In Australia, a pastoral call is a call made between basic telephone services which are either: in the same extended charging zone, in the same community access zone but with one service in an extended access zone, or in the same community access zone but with one service in an standard charging zone adjacent to one or more extended charging zones. Telstra (the dominant carrier in Australia) defines extended charging zones, community access zones and standard charging zones. For your enlightenment, I did not make the above up. I copied it from an Australian government report that purports to explain the Australian phone system. Good luck.
See Port Address Translation.
A small addition to the original software code, written to bypass or correct a problem. See Y2K.
To connect circuits temporarily with a jack and a cable. Patching is typically done on devices called PATCH BAYS, PATCHBOARDS or PATCH PANELS. See also Patching.
An RFID definition. A small square antenna made from a solid piece of metal or foil.
A collection of hardware put together in such a way that circuits appear on jacks and can be connected together for transmission, monitoring and testing. See Patch Panel.
A short length of wire or fiber cable with connectors on each end, a patch cord is used to join communication circuits at a cross connect point. A patch cord is much like an extension cord. In the context of telephony, it's much like the cords that the telephone operators in the early 1900s used to use on a manual switchboard. They would use a short cord with a plug on each end to connect to one jack for the calling party and another for the called party. Thereby, a unique physical and electrical path was established. When the call was concluded, the operator unplugged the cord from the jacks. The next call involved a repeat of the same process, and so on. Patch cords still have a very important purpose where semi-permanent and highly reliable connections must be made between links. See also Cross Connect.
A device in which temporary connections can be made between incoming lines and outgoing lines. It is used for modifying or reconfiguring a communications system or for connecting devices such as test instruments to specific lines. A patch panel differs from a distribution frame in that the connections on a distribution frame are intended to be permanent. See also Cross-Connect and DACS.
Same as a patch bay. See Patch Bay.
Means of connecting circuits via cords and connectors that can be easily disconnected and reconnected at another point. May be accomplished by using modular cords connected between jack fields or by patch cord assemblies that plug onto connecting blocks.
A patch panel in which multiple pair lines can be interconnected as a group .
A patent is a grant, limited in time and technological extent, of the right to exclude others from making, using or selling the invention. The temporal extent of a U.S. patent (other countries ' laws are similar) is usually at least 17 years . The technological extent of protection is defined by the claims of the patent. Claims are allowed only after examination by a technically degreed examiner of the Patent and Trademark Office to ensure that an opinion is defined that is nonobvious with respect to the predecessor technology, or "prior art." Having a patent does not confer the right to manufacture the thing claimed; others may have dominating patents. Independent invention is no defense to a charge of infringement. Rights in an invention made by an employee in performance of his normal duties belong to the employer in most states, even without a written agreement.
The claims made for the invention in applying for the patent may define a "process, machine, manufacture, or composition of matter". The great software patent controversy has largely been settled with the understanding that software is normally best claimed as a process, although sometimes claims usefully intermix hardware and software. The only software that remains per se unpatentable is that defining a process operating on pure numbers , that is, not tied to any particular end use, control process, or the like. A Fast Fourier Transform algorithm would thus not be patentable although an unobvious method of using it to (say) remove harmonic noise from a signal might be.
Patent serve several functions. A patent is a technical disclosure, forming part of the scientific literature, as the invention must be described with sufficient particularity that others can use it "without undue experimentation." The idea is that the inventor is given a limited monopoly in exchange for the benefit to the public of having inventions made and disclosed. A patent is also a legal document, in that the claims define the exact extent of protection. The third function of a patent is to market the invention.
A well-written patent explains the underlying technical problem, the deficiencies of the prior art, and the way in which the invention solves these problems, in clear and non-technical language. Only then can a federal judge or jury, or the CEO of a competitor being asked to pay damages, be expected to understand the relation of the claimed invention to the prior art and the allegedly infringing product. See also Intellectual Property, Patent Troll and Prior Art.
A company that buys a patent, often from a bankrupt firm, and then sues another company by claiming that one of its products infringes on their newly-pur- chased patent.
The physical route a telecommunications signal follows from transmitter to receiver. The path includes all circuits and all intermediate devices, such as switches and routers.
In through-the-air microwave transmission, you must find a line-of- sight path, free of obstruction of buildings , trees, other microwave towers , etc. In microwave line-of-sight communications, the perpendicular distance from the radio-beam axis to obstructions such as trees, buildings, or terrain. The required path clearance is usually expressed , for a particular k-factor, as some fraction of the first Fresnel zone radius. That's the technical definition of path clearance.
A bound on the combined value of a topology metric along a path for a specific connection.
IBM Corp.'s implementation of what is normally referred to as the network layer in the International Standards Organization Open Systems Interconnect (OSI) layered network architecture.
In IBM's SNA, the network processing layer that handles primarily the routing of data units as they travel through the network and manages shared link resources.
PDV. An indexed (i.e., relative) measurement of propagation delay in communications circuits. The point of reference is that of optical fiber, which has a designated PDV of 1.0. CAT 5 copper wire has a PDV of 1.11, meaning that the signal takes 111% as long to travel the same distance through the transmission medium. CAT 3 wire has a PDV of 1.14. A PDV of 1.11 may seem insignificant, since that translates into 200,000 kilometers per second, but it can be very important in the context of high-speed data transmission protocols. See also Propagation Delay.
The power loss which occurs when radio waves move through space along specific paths.
A method by which the normal physical path set up in support of a call is replaced by another path which is more efficient. Path replacement is intended to overcome the inefficiencies of tromboning associated with a preselected path which normally would be used to connect a call. See also Tromboning.
A technique for providing redundancy in a SONET network. Path switched rings use 2 fibers, with both transmitting simultaneously in both directions. Through this technique, a failure in a SONET ring will not prevent devices from communicating, as they transmit and receive in both clockwise and counter-clockwise directions. All devices monitor both rings, locking in on the better signal, thereby improving on the inherently high quality of fiber optic transmission. See Line Switched Ring.
