The Cable Center

This glossary of cable and telecommunications terms is intended to enhance your understanding of this dynamic industry. We are able to present this information with the generous help of CableLabs - consult their website for the most up-to-date information about cable technology.

0 - 9 | A | B | C | D | E | F | G | H | I | J | K | L | M | N | O | P | Q | R | S | T | U | V | W | X | Y | Z

Packet
A series of bits containing data and control information, including source and destination node addresses, formatted for transmission from one node to another.

Packet Identifier (PID)
A unique integer value used to identify elementary streams of a program in a single- or multi-program MPEG-2 stream.

Packet Internet Grouper (PING)
It is an Internet utility that verifies the connection between your computer and another IP address by sending packets to the address and checking for a response.

Packet Loop
A digital loop on which all information (signaling and user content) is encoded in packets.

Packet-switched network (PSN)
A PSN transports information by breaking up the bit stream into addressable digital “packets” that are transmitted independently and then reassembled in the correct sequence at the destination. Because these networks allow “sharing” of communications links, they are more efficient than circuit-switched networks.

Packetized Elementary Streams (PES)
An MPEG stream is composed of one or more elementary streams (ES), each containing audio, video or data. ES’s can be grouped into Program Streams, which are formed by breaking ES’s into chunks, the PES’s, and interleaving them.

Pairing
A partial or complete failure of interlace in which the scanning lines of alternate fields do not fall exactly between one another but tend to fall (in pairs) one on top of the other.

Partial Grant
A grant that is smaller than the corresponding bandwidth request from the CM.

Passive Component
A component that requires no external source of power for it to function.
Passive Device A circuit or network not using active devices such as tubes or transistors.

Password
A sequence of characters used to prevent unauthorized access to a computer or its files. It is entered along with its corresponding user ID, which are then compared against a list of authorized users before access is granted.

Pay Cable
Cable programming services for which subscribers pay an additional fee above the basic cable service charge. Also called Premium Cable.

Pay Cable Unit
Each premium service to which a household subscribes is counted as one unit.

Pay-Per-View (PPV)
Pay television programming for which cable subscribers pay a separate fee for each program viewed. Or a service that allows customers to buy content on a program by program basis. Most customers today order programming via phone. OCAP 1.0 systems will enable the development of services to allow customers to order pay-per-view programming directly from their TV.

Pay Programming
Movies, sports, and made-for-cable specials that are available to the cable customer for a charge in addition to the basic fee.

Payload Header Suppression
The suppression of the header in a payload packet. (e.g., the suppression of the Ethernet header in forwarded packets)

Payload Service Class Table (PSC)
A MIB table that maps RTP Payload Type to a Service Class Name.

Payload Unit Start Indicator (PUSI)
A flag in an MPEG header. A value of 1 indicates the presence of a pointer field as the first byte of the payload.

Peer Entities
Entities within the same layer
.
Penetration
Ratio of the number of cable customers to the total number of households passed by the system.

Per Hop Behavior (PHB)
In the IETF Differentiated Services (DiffServ) approach to quality of service differentiation, the treatment by a network router or switch of a group of network traffic flows for the “hop” to the next router switch. Packets “marked” or “tagged” with a common service classification in the packet header are aggregated into flow “bundles” which are treated the same, e.g., have the same priority or the same risk of being discarded in the event of network congestion.

Per-Inquiry Advertising
Direct response advertising for which the cable network or system running the commercial is paid based on the number of responses received rather than the air time used.

Percentage Sync
The ratio, expressed as a percentage, of the amplitude of the synchronizing signal to the peak-to-peak amplitude of the picture signal between blanking and reference white level.

Performance Standards
The minimum technical criteria that must be met by cable television systems, consistent with standard set by the FCC or the local ordinance.

