Jithead-JVM

Jithead

An international transportation term used to describe people who order goods on a "just in time" basis and then freak out when told they didn't order early enough. Definition courtesy Wireless Magazine.

Jitter

Jitter is variability in latency, or delay. If a network provides varying levels of latency (i.e. different waiting times) for different packets or cells , it introduces jitter, which is particularly disruptive to audio communications because it can cause audible pops and clicks. Jitter is also the tendency towards lack of synchronization caused by mechanical or electrical changes. Technically, jitter is the phase shift of digital pulses over a transmission medium. Three forms of jitter exist: Data Dependent Jitter (DDJ), Duty Cycle Distortion (DCD), and Random Jitter (RJ). Data Dependent Jitter is caused by limited bandwidth characteristics and imperfections in the optical channel components as it relates to the transmitted symbol sequence, according to Information Gatekeepers. This jitter results from less than ideal individual pulse responses and from variation in the average value of the encoded pulse sequence which may cause baseline wander and may change the sampling threshold level in the receiver. DCD Jitter is caused by propagation delay differences between lowto-high and high-to-low transitions. DCD is manifested as a pulse width distortion of the nominal baud time. RJ is the result of thermal noise.

Jitter Buffer Management

Most speech encoder algorithms have a set of rules concerning packet delivery and disposition management. This is often called jitter buffer management. "Jitter" in this case refers to when the signal is put into frames . The decoding algorithm must decompress and sequence data and make "smoothing" decisions (when to discard packets versus waiting for an out-of-sequence packet to arrive ). Given the real-time nature of a live connection, jitter buffer management policies have a large affect on voice quality. Actual sound losses range from a syllable to a word, depending on how much data is in a given packet. The first buffer size is often a quarter-second, large enough to be a piece of a word or a short word ” similar to drop-outs on a cellular connection in a poor coverage area. See also IP Telephony Algorithms.

Jitterati

What the digital generation becomes after tanking up on too much coffee. This definition courtesy Wired Magazine.

Job

A file, typically sent in batch mode. Specifically a set of data, including programs, files and instructions to a computer, that together amount to a unit of work to be done by a computer.

Joel

Vietnam was no preparation for Harry and the summer of 1997. Fortunately the green was bucks, not beret. Bucks are mitigating. Joel is a dear friend of mine. So, if you don't understand of this, don't worry. He will.

Join

1. A basic operation in a relational system that links the rows in two or more tables by comparing the values in specified columns .

2. A service/feature which allows a device to join an existing call, i.e., Conference.

Joining

An ATM term. The phase in which the LE Client establishes its control connections to the LE Server.

Joint

1. The place at which two separate things parts are brought together.

2. A disreputable gathering place, or a dive. The term is derived from fact that the pipes used in opium were made of bamboo, and had many joints.

3. A marijuana cigarette. Also known as a reefer or a doobie. See #2 for the likely origin of the term.

Joint Costs

A regulatory concept. Joint costs are essentially overhead costs. They cover the costs of providing more than one service. Most costs in the telecommunications industry are joint. And being "joint" they give regulators enormous pleasure trying to allocate those costs to various services and therefore trying to figure what prices for those services should be.

Joint Pole

A utility pole which supports the facilities of two or more companies. A typical joint pole supports three facilities: electric power, cable television and telephone. In many locations, joint poles also support other devices such as street lights, municipal communications systems, signs, traffic signals, seasonal decorations, fire and police call boxes, and alarm signal wiring. The figure below illustrates the typical allocation of space on utility poles in the United States. The allocation is similar in Canada except that cable television and telephone are sometimes lashed to the same strand . Starting at the top and working down, facilities on this pole are:

• Static wire: a grounded wire at the very top of the pole intended to protect lower conductors from lightning.

• Transmission: three uninsulated conductors which carry 3-phase high voltage (typically 69 to 200 kilovolts) circuits among substations.

• MGN (multi-grounded neutral): a single uninsulated grounded conductor. The currents in the three phases of the transmission line are never quite equal; the MGN carries the residual unbalance current. At many poles, the MGN is physically grounded to a groundrod at the base of the pole.

• Primary: one to four uninsulated conductors, frequently supported on a crossarm, which carry power from substations to pole-mounted stepdown transformers . Primary circuits may be single-phase or three-phase, and operate at 4 to 15 kilovolts.

