Abbreviation for Zulu time. See Greenwich Mean Time.


To eradicate all or part of a program or database, sometimes by lightning, sometimes intentionally.

Zapper Message

Sent by the Supervisor to teat down a virtual circuit after the transmission is complete.


See Zettabyte.


Zero Byte Time Slot Interchange. A technique used with the T carrier extended superframe format (ESF) in which an area in the ESF frame carries information about the location of all-zero bytes (eight consecutive "O"s) within the data stream.


Zero Code Suppression.


Zero Dispersion Shifted Fiber. A type of Dispersion Shifted Fiber (DSF) that is used in long haul, high speed fiber optical transmission systems. See DSF for a full explanation.


A Japanese sect of Buddhism that stresses attaining enlightenment through intuition rather than by studying scripture. In contemporary techie lingo, you zen something if you figure it out by meditation or a sudden flash of enlightenment. Zenning is a whole lot easier that groking, as it requires much less work. See also Grok and Zen Mail.

Zen Mail

Email messages that arrive with no text in the message body.

Zener Diode

A particular type of semiconductor which acts as a normal rectifier until the voltage applied to it reaches a certain point, or threshold voltage. At this point ” at the Zener voltage or the avalanche voltage ” the Zener diode becomes either conducting (i.e., "turns on") or non-conducting (i.e., "turns off"). These types of circuits include computer equipment (turn on), voice-activated circuits such as telephone wiretap devices (turn on), and surge protectors ( turn off). As the main use of a Zener diode is to provide a reference voltage, it often is known as a "reference diode". In a RF (Radio Frequency) clamp application, the Zener diode is used to clamp (i.e., supply) a specific voltage for other, protected components , perhaps in an integrated circuit (IC). The Zener diode is the device that made it possible to make digital integrated circuits. Without Zener diode on-chip reference voltage (and, thereby, the benefit of voltage regulation and transient voltage protection), we would not be able to just "hook 'em together", as we do now. See also Diode and Rectifier .


The basis of Arabic numerals, including the newly invented "zero," probably originated in India around the 6th century. This new knowledge followed the trade routes to the Arab world. The shape of most of the characters were greatly modified by the Arabs and the Arabic numerals, as we know them today, were introduced into Europe around the 10th century by the Moors in Spain, although they did not come into general use for several hundred years . The symbol "zero" was the last one of the group to be accepted because most scholars believed that it was unnecessary to have something that stood for nothing.

Zero Beat Reception

Also called "homodyne" reception. A method of reception using a radio frequency current of the proper magnitude and phase relation so that the voltage impressed on the detector will be of the same nature as that of the wave. An old radio term .

Zero Bit

The high-order bit in a byte or a word.

Zero Byte Time Slot Interchange

ZBTSI. A method of coding in which a variable address code is exchanged for any zero octet. The address information describes where, in the serial bit stream, zero octets originally occurred. It is a five-step process where data enters a buffer, zero octets are identified and removed, the nonzero bytes move to fill in the gaps, the first gap is identified, and a transparent flag bit is set in front of the message to indicate that one or more bytes originally contained zeros. See ZBTSI.

Zero Code Suppression

The insertion of a "one" bit to prevent the transmission of eight or more consecutive "zero" bits. Used primarily with digital T-1 and related telephone-company facilities which require a minimum "ones density" keep the individual sub channels of a multiplexed, high-speed facility active. Several different schemes are currently employed to accomplish this. Proposals for a standard are being evaluated by the ITU-T. See also Zero Suppression.

Zero Dispersion Shifted Fiber

ZDSF. A type of Dispersion Shifted Fiber (DSF) that is used in long haul, high speed fiber optical transmission systems. See DSF for a full explanation.

Zero Fill

See Zerofill.

Zero Frequency

The frequency (wavelength) at which the attenuation of the light- guide is at a minimum.

