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.

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S/T Interface
The eight-pin RJ-45 connector on the “back side” of an NT-1 or ISDN adapter that connects one or more ISDN adapters to the NT-1. Of the eight pins on the RJ-45 connector, the outside two pins on each side provide power, and the center four form a “transmit” and “receive” pairs. ISDN adapters with built-in NT-1s do not have an S/T Interface.

Sample
In analog to digital signal processing, a sample is taken at regular intervals to establish the electrical potential (voltage) present in an analog system at a given point in time. Each sample is then assigned a digital value. In telephony, sample values are established by a codex, and range from zero to 255. (Though, for most “voice grade” connections the actual range of codex values is between zero and 127.) Each sample value is transmitted across the digital phone network and used to re-create a facsimile of the original analog signal at the other end of a phone connection.

Sample Rate
In analog to digital signal processing, the sample rate is the interval at which samples of an analog signal are taken. The sample rate for digital telephony, for example, is 8000 per second.

Sandbox
Unsigned applications and signed applications without a permission file have access to all the APIs for which there is no permission signalling defined. This is commonly called the sandbox.

Satellite
Device located in geostationary orbit above the earth which receives transmissions from separate points and retransmits them to cable systems, DBS and others over a wide area.

Satellite Dish Antenna
A system for concentrating the weak signals sent from a satellite.

Satellite Downlink
A data service that broadcasts data from an orbital satellite to terrestrial receivers. Used by some satellite TV vendors to provide a high-speed feed for receiving data from the Internet. Data sent to the Internet (Web page requests, outbound email, etc.) must be sent by more conventional means, such as a dial-up modem connections to a local ISP.

Satellite Master Antenna Television System (SMATV)
Systems that serve a concentration of TV sets such as an apartment building, hotel, etc., utilizing one central antenna to pick up broadcast and/or satellite signals. Or RF distribution of satellite and antenna signals.

Scanning Line
A single continuous narrow strip of the picture area containing highlights, shadows, and halftones, determined by the process of scanning.

Scramble
A signal security technique for rendering a TV picture unviewable, while permitting full restoration with a properly authorized decoder or descrambler.

Second Audio Program (SAP)
In a BTSC-encoded television sound carrier, a monaural audio subcarrier that can be used to transmit supplemental foreign language translation audio or other information.

Second Harmonic
A second order beat whose two beating carriers have the same frequency.

Second Order Beat
An unwanted carrier created by two separate carriers beating against each other. These beating carriers may have the same or different frequencies.

Secret Key
The cryptographic key used in a symmetric key algorithm, which results in the secrecy of the encrypted data depending solely upon keeping the key a secret, also known as a symmetric key.

Secure Hash Algorithm 1 (SHA-1)
A standards-based method for computing a condensed representation of a message or a data file.

Secured Socket Layer (SSL)
Used to define standard encryption software to pass sensitive information over an unsecured Internet connection. SSL works on encryption of sensitive data using complex techniques and converting them back to original data using keys on the receiving side. Or a public key encryption based protocol for secure communications between client and server.

Security Association (SA)
A one-way relationship between sender and receiver offering security services on the communication flow.

Security Association Identifier (SAID)
Uniquely identifies Security Associations in the DOCSIS Baseline Privacy Plus Interface (BPI+) security protocol.

Selective Reception
A characteristic of spatial processing that monitors incoming signals and distinguishes between desirable information and interference; by filtering out interfering signals and appropriately combining the reception from all the antennas in the array, this approach provides significant improvement in signal quality.

Server
A computer and/or software that provides and controls resources for clients on a network. These resources can include hardware devices such as printers and storage systems, or files as in the case of a Web server.

Service
A service is a sequence of programs under the control of a broadcaster which can be broadcast as part of a schedule.

Service Access Point (SAP)
The point at which services are provided by one layer, or sublayer to the layer immediately above it.

Service application
An application is service-bound if, and only if, it is associated with one or more broadcast services.

Service Class
A set of queuing and scheduling attributes that is named and that is configured at the cable modem termination system (CMTS). A Service Class is identified by a Service Class Name. A Service Class has an associated QoS Parameter Set.

