V: V-Vyvx


V-Value Added Service

V

  1. Abbreviation for Volt.

  2. The International Morse Code representation of the letter V is ..._, which we hear as didididah. That refrain is reminiscent of the opening of Beethoven's Fifth Symphony, which is the reason that the British Army adopted that work as its unofficial theme music during WWII (World War, II for you youngsters). The connection, of course, is the V for Victory sign that Winston Churchill (British Prime Minister at the time) always made. Allied GI's who didn't know Schumann from shinola knew this was Beethoven and relished the irony of a German's music galvanizing the Allied effort to defeat Hitler.

V & H

V&H stands for Vertical and Horizontal. Below are vertical and horizontal coordinates of major continental US cities as presented in charts published by long distance carriers in North America. The monthly charge for many leased circuits provided by either an IXC (Inter-Exchange Carrier) or a LEC (Local Exchange Carrier) is billed on the basis of "air- line mileage" between the two points. The two points for an IXC (long distance carrier) private line circuit are IXC POP to IXC POP. The monthly charge for the IXC circuit is based on the mileage between the two POPs. The two points for a LEC (Local exchange carrier) are based on the customer premise SWC/CO to customer premise SWC/CO or IXC POP SWC/CO. When one end is an IXC POP, it's often called a dedicated access loop, The monthly charge is based on the mileage between them. To get your monthly charge for a dedicated circuit across the country, you typically add the IXC charge to the LEC charge. You may not need to pay an LEC charge if you're located in the same building or same complex as your IXC (long distance carrier) and can directly cable in.

Though it sounds as if the IXC charge is the distance a crow would fly directly between the two points, in reality, it is the distance in mileage between two Rate Centers whose position is laid down according to industry standards, originally created in 1956 by Jay K. Donald of AT&T Bell Telephone Laboratories. Mr. Donald referenced V&H projections in his paper "Map Projections ” A Working Model," in which he described the concept as "an ellipsoidal adaptation of the two-point equidistant ." Under this strange system, the entire U.S. is divided into a vertical and horizontal grid, based on a complex algorithm that projects the curvature of the earth onto a flat plane. This projection algorithm uses latitude and longitude, plus other factors, to develop a 10,000 by 10,000 V&H grid. The vertical and horizontal coordinates of each rate center are defined and applied to a square root formula which yields the "airline distance" between the two points. Think back to school. Think about a right-angled triangle. At the top is one Rate Center. At the side is the other Rate Center. The horizontal is the horizontal coordinate, in effect, the "airline mileage." The vertical is the vertical coordinate. The formula is simple: Square the vertical distance. Square the horizontal distance. Add the two together. Then take their square root. That will give you the distance across the hypotenuse ” the side opposite the right angle in the triangle ” i.e. the airline mileage. Here is the actual formula for calculating airline mileage. The airline mileage is the square root of ((V1 - V2) x (V1 - V2) + (H1 - H2) x (H1 - H2)) / 10. Dividing by ten is necessary in this case to allow for the way the coordinates are presented in North American mileage charts. This formula (without the division by ten) is called the Pythagorean theorem and is known to every schoolboy (and schoolgirl ” a reader already pointed out my misdemeanor). It is named for its inventor , Pythagoras, Greek philosopher, mathematician , and religious reformer, who lived 582-500 B.C.

 

V

H

 

V

H

 

V

H

ALABAMA

   

CALIFORNIA

   

Sunnyvale

8576

8643

Birmingham

7518

2304

Anaheim

9250

7810

Van Nuys

9197

7919

Huntsville

7267

2535

Bakersfield

8689

8060

COLORADO

   

Mobile

8167

2367

Fresno

8669

8239

Denver

7501

5899

Montgomery

7692

2247

Long Beach

9217

7856

Fort Collins

7331

5965

ARIZONA

   

Los Angeles

9213

7878

Grand Junction

7804

6438

Flagstaff

8746

6760

Oakland

8486

8695

Greeley

7345

5895

Phoenix

9135

6748

Redwood City

8556

8682

Pueblo

7787

5742

Tucson

9345

6485

Sacramento

8304

8580

CONNECTICUT

   

Yuma

9385

7171

San Bernardino

9172

7710

Bridgeport

4841

1360

ARKANSAS

   

San Diego

9468

7629

Hartford

4687

1373

Fayetteville

7600

3872

San Francisco

8492

8719

New Haven

4792

1342

Hot Springs

7827

3554

San Jose

8583

8619

New London

4700

1242

Pine Bluff

7803

3358

Santa Monica

9227

7920

Stamford

4897

1388

     

Santa Rosa

8354

8787

     

DELAWARE

   

MASSACHUSETTS

   

NORTH CAROLINA

   

Wilmington

5326

1485

Boston

4422

1249

Asheville

6749

2001

DISTRICT OF COLUMBIA

(D.C.)

 

Framingham

4472

1284

Charlotte

6657

1698

Washington

5622

1583

Springfield

4620

1408

Fayetteville

6501

1385

FLORIDA

   

Worchester

4513

1330

Raleigh

6344

1436

Clearwater

8203

1206

MICHIGAN

   

Winston-Salem

6440

1710

Daytona Beach

7791

1052

Detroit

5536

2828

NORTH DAKOTA

   

Fort Lauderdale

8282

0557

Flint

5461

2993

Bismarck

5840

5736

Jacksonville

7649

1276

Grand Rapids

5628

3261

Fargo

5615

5182

Miami

8351

0527

Kalamazoo

5749

3177

Grand Forks

5420

5300

Orlando

7954

1031

Lansing

5584

3081

OHIO

   

Tallahassee

7877

1716

MINNESOTA

   

Akron

5637

2472

Tampa

8173

1147

Duluth

5352

4530

Canton

5676

2419

GEORGIA

   