Zero Hop Routing

A layer 3 switch that offers cut-through services making every end station one hop away from each other

Zero Insertion

In SDLC, the process of including a binary 0 in a transmitted data stream to avoid confusing data and SYN characters; the inserted 0 is removed at the receiving end.

Zero Latency

A computer term describing a computer system in which there is virtually no time between the updating of an information record and its availability elsewhere in the network. See also Latency and Real Time.

Zero Latency Enterprise

The Gartner Group defines this new management buzzword as an organization that "exploits the immediate exchange of information across geographical, technical and organizational boundaries to achieve business benefit." I guess it means the place moves quickly. Nothing like saying something in big words that can't say more easily with smaller, fewer words.

Zero Out

Someone calls one of those infernal phone machines and hears: "Thank you for calling XYZ Corporation, press 1 for sales if you're above 12th Street, press 2 for sales on 12th Street, press 3 for below 12th street, etc." When many people (like me) hear incomprehensible messages like this one, they simply hit zero and hope they'll get a real live person. In the trade, this is called a "zero out." The measure of how many "zero outs" a site has is a measure of how badly the menus are written.

Zero Power Modem

A modem that takes its power from the phone line and therefore needs no battery or external power. Such modems are often limited in their speed and capabilities.

Zero Slot LAN

A Local Area Network (LAN) that uses a PC's serial port to transmit and receive data. It doesn't require a network interface card to be installed in a slot in the PC, thus the name "zero-slot" LAN. RS-232 LANs usually use standard RS-232 or phone cable to link PCs. Software does the rest of the work. Due to the slow speed of serial communications on a PC, RS-232 LANs are usually restricted to speeds of around 19.2K bits per second. What they lose in speed, however, they make up in low price.

Zero Stuffing

Get a cup of coffee right now. Synchronous data transmission is done by sending what IBM and AT&T call Frames , and what everyone else calls Packets. A frame starts off by sending a bit pattern of 01111110 (notice the six 1's in a row). Synchronous transmission is for sending a bit stream, which means that the bits may (but probably do not) have any relation to the transmission of characters. This is especially true when sending digitized voice. As the bits pass to the receiver, they go through a shift register. When the flag signifying the end of a frame goes by, the last 16 bits in the shift register are the check digits.

The receiver computes the check digits based on the data bits that have gone by. As the sender sent the data, it computed the check digit, sent it after the end of the frame, and then sent the flag. If the receiver computes the same check digit that the sender sent, then one can be reasonably assured the data came through without error. But that's not what I came to talk to you about. I came to talk about Zero Stuffing. The problem is that somewhere in the bit stream, there is the possibility of there being six 1 bits in a row. To the receiving computer, six 1's means a flag. Therefore the sending computer, if it "sees" six 1 bits, will send five 1 bits, and stuff a zero in the bit stream.

In fact, if it sees even five 1 bits, it will stuff a zero anyway, so there will be no ambiguity. The rule is, "If there are five ones in a row and it is NOT the end of a frame, stuff a zero into the bit stream." This way the receiver will know that this is in no way the end of the frame yet. Now if the receiver sees six 1's in a row, it knows without a doubt that it IS at the end of a frame, and should proceed with the error checking.

Zero Suppression

The elimination of nonsignificant zeros from a numeral. Zero suppression is the replacement of leading zeros in a number with blanks so that when the number appears, the leading zeros are gone. The data becomes more readable. For example, the number 00023 would be displayed on the monitor or printed as 23.

Zero Test Level Point

A level point used as a reference in determining loss in circuits. Analogous to using sea level when defining altitude. Written as 0 TLP.

Zero Transmission Level Point

ZTLP. In telephony, a reference point for measuring the signal power gain and losses of telecommunications circuit, at which a zero dBm signal level is applied.

Zero Transmission Level Reference Point

A point in a circuit to which all relative transmission levels are referenced. The transmission level at the transmitting switchboard is frequently taken as the zero transmission level reference point.

