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Bipolar Code
In telecommunication, bipolar encoding is a type of return-to-zero (RZ) line code, where two nonzero values are used, so that the three values are +, −, and zero. Such a signal is called a duobinary signal. Standard bipolar encodings are designed to be DC-balanced, spending equal amounts of time in the + and − states. The reason why bipolar encoding is classified as a return to zero (RZ) is that when a bipolar encoded channel is idle the line is held at a constant "zero" level, and when it is transmitting bits the line is either in a +V or -V state corresponding to the binary bit being transmitted. Thus, the line always returns to the "zero" level to denote optionally a separation of bits or to denote idleness of the line. Alternate mark inversion One kind of bipolar encoding is a paired disparity code, of which the simplest example is alternate mark inversion. In this code, a binary 0 is encoded as zero volts, as in unipolar encoding, whereas a binary 1 is encoded alter ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ami Encoding
AMI or Ami may refer to: Arts, entertainment and media *AMI (Romanian singer), a Romanian singer and songwriter *AMI-tv, a Canadian TV channel **AMI-télé, the French-language version *AMI-audio, a Canadian audio broadcast TV service *''Ami Magazine'', an Orthodox Jewish news magazine Businesses and organizations * AMI Paris, a French luxury brand * AMI Insurance, in New Zealand * AMI Semiconductor, acquired by Onsemi * Accessible Media Inc., a Canadian media company for the visually impaired * African Minerals Limited (AMI.L) * Alternative Miss Ireland, a Dublin beauty pageant * Amazon Malaria Initiative * American Meat Institute, a trade association * American Media, Inc., now A360media, a publisher * American Megatrends Inc., a computer company * American Monetary Institute, a non-profit * American Mustache Institute, an advocacy organization * Anugerah Musik Indonesia, an annual Indonesian music award ceremony * ''Armes-Militaria-Informations'', a Belgian magazine, later ''F ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Robbed-bit Signaling
In communications systems, robbed-bit signaling (RBS) is a scheme to provide maintenance and line signaling services on many T1 digital carrier circuits using channel-associated signaling (CAS). The T1 carrier circuit is a type of dedicated circuit currently employed in North America and Japan. Overview T1 is a protocol for digital transmission over telephone networks. A T1 circuit combines 24 DS0 channels through time-division multiplexing. Data is transmitted in frames, where each frame contains an 8-bit sample of each of the 24 channels, plus one extra framing bit for a total of 193 bits. Each channel carries 8,000 samples per second. The frames are transmitted either in sequences of 12 frames, known as superframes (SF), or sequences of 24 frames, known as extended superframes (ESF). Robbed-bit signaling is a method to provide signaling information alongside data within a superframe. Robbed-bit signaling uses the least-significant bit of every channel in every sixth frame ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Polar Encoding
In telecommunications, a non-return-to-zero (NRZ) line code is a Binary coding, binary code in which ones are represented by one significant condition, usually a positive voltage, while zeros are represented by some other significant condition, usually a negative voltage, with no other neutral or rest condition. For a given data signaling rate, i.e., bit rate, the NRZ code requires only half the Bandwidth (signal processing), baseband bandwidth required by the Manchester code (the passband bandwidth is the same). The pulses in NRZ have more energy than a return-to-zero (RZ) code, which also has an additional rest state beside the conditions for ones and zeros. When used to represent data in an asynchronous communication scheme, the absence of a neutral state requires other mechanisms for bit synchronization when a separate clock signal is not available. Since NRZ is not inherently a self-clocking signal, some additional synchronization technique must be used for avoiding bit s ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
MLT-3 Encoding
MLT-3 encoding (Multi-Level Transmit) is a line code (a signaling method used in a telecommunication system for transmission purposes) that uses three voltage levels. An MLT-3 interface emits less electromagnetic interference and requires less bandwidth than most other binary or ternary interfaces that operate at the same bit rate (see PCM for discussion on bandwidth / quantization tradeoffs), such as Manchester code or Alternate Mark Inversion. MLT-3 cycles sequentially through the voltage levels −1, 0, +1, 0. It moves to the next state to transmit a 1 bit, and stays in the same state to transmit a 0 bit. Similar to simple NRZ encoding, MLT-3 has a coding efficiency of 1 bit/baud, however it requires four transitions (baud) to complete a full cycle (from low-to-middle, middle-to-high, high-to-middle, middle-to-low). Thus, the maximum fundamental frequency is reduced to one fourth of the baud rate. This makes signal transmission more amenable to copper wires. The lack of ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
NICAM
