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Four-wire Terminating Set
A four-wire terminating set (4WTS) is a balanced transformer used to perform a conversion between four-wire and two-wire operation in telecommunication systems. For example, a 4-wire circuit may, by means of a 4-wire terminating set, be connected to a 2-wire telephone set. Also, a pair of 4-wire terminating sets may be used to introduce an intermediate 4-wire circuit into a 2-wire circuit, in which loop repeaters may be situated to amplify signals in each direction without positive feedback and oscillation. The 4WTS differs from a simple hybrid coil in being equipped to adjust its impedance to maximize return loss In telecommunications, return loss is a measure in relative terms of the power of the signal reflected by a discontinuity in a transmission line or optical fiber. This discontinuity can be caused by a mismatch between the termination or load co .... Four-wire terminating sets were largely supplanted by resistance hybrids in the late 20th century. References ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Balanced Line
In telecommunications and professional audio, a balanced line or balanced signal pair is a circuit consisting of two conductors of the same type, both of which have equal impedances along their lengths and equal impedances to ground and to other circuits. The chief advantage of the balanced line format is good rejection of common-mode noise and interference when fed to a differential device such as a transformer or differential amplifier.G. Ballou, ''Handbook for Sound Engineers'', Fifth Edition, Taylor & Francis, 2015, p. 1267–1268. As prevalent in sound recording and reproduction, balanced lines are referred to as balanced audio. Common forms of balanced line are twin-lead, used for radio frequency signals and twisted pair, used for lower frequencies. They are to be contrasted to unbalanced lines, such as coaxial cable, which is designed to have its return conductor connected to ground, or circuits whose return conductor actually is ground (see earth-return telegraph). Bal ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Transformer
A transformer is a passive component that transfers electrical energy from one electrical circuit to another circuit, or multiple circuits. A varying current in any coil of the transformer produces a varying magnetic flux in the transformer's core, which induces a varying electromotive force (EMF) across any other coils wound around the same core. Electrical energy can be transferred between separate coils without a metallic (conductive) connection between the two circuits. Faraday's law of induction, discovered in 1831, describes the induced voltage effect in any coil due to a changing magnetic flux encircled by the coil. Transformers are used to change AC voltage levels, such transformers being termed step-up or step-down type to increase or decrease voltage level, respectively. Transformers can also be used to provide galvanic isolation between circuits as well as to couple stages of signal-processing circuits. Since the invention of the first constant-potential transfo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Four-wire Circuit
In telecommunication, a four-wire circuit is a two-way circuit using two paths so arranged that the respective signals are transmitted in one direction only by one path and in the other direction by the other path. The four-wire circuit gets its name from the fact that is uses four conductors to create two complete electrical circuits, one for each direction. The two separate circuits (channels) allow full- duplex operation with low crosstalk. In telephony a four-wire circuit was historically used to transport and switch baseband audio signals in the phone company telephone exchange before the advent of digital modulation and the electronic switching system eliminated baseband audio from the telco plant except for the local loop. The local loop is a two-wire circuit for one reason only: to save copper. Using half the number of copper wire conductors per circuit means that the infrastructure cost for wiring each circuit is halved. Although a lower quality circuit, the local loop al ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Two-wire Circuit
In telecommunication, a two-wire circuit is characterized by supporting transmission in two directions simultaneously, as opposed to four-wire circuits, which have separate pairs for transmit and receive. The subscriber local loop from the telco central office are almost all two wire for analog baseband voice calls (and some digital services like ISDN), and converted to four-wire at the line card back when telephone switching was performed on baseband audio. Today the audio is digitized and processed completely in the digital domain upstream from the local loop. The reason for using two wires rather than four is simple economics—half the materials cost half as much to purchase and install. Note the use of the past-tense "cost," as installation of two-wire copper local loops for telephony was done primarily during the mid 20th century. In the first world there is no new infrastructure planning for new copper-based technology, and as customers are migrating to cellular telephony an ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Telecommunications
Telecommunication is the transmission of information by various types of technologies over wire, radio, optical, or other electromagnetic systems. It has its origin in the desire of humans for communication over a distance greater than that feasible with the human voice, but with a similar scale of expediency; thus, slow systems (such as postal mail) are excluded from the field. The transmission media in telecommunication have evolved through numerous stages of technology, from beacons and other visual signals (such as smoke signals, semaphore telegraphs, signal flags, and optical heliographs), to electrical cable and electromagnetic radiation, including light. Such transmission paths are often divided into communication channels, which afford the advantages of multiplexing multiple concurrent communication sessions. ''Telecommunication'' is often used in its plural form. Other examples of pre-modern long-distance communication included audio messages, such as coded drumb ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Telephone
