the agreement with the Carrier. Demurrage is the term used in the rail and ocean industry; detention is used in the motor industry.
Usually refers to the density of a Barcode. Barcodes printed with a small X Dimension are more dense than those printed with a large X Dimension because more information can be crammed into a given space. Density is usually expressed in Mils.
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X = 7.5 mils, high density
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X = 12 mils, medium density
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X = 15 mils, low density
Depth of Field (DOF) is the difference between the farthest scannable distance and the closest scannable distance to the Barcode.
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DHCP -Dynamic Host Configuration Protocol
DHCP is a communications
Protocol that lets network administrators manage centrally and automate the assignment of Internet Protocol (
IP) addresses in an organization's network. Each machine that can connect to the Internet needs a unique
IP Address. When an organization sets up its computer users with a connection to the network, an IP address must be assigned to each machine manually without DHCP. With DHCP, the IP addresses may be assigned to each computer automatically. DHCP lets a network administrator supervise and distribute IP addresses from a central point.
DIMM –Dual Inline Memory Module
Module A DIMM (dual in-line memory module) is a double SIMM (single in-line memory module). Like a SIMM, it's a module containing one or several random access memory (RAM) chips on a small circuit board with pins that connect it to the computer motherboard. A SIMM typically has a 32 data Bit (36 bits counting paritybits) path to the computer that requires a 72-pin connector. For Synchronous dynamic RAM (SDRAM) chips, which have a 64 data bit connection to the computer, SIMMs must be installed in in-line pairs (since each supports a 32 bit path). A single DIMM can beused instead. A DIMM has a 168-pin connector and supports 64-bit data transfer. It is considered likely that future computers will standardize on the DIMM.
A DIP is a common type used to mount and enclose semi-conductor chips.
See also DIP Switch.
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A series of tiny Switches built into circuit boards. The housing for the switches, which has the same shape as a chip, is the DIP. DIP switches enable you to configure a circuit board for a particular type of computer or application. The installation instructions should tell you how to set the switches. DIP switches are always toggle switches, which means they have two possible positions --on or off. (Instead of on and off, you may see the numbers 1 and 0.) Many data collection devices, especially legacy, such as printers and radios have DIP switches. These switches are set for certain conditions, this is how these devices were configured.
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Unlike an Isotropic Antenna, a dipole Antenna is a real antenna that has a 360° radiation pattern in the horizontal plane and a 75° radiation pattern in the Vertical plane if the antenna is mounted vertically. This creates a doughnut shaped radiation pattern. Because the beam is slightly concentrated, dipole antennas have a gain over isotropic antennas of 2.14dbi in comparison to an isotropic antenna. Some antennas are rated in comparison to a dipole antenna which is denoted by dBd. So, dipole antennas have a gain of 0dBd in relation to itself which is equivalent to 2.14dBi. A half wave dipole antenna (.5dBd) is rated at 1dBi. A quarter wave dipole antenna (.25dBd) is rated at .5dBi).
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Direct Sequence Spread Spectrum is an RF Modulation technology that uses three 22MHz wide channels. Typically only one channel is used at a time. Other channels can be used when interference is an issue. DSSS provides a larger range and throughput than FHSS.
DSSS is typically more costly than FHSS. DSS is more susceptible to interference than FHSS.
Direct thermal printing utilizes a heat sensitive chemically coated paper. The thermal print head is typically a long linear array of tiny resistive heating elements (about 100 to 300 per inch) that are arranged perpendicular to the paper flow. Each thermal print head element locally heats an area on the chemically coated paper directly under the print element. This induces a chemical reaction which causes a black dot to form in that area. The image, itself, is formed by building it from dot rows as the media passes underneath the active edge of the print head. Advantages: consistent, sharp edge image print quality, simplicity and environmental economy with recyclable materials available, simple to operate, Low, long-term maintenance cost, durable compared to other comparable print technologies Disadvantages: extremely sensitive to environmental conditions –e.G. heat and light (fluorescent and/or direct sunlight), remains chemically active after printing so thermal paper materials are top coated to resist UV light exposure, chemicals and minimal abrasion.