Peripheral Component Interface (PCI)
An interface standard for connecting hardware expansion cards to a computer. The typical PCI connection is a slot, or edge-card connector, on the computer’s motherboard allowing devices such as network cards, graphics cards or drive controllers to be connected to the computer. Some PCI devices are integrated onto the motherboard, especially in the case of “brand-name” computers. PCI has eclipsed ISA as the interface of choice due to its higher transfer rate, ease of configuration and improved Plug and Play ability.

Permanent Virtual Circuit (PVC)
A point-to-point connection between two specific locations on an ATM, Frame Relay, of X.25 network. PVCs are pre-defined by the ATM, Frame Relay, or X.25 network administrator. See also SVC.

Personal Communications Service (PCS)
Digital networks deployed in cellular; like configuration at 1.8GHz to 2.2GHz.

Personal Video Recorder (PVR)
A consumer device which uses a hard disk drive to record television programs based on the user’s preferences. Also provides pause of live television feature. Or a set of equipment that allows a user to timeshift television without removable media.

Phase
A relative quantity describing the time relationship between or among waves having identical frequency. The complete wave cycle is divided into 360 equal parts, called degrees of phase.

Phase Distortion
When the output of an amplifier fluctuates in phase, even though the input does not, the circuit introduces phase distortion into the signal.

Phase Jitter
Phase variations arising in a channel and caused by incidental frequency modulation of signals transmitted over the channel. This occurs when the carrier supply frequencies in a frequency-division-multiplexed carrier system are not perfectly constant.

Phase Modulation
When the information is impressed on a radio frequency signal by varying its phase angle.

Phased Array
A type of antenna design that incorporates two or more elements that integrate signal information received from the spatially separate elements, and that transmit in a coordinated manner (either simultaneously or alternately).

PHILA
POD Host Interface License Agreement.

Photodiode
A semiconductor device that converts light to electrical current.

Photoresistor
A device that exhibits a variable resistance, depending on the amount of light that strikes it.

Physical (PHY) Layer
Layer 1 in the Open System Interconnection (OSI) architecture; the layer that provides services to transmit bits or groups of bits over a transmission link between open systems and which entails electrical, mechanical and handshaking procedures.

Physical Media Dependent (PMD) Sublayer
A sublayer of the physical layer which is concerned with transmitting bits or groups of bits over particular types of transmission link between open systems and which entails electrical, mechanical and handshaking procedures.

Picture Element
One of many monochrome or color “dots” that make up a television picture.

Picture Tube
A cathode-ray tube used to produce an image by variation of the intensity of a scanning beam.

Plain Old Telephone Service (POTS)
This term often is used to refer to analog voice telephone services provided over the public switched telephone network.

Plain Text
The original (unencrypted) state of a message or data. Also called cleartext.

Plastic Optical Fiber (PoF)
A plastic cable used, for short distances only, as an alternative to fiber optic cable. Although plastic is not as transparent as glass, it is more malleable and less expensive. PoF is a possible choice for indoor networking.

Plug-and-Play
An Intel-developed hardware standard created to automate the setup and configuration of hardware devices connected to a computer. In theory, it allows you to “plug” a device into the computer and “play” it without going through a complicated setup process.

Plug-In
A plug-in refers to a set of functionality which can be added to a generic platform in order to provide interpretation of DVB registered, but non-DVB-J, application formats. For example, HTML3.2 or MHEG-5 are examples of plug-ins.

Plug-in Application
A plug-in application refers to an application that conforms to an application format for which a plug-in has been registered with DVB and which is only interoperable within terminals which have the appropriate plug-in resident or connected to networks where an appropriate plug-in is being broadcast.

Point-of-Deployment (POD)
Now referred to as CableCARDs. See CableCARD.

Point-of-Presence (POP)
The point where the inter-exchange carrier’s responsibilities for the line begin and the local exchange carrier’s responsibility ends. Location of a communications carrier’s switching or terminal equipment.

Point-to-Point
A circuit connecting two nodes only, or a configuration requiring a separate physical connection between each pair of nodes.

Point-to-Point Protocol (PPP)
A method of transmitting TCP/IP and other networking protocols over a dial-up or WAN connection.

