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Transmission Level Point
In telecommunications, a transmission level point (TLP) is a test point in an electronic circuit that is typically a transmission channel. At the TLP, a test signal may be introduced or measured.Whitham D. Reeve (1992) ''Subscriber Loop Signaling and Transmission Handbook—Analog'', IEEE Press, p.229 Various parameters, such as the power of the signal, noise, voltage levels, wave forms, may be measured at the TLP. The nominal transmission level at a TLP is a function of system design and is an expression of the design gain or attenuation (loss). Voice-channel transmission levels at test points are measured in decibel-milliwatts (dBm) at a frequency of ~1000 hertz. The dBm is an absolute reference level measurement (see ) with respect to 1 mW power. When the nominal signal power is at the TLP, the test point is called a ''zero transmission level point'', or ''zero-dBm TLP''. The abbreviation dBm0 stands for the power in dBm measured at a zero transmission level point. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Telecommunications
Telecommunication, often used in its plural form or abbreviated as telecom, is the transmission of information over a distance using electronic means, typically through cables, radio waves, or other communication technologies. These means of transmission may be divided into communication channels for multiplexing, allowing for a single medium to transmit several concurrent Session (computer science), communication sessions. Long-distance technologies invented during the 20th and 21st centuries generally use electric power, and include the electrical telegraph, telegraph, telephone, television, and radio. Early telecommunication networks used metal wires as the medium for transmitting signals. These networks were used for telegraphy and telephony for many decades. In the first decade of the 20th century, a revolution in wireless communication began with breakthroughs including those made in radio communications by Guglielmo Marconi, who won the 1909 Nobel Prize in Physics. Othe ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Frequency
Frequency is the number of occurrences of a repeating event per unit of time. Frequency is an important parameter used in science and engineering to specify the rate of oscillatory and vibratory phenomena, such as mechanical vibrations, audio signals (sound), radio waves, and light. The interval of time between events is called the period. It is the reciprocal of the frequency. For example, if a heart beats at a frequency of 120 times per minute (2 hertz), its period is one half of a second. Special definitions of frequency are used in certain contexts, such as the angular frequency in rotational or cyclical properties, when the rate of angular progress is measured. Spatial frequency is defined for properties that vary or cccur repeatedly in geometry or space. The unit of measurement of frequency in the International System of Units (SI) is the hertz, having the symbol Hz. Definitions and units For cyclical phenomena such as oscillations, waves, or for examp ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Nominal Level
Nominal level is the operating level at which an electronic signal processing device is designed to operate. The electronic circuits that make up such equipment are limited in the maximum signal they can handle and the low-level internally generated electronic noise they add to the signal. The difference between the internal noise and the maximum level is the device's dynamic range. The nominal level is the level that these devices were designed to operate at, for best dynamic range and adequate headroom. When a signal is chained with improper gain staging through many devices, clipping may occur or the system may operate with reduced dynamic range. In audio, a related measurement, signal-to-noise ratio, is usually defined as the difference between the nominal level and the noise floor, leaving the headroom as the difference between nominal and maximum output. The measured level is a time average, meaning that the peaks of audio signals regularly exceed the measured average l ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Alignment Level
The alignment level in an audio signal chain or on an audio recording is a defined anchor point that represents a reasonable or typical level. Analogue In analogue systems, alignment level in broadcast chains is commonly 0 dBu (0.775 volts RMS) and in professional audio is commonly ''0 VU'' (4 dBu, 1.228 volts RMS). Under normal situations, the 0 VU reference allows for a headroom of 18 dB or more above the reference level without significant distortion. This is largely due to the use of slow-responding VU meters in almost all analogue professional audio equipment, which, by their design and by specification, respond to an average level, not peak levels. Digital In digital systems alignment level commonly is at −18 dBFS (18 dB below digital full scale), in accordance with EBU recommendations. Digital equipment must use peak-reading metering systems to avoid severe digital distortion caused by the signal going beyond digita ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Telephone
A telephone, colloquially referred to as a phone, is a telecommunications device that enables two or more users to conduct a conversation when they are too far apart to be easily heard directly. A telephone converts sound, typically and most efficiently the human voice, into electronic signals that are transmitted via Electrical cable, cables and other communication channels to another telephone which reproduces the sound to the receiving user. The term is derived from and (, ''voice''), together meaning ''distant voice''. In 1876, Alexander Graham Bell was the first to be granted a United States patent for a device that produced clearly intelligible replication of the human voice at a second device. This instrument was further developed by many others, and became rapidly indispensable in business, government, and in households. The essential elements of a telephone are a microphone (''transmitter'') to speak into and an earphone (''receiver'') which reproduces the voice a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
End Instrument