Service Class Name
An ASCII string by which a Service Class may be referenced in modem configuration files and protocol exchanges.

Service Control Point (SCP)
A SCP is a node within a signaling system number 7 (SS7) network that provides centralized service logic and data, such as call routing information.

Service Data Unit (SDU)
The information that is delivered as a unit between peer service access points (SAPs).

Service Flow (SF)
A unidirectional flow of packets on the RF interface of a DOCSIS system. Or a MAC-layer transport service which provides unidirectional transport of packets from the upper layer service entity to the RF. It also shapes, polices and prioritizes traffic according to QoS traffic parameters defined for the Flow.

Service Flow Identifier (SFID)
A 32-bit integer assigned by the CMTS to each DOCSIS Service Flow defined within a DOCSIS RF MAC domain. Any 32-bit SFID must not conflict with a zero-extended 14-bit SID. SFIDs are considered to be in either the upstream direction (USFID) or downstream direction (DSFID). USFIDs and DSFIDs are allocated from the same SFID number space.

Service Identifier (SID)
An identifier appearing in the DOCSIS media access control (MAC) allocation map message, which identifies the entities which may make use of a particular upstream bandwidth assignment. A cable modem may have one or more unicast SIDs. A group of cable modems may share a multicast SID.

Service Information (SI)
That information that describes the broadcast services available on the network.

Service Profile Identifier (SPID)
A number that the telephone company switching equipment uses to keep track of configuration information for each terminal adapter connected to an ISDN telephone line. The telephone company should give you your SPIDs at the time they assign you your ISDN directory numbers.

Session Description Protocol (SDP)
A DDE-1 protocol that defines a multicast session that may or may not be concurrent with a TV program. Or IETF protocol that describes multimedia sessions for the purposes of session announcement, session invitation, and other forms of multimedia session initiation.

Session Initiation Protocol (SIP)
An Internet protocol used for negotiating multimedia sessions across the network.

Session Key
A cryptographic key intended to encrypt data for a limited period of time, typically between a pair of entities.

Set-Top Box
Any of several different electronic devices that may be used in a customer’s home to enable services to be on that customer’s TV. If the “set-top” device is used only for extending the channels available, it is called a converter. If it restores scrambled or otherwise protected signals, it is a descrambler.

Shannon’s Law
An arithmetic proof that defines the maximum data rate an analog device can achieve when sending information over a sampled, analog-to-digital connection when the analog device has no control over the timing of each individual sample. For the North American telephone system, which has a sample rate of 8,000 samples per second with a range of up to 128 sample values, Shannon’s Law shows the maximum data rate that can be achieved over voice grade lines to be about 36Kbps.

Share
The percent of television households tuned to a particular program or category of programming.

Shared Wired Network
A topology where multiple households connect to a common piece of wire.

Shop-At-Home
Programs allowing customers to view products and/or order them by cable TV, including catalogues, shopping shows, etc.

Signal Leakage
Undesired emission of signals out of a cable television system.

Signal-to-Noise Ratio (SNR)
The sensitivity of a communications receiver is generally specified in terms of the audio signal-to-noise ratio that results from an input signal of a certain number of microvolts.

Signal Switching Point (SSP)
SSPs are points within the signaling system number 7 (SS7) network that terminate SS7 signaling links and also originate, terminate, or tandem switch calls.

Signal Transfer Point (STP)
A STP is a node within signaling system number 7 (SS7) network that routes signaling messages based on their destination address. It is essentially a packet switch for SS7. It may also perform additional routing services such as Global Title Translation.

Signaling
The process by which an end system notifies a network that it wants service.

Signaling Connection Control Part (SCCP)
This is a protocol within the signaling system number 7 (SS7) suite of protocols that provides two functions: (1) The ability to address applications within a signaling point. (2) Global Title Translation.

Signaling Gateway (SG)
A signaling agent that receives/sends switched circuit network (SCN) native signaling at the edge of the Internet protocol (IP) network. In particular the signaling system number 7 (SS7) SG function translates variants ISUP and TCAP in an SS7-Internet Gateway to a common version of ISUP and TCAP.

