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Transmission system
Transmission system
Transmission system
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In telecommunications, a transmission system is a communication system that transmits a signal from one place to another. The signal can be an electrical, optical or radio signal. The goal of a transmission system is to transmit data accurately and efficiently from point A to point B over a distance, using a variety of technologies such as copper cable and fiber-optic cables, satellite links, and wireless communication technologies.

The International Telecommunication Union (ITU) and the European Telecommunications Standards Institute (ETSI) define a transmission system as the interface and medium through which peer physical layer entities transfer bits. It encompasses all the components and technologies involved in transmitting digital data from one location to another, including modems, cables, and other networking equipment.[1][2] Some transmission systems contain multipliers, which amplify a signal prior to re-transmission, or regenerators, which attempt to reconstruct and re-shape the coded message before re-transmission.

One of the most widely used transmission system technologies in the Internet and the public switched telephone network (PSTN) is synchronous optical networking (SONET).

Also, transmission system is the medium through which data is transmitted from one point to another. Examples of common transmission systems people use everyday are: the internet, mobile networks, cordless cables, etc.

Digital transmission system

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The ITU defines a digital transmission system as a system that uses digital signals to transmit information. In a digital transmission system, the data is first converted into a digital format and then transmitted over a communication channel. The digital format provides a number of benefits over analog transmission systems, including improved signal quality, reduced noise and interference, and increased data accuracy.

ITU defines digital transmission system (DTS) as following:

A specific means of providing a digital section.[3][4]

The ITU sets global standards for digital transmission systems, including the encoding and decoding methods used, the data rates and transmission speeds, and the types of communication channels used. These standards ensure that digital transmission systems are compatible and interoperable with each other, regardless of the type of data being transmitted or the geographical location of the sender and receiver.

Basic components of a DTS

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These techniques are used to improve signal-to-noise ratio, which helps to maintain the integrity of the signal during transmission.

See also

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References

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Transmission system

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from Grokipedia
A transmission system is an assembly that enables the conveyance of , signals, or from a source to one or more destinations via a or medium. In and , it consists of a transmitter that encodes, modulates, and sends the signal; a that propagates it (guided, such as cables, or unguided, such as ); and a receiver that demodulates and decodes the for use. These systems form the backbone of modern communication networks, supporting voice, video, and transfer across global infrastructures. Transmission systems operate on analog or digital principles, with the former using continuous signals and the latter employing discrete for greater reliability and in noisy environments. Key functions include signal amplification, to combine multiple channels, and error correction to mitigate impairments like and interference. Performance is evaluated through metrics such as bandwidth, , and , driving ongoing innovations in areas like and wireless technologies as of 2025.

Overview

Definition and principles

A transmission system in is a configuration of components designed to convey information-bearing signals from a sender to a receiver across a distance via a communication medium, with the goal of preserving signal and ensuring reliable delivery. These systems signals that may represent voice, , or video, adapting to various media such as wired connections or paths to bridge geographical separations. The foundational principles governing transmission systems derive from information theory, notably Claude Shannon's noisy-channel coding theorem, which establishes the theoretical maximum rate at which information can be reliably transmitted over a noisy channel. This channel capacity CC is given by the formula
C=Blog⁡2(1+SNR),C = B \log_2 (1 + \text{SNR}),
where BB represents the channel bandwidth in hertz and SNR is the signal-to-noise ratio. During propagation through the medium, signals experience attenuation, a progressive decrease in amplitude due to energy dissipation, and distortion, which modifies the signal's waveform through factors like dispersion or nonlinear effects, both of which limit effective communication range and quality. Transmission systems serve the essential purpose of facilitating point-to-point exchanges, such as in telephone networks or links, as well as one-to-many broadcasts, including radio and television distribution, thereby supporting core functions in telecommunications infrastructure, computer networks, and media broadcasting. A standard illustrates this as a comprising an source, transmitter, channel, receiver, and destination, where the source originates the message, the transmitter encodes it for transmission, the channel carries it (subject to impairments), the receiver decodes it, and the destination utilizes the recovered .

Historical development

The development of transmission systems began in the with foundational electrical communication technologies. demonstrated the first practical electromagnetic telegraph in 1837, enabling long-distance signaling via coded electrical pulses over wires, which marked the inception of electrical transmission as a reliable method for information conveyance. This was followed by Alexander Graham Bell's in 1876, which introduced voice transmission through modulated electrical currents, expanding transmission capabilities to continuous analog signals. Concurrently, the International Telegraph Union (ITU), established in 1865, began standardizing international telegraph practices to facilitate global . In the early 20th century, wireless transmission emerged as a transformative advancement. achieved the first successful radio transmission in 1895, using electromagnetic waves to send signals without physical conductors, laying the groundwork for broadcast and point-to-point radio systems. The invention of the amplifier in the early 1900s, notably Lee de Forest's tube invented in 1906 and refined during the 1910s, enabled signal amplification over longer distances, crucial for and early radio networks. By the 1930s, the introduction of coaxial cables by improved transmission by supporting higher frequencies and multiple channels, reducing in urban networks. The post-World War II era shifted transmission toward digital paradigms. The transistor's invention at in 1947 revolutionized electronics by enabling compact, efficient , paving the way for digital modulation and switching systems. Claude Shannon's 1948 paper, "," established fundamental limits on and error-free transmission, providing the theoretical bedrock for digital systems. This culminated in the ARPANET's launch in 1969, the first operational packet-switching network, which demonstrated scalable data transmission across distributed nodes. Modern transmission milestones reflect integration of optics, mobility, and quantum principles. Corning's development of low-loss in 1970 enabled high-bandwidth light-based transmission, transforming long-haul communications with minimal signal degradation. Mobile standards evolved from analog systems in the 1980s, which supported basic voice via cellular radio, to digital rollouts starting in 2019, offering ultra-high-speed data and low-latency connections under ITU's IMT framework. In the 2020s, entanglement-based quantum transmission experiments, such as those achieving secure key distribution over metropolitan networks, have advanced toward quantum-secure links resistant to . As of November 2025, pre-standardization efforts for networks are underway, with initial trials in progress and commercial deployment targeted for around 2030.