One of two tables contained in the volume descriptor of a CD-ROM and which comprises the file management for the disc. The path table contains the names of all directories on the disc and is the latest fastest way to access a directory that is not close to the root directory. Access to directory and path tables is handled automatically by the Virtual CD Changer Driver.
A Path Vector (PV) routing protocol, such as BGP (Border Gateway Protocol), is used by routers to select a path across a network. Path Vector protocols are similar to Distance Vector (DV) protocols, but with a key difference. A Distance Vector protocol selects the best path between two border routers based on the hop count (i.e., number of routers transversed). A border router (BR) running a Path Vector routing protocol advertises the destinations it can reach to its neighboring border routers. Further, a path vector protocol pairs each of those destinations with the attributes of the path to it. The attributes include the number of hops (i.e., routers transversed) and the administrative "distance." The attribute of administrative distance weights routes learned from IBGP (Internal BGP) more heavily than those learned from EBGP (External BGP). In other words, interior routes are weighted more heavily (and preferred) than are exterior routes, which cross network domains. Note, however, that BGP does not take into account factors such as link speed or network load. See also BGP, Distance Vector Routing Protocol, Link State Protocol, Policy Routing Protocol, Router, and Static Routing.
A facility for routing communications cables.
A small element of human intelligence. The ability to recognize and match visual patterns. (Auditory pattern recognition is the ability to recognize spoken words.) Pattern recognition basically works by having the computer seek out particular attributes of the character ( assuming it's pattern recognition for reading words) and then having the computer compare what it finds to what's in its database of patterns. By a process of breaking down letters into curves and lines, and by a process of elimination , the computer can figure out what it's seeing. As Forbes said, "think of pattern recognition as a kind of super detective, a tireless if unimaginative collector of clues, distinguished not by brilliance, but by ceaseless legwork.
This feature on some phone systems which, by hitting #, inserts a 1.5 second delay in a speed dialing sequence. This way you can program your phone to call a main number, wait a few seconds for the machine to answer and then punch out your person's extension.
Private Automatic eXchange. Typically an intercom system not joined to the public telephone system. PAXs are more common in Europe, where is it common for business people to have two phones on their desk ” one for internal intercom calls and one for external calls.
PPV. A television service which allows viewers to select movies or other programming for viewing for a fee which is charged to their bill. See Impulse Pay Per View.
From the perspective of a network service provider: of a data field, block or stream being processed or transported, the part that represents information useful to the user, as opposed to system overhead information. Payload includes user information and may include such additional information as user - requested network management and accounting information. In Sonet, the STS-1 signal is divided into a transport overhead section and an information payload section (similar to signaling and data). See SPE (Synchronous Payload Envelope) for a description of what would be found in the payload.
The activity carried out by a computer virus when it is activated by a triggering event. Depending on the virus, the payload may be as benign as putting a message on your screen or as destructive as erasing your hard disk or scrambling your data.
Payload Pointers indicate the beginning of the synchronous payload envelope. See Payload.
PTI. A three-bit field in the ATM cell header that indicates the type of information being carried in the payload. The PTI is used to distinguish between cells carrying user data and those carrying service information such as call set-up and call termination.
A business term used to predict the amount of time it will take for an investment such as a switch, new computers, new telephones, and applications to pay for itself in increased sales, reduced costs, or a combination.
Also known as a paystation, a payphone used to be just a public phone that accepted only coins . Now payphones can be coinless and can read credit cards. They also now commonly include keyboards, computer screens, and dataports for plugging in fax machines and laptop computers. Sadly, pay phones are disappearing rapidly , largely having been rendered obsolete by cell phones. Also, residents of some neighborhoods have pushed for their removal, associating them with such undesirable activities as drug-dealing. Further, they are expensive to operate and maintain, as the coins much be collected (assuming that they haven't been stolen), and the phones and phone booths are subject to acts of theft and vandalism. As of the end of 1999, only 2.5 million payphones remained in the U.S.; approximately 300,000 had been removed during the previous two years. Some of the ILECs (Incumbent Local Exchange Carriers), the primary operators of payphones, have announced their intentions to sell their remaining payphones to independent operators.
The payphone was invented by William Gray, an American whose previous inventions included the inflatable chest protector for baseball players. Mr. Gray's first phone lacked a dial. Its instructions read:
"Call Central in the usual manner. When told by the operator, drop coin in proper channel and push plunger down."
There are several different ways in which payphones can work. In today's nomenclature , Mr. Gray's original phone is known as a postpay coin phone. Postpay payphones require that you pay for the call only after it is completed. Semi-postpay payphones allow you to dial the number first, requiring that you pay with coins after the called party answers. Both postpay and semi-postpay phones were used for many years for local calling in rural areas, but now are considered to be obsolete for obvious reasons. Prepay pay- phones require that you pay for calls before they can be dialed . Virtually all contemporary payphones are prepay.
Calls are paid for after they are completed, typically with a credit card or calling card, etc. See Payphone.
At a coin phone, calls must be paid for before they can be dialed. Virtually all local calls are prepay. See Payphone.
Referred to as Customer Owned Coin Operated Telephone Companies (COCOTs). Private payphones are installed and maintained by companies other than the LECs (Local Exchange Carriers) that traditionally provided the service. Be very careful if someone calls you with an offer to invest in private payphones. According to the North American Securities Administrators Association (NASAA), payphone scams were among the top 10 investment fraud schemes in the U.S. in 2000. Such scams generally are characterized as Ponzi Schemes. See also Ponzi Scheme and Scam.
A coin phone installed in a "public" place. The owner of the property may get a commission for allowing the service provider to install it. See also Payphone-Semi-Public.
