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  • Acleris' -- Telecommunications Glossary -- AAL to AVT
    rate from CO to the subscriber is only about 500 Kbps The path length cannot exceed 5 5 Km or 3 4 miles Supports simultaneous transmission of data and voice over the same pair AFIRF Adaptive Finite Impulse Response Filter a time domain filter important in acoustic echo cancellers AEC and in removal of some types of noise from sound signals AGC General Usage Automatic Gain Control T 120 Usage AudioGraphic Conferencing AGT AudioGraphics Terminal Algorithm In audio video and data coding the step by step mathematical process or procedure often including repetition providing suitable encoding compression and or encryption for a specific application When used for either lossless or lossy compression a significant reduction in the number of bits required for transmission takes place Alias Aliasing A false signal produced by the analog to digital sampling process often caused by failure to observe the Nyquist criterion creating subjectively disturbing artifacts AM Amplitude Modulation as in the AM broadcast band AMI Alternate Mark Inversion a 1 s density control mechanism for T1 and E1 systems See also B8ZS and HDB3 AMSS Aeronautical Mobile Satellite Service Analog Signal Signal in which the amplitude value varies with time ANI Automatic Number Identification in telephony ANSI American National Standards Institute a globally recognized organization issuing IT and computing technical standards API Application Programming Interface a set of software routines useful for interfacing between high level systems such as users and low level systems such as operating systems or system level tasks Often the design basis for a man machine interface ARS Automatic Route Selection an important component of an automatic least cost routing system Artifact Spurious effects or imperfections introduced into a signal as a result of digital signal processing ASIC Application Specific Integrated Circuit ASCII American Standard Code for Information Interchange A

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  • Acleris' -- Telecommunications Glossary -- B2B to Byte
    BAS Bit rate Allocation Signal In Rec H 221 T 120 et al a data word within the frame structure used to transmit commands control and indication signals and capabilities BBC British Broadcasting Corporation BCH Bose Chaudhuri Hocquenghem A low overhead forward error correction technique often used for videoconferencing as in H 261 et al especially effective for correcting single non burst errors Bell System A group of affiliated RBOCs Regional Bell Operating Companies in the USA which operate under consistent rules and specifications many of which are set by AT T BER Bit Error Rate the absolute number of errors that may be present often expressed as FFx10 y where FF is a floating point value and y is an exponent For example 3 456x10 8 See also Bit Error Rate Bit BInary digiT the smallest unit of data In uncompressed or uncoded data it represents a binary 1 or 0 bps Bits Per Second a measurement of data rate generally excluding the contributions or effects of error correction encryption framing synchronization and similar such signals Bit Error Rate BER A measure of quality of digital transmission systems Expresses the ratio of correct bits to erroneous bits To overcome transmission errors many codecs include forward error correction important for accurate recovery of transmitted compressed data Bluetooth A wireless system operating in the 2 4 GHz ISM band intended initially as a short range cable replacement technology BNC Bayonet Neill Concelman A type of bayonet lock coaxial cable connector used for video and telecommunications BOC Bell Operating Company BRA European term for BRI Breezeway That portion of a composite video signal between the end of the trailing edge of each horizontal synchronization pulse and the beginning of the color reference burst signal television communications usage BRI ISDN Basic Rate Interface

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  • Acleris' -- Telecommunications Glossary -- C-band to CVSDM
    color information amplitude and phase information representing color hue and saturation in the image CIF Full Common Intermediate Format When used with ITU T Rec H 261 H 263 and other coding methods the CIF describes the type of coded video frame transmitted The CIF is 352H x 288V pixels at video frame rates of 7 5 10 15 and 30 fps Note that a codec providing no more than 7 5 fps is compliant with the recommendation If better motion handling is needed look for a numerically greater video frame rate specification The following table provides the range of resolutions possible under H 320 and H 323 Picture Format Luminance Pixels Video Mode H 261 H 263 SQCIF 128H x 96V O R QCIF 176H x 144V R R CIF 352H x 288V O O 4CIF 704H x 576V O 16CIF 1408H x 1152V O where S Sub Q Quarter H Horizontal pixels V Vertical pixels R Required O Optional and Not Defined CLEC Competitive Local Exchange Carrier CMOS Subjective testing case Comparison Mean Opinion Score ITU T P 800 subjective listening tests where test subjects compare samples of signals passing through a device under test with a known reference signal Semiconductor case Complimentary Metal Oxide Semiconductor a high speed technology used for integrated circuits and as CCDs used for imaging in cameras for example CNI Calling Number Identification in telephony C O Telco Central Office where telecommunications equipment is located Codec COder DECoder A digital device for the encoding and decoding of video and or audio signals usually to permit their transmission in a compressed and or encrypted form Color Burst The part of an NTSC or PAL composite video signal which provides a frequency and phase reference for the demodulation of the color information in codecs and video monitors Common Carrier A telephone company or similar supplier of non private telecommunications services telecommunications usage Compander COMPresser expANDER Both A law and μ law companders are used in telephony to improve the subjective signal to quantizing noise ratio for audio communications and telephony Component Video Signal A video signal where the red R green G and blue B picture components are present as individual signals Synchronization information may be included with the G signal or may be a separate signal Less commonly for videoconferencing s video luminance and chrominance signals YIQ or YUV may be provided as separate signals also referred to as component signals Composite Video Signal A video signal incorporating luminance chrominance and synchronizing information Compression data The process of reducing the quantity of data necessary to transmit or store See below Compression lossless A process allowing data compression and its subsequent restoration to its original form without any loss of information PKZip ZOO RAR and ARC are common examples See also Huffman Coding Compression lossy A data compression process that makes subsequent complete recovery of the original data impossible This approach is commonly used for still or motion images where the recovered image must only