• Secondary: one or two insulated conductors, accompanied by an uninsulated grounded neutral conductor. The secondary circuit (so named because it is fed from the secondary winding of the stepdown transformer) provides the standard 3-wire 115/230-volt electric service for residential and small commercial customers. Secondary conductors are usually twisted together in a bundle called "triplex," although older secondary lines may consist of three separate conductors.

• Stepdown transformer: an oil-cooled transformer which converts the primary voltage to the secondary voltage. Most stepdown transformers are designed for single- phase operation; if a three-phase secondary circuit is required, three physical transformers are sometimes mounted on the same pole.

  

• Neutral Space: an unused space which separates electric power facilities from communications facilities. This space is specified by the National Electrical Safety Code for safety reasons.

• CATV: cable television facilities supported by steel strand. An expansion loop at each pole absorbs expansion and contraction caused by temperature variations.

• Telephone: copper telephone cables supported by steel strand. Each telephone cable contains several individual wire pairs; a large cable may contain as many as several hundred pair.

Joint Procurement Consortium

An organization formed by Ameritech, BellSouth, Pacific Bell and SBC Communications to help them buy things.

Joint Trench

A company wants to lay cable under a busy street. It applies to the city for permission. The city wants to limit the number of times a trench will be dug under that street. So the city announces that this will be a "joint trench" and it tells you that you must contact all the other utilities in town (typically giving them 30 days to respond) and check out those who might wish to locate their cable in that trench. Once you've determined who wants to participate in the joint trench, the trench will probably change in depth and width. Something called the "Western Formula" will be applied. Each of the utilities will pay then less than what they would have, had they built it by themselves .

Joint User

A person, firm or corporation designated by the customer as a user of access facilities furnished to the customer by the company, and to whom a portion of the charges for such facilities are billed under a joint use arrangement.

Joint User Service

An arrangement whereby a corporation, association, partnership or individual whose telecommunications needs do not warrant the provision of separate leased service, is permitted to use the service of another customer by mutual agreement. The primary objective of joint user service is to save money by buying circuits in bulk.

Jose

A common Spanish name pronounced Ho-zeh. There is an old story of the Spanish fireman who had two sons. He named the first one Jose. And the second? Why Hose B, of course? See also Hosed.

Joule

The unit of work or energy. The energy expended when a current of one ampere flows through a resistance of one ohm for one second. Joule's Law says the heat produced in a circuit in joules is proportional to the resistance, to the square of the current and to the time.

Journal Printers

These are special purpose printers which provide hard copy output for audit trail and demand printing functions associated with hotel/motel management features.

Journalism

The last refuge of the vaguely talented.

Joy Clicker

One who nervously fiddles with a mouse.

Joystick

A pointing device for a computer whose upright level is used to manipulate a pointer on a screen. Named after a similar shaped control in airplanes. Joysticks are often used in computer gaming.

JPEG

Joint Photographic Experts Group . So called as it was developed jointly by the International Standards Organization (ISO) and the ITU-T, it formally is known as ISO 10918-1 Recommendation T.81. JPEG is a compression technique used primarily in the editing of still images, and in color fax, desktop publishing, graphic arts and medical imaging. JPEG is symmetrical in nature, requiring equal processing power, time and expense on both the transmitting side (compression) and the receiving side ( decompression ). Its complexity renders it ineffective for real-time video; imaging applications are not so delay-sensitive.

The JPEG compression standard works by converting a color image into rows of pixels (picture elements), which are dots of color image, each with a numerical value representing levels of brightness and color. The picture is then broken down into blocks, each 16 pixels x 16 pixels, and then reduced to 8 pixels by 8 pixels by subtracting every other pixel. The software uses a formula that computes an average value for each block, permitting it to be represented with less data. Further steps subtract even more information from the image. To retrieve the data and thus decompress the image, the process is reversed . A specialized chip decompresses the images hundreds of times faster than is possible on a standard desktop computer. JPEG is a lossy image-compression algorithm that reduces the size of bitmapped images by a factor of 20:1 to 30:1 which compromises the absolute quality of the image in terms of resolution and color fidelity; JPEG can be pushed to yield a 40:1 compression ratio, although the loss in quality is noticeable at this level. JPEG compression works by filtering out an image's high-frequency information to reduce the volume of data and then compressing the resulting data with a lossless compression algorithm. Low-frequency information does more to define the characteristics of an image than does high-frequency information which serves to define sharp edges ”losing some high-frequency information doesn't necessarily affect the image quality. In complex images, however, JPEG suffers from an effect known as "tiling," yielding a mosaic- like effect due to the block-oriented compression technique. When you see an image with the .JPG extension, that means it's JPEG image. See also JPEG 2000, JPEG ++, Motion JPEG, and MPEG.