Zero Usage Customer

An MCI definition. An MCI customer who has not placed a call over the network, even though he/she is an active customer. Sometimes used interchangeably, but incorrectly, with the term "no usage customer."


  1. To fill unused storage locations with the character "O."

  2. Here's definition from GammaLink, a fax board maker: A traditional fax device is mechanical. It must reset its printer and advance the pages as it prints each scan line it receives. If the receiving machine's printing capability is slower than the transmitting machine's data sending capability, the transmitting machine adds "fill bits" (also called Zero Fill) to pad out the span of send time, giving the slower machine the additional time it needs to reset prior to receiving the next scan line.


ZB. A combination of the Greek "zeta," the second last letter of the Greek alphabet (omega is the last letter), and the English "bite," meaning "a small amount of food." A unit of measurement for physical data storage on some form of storage device ” hard disk, optical disk, RAM memory etc. and equal to two raised to the 70th power, i.e. 1,180,591,620,717,400,000,000 bytes.

KB = Kilobyte (2 to the 10th power)

MB = Megabyte (2 to the 20th power)

GB = Gigabyte (2 to the 30th power)

TB = Terabyte (2 to the 40th power)

PB = Petabyte (2 to the 50th power)

EB = Exabyte (2 to the 60th power)

ZB = Zettabyte (2 to the 70th power)

YB = Yottabyte (2 to the 80th power)

One googolbyte equals 2 to the 100th power.


See Schlub.


Zero Insertion Force. Intel makes a bunch of math co-processor chips which are used with their 80XXX range of microprocessors. ZIF is a special device which is typically soldered to the motherboard. You place an 80387 chip on this device, move the handle down, it grabs the chip and pulls the chip down, seating it electrically. When you want to remove the chip, you simply lift the handle and up the chip comes. The device was invented by Intel because so many people were apparently breaking the legs on their math coprocessor chips each time they removed them. Apparently the problem was most prevalent in the computer rental business.


ZigBee was created to address the market need for a cost-effective , standards- based wireless networking solution that supports low data rates, low power consumption, security and reliability. The ZigBee Alliance is defining both star and mesh network topologies, a variety of data security features and interoperable application profiles. According to the Alliance, ZigBee is the only standards-based technology that addresses the unique needs of most remote monitoring and control and sensory network applications. The Alliance's members ' low cost, low power solutions will enable the broad-based deployment of wireless networks that are able to run for years on standard batteries for a typical monitoring application. ZigBee-compliant products operate in the unlicensed bands worldwide, including 2.4GHz (global), 915Mhz (Americas) and 868Mhz (Europe). Raw data throughput rates of 250Kbs can be achieved at 2.4GHz (10 channels), 40Kbs at 915Mhz (6 channels) and 20Kbs at 868Mhz (1 channel).

Transmission distance is expected to range from 10 to 75 meters , depending on power output and environmental characteristics. Will interference and coexistence be an issue for the ZigBee technology in the 2.4GHz band? According to the Alliance, the potential for interference exists in every band , including 2.4GHz. The IEEE 802.10 and 802.15.2 committees are addressing coexistence issues. Examples of ZigBee applications include: Wireless home security; Remote thermostats for air conditioner; Remote lighting, drape controller; Call button for elderly and disabled; Universal remote controller to TV and radio; Wireless keyboard, mouse and game pads; Wireless smoke; CO detectors; Industrial and building automation and control (lighting, etc.) According to the Alliance, the ZigBee stack is small (28Kbytes) compared to the Bluetooth stack (250K). This relates to lower cost and lower power consumption. Ultra-low power consumption is a key system design aspect of the ZigBee technology to allow long lifetime non- rechargeable battery powered devices versus rechargeable devices for Bluetooth. As an example the transition from sleep mode to data transition is much faster in ZigBee than for Bluetooth. ZigBee networking capabilities include 255 devices per network, compared to 8 for Bluetooth networks. The data rate for ZigBee technology is 250kbps compared to 1 Mbps for Bluetooth wireless technology. Range for ZigBee products is expected to be around 30 meters in a typical home, compared to around 10 meters for Bluetooth products (without power amplifier ).