A telephone is a telecommunications device that permits 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 cables and other communication channels to another telephone which reproduces the sound to the receiving user. The term is derived from el, τῆλε (''tēle'', ''far'') and φωνή (''phōnē'', ''voice''), together meaning ''distant voice''. A common short form of the term is ''phone'', which came into use early in the telephone's history. 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 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Repeater
In telecommunications, a repeater is an electronic device that receives a signal and retransmits it. Repeaters are used to extend transmissions so that the signal can cover longer distances or be received on the other side of an obstruction. Some types of repeaters broadcast an identical signal, but alter its method of transmission, for example, on another frequency or baud rate. There are several different types of repeaters; a telephone repeater is an amplifier in a telephone line, an optical repeater is an optoelectronic circuit that amplifies the light beam in an optical fiber cable; and a radio repeater is a radio receiver and transmitter that retransmits a radio signal. A broadcast relay station is a repeater used in broadcast radio and television. Overview When an information-bearing signal passes through a communication channel, it is progressively degraded due to loss of power. For example, when a telephone call passes through a wire telephone line, some of the powe ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Positive Feedback
Positive feedback (exacerbating feedback, self-reinforcing feedback) is a process that occurs in a feedback loop which exacerbates the effects of a small disturbance. That is, the effects of a perturbation on a system include an increase in the magnitude of the perturbation. That is, ''A produces more of B which in turn produces more of A''.Keesing, R.M. (1981). Cultural anthropology: A contemporary perspective (2nd ed.) p.149. Sydney: Holt, Rinehard & Winston, Inc. In contrast, a system in which the results of a change act to reduce or counteract it has negative feedback. Both concepts play an important role in science and engineering, including biology, chemistry, and cybernetics. Mathematically, positive feedback is defined as a positive loop gain around a closed loop of cause and effect. That is, positive feedback is Phase (waves), in phase with the input, in the sense that it adds to make the input larger. Positive feedback tends to cause Control theory#Stability, system i ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hybrid Coil
A hybrid coil (or bridge transformer, or sometimes hybrid) is a transformer that has three windings, and which is designed to be configured as a circuit having four ports that are conjugate in pairs. A signal arriving at one port is divided equally between the two adjacent ports but does not appear at the opposite port. In the schematic diagram, the signal into W splits between X and Z, and no signal passes to Y. Similarly, signals into X split to W and Y with none to Z, etc. Correct operation requires matched characteristic impedance at all four ports. Hybrids are a class of directional coupler in which the input port power is split equally between the two output ports. Forms of hybrid other than transformer coils are possible; any format of directional coupler can be designed to be a hybrid. These formats include transmission lines and waveguides. Explanation The primary use of a voiceband hybrid coil is to convert between 2-wire and 4-wire operation in sequential se ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Return Loss
In telecommunications, return loss is a measure in relative terms of the power of the signal reflected by a discontinuity in a transmission line or optical fiber. This discontinuity can be caused by a mismatch between the termination or load connected to the line and the characteristic impedance of the line. It is usually expressed as a ratio in decibels (dB); :RL(\mathrm) = 10 \log_ :where ''RL''(dB) is the return loss in dB, ''P''i is the incident power and ''P''r is the reflected power. Return loss is related to both standing wave ratio (SWR) and reflection coefficient (Γ). Increasing return loss corresponds to lower SWR. Return loss is a measure of how well devices or lines are matched. A match is good if the return loss is high. A high return loss is desirable and results in a lower insertion loss. From a certain perspective 'Return Loss' is a misnomer. The usual function of a transmission line is to convey power from a source to a load with minimal loss. If a tran ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Resistance Hybrid
Resistance may refer to: Arts, entertainment, and media Comics * Either of two similarly named but otherwise unrelated comic book series, both published by Wildstorm: ** ''Resistance'' (comics), based on the video game of the same title ** ''The Resistance'' (WildStorm), by Justin Gray, Jimmy Palmiotti, and Juan Santacruz * ''The Resistance'' (AWA Studios), an AWA Studios comic book meta series * ''Resistance: Book One'', graphic novel series by Carla Jablonski with art by Leland Purvis and published by First Second Books Fictional characters * Resistance (''Star Wars''), the primary protagonist organization in the Star Wars sequel trilogy *The Resistance, one of two factions in ''Ingress'' Films * ''Resistance'' (1945 film), a 1945 French film * ''Resistance'' (1992 film), a 1992 Australian film * ''Resistance'' (2003 film), a 2003 war film, with Bill Paxton * ''Resistance'' (2011 film), a 2011 war film, with Michael Sheen * ''Resistance'' (2020 film), a 2020 war film, with ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