Minneapolis

5777

4513

Cincinnati

6263

2679

Atlanta

7260

2083

St. Paul

5776

4498

Cleveland

5574

2543

Augusta

7089

1674

MISSISSIPPI

   

Columbus

5872

2555

Macon

7364

1865

Biloxi

8296

2481

Dayton

6113

2705

Savannah

7266

1379

Jackson

8035

2880

Toledo

5704

2820

IDAHO

   

Meridian

7899

2639

OKLAHOMA

   

Boise

7096

7869

MISSOURI

   

Lawton

8178

4451

Pocatello

7146

7250

Joplin

7421

4015

Oklahoma City

7947

4373

ILLINOIS

   

Kansas City

7027

4203

Tulsa

7707

4173

Chicago

5986

3426

St. Joseph

6913

4301

OREGON

   

Joliet

6088

3454

Springfield

7310

3836

Medford

7503

8892

Peoria

6362

3592

MONTANA

   

Pendleton

6707

8326

Rock Island

6276

3816

Billings

6391

6790

Portland

6799

8914

Springfield

6539

3518

Helena

6336

7348

PENNSYLVANIA

   

INDIANA

   

Missoula

6336

7650

Allentown

5166

1585

Bloomington

6417

2984

NEBRASKA

   

Altoona

5460

1972

Fort Wayne

5942

2982

Grand Island

6901

4936

Harrisburg

5363

1733

Indianapolis

6272

2992

Omaha

6687

4595

Philadelphia

5257

1501

Muncie

6130

2925

NEVADA

   

Pittsburgh

5621

2185

South Bend

5918

3206

Carson City

8139

8306

Reading

5258

1612

Terre Haute

6428

3145

Las Vegas

8665

7411

Scranton

5042

1715

IOWA

   

Reno

8064

8323

RHODE ISLAND

   

Burlington

6449

3829

NEW HAMPSHIRE

   

Providence

4550

1219

Cedar Rapids

6261

4021

Concord

4326

1426

SOUTH CAROLINA

   

Des Moines

6471

4275

Manchester

4354

1388

Charleston

7021

1281

Dubuque

6088

3925

Nashua

4394

1356

Columbia

6901

1589

Iowa City

6313

3972

NEW JERSEY

   

Spartanburg

6811

1833

Sioux City

6468

4768

Atlantic City

5284

1284

SOUTH DAKOTA

   

KANSAS

   

Camden

5249

1453

Aberdeen

5992

5308

Dodge City

7640

4958

Hackensack

4976

1432

Huron

6201

5183

Topeka

7110

4369

Morristown

5035

1478

Sioux Falls

6279

4900

Wichita

7489

4520

Newark

5015

1430

TENNESSEE

   

KENTUCKY

   

New Brunswick

5085

1434

Chattanooga

7098

2366

Danville

6558

2561

Trenton

5164

1440

Johnson City

6595

2050

Frankfort

6462

2634

NEW MEXICO

   

Knoxville

6801

2251

Madisonville

6845

2942

Albuquerque

8549

5887

Memphis

7471

3125

Paducah

6982

3088

Las Cruces

9132

5742

Nashville

7010

2710

Winchester

6441

2509

Santa Fe

8389

5804

TEXAS

   

LOUISIANA

   

NEW YORK

   

Amarillo

8266

5076

Baton Rouge

8476

2874

Albany

4639

1629

Austin

9005

3996

New Orleans

8483

2638

Binghamton

4943

1837

Corpus Christi

9475

3739

Shreveport

8272

3495

Buffalo

5076

2326

Dallas

8436

4034

MAINE

   

Nassau

4961

1355

El Paso

9231

5655

Augusta

3961

1870

New York City

4977

1406

Fort Worth

8479

4122

Lewiston

4042

1391

Poughkeepsie

4821

1526

Houston

8938

3563

Portland

4121

1384

Rochester

4913

2195

Laredo

9681

4099

MARYLAND

   

Syracuse

4798

1990

Lubbock

8596

4962

Baltimore

5510

1575

Troy

4616

1633

San Antonio

9225

4062

     

Westchester

4912

1330

     

UTAH

   

Richmond

5906

1472

Wheeling

5755

2241

Logan

7367

7102

Roanoke

6196

1801

WISCONSIN

   

Ogden

7480

7100

WASHINGTON

   

Appleton

5589

3776

Provo

7680

7006

Bellingham

6087

8933

Eau Claire

5698

4261

Salt Lake City

7576

7065

Kennewick

6595

8391

Green Bay

5512

3747

VERMONT

   

North Bend

6354

8815

La Crosse

5874

4133

Burlington

4270

1808

Seattle

6336

8896

Madison

5887

3796

VIRGINIA

   

Spokane

6247

8180

Milwaukee

5788

3589

Blacksburg

6247

1867

Yakima

6533

8607

Racine

5837

3535

Leesburg

5634

1685

WEST VIRGINIA

   

WYOMING

   

Lynchburg

6093

1703

Clarksburg

5865

2095

Casper

6918

6297

Norfolk

5918

1223

Morgantown

5764

2083

Cheyenne

7203

5958

Telcordia Technologies (previously Bellcore) and other independent companies develop and publish V&H data, and provide simple tables for conversion between V&H and Latitude/Longitude. As new central offices and POPS (points of presence) are installed and/or consolidated, the V&H coordinates table must be expanded and updated by the various publishers of the material. Thank you to Andrew Funk Manager, Access Pricing Strategy, Qwest Communications International for his help on this definition. Here are the Vertical and Horizontal coordinates of major North American cities:

V Band

A range of radio frequencies in the 40 GHz and 50 GHz range, also known as the Q Band. The "V" is a random, arbitrarily-assigned designation with its roots in the context of military security during World War II.