Zinc Spark Gap

A spark gap having zinc as the electrode.


An electronic "magazine" produced for distribution on the Internet.


It all started years ago with a very popular PC program called PKZIP. You could run this program on a file on your PC and bingo PKZIP would reduce the size of the file by as much as 90%. You could then transmit the zipped file over a phone line, saving 90% of the time and 90% of the cost. At the other end the recipient would run another file called PKUNZIP and bingo your file would be returned to its original size . You get the program from PKWARE, Inc. Glendale, WI 414-352-3670. www.pkware.com

Zip Code

ZIP codes are the specific codes assigned to addresses in the United States to speed up the sorting of mail and thus speed up its delivery. ZIP stands for Zoning Improvement Plan. ZIP codes were originally introduced into the United States in 1963. They were originally five digits. Then they grew to nine digits. The latest zip codes are 11 digits. Let's say you have a zip code 10036-3959-29. The 100 is the region, in this case New York City. The 36 indicates the specific post office in the region. The 3959 means the carrier route, i.e. the delivery sector in a neighborhood. The 29 is called the sequence. It indicates a specific address along a given route. Outside of the US, ZIP codes are often called postal codes. They do the same thing the American ZIP codes do. They allow machinery to sort the mail and thus get it to its destination faster. See also Missile Mail.

Zip Cord

Another name for a patch cable or jumper , often used to describe fiberoptics cable used in a zone wiring configuration.

Zip Tone

Short burst of dial tone to an ACD agent headset indicating a call is being connected to the agent console.


See Zip.


ZMODEM is an error-correcting file transfer, data transmission protocol for transmitting files between PCs. A file might be anything ” a letter, an article, a sales call report, a Lotus 1-2-3 spreadsheet. Always use ZMODEM if you can. It's the best and fastest data transmission protocol to use. This is not my sole advice. Virtually every writer in data communications recommends it. Here's an explanation, beginning with XMODEM, an older, more common and less efficient protocol.

Both XMODEM and YMODEM transmit, then receive, then transmit. The handshake (ACK or NAK) happens when the sender isn't sending. ZMODEM adds full duplex-trans- mission to the transfer protocol. ZMODEM does not depend on any ACK signals from the host computer. It keeps sending unless it receives a NAK, at which time it falls back to the failed block and starts to retransmit at that point. ZMODEM was written by Chuck Forsberg. According to PC Magazine (April 30, 1991) ZMODEM is the first choice of most bulletin boards . ZMODEM, according to PC Magazine, features relatively low overhead and significant reliability and speed. ZMODEM dynamically adjusts it packet size depending on line conditions and uses a very reliable 32-bit CRC error check. It has a unique file recovery feature. Let's say ZMODEM aborts a transfer because of a bad line (or whatever), it can start up again from the point it aborted the transfer. Other file transfer protocols have to start all over again. ZMODEM's ability to continue is a major benefit. ZMODEM in some communications program is a little more automated than other protocols. For example, ZMODEM will start itself when the other end gives a signal ” thus saving a keystroke or two and speeding things up. See File Transfer Protocol, XMODEM and YMODEM.


  1. A telephony definition. A zone is one of a series of specified areas, beyond the base rate area of an exchange. Service is furnished in zones at rates in addition to base rates.

  2. A LAN definition. A zone is part of a LAN (Local Area Network), typically defined by a router. A router will let you get into one part of someone else's network. They define what you are able to get access to. You might get to that router by an external telecommunications circuit ” dial up, ISDN, Switched 56, T-1 etc.

  3. A collection of all terminals, gateways, and MCUs (Multipoint Control Units) managed by a single gatekeeper in an H.323 context. See also H.323.