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  • Acleris' -- Telecommunications Glossary -- D4 to Dual Communications Interface
    V 35 X 21 and other similar digital communications signals Compare DTE Distributed Computing Environment a complex middleware platform providing security services DCR Degradation Category Rating an ITU T P 800 subjective testing protocol similar to CCR but is based on the test subject always listening first to the reference signal followed by the signal passed through the device under test a test performed by HEI DCT Discrete Cosine Transform see Cosine Transform DECT Digitally Enhanced Cordless Telephone operates in the 1880 GHz 1900 GHz band using Bluetooth s GFSK MC TDMA TDD technology DES Data Encryption Standard A 64 bit private key encryption technique developed by the US NBS An encryption system that encodes communications providing security and privacy of communication by making interception and decoding impossible for most practical purposes Double DES or DES2 uses tandem DES algorithms for greater security Variants may use variable length keys DLCI Data Link Connection Identifiers frame relay use Digital Access Cross connect System DACS A network central office device which enables any T1 facility or any of a T1 s 24 channels to be switched or cross connected to one or more T1 DS1 DS3 or other high order facilities Digital Signal Signal represented by a sequence of binary bits representing ones and zeros Differential Interframe Coding In motion video compression the transmission of only the difference information between adjacent video frames Diversity transmission use In telecommunications reliability may be improved by use of various forms of diversity within a system Techniques may include time space frequency route path or other forms of diversity In addition redundant equipment power and other systems can further increase reliability Different degrees of availability or reliability may be achieved depending upon the nature of the diversity used DMOS Degradation Mean Opinion Score an ITU T P 800 subjective listening test where the test subjects compare two signals first the reference then the signal passed through the device under test DNS Domain Name System an automatic Internet phone book translating an easy to remember domain name like acleris com to its Internet address like 71 18 25 37 and vice versa Dolby Digital 5 1 Formerly known as AC 3 Dolby Digital provides efficient encoding and noise reduction for high quality surround sound applications including home entertainment theatre and broadcasting including DBS and DVD source material Dolby Digital requires appreciable bandwidth 448 Kbps being typical a reason why it is not available for all material provided by direct broadcast satellite DPCM Differential Pulse Code Modulation A digital coding and compression process in which the analog signal is first sampled and the difference between each sample of the signal and its prior estimated value is quantized and digitally encoded DS0 The AT T Bell System level 0 digital standard for systems operating at 64 Kbps DS1 The AT T Bell System level 1 digital standard for systems operating at 1 544 Mbps and consisting of 24 DS 0 channels DS3 The AT T Bell System level 3

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  • Acleris' -- Telecommunications Glossary -- E1 to ETSI
    programming to its members Echo Return Loss Enhancement ERLE A figure of merit for acoustic and telephony echo cancellers expressed in dB An echo canceller electronically enhances the apparent loss between tends of a telecommunications circuit TEC or between the room loudspeaker and the microphones AEC Echo Suppression The insertion of mild attenuation in audio transmit and or receive signal path to eliminate howling caused by excessive closed loop gain Echo suppression may also be used with TECs and AECs to attenuate any residual echo signals EEPROM Electrically Erasable Programmable Read Only Memory A non volatile but electrically alterable form of semiconductor storage These devices are present in some telecommunications equipment such as codecs permitting long term storage of configuration dialing and related information for easy recall by the user A fast reliable EEPROM version is popularly known as FLASH memory EIA Electronic Industries Association A North American standards setting body Encryption One of a number of approaches to convert plain text or data into information that is unreadable except by the intended recipients Adjectives like weak and strong are often used to further describe the encryption systems Similarly under government or military applications encryption may be described as providing

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  • Acleris' -- Telecommunications Glossary -- FCC to Full Duplex
    a non volatile electrically alterable form of semiconductor storage present in some telecommunications equipment for long term storage of configuration dialing and related information FM Frequency Modulation Forced Intraframe Coding 1 In motion video compression immediately following a significant scene change the differential predictive and inter frame coding aspects are temporarily disabled Then information is transmitted for the first changed frame derived entirely from within that frame 2 In motion video compression the technique where static parts of the image are periodically refreshed to mitigate the effects of error build up in the system Forward Error Correction Forward error correction provides correction of data in error for applications where a return signal path is unavailable or system latency is excessive to permit retransmission of the data It is used for CDs videoconferencing and DBS for example FEC uses a mathematical technique in which a syndrome is generated and transmitted with the data At the receive location processing of the syndrome along with the data allows correction of errors caused by the transmission system Depending upon the specific FEC technique used and how it is applied transmitted signals can be made more robust in the presence of transmission errors FOTS Fiber Optic Transmission System With its minimal transit time delay and very low bit error rate FOTS is the superior method to transmit high speed data digital video signals and other compressed signals fps Frames usually motion video frames per second Frame Delete Compression In H 261 and H 263 motion video compression the act of totally discarding from zero to three consecutive video frames is part of the video compression process Its use depends upon the degree of video motion existing and the aggregate bit rate Because of the large data loss with this technique this is truly a compression