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Directional Antennas focuses the radiation pattern in a specific direction. They are available in a variety of from factors and strengths. Directional antennas are useful in covering long hallways and in bridging two Wireless networks together.
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Diversity Antennas is the use of two identical antennas for a single radio in an Access Point to counter act the effects of multipath distortion.
One antenna is the primary and the other is the secondary. When the access point encounters what it interprets as multipath errors, the access point checks the other antenna for a more reliable signal.
Diversity antennas are intended to be used as a last resort to reduce Multipathing. They should not be used as a default. Diversity theory dictates that identical antennas be used, they be mounted in the same orientation and that they be mounted very precise distances of odd multiples of ¼ Wavelength apart. λ= c / f
Wavelength = Speed of light in a vacuum / Frequency
A dongle (pronounced DONG-uhl) is a mechanism for ensuring that only authorized users can copy or use specific software applications, especially very expensive programs. Common mechanisms include a hardware key that plugs into a parallel or serial port on a computer and thata software application accesses for verification before continuing to run; special key diskettes accessed in a similar manner; and registration numbers that are loaded into some form of
ROM at the factory or during system setup. If more than one application requires a dongle, multiple dongles can be daisy-chained together from the same port. Dongles can come in different form factors such as serial and parallel port,
USB and PCCARD.
DOS –Disk Operating System
DOS was the first widely-installed operating system for personal computers. DOS is a non-graphical line-oriented command-or menu-driven operating system, with a relatively simple
Interface but not overly "friendly" user interface. Its prompt to enter a command looks like this:
C:>
The first version of DOS was PC DOS for IBM PCs developed by Microsoft. Bill Gates retained the rights to it and released MSDOS which is almost identical to PC DOS.
In printing, dpi is the usual measure of printed image quality on the paper. The average printer today provides 152 dpi or 607 dpi. Choosing the higher print quality usually reduces the speed of printing each page.
DRAM –Dynamic Random Access Memory
Dynamic random access memory is the most common kind of random access memory (RAM) for personal computers, workstations, printers and almost any kind of data collection equipment. DRAM is dynamic in that, unlike static RAM (SRAM), it needs to have its storage cells refreshed or given a new electronic charge every few milliseconds.
DSD –Direct Store Delivery
A logistics strategy to improve services and lower warehouse inventories in which merchandise is delivered from the manufacturer directly to the store, bypassing the warehouse.
DSL -Digital Subscriber Line
DSL is a technology for bringing high-bandwidth information to homes and small businesses over ordinary copper telephone lines. xDSL refers to different variations of DSL, such as ADSL, HDSL, and RADSL. Typically, individual connections will provide from 1.544 Mbps to 512 Kbps downstream and about 128 Kbps upstream. A DSL line can carry both data and voice signals and the data part of the line is continuously connected.
In computers, a terminal (sometimes qualified as a "dumb" terminal) is an end-use device (usually with display monitor and keyboard) with little or no software of its own that relies on a
Mainframe or another computer (such as a PC
Server) for its "intelligence." IBM's
3270 Information Display System was a widely-installed system of such terminals in corporations.
Many applications designed for the 3270 or other "dumb" terminals are still in use at PCs that emulate or act like a 3270. The IBM
5250 and the VT-100 from Digital Equipment Corporation are other examples of widely-used so-called "dumb" terminals. A variation of this kind of terminal is being revived in the idea of the thin client or network computer.
Duty cycle is the proportion of time during which a component, device, or system is operated. The duty cycle can be expressed as a ratio or as a percentage. Suppose a Barcode printer prints labels for four hours of each day. The printer prints 4 out of every 24 hours or 16.66%.
The more a circuit, machine or component is used, the sooner it will wear out. Therefore, the higher the duty cycle, the shorter the useful life, all other things being equal. If the above-mentioned printer has a life expectancy of 4,000 hours based on a 20 percent duty cycle, that same device's expectancy would probably be about 2,000 hours based on a duty cycle of 40 percent, and 8,000 hours based on a duty cycle of 10 percent.