Zone Bits

  1. One or two leftmost bits in a commonly used system of six bits for each character.

  2. Any bit in a group of bit positions that are used to indicate a specific class of items, i.e., numbers , letters , commands.

Zone Cabling

According to AMP, its inventor , zone cabling is the subsystem for companies on the move. Zone Cabling subsystems allow for flexible, changeable cabling of open office areas for voice, data, video and power. The open office area is divided into zones, with feeder cables running to a distribution point within each zone and short cable runs to each outlet. Zones are wired with reusable, pre- terminated cable assemblies. Office area reconfiguration is fast and easy when using plug and play assemblies not requiring retesting. Disruption and productivity loss during moves are minimal and confined to the zones you're moving. Zone cabling can be implemented in CNA or DNA architectures.

Zone Method

A ceiling distribution method in which ceiling space is divided into sections or zones. Cables are then run to the center of each zone to serve the information outlets nearby. See also Ceiling Distribution Systems.

Zone Multicast Address

Data-link-dependent multicast address at which a node receives the NBP broadcasts directed to its zone. See also NBNS.

Zone Prefix

A prefix that identifies the addresses to be serviced by a given gate- keeper. Zone prefixes are typically area codes and serve the same purpose as the domain names in the H.323-ID address space.

Zone Of Silence

Skip zone.

Zone Paging

Ability to page a specific department or area in or out of a building. "Page John in the Accounting Department." Zone paging is useful for finding people who wander, as most of us do.

Zoomed Video

ZV. A PC card standard that lets a computer run its operating system or application software directly from a PC card. It is a technology that allows certain streams of digital information to write directly to a laptop's screen, bypassing the CPU and its bus (ISA, PCI, EISA, etc.). Zoomed video can show full 30 frames per second movies to a laptop screen. Zoomed video used MPEG-2. To show NTSC on a laptop, you need a special ZV (Zoomed Video) CardBus PCMCIA card. It feeds NTSC video directly to the screen. Zoomed Video technology allegedly will bring full laptop screen video conferencing to laptops. See Zoom Video Port.

Zoomed Video Port

ZVP. Allows specially designed PC cards to send signals directly to the computer's video adapter bypassing the system processor and data bus.This allows full screen video to run at full speed freeing up the processor for other tasks . A PCMCIA standard which adapts the PC Card slot to allow the insertion of a ZV Port Card. Inserting a ZV Port Card establishes direct communications between the PC Card controller and the audio and video controllers, allowing large amounts of multimedia data to bypass the CPU or systems bus. The ZV Port standards makes full screen, full motion video accessible to the notebook computer user .

Zulu Time

Military terminology for Coordinated Universal Time (UTC), which has replaced Greenwich Mean Time (GMT) as the international clock reference. "Z" (phonetically "Zulu") refers to the time at the prime meridian in Greenwich, England. The U.S. time zones are Eastern ("R", "Romeo); Central ("S", "Sierra"); Mountain ("T", "Tango"); Pacific("U", "Uniform"); Alaska ("V", "Victor"), and Hawaii ("W", "William"). See also GMT and UCT.


Zone Usage Measured. Usage charges for calls that aren't quite local, but aren't quite long distance, either. ZUM charges are for calls to Central Office prefixes that are not within your local calling area. ZUM charges are a way for your friendly ILEC (Incumbent Local Exchange Carrier) to make extra money.


See Zoomed Video. See the next definition.

ZV Port

Short for zoomed video port, a port that enables data to be transferred directly from a PC Card to a VGA controller. The port is actually a connection to a zoomed video bus. This new bus was designed by the PCMCIA to enable notebook computers to connect to real-time multimedia devices such as video cameras . The first notebook computers with the ZV port arrived in late 1996.


Zentralamt fur Zulassungen im Fernmeldewessen (Approval Authority ” Germany).

Newton[ap]s Telecom Dictionary
Newton[ap]s Telecom Dictionary
ISBN: 979387345
Year: 2004
Pages: 133

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