V Chip

Violence Chip. A type of TV filter required in the Telecommunications Act of 1996. The Act requires the FCC to prescribe regulations, in conjunction with the electronic manufacturing industry, requiring that television sets manufactured after February 1998 include "features designed to enable viewers to block display of all programs with a common rating. This is commonly referred to as the 'V Chip.'" Similar capability is available through filtering agents for screening Internet content. The V Chip and Internet filtering agents primarily are intended to allow parents to filter content which they consider offensive and inappropriate for their children. These content filtering technologies can be overridden with the proper password. See also Filtering Agent.

V Commerce

See V-Commerce below.

V Disk

Digital Voice Storage cards.

V Fast

A new higher speed over-normal-phone-line modem called V.Fast Class (V.FC) for 28,800 bits per second speed. See V.34.

V Interface

The 2-wire ISDN physical interface used for single-customer termination from a remote terminal. See ISDN and U Interface.

V Reference Point

The proposed interface point in an ISDN environment between the line termination and the exchange termination.

V Series Recommendations

ITU-T standards dealing with data communications operation over the telephone network. The idea of standards is simple. If you have them and if every manufacturer conforms, then every modem can talk to every other one. That's the idea. But it's not always that simple. Sometimes you have to conform to several standards. For example, in the higher speed modems, for example those at 9,600 bps, you have to conform to speed. That's one standard. You have to conform to error control. That's another standard. And you also have to conform to data compression ” if you are using data compression. ISDN terminal adapters are V series recommendations, too. ITU-T uses the term "bis" to designate the second in a family of related standards and "ter" designates the third in a family.

V-Commerce

Voice Commerce. Imagine that you dial a phone number. Your bank answers. "What's your password, please ?" You say, "Harry Newton." It answers, "Thank you." You have three bills to pay, but only enough money to pay two. Here are the three..." You answer "Pay the Visa bill." You get the message. Voice commerce is a fancy name for interactive voice response using speech recognition as the input mechanism, not the buttons on a touchtone phone. With touchtone buttons, you often have to keep pressing buttons to progress through zillions of menus to get what you want. Speech recognition, if it works, is faster since it gets you to where you want to go a lot faster.

V.110

Terminal rate adaptation protocols for the ISDN B channel with a V-type interface. Includes V.120.

V.120

Terminal rate adaptation protocols for the ISDN B channel with a V-type interface. Includes V.110.

V.13

ITU-T standard for simulated carrier control. Allows a full-duplex modem to be used to emulate a half-duplex modem with interchange circuits changing at appropriate times.

V.14

ITU-T standard for asynchronous-to-synchronous conversion without error control. Allows a modem that is actually synchronous to be used to carry start/stop (async) characters . If a V.42 modem connects with another modem that doesn't have error-control, it falls back to V.14 operation to work without error-control.

V.17

ITU-T standard for simplex (one-way transmission) modulation technique for use in extended Group 3 Facsimile applications only. Provides 7200, 9600, 12000, and 14400 bps trellis -coded modulation (the modulation scheme is similar to V.33), MMR (Modified Modified Read) compression and error-correction mode (ECM).

V.18

An ITU recommendation aimed at enhancing the capability of the deaf or speech- impaired to use telecommunications. The V.18 recommendation describes a multi-function text telephone that, according to the ITU, "bridges the gap that has existed between several incompatible text telephones in use today." See T.140.

V.21

ITU-T standard for 300 bit per second duplex modems for use on the switched telephone network. V.21 modulation is used in a half-duplex mode for Group 3 fax negotiation and control procedures (ITU-T T.30). Modems made in the U.S. or Canada follow the Bell 103 standard. However, the modem can be set to answer V.21 calls from overseas.

V.21 CH 2

ITU-T standard for 300 bps modem, describing the operation of modems at 300 bps, and used for critical control and handshaking functions. This low speed is highly tolerant of noise and impairments on the phone line. Fax machines use only Channel 2 of the V.21 recommendations (half duplex channel).

V.21 Fax

An ITU-T standard for facsimile operations at 300 bps.

V.22

ITU-T standard for 1,200 bit per second duplex modems for use on the switched telephone network and on leased circuits. V.22 is compatible with the Bell 212A standard observed in the U.S. and Canada. See V.22 bis.

V.22 bis

ITU-T standard for 2,400 bit per second duplex modems for use on the switched telephone network. "Bis: is used by the ITU-T to designate the second in a family of related standards. "ter" designates the third in a family. The standard includes an automatic link negotiation fallback to 1200 bps and compatibility with Bell 212A/V.22 modems.

The principal characteristics of the V.22bis modems are:

Duplex mode of operation on the PSTN and point-to-point 2-wire leased circuits, Channel separation by frequency division, Quadrature amplitude modulation for each channel with synchronous line transmission at 600 baud, An adaptive equalizer and a compromise equalizer, Test facilities, Data signaling rates of 1200bps and 2400bps. V.22bis is compatible with the V.22 modem and includes automatic bit rate recognition. The V.22bis modem technology is used for applications that require transactions at a rate of 2400 bps or slower. Some such applications include set-top boxes, credit card transactions, fax relay systems, satellite receivers, utility meters , and network control.

V.23

V.23 is the standard for a modem with a 600 bps or 1200 bps "forward channel" and a 75 bps "reverse" channel for use on the switched telephone network.

V.24

ITU-T definitions for interchange circuits between data terminal equipment (DTE) and data communications equipment (DCE) equipment. In data communications, V.24 is a set of standards specifying the characteristics for interfaces. Those standards include descriptions of the various functions provided by each of the pins. This standard is similar (but not identical) to the RS-232-C as established by the American TIA/EIA ”- Telecommunications Industry Association / Electronics Industries Association. V.24 is a CCITT data communications hardware interface standard for communications at speeds up to 19.2 kbps.