Signaling System Number 7 (SS7)
SS7 is an architecture and set of protocols for performing out-of-band call signaling with a telephone network.

Signed and Sealed
An “envelope” of information which has been signed with a digital signature and sealed using encryption.

Simple Gateway Control Protocol (SGCP)
A call signaling protocol used for controlling media gateways from a call agent (or Call Management Server) within the network. SGCP was the precursor to the PacketCable Network-based Call Signaling (NCS) protocol.

Simple Mail Transfer Protocol (SMTP)
A TCP/IP protocol used to send e-mail on a network or to route e-mail on the Internet.

Simple Network Management Protocol (SNMP)
SNMP allows a TCP/IP host running an SNMP application to query other nodes for network-related statistics and error conditions. The other hosts, which provide SNMP agents, respond to these queries and allow a single host to gather network statistics from many other network nodes.

Skin Effect
The behavior whereby electricity migrates to the outside wall of a wire.

Slope
Difference in amplifier gain, or change in cable attenuation, between lowest and highest frequency present.

Slope-compensation
The action of a slope-compensated gain control, whereby slope of amplifier equalization is simultaneously changed with the gain so as to provide the correct cable equalization for different lengths of cable; normally specified by range and tolerance.

Small Office/Home Office (SOHO)
An industry term used to refer to a telecommunications market segment comprised of people working out of their homes or small offices.

Smear
A term used to describe a picture condition in which objects appear to be extended horizontally beyond their normal boundaries in a blurred or “smeared” manner.

Snow
Heavy random noise.

Society for Cable Telecommunications Engineers (SCTE)
A non-profit professional organization serving the cable industry by providing training, certification and standards.

Society for Motion Picture and TV Engineers (SMPTE)
A professional society for motion picture and TV engineers with more than 9,000 members worldwide. It prepares standards and documentation for TV production. SMPTE time code records hours, minutes, seconds and frames on audio or videotape for synchronization purposes.

Software
Programming and programming materials such as films, videotapes, and slides.

Solid State
A term taken from physics, used interchangeably with the word transistorized; also includes other semiconductor elements, such as diodes. Generally refers to tubeless equipment.

Spacing
Length of cable between amplifiers expressed as dB loss at the highest TV channel provided for in a system, equal to amplifier gain in main trunks.

Span
Distance between line extenders or distribution amplifiers; also, distance between taps.

Spatial Diversity
An antenna configuration of two or more elements that are physically spaced (spatially diverse) to combat signal fading and improve signal quality; the desired spacing depends on the degree of multipath angle spread.

Spatial Division Multiple Access (SDMA)
A complement (not an alternative) to CDMA and TDMA, this technology increases the number of users that can access an existing wireless phone or data system by exploiting the spatial characteristics of the channel itself through highly developed implementation of an intelligent antenna system’s capabilities for receiving and transmitting.

Special Effects Generator
A device permitting combinations of images on a television screen supplied by one or more video inputs.

Special Keycodes
Keycodes other than the Mandatory Ordinary Keycodes that have been reserved for special purposes by special applications such as the monitor application, or some other implementation-dependent application with special privileges, such that they will not be treated the same as the Mandatory Ordinary Keycodes and may not be available to the application that has focus.

Spectrum Management System (SMS)
A system for managing the radio frequency (RF) cable spectrum.

SPID Guessing
A process that can greatly simplify the process of installing an ISDN adapter. Given the regular 10-digit telephone number(s) assigned to an ISDN line, a SPID guessing algorithm tries combining the seven and 10-digit phone numbers with various prefixes and suffixes until it finds it can communicate with the phone company’s central office switch. Once it discovers the right combination, the algorithm also can figure out the kind of central office switching system to which the adapter is connected.

Splitter
A passive device (one with no active electronic components) which distributes a television signal carried on a cable in two or more paths and sends it to a number of receivers simultaneously.

Sports Blackout
Federal law requires cable systems and television stations to delete coverage of local sports events to protect gate receipts.

Spot Revenue
Revenue gained from advertising that is placed on a cable system by a local or national advertiser.