A coin phone installed for public use but installed in a "semi-public" place, such as a restaurant or bar. The proprietor of the establishment is obliged to guarantee that the service provider will realize a minimum amount of revenue from the phone. However, the service provider typically will not pay a commission on this type of phone. What is a "public" and what is a "semi-public" phone is a decision made by the local telephone company for whatever reason it chooses. The pay phone business is rapidly deregulating. It is now legal to own your own payphone.
Calls are paid for after they are completed, typically with a credit or calling card, etc.
Calls must be paid for before they can be dialed. Virtually all local calls are prepay.
A coin phone installed in a "public" place. The phone company is totally responsible for its installation. The phone company will typically pay someone ” the city, the bus station owner ” a commission on the calls made from this phone. See Paystation, Semi-Public.
A coin phone installed for public use but installed in a "semi-private" place, such as a restaurant or bar. The proprietor of the establishment is obliged to guarantee that the phone company will receive a minimum amount of money out of the phone. The phone company will typically not pay a commission on this type of phone and takes all the money in the coin box for itself. What is a "Public" and what is a "Semi- Public" phone is a decision made by the local telephone company for whatever reasons it chooses. The pay phone business is rapidly deregulating. So the rules are changing. And it is now legal to own your own payphone.
Petabyte. See Petabyte.
See Polarization Beam Combiner.
Policy-Based Network Management. See Policy-Based Networking.
Personal Base Station. A PCS (Personal Communications System) term. A PCS subscriber might use a "High-Tier" PCS service, which effectively is cellular service using PCS frequencies. When at home, the PCS set acts as a cordless phone, establishing a wireless link to the PBS. When in close enough proximity to have sufficient signal strength, the PBS takes over from the PCS carrier's cell site. All PBS calls then are routed over the landline PSTN, thereby avoiding cellular usage charges. In a business environment using a PCS wireless office system, the PCS set and the wireless controllers establish the same relationship.
Private Branch eXchange. A private (i.e. you, as against the phone company owns it), branch (meaning it is a small phone company central office), exchange (a central office was originally called a public exchange, or simply an exchange). In other words, a PBX is a small version of the phone company's larger central switching office. A PBX is also called a Private Automatic Branch Exchange, though that has now become an obsolete term. In the very old days, you called the operator to make an external call, except in Europe. Then later someone made a phone system that you simply dialed nine (or another digit ” in Europe it's often zero), got a second dial tone and dialed some more digits to dial out, locally or long distance. So, the early name of Private Branch Exchange (which needed an operator) became Private AUTOMATIC Branch Exchange (which didn't need an operator). Now, all PBXs are automatic. And now they're all called PBXs, except overseas where they still have PBXs that are not automatic.
At the time of the Carterfone decision in the summer of 1968, PBXs were electromechanical step-by-step monsters. They were 100% the monopoly of the local phone company. AT&T was the major manufacturer with over 90% of all the PBXs in the U.S. GTE was next. But the Carterfone decision allowed anyone to make and sell a PBX. And the resulting inflow of manufacturers and outflow of innovation caused PBXs to go through five, six or seven generations ” depending on which guru you listen to. (See my definition for GENERATIONS in this dictionary). Anyway, by the fall of 1991, PBXs were thoroughly digital, very reliable, and very full featured. There wasn't much you couldn't do with them. They had oodles of features. You could combine them and make your company a mini-net- work. And you could buy electronic phones that made getting to all the features that much easier. Sadly, by the late 1980s the manufacturers seemed to have finished innovating and were into price cutting. As a result, the secondary market in telephone systems was booming. Fortunately, that isn't the end of the story. For some of the manufacturers in the late 1980s figured that if they opened their PBXs' architecture to outside computers, their customers could realize some significant benefits. (You must remember that up until this time, PBXs were one of the last remaining special purpose computers that had totally closed architecture. No one else could program them other than their makers .) Some of the benefits customers could realize from open architecture included:
Simultaneous voice call and data screen transfer.
Automated dial-outs from computer databases of phone numbers and automatic transfers to idle operators.
Transfers to experts based on responses to questions, not on phone numbers. And a million more benefits.
There are two alternatives to getting a PBX. You can buy the newer , open more full- featured version called a communications server. Or you can subscribe to your local telephone company's Centrex service. For a long explanation on Centrex and its benefits, see Centrex. Here are some of the benefits of a PBX versus Centrex:
Ownership. Once you've paid for it, you own it. There are obvious financial and tax benefits.
Flexibility. A PBX is a far more flexible than a central office based Centrex. A PBX has more features. You can change them faster. You can expand faster. Drop another card in, plug some phones in, do your programming and bingo you're live.
Centrex benefits. You can always put Centrex lines behind a PBX and get the advantages of both. In some towns, Centrex lines are cheaper than PBX lines. So buy Centrex lines and put them behind your PBX. Make sure you don't pay for Centrex features your PBX already has. (It has most.)
PBX phones. There are really no Centrex phones ” other than a few Centrex consoles. If you want to take advantage of Centrex features, you have to punch in cumbersome, difficult-to-remember codes on typically single line phones. PBXs have electronic phones, often with screens and dedicated buttons . They're usually a lot easier to work. A lot easier to transfer a call. Conference another, etc. A lot more productive.
Footprint savings. Modern PBXs take up room, more than Centrex. But the space they take up is far less than it used to be. PBXs are getting smaller.
Voice Processing/Automated Attendants. Centrex's DID (Direct Inward Dialing) feature was always pushed as a big "plus." You saved operators. However, you can now do operator-saving things with PC-based voice processing and automated attendants you could- n't do five years ago. These things work better with on-site standalone PBXs than with distant , central office based Centrex. Moreover, virtually every PBX in existence today supports DID. You can dial directly into PBXs and reach someone at their desk just as easily as you can dial directly using Centrex.
Open Architecture. Most PBXs have open architecture. See OAI for the benefits. Central offices don't.
