UDF
This is the ISO 13346 Universal Data Format which supports
writing to CD-Recordable (CD-R) devices in 64KByte
increments. (Prior formats required the entire CD to be
written at once.)
UHF remote
A handheld remote control that can be sensed by an IRD (Infrared Remote Diode) sensor from up to 150 feet away--even through walls.
Unattended-Remote File Transfer
Permits users to use a communication software's "script-language," keystroke "macro," or menu-driven command feature to: power-on their system (perhaps after hours), dial another remote system (which may have no one at its keyboard), access that system's data, initiate a file transfer from the remote system, save the received data to disk, hang-up the phone, and then power-down the system.
Dual-tone modulated frequency ( DTMF ), lets modems dial independent of a phone.
Other file transfer references: File Transfer - Basic Capture, File Transfer - Basic Send, Full-Feature File Transfer, and Remote File Transfer
USB
Universal Serial Bus can be implemented in a tiered, star topology. Each PC has its own builtin hub (or "pod"), which is at the center of each star. Devices or other hubs are connected to the PC with cables as long as five-meter. This "Plug and Play" bus lets you add or remove devices without powering down or rebooting the computer. Devices are online automatically as soon as they are attached.
USB supports a data transfer rate of 12 Megabits per second (12 Mbps). Windows supports USB transfers up to 64KBytes.
Multiple slave hub/repeaters are supported. 5 meter, point-to-point 4-wire cables can connect up to 63 peripherals and provide power to passive peripherals such as keyboards and mice. However, modems, speakers, video cameras, and other relatively low-speed, low-bandwidth devices will need their own AC power sources. USB supports both asynchronous and isochronous data transfers.
Note: PC What's The Problem? includes installation and troubleshooting suggestions.
UTP "Link" Cables
Unshielded Twisted-Pair cables have solid copper conductors and should not be flexed, bent or twisted repeatedly. Once installed, they are seldom moved. These cables are designed for horizontal and backbone installation. They can also connect two wiring closets or a wiring closet to a wall plate. Link cables can be up to 90 meters in length.
UTP Patch Cables also have stranded copper conductors and can be repeatedly flexed without cable damage. They may be moved with some frequency. These cables are designed to connect a computer's network interface to a wall plate or to other equipment such as a network hub. Patch cables are generally shorter in length than the link cables to keep attenuation to a minimum.
Only twisted-pair cable standards specify the connectors used to terminate the cable. For Type 1 cable, the connector is a DB-9. For Category 3, 4, and 5, the EIA-568 connector standard specifies an RJ-45 connector. Most Ethernet installations use cable based on the EIA standards, and most installations of IBM or Token Ring equipment use cable that meets IBM's standards. The only exception is a Token Ring installation using Category 4 unshielded twisted-pair (UTP) cable.
Note: PC What's The Problem? includes installation and troubleshooting suggestions.
V or vertical
A vertical Drive unit can be formatted to operate on its side.
v -Variable
Abbreviation used to indicate a variable specification; e.g., variable sectors per track is represented as: v-spt.
V-Series Modems
These modems have several distinct features:
(1) they have hardware-based data compression, and error-correction components for fast error-free throughput;
(2), they are both asynchronous and synchronous, and will switch communications protocols to match the remote modem's protocol;
(3), the modem's synchronous communications (using X.25 synchronous protocol), when paired with emulation software and adapter board, can interact with a mainframe's modem;
(4), the receiving modem automatically matches the speed of the sending device;
(5), V.28 electrical specification and ISO 2110 mechanical connector;
(6), most create self-synchronized signals that are scrambled-descrambled, sender-to-receiver;
(7) some use the V.54 loopback procedure to return signals to the transmitter to be checked for accuracy;
(8), they support Hayes® AT (ATtention) commands.
These high-speed modems use different modulation techniques: frequency only; frequency- shift keying (FSK); phase-shift keying (PSK); Quad-Amplitude modulation, (QAM); and trellis-coding, which improves S/N (the signal-to-noise ratio) by allowing only certain changes in phase to occur.
Variable resistors
They are referenced with the other resistors.
VC
Programming language for the NGSP consisting of C++ with
classes and libraries. Also, Vector Counter.
VCM
Vector Cache Memory. Same as ACM.
VCRS Descrambler
The standard descrambler manufactured by General Instruments. It is used.for residential C-band services in the US.
VDD
This label indicates a circuit's supply voltage. It is determined by the circuit or the designer. For example, most desktop computer systemboards use 5VDC (5 volts direct current); while most laptop computer systemboards use 3.3VDC.
Video CD
This MPEG-1 format (v 2.0) includes hooks that let software developers use the format for everything from still images to branched video. Video CDs have a 650 MB storage capacity. Typically, image quality is similar to SVHS (Super VHS) which is between a VCR's VHS format and a laserdisk.
Note: PC What's The Problem? includes functional troubleshooting suggestions.
Virtual memory
Graphics and imaging applications often need access to more RAM than a computer has. These applications can use hard drive capacity allocated to simulate RAM chip capacity, but there is a speed penalty. For example, a hard drive with 10ms access times is the equivilant of RAM with a 10,000,000 nanosecond (ns) speed rating. "Slow" computers use 80ns RAM. For MacOS, access to this feature is through the Control Panel's Memory file.
VLIW
Very Large Instruction Word-type processor.
VLSI
Very Large Scale Integrated IC (integrated circuit) chips are used in application-specific devices.
VME
A standard computer bus.
VMP
Vector Math Processor.Voice Coil (VC) mechanism's spring-like coil, is expanded or contracted by a motor responding to electrical signals of various amplitudes. Inside a drive, the coil moves the actuator-arm with its read/write head to the specified track. Movement and motor sounds are smooth and con-tinuous until it reaches the desired position.
Voice Coil (VC) mechanism
A spring-like coil, is expanded or contracted by a motor responding to electrical signals of various amplitudes. Inside a drive, the coil moves the actuator-arm with its read/write head to the specified track. Movement and motor sounds are smooth and con-tinuous until it reaches the desired position.
Voltage (V)
This is the pressure of an electrical flow. Two cells, each having a voltage-pressure of 1.5 volts, when placed in a series they combine to provide (1.5V + 1.5V) a total of 3 volts.
When working with computers and related business equipment, it would be rare to encounter large voltages, such as those in the one-thousand-volt range as represented by this abbreviation: 1kV. (1000 = k.) Low voltages are more likely; they are measured in milli-volts, abbreviated as: mV. (1000mV = 1V.) Very-low voltages are measured in micro-volts, represented as: µV. (1000-µV = 1mV.)
VRAM (Video RAM) chips
These memory chips have both a serial-access port and a random-access port for page-mode memory accesses. The serial-access port is used for sequential operations, such as updating the screen image. Operating concurrently with the screen refreshing, the random-access port handles display-memory writes and drawing (pixel-manipulation). (DRAMs only have a random-access port and are therefore less expensive than VRAMs.)
VRAMs also handle simple pixel-processing and block writing so that the processor and/or graphic controller can more easily perform repetive operations, such as filling objects with colored patterns. VRAM is faster than DRAM and has graphics capabilities. Prior to the development of the cheaper SGRAM, it was often chosen for the main video memory on systemboards.
VTSOP (Very Thin, Small-Outline Package) chips
This chip design is fabricated by grinding down standard TSOP chips to be wafer thin.
References are samples only. Each one is presented in greater detail in the
Technical Research Assistant for 2001
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