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DCME
Digital circuit multiplication equipment (DCME) was a type of voice compression equipment that is installed at both ends of a long-distance telecommunication link, typically a link via communications satellite or submarine communications cable. The main characteristics of DCME are defined in ITU-T recommendation G.763. DCME consists of a time-assignment speech interpolation (TASI) voice interpolation stage, which is a form of statistical multiplexor applied to voiceband signals, and a low rate encoding stage which exploits correlation between successive voiceband samples on an individual input channel to reduce the transmitted bitrate from that required by PCM of equivalent quality. Under heavy loading conditions, for example when a large number of channels show continuous activity due to voiceband data or Group III facsimile signals, the voice interpolation may not be able to operate within a satisfactory quality range – discontinuous signals such as speech being affected b ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Speech Coding
Speech coding is an application of data compression to digital audio signals containing speech. Speech coding uses speech-specific parameter estimation using audio signal processing techniques to model the speech signal, combined with generic data compression algorithms to represent the resulting modeled parameters in a compact bitstream. Common applications of speech coding are mobile telephony and voice over IP (VoIP). The most widely used speech coding technique in mobile telephony is linear predictive coding (LPC), while the most widely used in VoIP applications are the LPC and modified discrete cosine transform (MDCT) techniques. The techniques employed in speech coding are similar to those used in audio data compression and audio coding where appreciation of psychoacoustics is used to transmit only data that is relevant to the human auditory system. For example, in voiceband speech coding, only information in the frequency band 400 to 3500 Hz is transmitted but the re ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Communications Satellite
A communications satellite is an artificial satellite that relays and amplifies radio telecommunication signals via a Transponder (satellite communications), transponder; it creates a communication channel between a source transmitter and a Radio receiver, receiver at different locations on Earth. Communications satellites are used for television, telephone, radio, internet, and military applications. Many communications satellites are in geostationary orbit above the equator, so that the satellite appears stationary at the same point in the sky; therefore the satellite dish antennas of ground stations can be aimed permanently at that spot and do not have to move to track the satellite. Others form satellite constellations in low Earth orbit, where antennas on the ground have to follow the position of the satellites and switch between satellites frequently. The radio waves used for telecommunications links travel by Line-of-sight propagation, line of sight and so are obstructe ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Submarine Communications Cable
A submarine communications cable is a cable laid on the seabed between land-based stations to carry telecommunication signals across stretches of ocean and sea. The first submarine communications cables were laid beginning in the 1850s and carried telegraphy traffic, establishing the first instant telecommunications links between continents, such as the first transatlantic telegraph cable which became operational on 16 August 1858. Submarine cables first connected all the world's continents (except Antarctica) when Java was connected to Darwin, Northern Territory, Australia, in 1871 in anticipation of the completion of the Australian Overland Telegraph Line in 1872 connecting to Adelaide, South Australia and thence to the rest of Australia. Subsequent generations of cables carried telephone traffic, then data transmission, data communications traffic. These early cables used copper wires in their cores, but modern cables use optical fiber technology to carry digital data, whic ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Time-assignment Speech Interpolation
In telecommunications, a time-assignment speech interpolation (TASI) was an analog technique used on certain long transmission links to increase voice transmission capacity. TASI was invented by Bell Labs in the early 1960s to increase the capacity of transatlantic telephone cables. It was one of their first applications requiring electronic switching of voice circuits. Later digital circuit multiplication equipment included TASI as a feature, not as distinct hardware. Operation TASI takes advantage of the fact that in typical person-person conversation, speech in a single direction occurs for approximately 40% of the time, the remaining time being occupied with pauses and/or silence. Statistical analysis demonstrated that for an average voice channel usage of 40%, over 74 speech conversations could be handled using 37 full Duplex speech circuits thereby doubling potential revenue for a small capital outlay relative to a highly expensive cable. e.g. £12.5 million (£263 mill ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Statistical Multiplexor
Statistical multiplexing is a type of digital communication link sharing, sometimes abbreviated as STDM. It is very similar to dynamic bandwidth allocation (DBA). In statistical multiplexing, a communication channel is divided into an arbitrary number of variable bitrate digital channels or data streams. The link sharing is adapted to the instantaneous traffic demands of the data streams that are transferred over each channel. This is an alternative to creating a fixed sharing of a link, such as in general time division multiplexing (TDM) and frequency division multiplexing (FDM). When performed correctly, statistical multiplexing can provide a link utilization improvement, called the ''statistical multiplexing gain''. Statistical multiplexing is facilitated through packet mode or packet-oriented communication, which among others is utilized in packet switched computer networks. Each stream is divided into packets that normally are delivered asynchronously in a first-come first-se ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pulse-code Modulation
Pulse-code modulation (PCM) is a method used to digitally represent analog signals. It is the standard form of digital audio in computers, compact discs, digital telephony and other digital audio applications. In a PCM stream, the amplitude of the analog signal is sampled at uniform intervals, and each sample is quantized to the nearest value within a range of digital steps. Alec Reeves, Claude Shannon, Barney Oliver and John R. Pierce are credited with its invention. Linear pulse-code modulation (LPCM) is a specific type of PCM in which the quantization levels are linearly uniform. This is in contrast to PCM encodings in which quantization levels vary as a function of amplitude (as with the A-law algorithm or the μ-law algorithm). Though ''PCM'' is a more general term, it is often used to describe data encoded as LPCM. A PCM stream has two basic properties that determine the stream's fidelity to the original analog signal: the sampling rate, which is the number of ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
ITU-T
The International Telecommunication Union Telecommunication Standardization Sector (ITU-T) is one of the three Sectors (branches) of the International Telecommunication Union (ITU). It is responsible for coordinating Standardization, standards for telecommunications and Information Communication Technology, such as X.509 for cybersecurity, Y.3172 and Y.3173 for machine learning, and H.264/MPEG-4 AVC for video compression, between its Member States, Private Sector Members, and Academia Members. The World Telecommunication Standardization Assembly (WTSA), the sector's governing conference, convenes every four years. ITU-T has a permanent Secretariat (administrative office), secretariat called the Telecommunication Standardization Bureau (TSB), which is based at the ITU headquarters in Geneva, Switzerland. The current director of the TSB is Seizo Onoe (of Japan), whose 4-year term commenced on 1 January 2023. Seizo Onoe succeeded Chaesub Lee of South Korea, who was director from 1 J ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Time-assignment Speech Interpolation
In telecommunications, a time-assignment speech interpolation (TASI) was an analog technique used on certain long transmission links to increase voice transmission capacity. TASI was invented by Bell Labs in the early 1960s to increase the capacity of transatlantic telephone cables. It was one of their first applications requiring electronic switching of voice circuits. Later digital circuit multiplication equipment included TASI as a feature, not as distinct hardware. Operation TASI takes advantage of the fact that in typical person-person conversation, speech in a single direction occurs for approximately 40% of the time, the remaining time being occupied with pauses and/or silence. Statistical analysis demonstrated that for an average voice channel usage of 40%, over 74 speech conversations could be handled using 37 full Duplex speech circuits thereby doubling potential revenue for a small capital outlay relative to a highly expensive cable. e.g. £12.5 million (£263 mill ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