Good Reliability. There have been sufficient central office crashes and sufficient improvement in the reliability of PBXs that you could happily argue that the two are on a par with each other today. Both are equally reliable, or unreliable. The only caveat, of course, is that you back your PBX up with sufficient batteries that it will last a decent power outage . Of course, that assumes that your people will be prepared to hang around and answer the phones during a blackout .
Expansion. Central offices are big. Allegedly you can grow your lines to whatever size you want. In contrast, PBXs have finite growth. It's true about PBXs. But it's equally true about central offices. I've personally heard too many stories about central office line shortages to believe in the nonsense about "infinite Centrex" growth. Fact is central offices grow out, just like PBXs. Given the tight economy of recent years, local phone companies have not been buying the central offices they should have. And they have been filling central offices up a little too tight for my taste.
Technological obsolescence. Allegedly central offices are upgraded faster than PBXs and therefore are always up to date technologically. It's nonsense. The life cycle of a typical central office was 40 years until recently. It's now around 20 years. Think of what's happened to PCs in the past 10 years ” the IBM PC debuted only in 1981 ” and you can imagine how obsolete many of the nation's central offices are.
PBX central office (CO) trunks connect the PBX switch to the central office serving the PBX location. The trunks appear as station lines at the central office equipment.
Telephony Services (also called TSAPI) is software which AT&T (now Lucent) invented to run on NetWare servers and allow those servers to communicate with PBXs. According to a presentation made by Oliver Tavakoli of Novell in late August, 1994, "The purpose of TSAPI is to make it easier for developers to create telephony applications. Given the broad scope of TSAPI and the number of ways in which PBX vendors can package and deliver solutions, applications being developed against TSAPI are unlikely to work with a large cross-section of PBXs. This is particularly problematic for application developers wishing to add simple telephony features to a product that is not telephony centric. In order to spur the growth of CTI application development, Novell has created 'profiles' that are placed on top of TSAPI. The profiles listed in this document (i.e. the speech) are based on documents created by other organizations:
"- A NOTA document entitled PABX Driver NLM Conference Meeting and Draft Recommendations dated July 20th, 1994.
"- An ECMA document entitled 'Technical report on CSTA Scenarios/Second Draft' dated July 1994.
"Each profile is made up of the following components : Functions (and matching confirmation events) included in the profile; unsolicited events that may be encountered in the event flow scenarios in the profile; event flow scenarios that attempt to describe what should occur in the common scenarios encountered when using the functions in the profile.
"Group A Profile: Using the functions and event flows in the Group A profile, an application should be able to: provide "screen pops" to the end user; make outbound calls originating at an end user's device; provide hands-free operation for answering the phone and making calls (assuming the PBX and end user's device support hands-free operation)
"Group B Profile: Using the functions and event flows in the Group B profile, an application should be able to: perform operations involving two calls on a single device (the connection to one of the calls is in the held state); perform operations involving more than two parties on the same call; obtain information and unsolicited events from a call-centric view (as opposed to a device-centric view).
"Group C Profile: Using the functions and event flows in the Group C profile, an application should be able to: perform the rest of the telephony functions usually done from a phone ” pickup, group pickup, call completion and perform more sophisticated monitoring functions.
(There is apparently no Group D profile.) "Group E Profile: Using the functions in the Group E ('E' for Environmental) profile, an application should be able to: activate and deactivate features of a device, query the state of features on a device, query the generic information about a device."
Once the profiles are finalized, they will be incorporated into Novell's PBX Driver certification process; groups supported by the driver will be included in literature describing all certified drivers. See also Netware Telephony Services.
A telephone phone line connected to a PBX.
Same as Toll Fraud.
See Generations, PBX.
A loose term to mean joining the PBX to any number of outside computer based gadgets and services, from voice mail to call accounting. To make voice mail integrate into PBXs, you minimally need the ability to provide a message waiting indicator (light or stutter dial-tone) at the user's phone when a message is received, and to forward a call to the user's mailbox when a call is sent to the recipient and they are on the phone or do not answer (forward on busy or ring no answer). This requires PBX "integration." Most PBX integrations provide the attached voice mail system call data that includes the calling phone number, the number of the caller, why the call was presented (such as forwarded on busy, or ring no answer), to pass message waiting on or off indications . PBX integration data may be implemented in-band or out-of- band on a separate link, most often a serial link. Some PBXs "integrate" with outside equipment better than others.
PBXs do things differently. To make a conference call, one PBX's phone may put the caller on hold automatically, while another may insist that you put that person on hold manually and then dial the next person to join the conference call. As Novell in the fall of 1994 attempted to get as many PBXs to conform to TSAPI, it discovered that PBX features often work very differently. So it decided to categorize PBXs and their features. This, it called, PBX profiles. The idea being that Profile A would contain the most common, easy-to-integrate-to-TSAPI features. B would contain the second most common, etc. Novell also calls PBX Profiles PBX Driver Profiles. See PBX Driver Profiles for a much bigger explanation.
A transmission path extending from the station (phone instrument) location to the switching equipment.
A tie line between two PBX's, permitting extensions in one PBX to be connected to extensions in the other without having to dial through the public switched network. See also OPX and OPS, which are different and are lines between PBXs and distant extensions, not tie lines between PBXs.
A circuit which connects the PBX to the local telephone company's central office switching center or other switching system center.
Personal Computer. See Personal Computer for a bigger explanation.
AT&T uses this acronym for "project coordinator ".
A Sun Microsystems term, Part of Solaris' Server Suite. Automates and centralizes PC network administration.
See also Handset Management.
A memory or I/O card compatible with the PCMCIA PC Card Standard. In short, PC Cards are a new name for PCMCIA cards. For a much fuller definition, see PCMCIA, which stands for the Personal Computer Memory Card International Association.