Spread Spectrum
Enables the successful transmission to hostile transmission environments.

Staggercast
This term is used to designate the interval of time, in NVOD; that is, the time between the beginning of a movie or program, on one channel and the beginning of the same program on another channel. (Ex: A movie starts at 7:00 on channel 50, at 7:15 on channel 51, at 7:30 on channel 52-the movie is staggercast 15 minutes.)

Standalone MTA (S-MTA)
A single node that contains an MTA and a non-DOCSIS MAC (e.g., ethernet).

Start Bits
A sequence of bits sent by a device transmitting data so that the device receiving the data can synchronize its clock, which dictates the intervals at which individual bits are expected to be sent and received.

Stop Bits
A sequence of bits sent by a device transmitting data so that the device receiving the data can synchronize its clock, which dictates the intervals at which individual bits are expected to be sent and received.

Store and Forward
Technique for examining incoming packets on an Ethernet switch or bridge whereby the whole packet is read before forwarding or filtering takes place. Store and forward is a slightly slower process than cut-through, but it does insure that all bad or misaligned packets are eliminated from the network by the switching device.

Streaking
A term used to describe a picture condition in which objects appear to be extended horizontally beyond their normal boundaries.

Stream Control Transmission Protocol (SCTP)
IETF protocol that supports reliable data exchange between two endpoints.

Streaming Media
Digital Video, Audio, and Data Services that are selectively delivered to individual users, either in response to a user request or based upon a user profile. These services are delivered over a data transport stream, either via real-time transmission to the user, or via off-peak data-carousel transmission to a storage device at or near the user’s location for subsequent retrieval.

Sub
Subscriber; a cable customer.

Sub Band
The frequency band from 6 MHz to 54 MHz, which may be used for two-way data transmission.

Subflow
A unidirectional flow of IP packets characterized by a single source and destination IP address and single source and destination UDP/TCP port.

Sublayer
A subdivision of a layer in the Open System Interconnection (OSI) reference model.

Subnetwork
Subnetworks are formed by connecting adjacent nodes physically with transmission links.

Subnetwork Access Protocol (SNAP)
An extension of the LLC header to accommodate the use of 802-type networks as Internet Protocol (IP) networks.

Subscriber
A household or business that legally receives and pays for cable and/or pay television service for its own use. Alternate definition is: The entity that is the subject of, and has been issued, a Certificate. The Subscriber is capable of using, and is authorized to use, the private key that corresponds to the public key listed in the Certificate.

Subscriber Media Gateway (SMG)
A media gateway located within the subscriber’s network which “bridges” calls between the Internet Protocol (IP) network and the subscribers telephones (or telephony-type devices). Typically such a media gateway provides an external interface to one or more 2500-type telephony handsets and also supports common standard add-on devices such as caller-id display units and message-waiting lights.

Subscriber Unit
The fixed, typically wall-mounted equipment used by the subscriber in a wireless local-loop system to send and receive messages; a standard telephone is attached to it by wire to complete the connection to the user.

Subsplit
A frequency-division scheme that allows bi-directional traffic on a single cable. Reverse path signals come to the headend from 5 to 30 (up to 42 on extended subsplit systems) MHz. Forward path signals go from the headend from 50 or 54 MHz to the upper frequency limit of the cable network.

Subsystem
An element in a hierarchical division of an open system that interacts directly with elements in the next higher division or the next lower division of that open system.

Superband
The band of cable television channels J through W lying between 216 and 300 MHz.

Superstation
Originally referred to television station WTBS in Atlanta; now generally used to describe any broadcast TV station that has its signal distributed nationally by satellite.

Supplemental Ordinary Keycodes
Keycodes other than the Mandatory Ordinary Keycodes that have not been reserved for special purposes, and thus will be treated the same as the Mandatory Ordinary Keycodes, i.e., will be available to the application that has focus.

Switch
A mechanical or electrical device that is used to deliberately interrupt or alter the path of the current through the circuit. Also could be used to refer to a switched hub, a device used for connecting Ethernet LANs.

Switched Circuit Network (SCN)
Synonym for the Public Switched Telephone Network.