V.25

Automatic calling and/or answering equipment on the general switched telephone network, including disabling of echo suppressors on manually established calls. Among other things, V.25 specifies an answer tone different from the Bell answer tone. Many modems, including U.S. Robotics modems, can be set with the BO command so that they use the V.25 2100 Hz tone when answering overseas calls.

V.25 bis

An ITU-T standard for synchronous communications between the mainframe or host and the modem using the HDLC or character-oriented protocol. Modulation depends on the serial port rate and setting of the transmitting clock source.

V.26

V.26 is the ITU-T standard for 2400 bps modem for use on 4-wire leased lines.

V.26 bis

ITU-T standard for 1.2/2.4 Kbps modem. It is important to note that V.26 bis is a half-duplex modem (1200 or 2400 bps in only one direction at a time); it provides an optional 75 bps reverse channel as well.

V.26 ter

V.26 ter is a FULL DUPLEX 2400 bps modem, like V.22 bis. The difference is that V.26 ter uses echo cancellation (like V.32) instead of frequency division (like V.22 bis), making it more expensive than V.22 bis. It was intended to serve as a fallback mode from V.32, but most manufacturers ignored it and provide V.22 bis as a fallback instead (V.26 ter is used only in a few installations in France, as far as we know).

V.27

ITU-T standard for 4,800 bits per second modem with manual equalizer for use on leased telephone-type circuits. May be full-duplex on four wire leased lines, or half-duplex on two wire lines.

V.27 bis

ITU-T standard for 2,400 / 4,800 bits per second modem with automatic equalizer for use on leased telephone-type circuits. 2.4 Kbps modem for 4-wire leased circuits. Either speed (2,400 is a fallback) can be used on either 4-wire leased lines (full duplex) or 2-wire leased lines (half-duplex). It also provides an optional 75 bps reverse channel.

V.27 ter ITU-T standard for 2,400 / 4,800 bits per second modem for use on the switched telephone network. Half-Duplex only. V.27 ter is the modulation scheme used in Group 3 Facsimile for image transfer at 2400 and 4800 bps. 4800 bps is a common "fall- back" speed.

V.28

V.28, entitled "Electrical Characteristics for Unbalanced Double-Current Interchange Circuits" provides the ITU-T equivalent of the electrical characteristics defined in EIA-232.

V.29

ITU-T standard for 9,600 bits per second modem for use on point-to-point leased circuits. Virtually all 9,600 bps leased line modems adhere to this standard. V.29 uses a carrier frequency of 1700 Hz which is varied in both phase and amplitude. V.29 also provides fallback rates of 4800 and 7200 bps. V.29 can be full-duplex on 4-wire leased circuits, or half-duplex on two wire and dial up circuits. V.29 is the modulation technique used in Group 3 fax for image transfer at 7200 and 9600bps.

V.3

ITU-T specification that describes communications control procedures implemented in 7-bit ASCII code. A CCITT data communication recommendation that defines the 7-bit code for the alphanumeric and control characters in a character-oriented application, such as ASCII for character coding.

V.32

ITU-T standard for 9,600 bit per second two wire full duplex modem operating on regular dial up lines or 2-wire leased lines. If you're buying a 9,600 bps modem for use on the normal dial up switched phone lines, make sure it conforms to V.32. If your modem also conforms to V.42 bis, you should be able to transmit and receive at up to 38,400 bps with other modems that conform to these two specifications. I personally use a number of V.32/V.42 bis modem and they work wonderfully fast. V.32 also provides fallback operation at 4,800 bps. See also V.32 bis, V.42 bis Error Correction and V.42 bis Data Compression and Modulation Protocols.

V.32 bis

New higher speed ITU-T standard for full-duplex transmission on two wire leased and dial up lines at 4,800, 7,200, 9,600, 12,000, and 14,400 bps. Provides backward compatibility with V.32. Modems running at V.32 bis at its highest speed of 14,400 bps are actually transmitting that many bits per seconds. They do not rely on compression to achieve that high speed. However, with data compression ” such as V.42 and V.42 bis ” they can achieve higher speeds. The V.32 bis standard also includes "rapid rate renegotiation" feature to allow quick and smooth rate changes when line conditions change. See Modulation Protocols V.42 and V.42 bis.

V.32 terbo

Modulation scheme that extends the V.32 connection range: 4800, 7200, 9600, 12K and 14.4K bps. V.32 bis terbo modems fall back to the next lower speed when line quality is impaired, and fall back further as necessary. They fall forward to the next higher speed when line quality improves .

V.33

ITU-T standard for 14,400 and 12,000 bps modem for use on four wire leased lines.

V.34

V.34 is the international standard for dial up modems of up to 28,800 bits per second. Since the standard suggests speeds twice as fast as the top standard they replace, they carry the nickname "V.Fast." New V.34 modems have a feature called line probing that will allows them to identify the capacities and quality of the specific phone line and adjust themselves to allow, for each individual connection, for maximum throughput. The standard also supports a half-duplex mode of operation for fax applications. The new V.34 technology includes an optional auxiliary channel with a synchronous data signaling rate of 200 bits/second. Data conveyed on this channel consists of modem control data. V.34 modems contain multidimensional trellis coding, which is used to gain higher immunity to noise and other phone line impairments. V.34 modems are the first modems to identify themselves to telephone network equipment (handshaking). V.34 technology has been long in coming and has had to overcome many obstacles. At one point, members of the modem manufacturing industry became so impatient, that some of them began shipping their own proprietary versions of what they thought V.34/V.Fast/28,800 bps modems would be. Many of these modems are only compatible, at higher than 14,400 bps speeds, with themselves. See V.34bis.