There are two ways you can organize a computer to control telephone calls on an office telephone system. One way is to join a file server on a local area network to a phone system. Commands to move calls around are passed from the desktop PC over the LAN to the server and then to the phone system via the cable connection between the server and the system. A second way to get a computer to control phone calls is through a connection at the desktop. This is called PC Centric. There are two ways you can do this. The first is to join the desktop phone to the computer with a cable. This is often done via the PC's serial port connecting via cable to the phone's data communications port (if it has one ” if it doesn't, you get one). The second way to be PC Centric is by simply replacing the standalone phone with a board that emulates in a phone and drop it into the PC's bus.
This generic term is used to describe a handheld PC that acts as a satellite, companion, or backup to a user's main PC. It contains communications. It is different to a HPC, Handheld PC. It is also different to a PDA. PDAs can generally be classified as stand-alone, keyboardless devices with proprietary user interfaces and applications that require pen-based entry and navigation.
IBM's first LAN (Local Area Network).
Another term for Computer Telephony. See Computer Telephony.
The plural of the word PC, according to the New York Times. However, every other computer and general magazine spells them PCs. And that's the spelling which this dictionary writer prefers also.
Premises Cabling Association. A association in Great Britain.
Protective Connecting Arrangement. A device that AT&T and members of the Bell System insisted be connected between a telecommunications device (like a phone) that wasn't made and sold by AT&T and a phone line provided by a local Bell operating phone company. Many years later, the PCAs were found by the FCC to be totally unnecessary and AT&T and members of the Bell System were ordered to refund all payments received for rental of PCAs. The Bell System insisted on the PCAs as a way of protecting AT&T's effective monopoly of telecommunications equipment. See also Voice Connecting Arrangement.
Printed Circuit Board.
Personal Companion Computer. What other companies call a PDA (Personal Digital Assistant), Intel calls a PCC. A PCC or PDA is meant to have significant telecommunications abilities ” including wired and wireless. See PDA.
Portable Computer and Communications Association. An association formed to provide a forum for exchange of information between the computer and communications industries. PCCA has developed standards for wireless and mobile computing. www.pcca.org.
The new PCCA AT command set for wireless modems contains well-defined commands for obtaining link status information.See PCCA and www.pcca.org.
See Post Completion Discrepancy.
Physical Control Fields. The AC (Access Control) and FC (Frame Control) bytes in a Token Ring header.
Paging CHannel. Specified in IS-136, PCH carries signaling information for set up and delivery of paging messages from the cell site to the user terminal equipment. PCH is a logical subchannel of SPACH (SMS (Short Message Service) point-to-point messaging, Paging, and Access response CHannel), which is a logical channel of the DCCH (Digital Control CHannel), a signaling and control channel which is employed in cellular systems based on TDMA (Time Division Multiple Access). The DCCH operates on a set of frequencies separate from those used to support cellular conversations. See also DCCH, IS-136, PAGING, SPACH and TDMA.
Protocol Control Information. The protocol information added by an OSI entity to the service data unit passed down from the layer above, all together forming a Protocol Data Unit (PDU).
Peripheral Component Interconnect. A 32-bit local bus inside a PC or a Mac, PCI was designed by Intel for the PC. According to Intel's original specifications, it can transfer data between the PC's main microprocessor (its CPU) and peripherals (hard disks, video adapters, etc.) at up to 132 megabytes per second, compared to only five megabytes per second for the original ISA bus. The PCI design calls for one 64-bit bus running at 66 MHz, and additional busses are either 32-bit running at 66 MHz or 64-bit running at 33 MHz. The maximum amount of data transfer that the PCI design currently will support between the processor and peripherals is 532 MB (MegaBytes, or millions of bytes) per second. The newer PCI-X bus is much faster. PCI is one of two widely adopted local-bus standards. The other, the VL-Bus, is primarily used in 486 PCs. See also CompactPCI, PCI-X, and VLB.
Peripheral Component Interconnect-Extended. An extension of the original PCI design, PCI-X increases the internal bus speed from 66 MHz to 133 MHz. PCI-X calls for one 64-bit bus to run at 133 MHz, with the others running at 66 MHz. Thereby, PCI-X supports a maximum rate of data exchange of 1.06 GB (GigaBytes, or billions of bytes) per second. This level of bandwidth is critical for servers running Gigabit Ethernet, Fibre Channel, and other high-speed networking applications. PCI-X was developed by IBM, HP and Compaq, and was submitted to the PCI SIG (PCI Special Interest Group) of the (ACM) Association for Computing Machinery) in 1998. See also PCI.
Personal Communications Industry Association. A leading association of providers of wireless voice and data communications services. PCIA member companies include PCS licensees and others in the cellular, paging, ESMR, SMR, mobile data, cable, computing, manufacturing, and local and interexchange sectors of the industry. www.pcia.com.
Hewlett-Packard's Printer Control Language, developed by HP in 1984 as a way for the then-new PC to communicate with a new breed of laser printers ” the HP LaserJet printer. HP's PCL language is now the de facto industry standard for PC printing. Most of the printers in the world today are equipped with PCL or a PCL-compatible language. PCL allows the type of sophisticated page creation generally referred to as "laser quality output." PCL supports such advanced features as fully scalable typefaces and rotation of text. PCL defines a standard set of commands enabling applications to communicate with HP or HP-compatible printers. PCL has become a de facto standard for laser and ink jet printers and is supported by virtually all printer manufacturers. On April 8, 1996 HP announced PCL 6 which it billed as "the next generation" of HP Printer Control Language). HP said that PCL 6 includes font synthesis technology for true what-you-see-is-what-you-get (WYSIWYG) printing and better document fidelity. PCL 6 commands were designed by HP to closely match Microsoft Windows GDI (Graphical Direct Interface) commands.
Product Compute-Module Load.
Packet Competitive Local Exchange Carrier. Covad invented this term for a CLEC who provides dedicated high-speed digital communications services using DSL technology to Internet Service Providers ("ISPs") and corporate enterprise customers.