JPEG 2000

A newer form of JPEG encoding for photographs and illustrations. JPEG 2000 uses wavelet compression, which encodes and sends an image in a continuous stream, yielding a higher resolution (than normal JPEG) as the file opens. Users with web browsers equpped to handle the JPEG 2000 images can choose to download only what is appropriate for their screen size or Internet connection. Someone surfing the web on a wireless handheld device will get just the photo or illustration's core , while someone using a 21 inch monitor and a high-speed connectikon will get everything.

JPEG++

Storm Technology's proprietary extension of the JPEG algorithm. It lets users determine the degree of compression that the foreground and background of an image receive; for example, in a portrait, you could compress the face in the foreground only slightly, while you could compress it in the background to a much higher degree. See JPEG.

JPG

See JPEG.

JPIX

Japan Internet Exchange. See IX.

JSP

Java Server Page. See JHTML.

JT-2

6.312 Mb/s data rate. Same as T-2. Signal compatible with ITU-T document G.704 signal specification.

JTAG

Joint Test Action Group. A consortium of North American manufacturers of ASICs (Application-Specific Integrated Circuits) which was formed in 1988 to explore the idea of building test capabilities into the chips for automated testing on a software-controlled basis. Previously, all chips had to be tested on a "bed-of- nails " approach, which involved gaining access to a great many hardware test points on each chip, and the use of expensive in-circuit test equipment. This approach was cumbersome, time-consuming and expensive, particularly with the advent of ASICs, which are densely packed with circuits. In 1990, the IEEE refined the concept, which was standardized as IEEE 1149.1, which commonly is known as the Standard Test Access Port and Boundary Scan Architecture. Boundary scan allows observability and controllability of the test procedure through Test Access Ports (TAPs) in the form of the input and output boundary pins (pins at the edge of the ASIC) on a software-controlled basis.

JTAPI

See Java Telephony API and the definitions below.

JTAPI Address Object

Part of the JTAPI Core call model. The Address object represents a telephone number. It is an abstraction for the logical endpoint of a phone call. This is distinct from a physical endpoint. In fact, one address may correspond to several physical devices.

JTAPI Call Model

The JTAPI Core call model is defined in the Core API package. A call model describes a set of software objects that correspond to physical and conceptual entities in the telephony world. These objects fit together in a specified way to represent a telephone call. The Core API objects are: Provider Object, Call Object, Connection Object, TerminalConnection Object, Terminal Object and Address Object. In the physical view, each Core object represents a tangible property or telephony equipment. From a logical view, the call model represents an abstraction of telephony software entities or the functional properties of the objects. In describing these objects, it is difficult to separate the objects' physical representation from their logical properties, therefore, the description of these objects changes perspective frequently.

JTAPI Call Object

Part of the JTAPI Core call model. The Call object represents a telephone call, the information flowing between the service provider and the call participants . A telephone call comprises a Call object and zero or more connections. In a two-party call scenario, a telephone call has one Call object and two connections. A conference call is three or more connections associated with one Call object.

JTAPI Connection Object

Part of the JTAPI Core call model. A Connection object models the communication link between a Call object and an Address object. Relationships between Call and Address like connected, disconnected, and alerting are modeled by the Connection object as states. The Connection object also serves as a container for zero or more TerminalConnection objects. Connection objects model the logical aspects of a call connection.

JTAPI Core Package

All JTAPI implementations make use of the Core package. Many application developers will only need basic telephony, in which case they will only need to use the Core API package. The Core API package provides basic telephony: placing calls, answering calls, and dropping calls. It defines the basic call model that the extension packages follow in design.

JTAPI Provider Object

Part of the JTAPI Core call model. The Provider object is an abstraction of telephony service provider software. The provider might manage a PBX connected to a server, a telephony/fax card in a desktop machine, or a computer networking technology, such as IP. A Provider hides the service-specific aspects of the telephony subsystem and enables Java applications and applets to interact with the telephony subsystem in a device-independent manner.