Switched Network
Any network in which switching is present and is used to direct messages form the sender to the ultimate recipient. Usually switching is accomplished by deconnecting and reconnecting lines in different configurations in order to set up a continuous pathway between the sender and the recipient.

Switched Service
A cable communications service in which each subscriber has a terminal and may communicate with any other subscriber.

Switched Virtual Circuit (SVC)
Allow an end-user to establish on-demand data connections between two end points on an ATM, Frame Relay, or X.25 network. See also Permanent Virtual Circuit (PVC).

Switcher
A control which permits the selection of one image from any of several cameras to be fed into the television display or recording system.

Switcher/Fader
A device permitting gradual, overlapping transition from the image of one camera to another. Sometimes incorporated as part of a special effects generator.

Symmetric Key
The cryptographic key used in a symmetric key algorithm, which results in the secrecy of the encrypted data depended solely upon keeping the key a secret, also known as a secret key.

Sync
An abbreviation for the words “synchronization”, “synchronizing”, etc. Applies to the synchronization signals, or timing pulses, which lock the electron beam of the picture monitors in step, both horizontally and vertically, with the electronic beam of the pickup tube. The color sync signal (NTSC) is know as the color burst.

Sync Compression
The reduction in the amplitude of the sync signal, with respect to the picture signal, occurring between two points of a circuit.

Sync Generator
A device used to supply a common or master sync signal to a system of several cameras. This ensures that their scanning pulses will be in phase. Scanning pulses out of phase produce distortion or rolling, sometimes called “sync loss.”

Sync Level
The level of the tips of the synchronizing pulses.

Synchronous Code Division Multiple Access (S-CDMA)
A multiple access physical layer technology in which different transmitters can share a channel simultaneously. The individual transmissions are kept distinct by assigning each transmission an orthogonal “code.” Orthogonality is maintained by all transmitters being precisely synchronized with one another. S-CDMA is one of the physical layer technologies included in DOCSIS 2.0.

Synchronous Optical NETwork (SONET)
SONET is an optical interface standard to transport digital signals that allows inter-working of transmission products from multiple vendors. Among other things, it defines optical line rates known as optical carrier (OC) signals; the base rate is 51.84Mbps (OC-1), with higher rates being direct multiples of the base rate. (For example, OC-3 runs at 155.52 Mbps, or three times the rate of OC-1.)

Synchronous Transmission Protocol
A method of encoding a data transmission that does not use start and stop bits at the beginning and end of each byte to synchronize the data time clocks at each end of a connection. Instead it sets its timing signal at the beginning and end of each connection, and corrects discrepancies that arise over time by using the changing values each device on the connection sends and receives to keep their clocks “in sync.” Eliminating the start and stop bits reduces the “overhead” required to transmit each byte, and allows for increased throughput.

Syndicated Exclusivity
Requirement by which cable systems must black out significant portions of their distant signals in order to protect syndicated programming offered by local television broadcasters under an exclusive contract. The FCC eliminated this requirement in 1980 and re-imposed it in 1990.

System Integrators (SI)
Companies that provide installation of networking equipment and possibly other services such as training or network management.

System Level
The level of signal in a cable television system at the output of each amplifier. Must be carefully chosen and maintained for least distortion and noise.

System Loss
Cable TV distribution systems are designed to compensate the cable and device losses. The spacing between cable amplifiers can increase as system losses are minimized through the proper choice of connectors, cable and related hardware. System losses are referred to as a “dB of cable” without reference to specific cable size or device losses. Generally these losses are understood to be at the highest operating frequency of the system.

System Noise
Refers to the random energy generated by thermal and shot effects in the system. It is specified in terms of its rms level as measured in a 4-MHz bandwidth centered within a 6-MHz cable television channel.

System Operator
The individual, organization, company or other entity that operates a cable TV system.

System Test Plan (STP)
A plan or policy for verifying system function, performance and/or compliance to a specification.

Systems Management
Functions in the application layer related to the management of various Open Systems Interconnection (OSI) resources and their status across all layers of the OSI architecture.

Systems Network Architecture (SNA)
IBM’s layered protocols for mainframe communications.