Pulse Code Modulation. The most common method of encoding an analog voice signal into a digital bit stream. First, the amplitude of the voice conversation is sampled. This is called PAM, Pulse Amplitude Modulation. This PAM sample is then coded (quantized) into a binary (digital) number. This digital number consists of zeros and ones. The voice signal can then be switched, transmitted and stored digitally. There are three basic advantages to PCM voice. They are the three basic advantages of digital switching and transmission. First, it is less expensive to switch and transmit a digital signal. Second, by making an analog voice signal into a digital signal, you can interleave it with other digital signals ” such as those from computers or facsimile machines. Third, a voice signal that is switched and transmitted end-to-end in a digital format will usually come through "cleaner," i.e. have less noise, than one transmitted and switched in analog. The reason is simple: An electrical signal loses strength over a distance. It must then be amplified. In analog transmission, everything is amplified, including the noise and static the signal has collected along the way. In digital transmission, the signal is "regenerated," i.e. put back together again, by comparing the incoming signal to a logical question: Is it a one or a zero? Then, the signal is regenerated, amplified and sent along its way.
PCM refers to a technique of digitization. It does not refer to a universally accepted standard of digitizing voice. The most common PCM method is to sample a voice conversation at 8000 times a seconds. The theory is that if the sampling is at least twice the highest frequency on the channel, then the result sounds OK. Thus, the highest frequency on a voice phone line is 4,000 Hertz. So one must sample it at 8,000 times a second. Many PCM digital voice conversations are typically put on one communications channel. In North America, the most typical channel is called the T-1 (also spelled T1). It places 24 voice conversations on two pairs of copper wires (one for receiving and one for transmitting). It contains 8000 frames each of 8 bits of 24 voice channels plus one framing (synchronizing bit) bit which equals 1.544 Mbps, i.e. 8000 x (8 x 24 + 1) equals 1.544 megabits.
Countries outside of the United States and North America use a different scheme for multiplexing voice conversations. It is based not on 24 voice channels, but on 32. This scheme keeps two of the 32 channels for control, actually transmitting 30 voice conversations at a data rate of 2.048 Mbps. The European system is calculated as 8 bits x 32 channels x 8000 frames per second. European PCM multiplexing is not compatible with North American multiplexing. The two systems cannot be directly connected. Some PBXs in the U.S. conform to the U.S. standard only. Some (very few) conform to both. Both the European and North American T-1 "standards" have now been accepted as ISDN "standards." In addition to PCM, there are many other ways of digitally encoding voice. PCM remains the most common. See also ADPCM, DPCM, Nyquist Theorem, Shannon's Law, T-1 and Voice Compression.
There are three levels in PCM voice transmission synchronization:
Bit Level Synch ” operating the transmitter and receiver at the same bit rate so the bits are not lost.
Frame Level Synch ” phase alignment between the transmitter and receiver so the beginning of the frame can be identified.
Time Slot Synch ” phase alignment between the transmitter and receiver so the time slots are lined up for information retrieval.
Short name of international 2.048 Mbps T-1 (also known as E1) service derived from the fact that 30 channels are available for 64 Kbps digitized voice each using pulse code modulation (PCM).
The Personal Computer Memory Card International Association (an awful mouthful) standardizes credit-card size packages for memory and input/output (modems, LAN cards, etc.) for computers, laptops, palmtops, etc. There are three physical standards for PCMCIA cards ” Type I, II, and III and undefined standard called Type IV, which only Toshiba has at this moment. The cards are 69.2 millimeters (3.37 inches) long x 51.46 millimeters (2.126 inches) wide. All three types use the same 68 female pin edge connector for attachment to the computer, and differ only in thickness. The thickness for Type I, Type II and Type III are 3.3, 5.0, 10.5 millimeters respectively. Toshiba's Type IV is 16 mm. A Type I PC Card is typically used for various types of memory enhancements, including RAM, FLASH memory, one-time programmable (OTP) memory, and electronically erasable programmable read only memory (EEPROM). A Type II PC Card (the most common) is typically used for input/output such as modem, LANs, host communications and SCSI device connection. A Type III PC Card is twice the thickness of the Type II and is typically used for I/O features that require a larger size, such as rotating mass storage devices (removable hard disk drives ) and radio communication devices. Since Type I, Type II and Type III Cards all use the same interface, the size of the card chosen for the application is dependent on the miniaturization of the technology to be implemented.
PCMCIA's first standards were issued in September, 1991. The idea is that small computers will use these cards for modems, fax cards, hard disks, LAN connections, Ethernet connections, SCSI device connections, etc. A PCMCIA card is, in most cases, the only way to get to a laptop's bus without attaching a docking station. In terms of performance, the bus is comparable, but not equivalent to the ISA bus on desktops. The PCMCIA bus is 8 bits wide and does not allow for direct memory access (DMA) transfers or bus mastering. This means, for example, that you can't equip a laptop with a sound blaster compatible PCMCIA card, since it requires DMA transfers. A new spec called PCMCIA v3 (now called CardBus) calls for a number of improvements, including 32-bit data paths, DMA, bus mastering and significant improvements in speed with the bus as fast as the PCI bus.
PCMCIA standards exist so others can make these cards. Some computers ” like some pre-summer 1991 notebooks and laptops from Compaq and Toshiba ” don't comply because these computers were released before the standards were released. The PCMCIA v2.0 standard contains a software specification for XIP, the "eXecute In Place" mechanism that maps application software stored on the PCMCIA card into the system address space. This means application software will run directly from the card, start faster and not require precious RAM from the host computer.
One key element of the PCMCIA software architecture are Socket Services and Card Services. Socket Services is a BIOS level software interface that provides a way to access the PCMCIA sockets (slots) of a computer. Socket Services identifies how many sockets are in your computer system and detects the insertion or removal of a PC Card while the system is powered on. Socket Services is part of the PCMCIA Specification and interfaces with Card Services. Card Services is a software management interface that allows the allocation of system resources (such as memory and interrupts) automatically, once the Socket Services detects that a PC Card has been added. Card Services also releases these resources when the PC Card has been removed. Card Services also provides you with an interface to higher level software to load any needed hardware drivers.