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  • Acleris' -- Telecommunications Glossary -- G.711 to GUI
    An ITU T recommendation detailing 7 KHz and 14 KHz bandwidth audio coding algorithms working at 24 and 32 Kbps It forms part of the H 320 and H 323 codec requirements May be licensed from Polycom who acquired PictureTel Corp IP assets G 722 1 also includes testing and packetizing considerations G 723 1 An ITU T recommendation for a Dual Rate Speech Coder for Multimedia Communications Transmitting at 5 3 and 6 3 Kbps G 726 ITU T recommendation for ADPCM adaptive differential pulse code modulation coding at 16 24 32 and 40 Kbps Includes useful annexes G 727 ITU T recommendation using ADPCM adaptive differential pulse code modulation with 2 to 5 bits sample Includes useful annexes with test sequences G 728 An ITU T recommendation detailing a 16 Kbps 3 4 KHz bandwidth audio coding algorithm known as LD CELP or low delay code excited linear prediction Part of the H 320 and H 323 codec recommendations Produces good speech intelligibility and is a good choice for videoconferencing operating at 112 or 128 Kbps aggregate transmission rates Appendix I includes frame or packet loss concealment methods for VoIP and similar applications G 729 ITU T recommendation about an 8 Kbps speech coder using the CS ACELP or conjugate structure algebraic code excited linear prediction speech coder Annexes provide algorithms at 6 4 and 11 8 Kbps C code and test verification suites G T The figure of merit or carrier to noise ratio of a satellite receive earth station where G is gain and T is noise temperature The value includes contributions of factors including antenna gain noise temperature of the low noise amplifier and other aspects A typical value for a modern earth station might be 25db K G Green The green video signal part

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  • Acleris' -- Telecommunications Glossary -- H to Hz
    Note that motion compensation and field sub sampling loop filter are implementation optional in the standard Users considering the H 261 codec at bit rates of 384 Kbps or below should verify that the manufacturer has implemented these optional aspects H 261 Annex D ITU T codec recommendation for simultaneous graphics transmission in the North American region Other administrations may use JPEG H 263 ITU T recommendation regarding a video codec for audio visual services video coding for low bit rate communication Considerably broadens H 261 capabilities extending from low resolution credit card size images to high quality exceptionally detailed images for applications such as telemedicine Backward compatibility is provided with H 320 QCIF Quarter Common Intermediate Format and optionally to CIF and SQCIF Sub QCIF The following table compares H 320 and H 324 video capabilities Picture Format Luminance Pixels Video Modes H 320 H 261 H 324 H 263 SQCIF 128H x 96V O R QCIF 176H x 144V R R CIF 352H x 288V O O 4CIF 704H x 576V O 16CIF 1408H x 1152V O Where S Sub Q Quarter H Horizontal pixels V Vertical pixels R Required O Optional and Not Defined H 262 ITU T recommendation regarding advanced video coding for high quality applications This standard is the result of the merging of the ISO IEC MPEG2 which see work and the ITU T H 262 H 264 ITU T recommendation regarding advanced video coding for high quality motion video applications This standard is the result of the merging of the ISO IEC MPEG4 Part 10 AVC and the ITU T H 26L committees to avoid duplication of parallel development efforts In general H 264 provides quality superior to MPEG2 at about 30 per cent of the bit rate or less It is expected to fully replace MPEG2 over time There are two significant versions of H 264 Level 3 provides for mainstream video while Level 4 focuses on HDTV Significant changes from MPEG2 include 4x4 PEL block size and what is called foreground background video coding H 281 ITU T recommendation regarding far end camera control protocol for videoconferencing using H 224 H 282 ITU T recommendation regarding remote device control protocol for multimedia applications H 310 ITU T recommendation regarding broadband audio visual terminals and communication systems H 320 suite spec ITU T codec recommendation bringing together other recommendations to produce an overall visual telephony system specification including terminal equipment operating over a narrow bandwidth between 56 Kbps and 1920 Kbps H 321 ITU T recommendation describing adaptation of H 320 to an ISDN n times ISDN B channel environment H 322 ITU T recommendation describing visual telephone systems and terminal equipment for local area networks that provide a guaranteed quality of service guaranteed bandwidth This standard makes direct reference to the Draft IEEE P802 9a which see These standards describe low latency LANs suitable for videoconferencing Iso Ethernet H 323 suite spec ITU T recommendation describing packet based visual telephone systems

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