Types of transmission systems

Transmission systems in automobiles are primarily classified into manual, , and semi-automatic types, each designed to transmit to the wheels while allowing gear ratio adjustments for varying speeds and loads. These classifications differ in driver involvement, mechanism, and application suitability, with modern variants integrating electronic controls for enhanced efficiency.

Manual transmission systems

Manual transmissions, also known as standard or stick-shift transmissions, require the driver to manually select gears using a clutch pedal and gear lever. The system consists of a clutch that disconnects the engine from the transmission during shifts, a gearbox with multiple gear ratios (typically 5 or 6 forward gears plus reverse), and a gear stick to engage synchromesh mechanisms that match speeds for smooth shifting. Power flows from the engine through the clutch to the input shaft, then via selected gears to the output shaft, which connects to the driveshaft. This setup provides direct mechanical control, allowing precise torque and speed management. Historically, manual transmissions dominated early automobiles, evolving from 3-speed units in the to more efficient multi-gear designs by the mid-20th century. Advantages include better fuel economy (up to 10-15% higher than automatics in highway driving) and lower maintenance costs due to fewer components, making them popular in performance and economy vehicles. However, they demand driver skill, especially in traffic, and are less common in modern markets, comprising about 30% of new car sales in the U.S. as of 2023. In recent developments, manuals are increasingly paired with hybrid systems for optimized efficiency.

Automatic transmission systems

Automatic transmissions shift without driver input, using hydraulic or electronic systems to select ratios based on speed, load, and position. Core components include a (replacing to multiply and allow slip-free engagement), planetary gearsets for multiple ratios (typically 6-10 forward ), and a valve body that directs to engage clutches and bands. The uses to transmit power smoothly, with lock-up clutches in modern units to reduce slippage and improve efficiency at cruising speeds. Introduced in the 1940s with ' , automatics became widespread by the 1960s, offering convenience for urban driving. Subtypes include traditional torque-converter automatics, continuously variable transmissions (CVTs), and dual-clutch transmissions (DCTs). CVTs use belts or chains between variable-diameter pulleys to provide infinite gear ratios, enabling seamless acceleration and better fuel economy (e.g., 5-10% improvement over stepped automatics); they are common in compact cars like the . DCTs employ two clutches for odd and even gears, enabling rapid shifts (under 0.1 seconds) similar to manuals but automated, as seen in vehicles like the , balancing performance and efficiency. Automatics now dominate, accounting for over 80% of U.S. sales as of 2024, with 8-10 speed units standard for reduced emissions. Challenges include higher complexity and cost, though advances in address this.

Semi-automatic transmission systems

Semi-automatic transmissions automate operation or gear selection while retaining some manual elements, bridging manual control and automatic convenience. Common variants include automated manual transmissions (AMTs), which use electronic actuators to shift a conventional manual gearbox without a pedal, and dual- systems that can operate in semi-auto mode via paddle shifters. The driver selects (e.g., via buttons or levers), but or electrics handle engagement, reducing effort in stop-start conditions. Originating in with preselector designs like Wilson's, semi-automatics gained traction in the with AMTs in economy cars (e.g., ) and DCTs in performance models. Advantages include fuel savings akin to manuals (up to 5% better than full automatics) and quicker shifts than traditional manuals, with no wear for the driver. Drawbacks involve potential jerkiness in low-speed maneuvers, though refined electronics mitigate this. As of 2025, semi-automatics are prevalent in emerging markets and hybrids, such as the with e-CVT semi-auto features, supporting electrification trends.

Transmission media

Guided media

Guided media encompass physical pathways that confine electromagnetic signals to propagate along defined structures, minimizing dispersion and interference compared to free-space transmission. These media include twisted-pair cables, cables, and fiber optic cables, each designed to support specific signal types and bandwidth requirements while maintaining over distance. The choice of guided media depends on factors such as data rate, , and installation constraints, with common characteristics including for efficient power transfer and metrics to quantify signal loss. Twisted-pair cable consists of two insulated conductors twisted around each other to reduce through cancellation of induced noise fields. Categories of twisted-pair cables, such as Category 5 (Cat5), support Ethernet applications with a bandwidth up to 100 MHz, enabling data rates suitable for local area networks. The twisting minimizes near-end (NEXT) and far-end (), particularly in multi-pair configurations where adjacent pairs can couple signals, though advanced shielding in higher categories like Cat6 further suppresses this interference. in twisted-pair systems, typically around 100 ohms, is modeled as Z0=LCZ_0 = \sqrt{\frac{L}{C}}
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