The combination of PC Card hardware, Card Services software and Socket Services software provides an almost "plug-and-play" capability in the portable computing environment. Once the software has been installed, it is theoretically possible to add and remove PC Cards without powering off the system. But this is theory. And in practice, it has worked only intermittently for this writer. It doesn't work for network cards. It's meant to be possible, for example, to insert a modem PCMCIA Card to access another computer system, download information into the portable computer's memory, remove the modem PCMCIA Card, replace it with a flash PCMCIA Card, and store the downloaded information ” all while your portable computer is still powered on. Great theory.
The PCMCIA has around 300 members, including manufacturers of semiconductors, connectors, peripherals and systems, as well as BIOS and software developers and related industries. Members include Intel, IBM, Toshiba, Lotus, Epson and Fujitsu. The association is based in Sunnyvale, CA. 408-720-0107. It has an electronic bulletin board ” 408- 720-9388. Its standards are also recognized by the Japanese Electronic Industry Development Association (JEIDA). The Association publishes a free book listing all the manufacturers making cards which comply to their standards.
Advice in buying PCMCIA cards: PCMCIA standards are still being formed and are thus not truly standards. Check that cards you buy work in your machine. The manufacturer should have tested it in your machine. Don't assume compatibility. Check your socket and card services supports that card. It may not. Use " enabler " software instead. Avoid PCMCIA cards with "pigtails." They break. You lose them. Use PCMCIA cards with an "X-JACK." You can plug directly into a PCMCIA card with an X-JACK, or equivalent. If you have to buy a card with a pigtail, buy a second pigtail , just in case.
In 1994, the PCMCIA started calling its specs , PC Card. Some people said it was because many people claimed that PCMCIA stood for "People Can't Memorize Computer Industry Acronyms."
In the latter part of 1995, the PCMCIA came out with a new specification called CardBus which is a 32-bit bus, as against the present 16-bit cards. CardBus is an extension of the PCI bus. This means that new CardBus will support 132 Mbps, much faster than the present 8 Mbps. See CardBus for a full explanation of that new standard. See also Card Services, CardBus, PCMCIA standards, Socket Services, and Slot Sizes. www.pcmcia.org
The complete set of all of the PCMCIA PC Card Standards. It includes the PC Card Standard Release v2.01, Socket Services Specification Release v2.0, Card Services Specification Release v2.0, ATA Specification Release v1.01, AIMS Specification Release v1.0, and the Recommended Extensions Release v1.0. Standard v3.0 has been proposed. See PCMCIA. www.pcmcia.org
Personal Communications Network. Another name for GSM 1800 (it is also known as DCS 1800). It is used in Europe and Asia Pacific. Originally PCN was a type of wireless telephone system that would use light, inexpensive handheld handsets and communicate via low-power antennas. When it was originally conceived, PCN was primarily seen as an a city communications system, with far less range than cellular. Subscribers would be able to make and receive calls while they are traveling, as they can do today with cellular radio systems, but at a low price. One idea for PCN was to locate a PCN cell site (transmitter/receiver) in a residential community. When someone wanted a new phone line, they'd simply drop down to their local phone store, pick up a PCN portable phone and, by the time, they got back home, their frequency would be "switched on" and they'd be "live."
The original plans for PCN never materialized fully. However, the concept has been somewhat implemented in the forms of Personal Communications Service (PCS) and Wireless Local Loop (WLL). Now PCN is simply another name for GSM 1800. See also PCS, Personal Communications Network, Wireless Local Loop.
Point of Control and Observation: A place (point) within a testing environment where the occurrence of test events is to be controlled and observed as defined by the particular abstract test method used.
Post Call Processing.
Program Clock Reference: A timestamp that is inserted by the MPEG-2 encoder into the Transport Stream to aid the decoder in the recovering and tracking the encoder clock.
An ATM term. Peak Cell Rate: The Peak Cell Rate, in cells/sec, is the cell rate which the source may never exceed.
the plural of PCs, i.e. PCs.
Personal Communications Service. A low-powered, high-frequency alternative to traditional cellular, mainly in the US. Whereas cellular typically operates in the 800-900 MHz range, PCS operates in the 1.9 GHz range. The specific technologies include CDMA, Digital AMPS, and GSM 1900. PCS is a digital system making use of relatively cheap phones. The higher frequency range limits the cell size, as 1.9 GHz signals attenuate (weaken) more quickly than signals in 800-800 MHz range. The FCC awarded PCS licenses as follows:
"C-Block" Carrier - A 30 MHz PCS carrier serving a Basic Trading Area (BTA) in the frequency block 1895-1910 MHz paired with 1975-1990 MHz.
"D-Block" Carrier - A 10 MHz PCS carrier serving a Basic Trading Area (BTA) in the frequency block 1865-1870 MHz paired with 1945-1950 MHz.
"E-Block" Carrier - A 10 MHz PCS carrier serving a Basic Trading Area (BTA) in the frequency block 1885-1890 MHz paired with 1965-1970 MHz.
"F-Block" Carrier - A 10 MHz PCS carrier serving a Basic Trading Area (BTA) in the frequency block 1890-1895 MHz paired with 1970-1975 MHz. See Personal Communications Networks and Personal Communication Services.
Private Client Services. A term used in the investment banking for taking money from rich people and providing them investments that, hopefully, don't go down.
PCS 1900 is a GSM system offering 148 full-duplex voice channels per cell. The system operates in the 1.9-GHz band used in the United States and is now known as GSM 1900.