V.34 bis

Also known as V.34+. A faster version of the data communications standard, V.34, which supports up to 28,800 bps. V.34 bis adds two higher data rates to V.34. These speeds are 31,200 bits per second and 33,600 bits per second. V.34 bis is now the most common standard for PC data communications over dial-up phone lines.

V.35

ITU-T standard for trunk interface between a network access device and a packet network that defines signaling for data rates greater than 19.2 Kbps. It is an international standard termed "data transmission up to 1.544 Mbps" (i.e. T-1). It's typically used for DTE or DCE equipment that interface to a high-speed digital carrier. The physical interface is a 34-pin connector, which can't connect, either physically or electrically, to any other interface without a special converter. See V.36.

click to expand

V.36

ITU-T recommendation for 4-wire communications at speeds greater than 48 Kbps. It is intended to replace V.35. See V.35.

V.42 Error Correction

ITU-T error-correction standard specifying both MNP4 and LAP-M. The ITU-T title says "Error-correcting procedures for DCEs using Asynchronous-to- Synchronous Conversion". It also notes in the text that it applies only to full-duplex devices. The ITU-T modulation schemes with which V.42 may be used are V.22, V.22 bis, V.26 ter, and V.32, and V.32 bis. LAPM, based on HDLC, is the "primary" protocol, on which all future extensions will be based. The Alternative Protocol specified in Annex A of the Recommendation is for backward compatibility with the "installed base" of error-correcting modems. See V.42 bis and V.44.

V.42bis

An ITU-T data compression standard, with "bis" being the French term for "second" or "encore." It is used by the ITU/ITU to designate the second in a family of related standards. ("ter" designates the third in a family.) V.42bis compresses files "on the fly" at an average ratio of 3.5:1 (3.5 to 1) and can yield file transfer speeds of up to 9,600 bps on a 2,400 bps modem, 38,400 bits per second with a 9,600 bps modem, 57,600 bps with a 14,400 bps modem, or 115,600 bit/s on a 28,800 bps modem. On-the-fly data compression only has value if you use it to transfer and receive material that is not already compressed. Compressing stuff a second time yields no significant improvement in speed ( assuming your compression technique worked the first time around). So the decision to buy a V.42 bis modem depends on the material you're working with and your pocketbook. V.42bis modems are more expensive than predecessor modems.

V.42bis was approved by the ITU-T because of its technical merits. Existing data compression methods (MNP 5 for example) only provided up to two-to-one compression. Also, V.42bis provides for built-in "feedback" mechanisms, so that the modem can monitor its own compression performance. If the DTE starts send pre-compressed or otherwise uncompressible data, V.42bis can automatically suspend its operation to avoid expansion of the data. It continues to monitor performance even when sending data "in the clear," and when a performance improvement can be gained by reactivating compression, it will do so automatically.

V.42bis was selected because it would work with a wide variety of different implementations ” different amounts of memory, different processor speeds, etc. Because of this, there are differences between various manufacturers' products in terms of throughput performance (although they will all properly compress and decompress, some will do it faster than others). If maximum throughput is important, you should check published benchmark tests to find the modem that provides the best performance.

This chart, courtesy Hayes, shows the speedup that's possible. It includes information on a modem called the Hayes Optima 288, which includes a proprietary (i.e. not compatible with anyone else) Hayes enhanced implementation of V.42 bis.

V.32                                                        9,600 + data compression           = 38,400 bit/s

V.32bis                                            14,400 + data compression           = 57,600 bit/s

V.34                                                      28,800 + data compression         = 115,600 bit/s

Hayes Optima 288          28,800 + Hayes V.42 bis                = 230,400 bit/s

See also V.44.

V.44

A compression standard finalized on June 30, 2000 by the ITU-T. V.44 makes use of the LZJH (Lempel-Ziv-Jeff.Heath) compression algorithm developed by Jeff Heath of Hughes Network Systems for use over satellite links. Supplanting the earlier V.42bis modem compression technology, V.44 provides 6:1 (i.e., 6 to 1) compression performance. V.44 is intended for use in V.92 modems, the successor to V.90. In combination with V.92 modems, V.44 will have a significant effect on the speed of data transmission, as did the earlier move from V.34 to V.90 modems. In the case of V.90, transmission speed is determined primarily by the quality of the local loop. In the case of V.44, performance is dynamic (i.e., variable) and depends on the data content, as well as the quality of the local loop, which can vary during the course of a data call. When compared to V.42bis running in V.90 modems, V.44 running in V.92 modems can yield speed improvements of 20% to 60%, up to as much as 200% for certain types of highly compressible data. Taken together, V.90 and V.44 can yield effective downstream throughput of more than 300 Kbps (6:1 compression times 56 Kbps), under optimum conditions. This compares to the maximum rate of 150-200 Kbps supported by V.90 modems running V.42bis. Like the predecessor combination V.90 and V.42bis, the combination of V.92 and V.44 provides asymmetric bandwidth. While V.90 modems can support upstream speed up to 33.6 Kbps, V.92 will support up to 48 Kbps in the upstream direction. Both standards support downstream transmission rates of up to 56 Kbps, theoretically and under optimum conditions. Note that the difference between raw transmission speed and throughput is a result of the compression of the data prior to its being put on the circuit. See also LZJH, V.42bis, V.90, and V.92.

V.5

See V5

V.54

ITU-T standard for loop test devices in modems, DCEs (Data Communications Equipments) and DTEs (Data Terminal Equipment). Defines local and remote loopbacks. There are four basic tests ” a local digital loopback test that is used to test the DTE's send and receive circuits; a local analog loopback test that is used to test the local modem's operation; a remote analog loopback test that is used to test the communication link to the remote modem; and a remote digital loopback test that is used to test the remote modem's operation. If a modem has V.54 capability (most V.32 and V.32 bis modems do), its manual should include documentation on performing the various tests. Version 7 of the Norton Utilities (from Symantec) also includes a local digital loopback test for your PC's COM ports, for which you will need the optional jumper plug offered with the software. Where a modem supports local digital loopback testing, it simulates the jumper plug and does not, therefore, need to be disconnected.