Pole Attachment
When cable television systems use existing pole lines maintained by utilities, an attachment contract must be negotiated between the parties of interest.

Port
The physical connector on a device enabling the connection to be made.

Post Office Protocol 3 (POP3)
The current version of the most common protocol for receiving e-mail on a TCP/IP network.

Power Amplifier
An amplifier that delivers a certain amount of alternating-current power to a load. Used in audio frequency and radio frequency applications.

Power Cycle
The act of turning the electrical power to a device off and then back on, often used to reset the device.

Power Gain
An increase in signal power between one point and another. Used as a specification for power amplifiers.

Power Transistor
A semiconductor transistor designed for power-amplifier applications at audio and radio frequencies.

Predicted Grade A Contour
The line representing the service area in which a good picture is computed to be available 90 percent of the time at 70 percent of the receiver locations. Signal contours determine what educational channels are carried on a cable system and, in similar markets, what stations must be carried from other small markets.

Predicted Grade B Contour
The concentric area marking a television station’s service area in which a good analog picture is computed to be available 90 percent of the time at 50 percent of the receiver locations.

Premium Cable
Cable programming services for which subscribers pay an additional fee above the basic cable service charge. Also called Pay Cable.

Presentation Engine (PE)
In OCAP, the presentation engine is responsible for the appearance of information on the user interface (the display), and enables content to be displayed on a variety of devices. The PE incorporates native code that decodes text (HTML, ECMAScript) into meaningful operations, and utilizes Web-based software from the computer world, the Web browser. However, the PE has only limited ability to perform complex logic and arithmetic operations and lacks the security of the Execution Engine, which is why the EE is also required by OCAP.

Pre-Shared Key
A shared secret key passed to both parties in a communication flow, using an unspecified manual or out-of-band mechanism.

Primary Rate Interface (PRI)
An ISDN PRI is an industrial-strength ISDN telephone connection commonly used to service multiple dial-up data connections, large central switchboard “PBX” systems, and other highly-specialized needs. Each ISDN PRI has twenty-three 56 or 64Kbps B Channels and one 64Kbps D Channel.

Primary Service Flow
All CMs have a Primary Upstream Service Flow and a Primary Downstream Service Flow. They ensure that the CM is always manageable and they provide a default path for forwarded packets that are not classified to any other Service Flow.

Privacy
A way to ensure that information is not disclosed to any one other than the intended parties. Information is usually encrypted to provide confidentiality. Also known as confidentiality.

Private Branch Exchange (PBX)
A private switching system, either manual or dial, usually serving an organization such as a business company or a government agency and usually located on the customer’s premises.

Private Key
The key used in public key cryptography that belongs to an individual entity and must be kept secret.

Processing Gain
A function of spread spectrum CDMA technology used in digital cellular; a measure of the robustness of the system; recovers the processed low power signal used to eliminate noise.

Profile
A record stored on a computer containing the settings and preferences for each of the users sharing that computer. Profiles can be set up in Windows, as well as Netscape and other shared Internet applications, and are also used to enable security features in a program (e.g., separate email profiles). Or a profile is a description of a series of minimum configurations, defined as part of the specification, providing different capabilities of the OpenCable system. A profile maps a set of functions which characterize the scope of service options. The number of profiles is small. The mapping of functions into resources and subsequently into hardware entities is out of the scope of the specification and is left to manufacturers.

Program Map Table (PMT)
This is an MPEG-2 entity that contains all of the PIDs that make up a program.

Program Non-duplication
Under FCC rules, a cable system must black-out the programming of a distant television station it carries when the system would duplicate a local station’s programming, on the request of the local station.

Program Stream
In MPEG-2, a multiplex of variable-length digital video and audio packets from one or more program sources having a common time-base.

Program-Specific Information (PSI)
In MPEG-2, normative data necessary for the demultiplexing of Transport Streams and the successful regeneration of programs.