JTAPI Standard Extension Packages

The JTAPI specification defines standard extension packages. The core telephony package, Call Control, Call Center, Private Data and Terminal Set Management extension packages are at version 1.0. The specifications for Media, and Capabilities extension packages are at version 0.3. Mobile, and Synchronous are still under consideration. There are currently eight standard extension packages: Call Control, Call Center, Private Data, Terminal Set Management, Capabilities, Media Services, Mobile Phones and Synchronous.

JTAPI Terminal Object

Part of the JTAPI Core call model. The Terminal object represents a physical device like a telephone and its associated properties. Each Terminal object may have one or more Address Objects (telephone numbers ) associated with it, as in the case of some office phones capable of managing multiple call appearances . Additionally, Terminal objects that have more than one phone line may share a telephone number and a single Address object with another Terminal in an adjacent office. However, each Terminal has a unique TerminalConnection associated with a Call even though it may share an Address.

JTAPI TerminalConnection Object

Part of the JTAPI Core call model. TerminalConnection objects model the relationship between a call and physical entities, represented by the Terminal object. The TerminalConnection object signals a Terminal when there is an incoming call and monitors the Terminal's activity during the process of a call. This object also closely communicates with the Connection object to receive information on a Call's change in state and to send information on the Terminal's state change. It models the physical aspects of a call connection.

JTC

Joint technical Committee.

JTWROS

Joint Tenants With Right of Survivorship. When two or more people maintain a Joint Account with a brokerage firm or a bank, upon the death of one account holder, ownership of the account assets passes to the remaining account holder(s). This transfer of assets escapes probate, but estate taxes may be due, depending on the amount of assets transferred.

JUCA

Joint Use Collate Access is a bullpen environment where multiple customers are located at a site. JUCA is sold by the rack, not by the square footage.

Judge Harold Greene

Judge Greene presided over the 1982 AT&T Antitrust settlement , enforcing its provisions and making decisions about requests from the participants to modify or reinterpret the provisions of the settlement. As long as he doesn't allow AT&T to be completely free of regulation, Judge Greene will probably always be involved in figuring the future of the telecommunications industry.

Juggling On-demand Connection

An Internet Access Term. The ability to have more suspended on-demand connections than there are ports on the Dialup Switch.

Jughead

Jonzy's Universal Gopher Hierarchy Excavation And Display. A database of Gopher links which accepts word searches and allows search results to be used on many remote Gophers. See Archie.

Juice a Brick

From Wired's Jargon Watch column. To recharge the big and heavy NiCad batteries used in portable video cameras . "You better start juicin' those bricks , we got a long shoot tomorrow."

Jukebox

A jukebox is a piece of hardware that holds storage media, such as optical disks or cartridge tapes. Jukeboxes are typically designed to hold as few as five and as many as 120 devices. Like old-fashioned record playing jukeboxes, media is moved by a robot-like device from the storage slot to the drive reading it. This lets the user share one drive among several cartridges or disk. Jukeboxes are typically used for secondary and archival storage. Access to information is not fast. See Jukebox Management.

Jukebox Management

In a network, tasks like retrieval and writes to a jukebox come randomly from all the users. These tasks vary in urgency ” retrievals are higher priority than writes, for example. Jukebox management software sorts out requests from the network by priority. Management also enhances the performance of a jukebox, by intelligently reordering requests. For example, if there are three requests for images on platter 1 and two from platter 2 and the another from platter 1, jukebox management means the requests from platter 1 will get handled together, then go to platter two. Sometimes it's called "elevator sorting" ” responding to requests in logical order, not in the order in which they were made.

Julian Date

Not as often supposed a date according to the Julian calendar introduced by Julius Caesar, but rather a date in the Julian Period chronological system, now used chiefly in astronomy and hence in computations of satellite orbits. The Julian Period was devised by Joseph Justus Scaliger (1540-1609), a French historian of Italian extraction, principally to permit comparison of the differing computations of time made by ancient civilizations . Scaliger named the system after his father, Julius Caesar Scaligeri, and chose its period as 28 X 19 X 15 = 7,980 years, where 28 is the number of years in the solar cycle of the Julian calendar, 19 is the number of phases in the lunar cycle in which the phases of the Moon recur on a particular day in the solar year, and 15 was the cycle of indication, which originally an ancient Roman governmental tax schedule. He chose a starting point of 4713 BC, which was the nearest past year in which the three cycles began together. In astronomical computations, such as locating the Greenwich meridian with respect to a satellite orbit , Julian days are referenced to 12.00 noon (Universal Time, equivalent to GMT) on "0 January" (actually 31 December) of the year 2000, which is Julian day 2,451,545.0. Zero days of the month are used to simplify adding. The decimal place is carried to permit writing 0.5 to indicate the start of a day.