V.61

ITU-T V.61 is a 14.4 kbps V.32bis analog multiplexing technology standard developed by AT&T Paradyne and marketed as VoiceSpan. The data rate is reduced to 4800 bps during simultaneous voice and data. This analog Simultaneous voice and data (ASVD) standard has now been effectively obsoleted by V.70.

V.70

ITU-T standard for Digital Simultaneous Voice and Data (DSVD) modems. DSVD allows the simultaneous transmission of data and digitally-encoded voice signals over a single dial-up analog phone line. DSVD modems use for V.34 modulation (up to 33.6 kilobits per second), but may also use V.32 bis modulation (14,400 kilobits per second). The DSVD voice coder is a modified version of an existing specification and is defined as G.729 Annex A. The DSVD voice/data multiplexing scheme is an extension of the V.42 error correction protocol widely used in modems today. DSVD also specifies fallbacks that enable DSVD modems to communicated with standard data modems (i.e. V.34, V.32 bis, V.32 and V.22). See DSVD for a bigger explanation.

V.75

ITU-T recommendations which specify DSVD control procedures. See V.70.

V.76

ITU-T recommendations which define V.70 multiplexing procedures.

V.8

A way V.34 modems negotiate connection features and options.

V.8 bis

New start-up sequence for multimedia modems.

V.80

V.80 is the application interface defined in the H.324 ITU video conferencing standard. A V.80 modem provides a standard method for H.324 applications to communicate over modems. A V.80 modem provides three main functions:

  1. Converts synchronous H.324 streams to run on asynchronous modem connections. That is, they accept and send data in synch with a timing device ("clock"). Serial ports and modems are asynchronous, meaning they accept and receive data independent of any clocking device. V.80 converts the synchronous data stream of an H.324 application so that it can communicate through an asynchronous modem connection.

  2. Allows for rate adjustments based on line conditions. Modems adjust to different line conditions throughout a call. Under bad conditions a modem will slow down. When conditions clear, a modem will resume at top speed. A V.80 modem alerts an H.324 video phone of its rate adjustments thereby allowing the application to adjust the rate at which it sends video and audio.

  3. Communicates lost packets to the H.324 application. During transmission, data can be lost due to buffer overflows, phone line errors and a number of other issues. Under these conditions, a V.80 modem communicates lost data information to the H.324 application, helping it to keep real-time audio and video flowing to both sides of the call. See H.324.

V.90

An ITU-T standard for Pulse Code Modulation (PCM) modems running at speeds to 56 Kbps. It informally and variously was known as V.PCM and V.fast until the numeric designation, V.90, was assigned when the formal standard was approved on February 6, 1998. V.90 modems support transmission on an asymmetric basis. They support speeds of up to 56 Kbps in the downstream direction, from the central site equipment to the end user. The upstream "back channel" from the end user to the central site remains limited to 33.6 Kbps (i.e., V.34+ speeds). Actually and currently, the maximum downstream rate is 53.5 Kbps, as the standard exceeds the maximum amplitude levels supported over copper local loops . This restriction is expected to ease into the future, thereby allowing V.90 signaling rates to reach the full potential of 56 Kbps. See 56 Kbps Modem (for a longer technical explanation), V.91, V.92 and V.PCM.

V.91

A developing standard from the ITU-T, V.91 is the all-digital extension to V.90.

V.91 will allow modem signals to be transmitted over digital circuits, such as ISDN BRI (Basic Rate Interface) local loops in consumer and home office applications, and PRI (Primary Rate Interface) local loops that connect to corporate PBXs. Thereby, end users can achieve connectivity to ISPs and others supporting V.90 modem access. In the absence of V.91, such users can connect to an ISP, for example, only if the ISP also supports IDSN.

V.91 is intended to operate at signaling rates up to 64 Kbps, and will make use of both 4-wire circuit-switched connections and leased point-to-point 4-wire digital connections. See also V.90, V.92 and V.PCM.

V.92

A dial-up modem standard finalized by the ITU-T in late 2000, as the successor to V.90. V.92 improves on V.90 in a number of ways. First, while V.92 runs at the same maximum 56-Kbps downstream signaling rate as V.90, it runs at a maximum of 48 Kbps upstream, compared with V.90 upstream speed of 33.6 Kbps. This improvement in upstream signaling speed is due to the use of a modulation standard known as PCM upstream, with PCM meaning Pulse Code Modulation. PCM upstream improves the speed of the upstream channel by making use of the same clocking source for synchronization purposes as does the downstream channel. Second, V.92 makes use of the V.44 compression standard, finalized by the ITU-T in November, 2000. V.44 offers considerable improvement over the V.42bis standard used in V.90 modems. Specifically, V.44 offers a compression ratio of 6:1 (6 to 1), while V.42bis was limited to 3.5:1. Depending on the compressibility of the subject data, V.44 therefore improves throughput up to 200% or more over V.42bis. As a result, V.92 modems offer downstream throughput performance of as much as 300 Kbps, compared with the 150-200 Kbps supported by V.90 modems.

Third, the V.92 standard includes a feature known as QuickConnect, which reduces the time consumed in the handshaking process between two modems. QuickConnect accomplishes this by remembering and reusing information gained during previous handshaking processes; as the same connection typically is used repeatedly, there often is no reason for the characteristics of the connection to be re-learned every time. QuickConnect can shave 10 to 20 seconds off the 20 to 30 seconds required to establish a dial-up connection required by V.90 modems. Fourth, V.92 modems can both recognize and respond to a call waiting tone, and place the data call "on hold" while the voice call is answered . This feature can eliminate the need for a second modem/fax line. As the server pauses the data session, it is easily and quickly resumed without the need for establishing another dialup session. Lastly, there is hope V.90 modems will be upgradable to V.92 modems through a software download. See also V.42bis, V.44, V.90, and V.91.