In the context of telecommunications, a terminal is a device which ends a telecommunications link and is the point at which a signal enters or leaves a network. Examples of terminal equipment include telephones, fax machines, computer terminals, printers and workstations. An end instrument is a piece of equipment connected to the wires at the end of a telecommunications link. In telephony, this is usually a telephone connected to a local loop. End instruments that relate to data terminal equipment include printers, computers, barcode readers, automated teller machines (ATMs) and the console ports of routers. See also * Communication endpoint * Data terminal equipment * End system * Host (network) * Node (networking) * Terminal equipment In telecommunications, the term terminal equipment has the following meanings: * Communications equipment at either end of a communications link, used to permit the stations involved to accomplish the mission for which the link was est ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
DBm0
dBm0 is an abbreviation for the power in decibel-milliwatts (dBm) measured at a zero transmission level point (ZLP). dBm0 is a concept used (amongst other areas) in audio/telephony processing since it allows a smooth integration of analog and digital chains. Notably, for A-law and μ-law codecs the standards define a sequence which has a output. The unit dBm0 is used to describe levels of digital as well as analog signals and is derived from its counterpart dBm. Although today dBm0 may be considered supplanted by the similar unit decibels relative to full scale (dBFS) (discussion at ), dBm0 can be viewed as connecting both the old world of analog telecommunication and the new world of digital communication. The level corresponds to the digital milliwatt (DMW) and is defined as the absolute power level at a digital reference point of the same signal that would be measured as the absolute power level, in dBm, if the reference point was analog. The absolute power in dBm scale ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hertz
The hertz (symbol: Hz) is the unit of frequency in the International System of Units (SI), often described as being equivalent to one event (or Cycle per second, cycle) per second. The hertz is an SI derived unit whose formal expression in terms of SI base units is 1/s or s−1, meaning that one hertz is one per second or the Inverse second, reciprocal of one second. It is used only in the case of periodic events. It is named after Heinrich Hertz, Heinrich Rudolf Hertz (1857–1894), the first person to provide conclusive proof of the existence of electromagnetic waves. For high frequencies, the unit is commonly expressed in metric prefix, multiples: kilohertz (kHz), megahertz (MHz), gigahertz (GHz), terahertz (THz). Some of the unit's most common uses are in the description of periodic waveforms and musical tones, particularly those used in radio- and audio-related applications. It is also used to describe the clock speeds at which computers and other electronics are driven. T ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Voice Channel
A communication channel refers either to a physical transmission medium such as a wire, or to a logical connection over a multiplexed medium such as a radio channel in telecommunications and computer networking. A channel is used for information transfer of, for example, a digital bit stream, from one or several '' senders'' to one or several '' receivers''. A channel has a certain capacity for transmitting information, often measured by its bandwidth in Hz or its data rate in bits per second. Communicating an information signal across distance requires some form of pathway or medium. These pathways, called communication channels, use two types of media: Transmission line-based telecommunications cable (e.g. twisted-pair, coaxial, and fiber-optic cable) and broadcast (e.g. microwave, satellite, radio, and infrared). In information theory, a channel refers to a theoretical ''channel model'' with certain error characteristics. In this more general view, a storage device is ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Test Point
A test point is a location within an electronic circuit that is used to monitor the state of the circuitry or inject test signals. Test points have three primary uses: * During development they are used to analyze hardware behavior. This allows characterization of circuit boards (e.g. power consumption, bus bandwidth), validation of the design and evaluation of component selection. For hardware with software components, test points are used to monitor bus signal, provide engineering interfaces and to force behaviors. Not all development test points are incorporated in production devices. * During manufacturing they are used to verify that a newly assembled device is working correctly. Any equipment that fails this testing is either discarded or sent to a '' rework station'' to attempt to repair the manufacturing defects. * After sale of the device to a customer, test points may be used at a later time to repair the device if it malfunctions, or if the device needs to be re-calibr ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Attenuation
In physics, attenuation (in some contexts, extinction) is the gradual loss of flux intensity through a Transmission medium, medium. For instance, dark glasses attenuate sunlight, lead attenuates X-rays, and water and air attenuate both light and sound at variable attenuation rates. Hearing protection device, Hearing protectors help reduce Sound power, acoustic flux from flowing into the ears. This phenomenon is called acoustic attenuation and is measured in decibels (dBs). In electrical engineering and telecommunications, attenuation affects the Wave propagation, propagation of waves and signals in electrical circuits, in optical fibers, and in air. Attenuator (electronics), Electrical attenuators and optical attenuators are commonly manufactured components in this field. Background In many cases, attenuation is an exponential function of the path length through the medium. In optics and in chemical spectroscopy, this is known as the Beer–Lambert law. In engineering, attenu ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gain (electronics)
In electronics, gain is a measure of the ability of a two-port circuit (often an amplifier) to increase the power or amplitude of a signal from the input to the output port by adding energy converted from some power supply to the signal. It is usually defined as the mean ratio of the signal amplitude or power at the output port to the amplitude or power at the input port. It is often expressed using the logarithmic decibel (dB) units ("dB gain"). A gain greater than one (greater than zero dB), that is, amplification, is the defining property of an active device or circuit, while a passive circuit will have a gain of less than one. The term ''gain'' alone is ambiguous, and can refer to the ratio of output to input voltage (''voltage gain''), current (''current gain'') or electric power (''power gain''). In the field of audio and general purpose amplifiers, especially operational amplifiers, the term usually refers to voltage gain, but in radio frequency amplifiers it usua ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