You run a CATV ” cable TV company. You have a wires strung all over the neighborhood. On one of your wires you attach a six foot by four foot by four box of electronics and three two feet attennae. Bingo, you're now a way station ” also called a cell site ” for a PCS cellular phone system. People who are PCS subscribers will talk and receive calls when they're close to your cell site. Calls come and go via your coax cable, up it to a landline connection point with the PCS carrier. You, the CATV company, get paid money for completing calls. See www.sanders.com/telecomm
Personal Computing System Architecture. A PC implementation of DECnet, that lets PCs work in a DECnet environment. PCSA is a network architecture defined and supported by Digital Equipment Corporation for the incorporation of personal computers into server- based networks.
Personal Communications Technology. A security protocol developed by Microsoft for online Web commerce and financial transactions. Transparent to the user, PCT provides authentication and encryption routines that complement credit-card based commerce on the World Wide Web. Internet Explorer, Microsoft's Web browser, makes use of PCT. See also Authentication and Encryption.
Personal Computer Terminal Adapter. A printed circuit card that slips into an IBM PC or PC compatible and allows that PC to be connected to the ISDN T-interface. See Personal Computer Terminal Adapter.
Portable Common Tool Environment.
Public Cordless Telephone Service. A Canadian digital cordless telephone service for residential, business and public use. For other variations of digital cordless telephone service, see CT1, CT2, CT2Plus, CT3, and DECT.
Personal Conferencing Work Group. www.gogcwg.org/pcwg.
PCX server software turns your PC into a graphics terminal front-end for Unix and X applications. Thus, your PC can display application output generated by remote X-based client applications.
Personal Digital Assistant. A consumer electronics gadget that looks like a palmtop computer. Unlike personal computers, PDAs perform specific tasks ” acting like an electronic diary, carry-along personal database, multimedia player, personal communicator, memo taker, calculator, alarm clock. The communications take place through wire to the PC, infrared link, modem and the phone or through wireless. Apple announced a PDA, which it has named Newton, and which now is MD (Manufacturer Discontinued). When I added this definition initially in the late fall of 1992, sales of PDAs weren't doing well and some wag in Silicon Valley called them Probably Disappointed Again. IBM prefers to call them Personal Communicators. General Magic preferred to called them PICs, Personal Intelligent Communicators, but then General Magic no longer exists. The biggest-selling PDA is the Palm Pilot, which was created by US Robotics, which subsequently was acquired by 3Com and then spun out as a separate company called Palm. See HPC.
PDA Industry Association. A not-for-profit industry organization formed to create a marketplace for PDAs by promoting the awareness of the usage of PDAs and hand-held technology, in general. Although the PDAia does not develop standards, it does act as a clearinghouse for standards being discussed. Working relationships exist with IrDA, PCCA, PCMCIA, and other associations which relate to the PDA market. www.pdaia.org.
Physical Delivery Access Unit. A gateway device that facilitates the delivery of messages (excluding probes and reports ) in physical form. This is an X.400 term.
Personal Digital Cellular: the 2G TDMA-based protocols used in Japan, owned by NTT DoCoMo. PDC services operate in the 800 and 1500 MHz bands. PDC is the Japanese equivalent of GSM but is incompatible with other systems. It is operated by NTT DoCoMo, as well as by all the other Japanese operators, but the technology was developed by NTT DoCoMo. Previously known as PHP (Personal HandyPhone) and Japanese Digital Cellular (JDC). See PHS.
See Primary Domain Controller.
Pacific Digital Cellular.
Portable Document Format. Let's say you produce a document. You use Microsoft Word to write it. On a PC, that program will produce a file with an extension .doc. You now want to send someone your document. You send them your file electronically. They will need a copy of Microsoft Word to read it. What happens if they don't have it? Tough. They're out of luck. They can't read it. Of course, you say Harry, everyone has Word. What happens if you write the document in QuarkXpress? Few people have copies of that program. Here's how to solve the problem. Write the program with whatever program you wish, then use a program called Adobe Acrobat to convert it to an Adobe Acrobat file, which typically ends with a .pdf. PDF is the file format for documents viewed and created by Adobe's Acrobat. The PDF file format was developed to allow everyone to be able to read documents ” even though they don't have the program which created them. Note that PDF files are read-only, which also means that the reader can't change them or otherwise steal your work. All you need to view a PDF document is a free version of Acrobat Reader, which is available from www.adobe.com. In order to create a PDF file, however, you must buy a copy of Adobe Acrobat. PDF documents can include text, colors, diagrams, and photographs. A PDF image of a document is very good quality. You can typically read even the smallest type. Here, according to Adobe, are some highlights of how documents are stored in PDF:
PDF represents text and graphics by using the imaging model of the PostScript language. Like a PostScript program, a PDF page description draws a page by placing "paint" on selected areas, which allows for device independence and resolution independence.
PDF files are extremely portable across diverse hardware and operating-system environments. PDF makes use of binary as well as ASCII-encoded data.
To reduce file size, PDF supports JPEG, CCITT Group 3, CCITT Group 4, ZIP, and LZW industry-standard compression filters.
PDF files contain information necessary for either displaying embedded fonts or for font substitution. A PDF file contains a font descriptor for each font used in the document. The font descriptor includes the font name, character metrics, and style information. If a font used in a document is available on the computer on which the document is viewed, or if it's embedded in the PDF file, it is used. If the font is not available or is not embedded, a special serif or sans serif Multiple Master font is used to simulate the font. This solution applies to Type 1 fonts and to fonts in the TrueType format. Symbol fonts and Expert fonts are automatically embedded or converted to graphics.
PDF font substitution does not cause documents to reformat . Substitute fonts created from serif and sans serif Multiple Master fonts retain the width and height of the original characters .
A PDF file contains a cross-reference table that can be used to locate and directly access pages and other important objects in the file. Because it uses this cross-reference table (called xref), the time needed to view a given page can be nearly independent of the total number of pages in a document.
PDF is designed to be extensible; that is, new features can easily be added to the file format through the plug-in architecture. (Plug-ins are software programs that add functionality to a base program such as Acrobat.)
Power Distribution Frame.