Near Instantaneous Companded Audio Multiplex (NICAM) is an early form of lossy compression for digital audio. It was originally developed in the early 1970s for point-to-point links within broadcasting networks.Croll, M.G., Osborne, D.W. and Spicer, C.R. (1974), ''Digital sound signals: the present BBC distribution system and a proposal for bit-rate reduction by digital companding''. IEE Conference publication No. 119, pp. 90–96 In the 1980s, broadcasters began to use NICAM compression for transmissions of stereo TV sound to the public. History Near-instantaneous companding The idea was first described in 1964. In this, the 'ranging' was to be applied to the analogue signal before the analogue-to-digital converter (ADC) and after the digital-to-analogue converter (DAC). The application of this to broadcasting, in which the companding was to be done entirely digitally after the ADC and before the DAC, was described in a 1972 BBC Research Report. Point-to-point links NI ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Multiplexed Analogue Components
Multiplexed Analogue Components (MAC) was an analog television standard where luminance and chrominance components were transmitted separately. This was an evolution from older color TV systems (such as PAL or SECAM) where there was interference between chrominance and luminance. MAC was originally proposed in the 1980s for use on a Europe-wide terrestrial HDTV system. Terrestrial transmission tests were conducted in France, although the system was never used for that purpose. Various variants were developed, collectively known as the "MAC/packet" family. In 1985 MAC was recommended for satellite and cable broadcasts by the European Broadcasting Union (EBU), with specific variants for each medium. C-MAC/packet was intended for Direct Broadcast Satellite (DBS), D-MAC/packet for wide-band cable, and D2-MAC/packet for both for DBS and narrow-band cable. History MAC was originally developed by the Independent Broadcasting Authority in the early 1980, as a system for deli ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
B-MAC
B-MAC is a form of analog video encoding, specifically a type of Multiplexed Analogue Components (MAC) encoding. MAC encoding was designed in the mid 80s for use with Direct Broadcast Satellite systems. Other analog video encoding systems include NTSC, PAL and SECAM. Unlike the Frequency-division multiplexing, Frequency-Division Multiplexing (FDM) method used in those, MAC encoding uses a Time-division multiplexing, Time-Division Multiplexing (TDM) method. B-MAC was a proprietary MAC encoding used by Scientific Atlanta, Scientific-Atlanta for encrypting broadcast video services; the full name was "Multiple Analogue Component, Type B". Usage Both 625 lines, 625 and 525 lines, 525 line versions of B-MAC were developed and used. This system was used in South Africa by Multichoice, and Australia by Optus (for Television receive-only, TVRO until 2000). B-MAC was used for satellite broadcasts of the American Forces Network, American Forces Radio and Television Service from the earl ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
HDB3
Modified AMI codes are a digital telecommunications technique to maintain system synchronization. Alternate mark inversion (AMI) line codes are modified by deliberate insertion of bipolar violations. There are several types of modified AMI codes, used in various T-carrier and E-carrier systems. Overview The clock rate of an incoming T-carrier is extracted from its bipolar line code. Each signal transition provides an opportunity for the receiver to see the transmitter's clock. The AMI code guarantees that transitions are always present before and after each mark (1 bit), but are missing between adjacent spaces (0 bits). To prevent loss of synchronization when a long string of zeros is present in the payload, deliberate bipolar violations are inserted into the line code, to create a sufficient number of transitions to maintain synchronization; this is a form of run length limited coding. The receive terminal equipment recognizes the bipolar violations and removes from the user data ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bipolar Violation
A bipolar violation, bipolarity violation, or BPV, is a violation of the bipolar encoding rules where two pulses of the same polarity occur without an intervening pulse of the opposite polarity. This indicates an error in the transmission of the signal. T-carrier and E-carrier signals are transmitted using a scheme called bipolar encoding, a.k.a. Alternate Mark Inversion (AMI), where ONE is represented by a pulse, and a ZERO is represented by no pulse. Pulses (which represent ones) always alternate in polarity, so that if, for example two positive pulses are received in succession, the receiver knows that an error occurred (a violation) in that one or more bits were either added or deleted from the original signal. Reliable transmission of data using this scheme requires a regular stream of pulses; too many zero bits in succession can cause a loss of synchronization between transmitter and receiver. To ensure that this is always present, there exist a number of modified AMI ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Error Detection
In information theory and coding theory with applications in computer science and telecommunications, error detection and correction (EDAC) or error control are techniques that enable reliable delivery of digital data over unreliable communication channels. Many communication channels are subject to channel noise, and thus errors may be introduced during transmission from the source to a receiver. Error detection techniques allow detecting such errors, while error correction enables reconstruction of the original data in many cases. Definitions ''Error detection'' is the detection of errors caused by noise or other impairments during transmission from the transmitter to the receiver. ''Error correction'' is the detection of errors and reconstruction of the original, error-free data. History In classical antiquity, copyists of the Hebrew Bible were paid for their work according to the number of stichs (lines of verse). As the prose books of the Bible were hardly ever w ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