Jumbo Frame

In networking language, a frame is a packet of information. When information is sent across telecom lines A bigger A Gigabit Ethernet (GE) term. Gigabit Ethernet standards have adjusted the standard Ethernet frame size. The minimum size has been increased from 64 bytes to 512 bytes. The maximum frame size has been increased from 1,518 bytes to a "jumbo frame" of 9,000 bytes. This larger frame size reduces the number of frames that must be processed by a Gigabit Ethernet switch in the process of switching a large data set. As each frame must be processed by the switch, the fewer frames involved, the less the processing demands on the switch, and the less the delay in doing so. Jumbo frames, therefore, increase the throughput of the switch. However, jumbo frames require that multiple standard Ethernet frames be consolidated through a relatively minor process of protocol conversion. See also Gigabit Ethernet.

Jumbo Group

A 3,600 channel band of frequencies formed from the inputs of six master groups. See Mastergroup and Supergroup.

Jump Hunting

See Nonconsecutive Hunting.

Jump Scrolling

Characteristic of a terminal with vertical motions of a whole line of characters at a time in discrete steps of one line, much as a teleprinter terminal might do. Contrast with "smooth scrolling" as done by graphics terminals.

Jumper

1. A wire used to connect equipment and cable on a distributing frame.

2. A patch cable or wire used to establish a circuit, often temporarily, for testing or diagnostics.

3. Jumpers are pairs or sets of small prongs on adapters and motherboards. Jumpers allow the user to instruct the computer to select one of its available operation options. When two pins are covered with a plug, an electrical circuit is completed, When the jumper is uncovered the connection is not made. The computer interprets these electrical connections as configuration information.

4. When errors are found on printed circuit boards , a Jumper cable is sometimes soldered in to correct the problem.

Jumper Wire

A short length of wire used to route a circuit by linking two cross connect points. See also Jumper.

Jumperless

No jumpers on the hardware. Settings are accomplished with software ” but not by setting jumpers. See Jumper.

Junction Box

A metal or plastic box used as an access for cable or wire (coax, fiber, UTP, STP). When companies build a network in a building, building management usually require the J box to be located close to the building's entry point.

Junctor

A connection or circuit between inlets and outlets of the same or different switching networks.

June

In the 1500s, most people got married in June because they took their yearly bath in May. The weather improved in June. However, they were starting to smell, so brides carried a bouquet of flowers to hide their body odor. Hence the custom today of carrying a bouquet.

JUNET

Japan UNIX Network.

Junk Bonds

Junk bonds, or high-yield bonds, are rated below investment grade because they are allegedly riskier. As a result, they carry a higher yield than investment grade bonds. I included this definition because in April, 1998, Level 3 Communications, Inc., one of the newest telecommunications transmissions companies sold $2 billion in junk bonds, equaling the largest junk bond deal up to that point in the 1990s. According to the rating agencies, junk bonds are rated BB+ and below. Investment grade bonds are rated BBB- or above. Bonds from a record 60 companies were downgraded from investment grade to junk in the year 2001.

Junk Dealer

A pejorative term for a broker of used telecom equipment in what's known as the "secondary market." See also Broker.

Junos Code

The operating system which Juniper Networks has created for its router. According to Juniper, Junos allows high-speed forwarding across ever-more complex sets of paths. Junos will compete with IOS, the Cisco Internetwork Operating System (IOS) that runs the vast majority of routers now deployed in the core of the Internet.

Jurisdiction

A geographic area associated with and bounded by state and/or LATA boundaries. The following are the four categories: Interstate/InterLATA, Interstate/IntraLATA, Intrastate/InterLATA, Intrastate/IntraLATA. and an area in which a common carrier is authorized to provide service.

JV

Joint Venture.

JVM

See Java Virtual Machine.