V.ASVD Analog

Simultaneous Voice and Data modem.

V.AVD

Alternating Voice and Data. This is the same function as provided by VoiceView products.

V.DSVD

Digital Simultaneous Voice and Data.

V.Fast

V.FC. An interim modem standard to support speeds to 28,800 bits per second for uncompressed data transmission rates over regular dial up, voice-grade lines. V.FAST stands for Very Fast. V.Fast was a "standard" that only a few manufacturers of modems adopted. These manufacturers adopted V.Fast because they were impatient with the ITU's slowness. Eventually, however the ITU did adopt a new standard, called V.34. See V.34 and V.34bis.

V.FC

Version Fast Class. It is an interim standard that was developed for use until the ITU-T ratified V.Fast, i.e. V.34, which is the speed that a V.34 modem communicates at ” namely at 28,800 bits per second. V.FC was eventually obsoleted by V.34, which the ITU-T eventually adopted. See V.34.

V.GMUX

The multiplexer for V.DSVD.

V.PCM

All the makers of 56 Kbps modems had been promising an interoperable 56 Kbps specification, and the International Telecommunication Union (the ITU). They got tired of waiting for a standard, and developed pre-standard versions known as x2 and K56flex. In February of 1998, ITU-T finally obliged with a new standard, called V.PCM (later termed V.90), which is an amalgamation of the pre-standard solutions from Lucent, 3Com, and Motorola. See also x2, K56flex, V.90, V.91, and V.92.

V.Standards

Standards recommended by the ITU-T. See above.

V/T

Internet-speak for Virtual Time. R/T means the time it takes to download stuff. Writing in the New York Times, Charles McGrath said it was "customary in Net-speak to make a distinction between r/t, or real time ” the time in which all these delays and jamups occur and v/t, or virtual time, which is time on the Net: a kind of external present in which it is neither day nor night and the clock never ticks . V/t is time without urgency, without priority."

V11

The V11 interface is the same as the RS-422 interface., as well as supporting more than 32 remote stations , and authorizing mode changes from HDX to FDX. The ELV11 provides galvanic isolation between the two V11 interfaces via its internal opto coupler circuits. V11 I/Os use two twisted pairs, transmit data and receive data with a common signal. Specifications

V5

A standard approved by ETSI (European Telecommunications Standards Institute) in 1997 for the interface between the access network and the carrier switch for basic telephony, ISDN and semi-permanent leased lines. The V5 standard effectively provides for open access to both wired and wireless networks, thereby encouraging competition in a deregulated environment. V5 is European Telecommunications Standards Institute's (ETSI's) open standard interface between an Access Node (AN) and a Local Exchange (LE) for supporting PSTN (Public Switched Telephone Network) and ISDN (Integrated Services Digital Network). Examples of Access Nodes include Digital Loop Carrier (DLC) systems, wireless loop carrier system, and Hybrid Fiber Coax (HFC) systems. The V5 series includes V5.1, which is a non-concentrating 2.048 Mbps (i.e., E-1) Subscriber Network Interface (SNI), and V5.2, which is a concentrating SNI supporting as many as 16 2.048 Mbps physical interfaces. See also E-1 and ETSI.

VA

This is a form of power measurement called "Volt-Amps". A VA rating is the Volts rating multiplied by the Amps (current) rating. The VA rating can be used to indicate the output capacity of a UPS (Uninterruptible Power Supply) or other power source, or it can be used to indicate the input power requirement of a computer or other AC load. For loads, the VA rating multiplied by the Power Factor is equal to the Watts rating. The VA rating of a load must always be greater than or equal to the Watts rating because Power Factor cannot be greater than 1. This definition courtesy American Power Company.

VAB

Value Added Business partner. A term which Hewlett-Packard uses for developers which write software for its computers. HP helps its VABs sell software. Clearly, by doing so, it helps sell more HP computers.

VAC

Voice Activity Compression.

vAC

Volts, Alternating Current

Vacant Code

An unassigned area code, central office or station code.

Vacant Code Intercept

Routes all calls made to an unassigned "level" (first digit dialed ) to the attendant, a busy signal, a "reorder" signal or to a recorded announcement.

Vacant Number Intercept

Routes all calls of unassigned numbers to the attendant, a busy signal or a prerecorded announcement.

Vacation Message

See Auto Responder.

Vacation Service

A service offered by local telephone companies to subscribers who will be away. A live operator or a machine intercepts the calls and delivers a message. When you come back, you get your old number. But in the meantime, while you're away, you pay less money per month than you would for normal phone service. Also known as Absent Subscriber Service.

VACC

Value Added Common Carrier. A common carrier that provides some network service other than simple end-to-end data transmission. Services include least-cost routing, accounting data, and delivery clarification .

Vacuum Tubes

Before there were solid state devices there were vacuum tubes. A vacuum tube is an air-evacuated glass bulb with at least two electrodes: a cathode and an anode. The cathode is heated causing the electrons to "boil off." If a voltage is placed across the cathode and the anode, the electrons will be attracted to the anode completing the electric circuit. A tube with just a cathode and anode is called a diode. If a grid is placed between the anode and cathode, a small current placed on the grid can control the much larger cathode-anode current. This type of tube is called a triode. As vacuum tubes evolved, additional grids were inserted between the cathode and anode to produce tetrodes, pentodes, etc. Today, transistors have replaced vacuum tubes in all except a few specialized applications.