Program and System Information Protocol (PSIP)
A transport and data format specification formulated by the Society of Cable and Telecommunications Engineers (SCTE) to deliver Service Information to the receiver. See Service Information.

Protocol
The set of rules or standards which enables communication between computers on a network. In its simplest form, a protocol is the language used by two computers to transfer information. Or a set of rules and formats that determines the communication behavior of layer entities in the performance of the layer functions.

Protocol Data Unit (PDU)
A packet of data passed across an IP network.

Provisioning
A telephone company term meaning to configure. Before an ISDN line can be used, it has to be correctly provisioned to work with the ISDN equipment the customer is installing and enabled for the various options the customer has requested.

Provisioned Service Flow
A Service Flow that has been provisioned as part of the Registration process, but has not yet been activated or admitted. It may still require an authorization exchange with a policy module or external policy server prior to admission.

Proxy
A facility that indirectly provides some service or acts as a representative in delivering information, thereby eliminating the need for a host to support the service.

Proxy Server
A network component between a LAN and the Internet providing security, administrative control and data caching. It is also a firewall that protects the network from intrusion.

Public Access
A non-commercial channel set aside by a cable system for use by the public, on a first come first serve, non-discriminatory basis.

Public Key
The key used in public key cryptography that belongs to an individual entity and is distributed publicly. Other entities use this key to encrypt data to be sent to the owner of the key.

Public Key Certificate
A binding between an entity’s public key and one or more attributes relating to its identity, also known as a digital certificate.

Public Key Cryptography
A procedure that uses a pair of keys, a public key and a private key, for encryption and decryption, also known as an asymmetric algorithm. A user’s public key is publicly available for others to use to send a message to the owner of the key. A user’s private key is kept secret and is the only key that can decrypt messages sent encrypted by the user’s public key.

Public Key Cryptography for Cross-Ream Authentication (PKCROSS)
Utilized PKINIT for establishing the inter-realm keys and associated inter-realm policies to be applied in issuing cross-realm service tickets between realms and domains in support of Intradomain and Interdomain CMS-to-CMS signaling (CMSS).

Public Key Cryptography for Initial Authentication (PKINIT)
The extension to the Kerberos protocol that provides a method for using public key cryptography during initial authentication.

Public Key Cryptography Standards (PKCS)
Published by RSA Data Security Inc., these standards describe how to use public key cryptography in a reliable, secure and interoperable way.

Public Key Infrastructure (PKI)
The architecture, organization, techniques, practices, and procedures that collectively support the implementation and operation of a Certificate-based public key cryptographic system. Also a process for issuing public key certificates, which includes standards, Certification Authorities, communication between authorities and protocols for managing certification processes.

Public Switched Telephone Network (PSTN)
The PSTN is the worldwide circuit-switched telephone network. Once only an analog system, telephone networks today increasingly are digital, even though most subscribers are connected via analog circuits. Or the international telephone system based on copper wires carrying analog voice data.

Public Switched Telephone Network Media Gateway (PMG)
A media gateway located within the backbone of the PacketCable™ network which “bridges” calls between the Internet Protocol (IP)-network and the PSTN-network. The PSTN media gateway is responsible for supporting all management interfaces to the PSTN and also supports switching system number 7 (SS7) signaling and various time-domain interface options (e.g., channelized T-1 trunks).

Public Television
Noncommercial television broadcasting.

Pull Mode
The delivery method in which a subscriber demands and receives data from the provider.

Pulse Code Modulation (PCM)
The internationally accepted Codex used by telephone companies to translate between the 56 and 64Kbps digital signaling technologies and the analog signals sent across POTS telephone lines. PCM codes are seven or eight bits in size, meaning each code byte has 128 or 256 possible values. (North American POTS connections generally only use 7 bit codes.) Or a commonly employed algorithm to digitize an analog signal (such as a human voice) into a digital bit stream using simple analog to digital conversion techniques.

Push Mode
A delivery method where the service provider transmits on a fixed, predictable schedule, or in response to an event such as the updating of data in the subscriber’s database.