The first electronic computers, Eniac and Univac, built in the wartime secrecy of the 1940s, employed vacuum tubes. They had an average life span of about 20 hours, but with thousands of hot glowing tubes in a single machine, some computers shut down every seven to twelve minutes. Vacuum tubes imposed a limit on the size and power of planned next generations of computers. The second generation of computers, never used vacuum tubes. It used transistors, which were invented in 1947.

VAD

  1. Value Added Dealer. Another term for Value Added Reseller (VAR). Essentially, VARs or VADs are companies who buy equipment from computer or telephone manufacturers, add some of their own software and possibly some peripheral hardware to it, then resell the whole computer or telephone system to end users, typically corporations.

  2. Voice Activated Dialing.

  3. Voice Activity Detection. When enabled on a voice port or a dial peer, silence is not transmitted over the network, only audible speech. When VAD is enabled, the sound quality is slightly degraded but the connection monopolizes much less bandwidth.

VADSL

Very-high-speed ADSL. A variation on the theme of VDSL (Very-high-data-rate Digital Subscriber Line), which likely will support symmetric, bidirectional transmission. See also ADSL, VDSL and xDSL.

Vail, Theodore N.

Theodore N. Vail began his career with the Bell System as general manager of the Bell Telephone Company in 1878. He later became the first president of the American Telephone & Telegraph Company in 1885. He left AT&T two years later. After pursuing other interests for 20 years , he returned as president of AT&T in 1907, retiring in 1919 as chairman of the board. Vail believed in "One policy, one system, universal service." He regarded telephony as a natural monopoly. He saw the necessity for regulation and welcomed it.

VAIVR

Voice Activated Interactive Voice Response.

Validation

  1. Generally, all long distance carriers, operator service providers and private pay phone companies will not put a call through unless they can "validate," the caller's telephone company calling card, home/business phone number or credit card. Until the advent of US West's Billing Validation Service and other similar databases in 1987, the companies who needed to validate their callers ' billing requests had to turn back the caller or accept the call on faith. Validating a user's calling card is, simply, a Yes-No. If the card number is validated , it is Yes. Getting the validation involves a data call from the provider to the owner of the database. There are many ways of doing this, including a dedicated trunk and an port through an X.25 network. Here's an explanation from material put out by Harris, maker long distance switches, including the P2000V: "Validation processing starts with a check of the P2000V's own internal database of invalid 'billed to' numbers. This database contains numbers that the system administrator wishes to temporarily block. If a call's 'billed to' number does not appear in the database, the P2000V then queries the external validation service. The P2000V directly accesses external validation services via an X.25 modem connected to a leased line. The P2000V can also access Line Information Database (LIDB) through LIDB service bureau providers."

  2. Tests to determine whether an implemented system fulfills its requirements. The checking of data for correctness or for compliance with applicable standards, rules, and conventions. The portion of the development of specialized security test and evaluation, procedures, tools, and equipment needed to establish acceptance for joint usage of an automated information system by one or more departments or agencies and their contractors.

  3. A telephone company term. The determination of the degree of validity of a measuring device. The validation checks that can be made using output data are of six general types:

  4. Compare related sets of registers;

  5. Compare like groups of equipments;

  6. Compare past and present data;

  7. Compare usage and peg count;

  8. Compare usage against grade of service.

Validity Check

Any check designed to insure the quality of transmission.

Value Added

  1. Refers to a voice or data network service that uses available transmission facilities and then adds some other service or services to increase the value of the transmission. For example, a value added service might be a "never busy" fax service, where call-forward-busy calls are sent to a PC, which holds the incoming fax for transmission back to the fax machine when the line is free. Value-added tends to mean the addition of some computer or smart switch to the network.

  2. Programmers who work overtime for free are often considered "value added."

Value Added Carrier

VAC. A voice or data common carrier that adds special service features, usually computer related, to services purchased from other carriers and then sells the package of service and features.

Value Added Common Carrier

VACC. A common carrier that provides some network service other than simple end-to-end data transmission. Services include least-cost routing, accounting data, and delivery clarification.

Value Added Network

VAN. A data communications network in which some form of processing of a signal takes place, or information is added by the network. No one knows , however, exactly what a VAN is. The general idea is that a VAN buys "basic" transmission and sometimes switching services from local and long distance phone companies and adds something else ” typically an interactive computer with a database, a computer and massive storage. In this way, the VAN adds value to basic communications services. Dial up stock market quoting services are VANs. Electronic mail providers are VANs. But VANs can also simply be basic X.25 packet switching networks which are open to the public. Such a network will use X.25 packet switching to provide error correction, redundancy, and other forms of network reliability. Private organizations (companies, universities, etc.) may set up their own value-added networks, or ” as in the case of PDNs (Public Data Networks) ” another fancy name for a VAN that offers its services to the public. The classic VAN is a packet-switched operation like Tymnet, GTE Telenet, MCI Mail or AT&T Mail.

A VAN can also be communication network that provides features other than transmission of information, such as translation of one type of computer signal to another type of computer signal, called protocol conversion. VAN sometimes refers to packet-switched networks with protocol conversion. The value added is referred to as dissimilar system interface capability.

Value Added Network Service

VANS. A data transmission network routing transmissions according to available paths, assures that the message will be received as it was sent, provides for user security, high speed transmission and conferencing among terminals. Closely akin to courier services or shipping forwarders in physical commerce.

Value Added Reseller

See OEM and VAR.

Value Added Service

A communications facility using common carrier networks for transmission and providing extra data features with separate equipment. Store and forward message switching, terminal interfacing and host interfacing features are common extras. See also Value Added Network.




Newton[ap]s Telecom Dictionary
Newton[ap]s Telecom Dictionary
ISBN: 979387345
EAN: N/A
Year: 2004
Pages: 133

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