A transducer is a device that converts energy from one form to another. Usually a transducer converts a signal in one form of energy to a signal in another. Transducers are often employed at the boundaries of automation , measurement , and control systems , where electrical signals are converted to and from other physical quantities (energy, force, torque, light, motion, position, etc.). The process of converting one form of energy to another is known as transduction.
11-633: Scanet is a defunct, analog train radio system used by the Norwegian State Railways (NSB) and later the Norwegian National Rail Administration . The system was developed by Ascom Radiocom and was installed on the primary railways in Norway between 1993 and 1996. The system allows radio communication between a train dispatcher, and train drivers and other users involved in railway operations. Scanet has three main components:
22-425: A microphone induces corresponding fluctuations in the current produced by a coil in an electromagnetic microphone or the voltage produced by a condenser microphone . The voltage or the current is said to be an analog of the sound. An analog signal is subject to electronic noise and distortion introduced by communication channels , recording and signal processing operations, which can progressively degrade
33-446: Is any continuous-time signal representing some other quantity, i.e., analogous to another quantity. For example, in an analog audio signal , the instantaneous signal voltage varies continuously with the pressure of the sound waves . In contrast, a digital signal represents the original time-varying quantity as a sampled sequence of quantized values. Digital sampling imposes some bandwidth and dynamic range constraints on
44-634: Is irreversible as there is no reliable method to distinguish the noise from the signal. Converting an analog signal to digital form introduces a low-level quantization noise into the signal due to finite resolution of digital systems. Once in digital form, the signal can be transmitted, stored, and processed without introducing additional noise or distortion using error detection and correction . Noise accumulation in analog systems can be minimized by electromagnetic shielding , balanced lines , low-noise amplifiers and high-quality electrical components. Transducer Transducers can be categorized by
55-938: The Meråker Line , the Nordland Line , the Rauma Line , the Røros Line , the Eastern Østfold Line , the northern part of the Gjøvik Line , and several tunnels along the Bergen Line and the Sørlandet Line . The Åsta accident in 2000 spurred the need to give all parts of the railway coverage with train radio. On these lines, the dispatcher and drivers must communicate using the Nordic Mobile Telephone (NMT 450) standard, which by 2002
66-454: The signal-to-noise ratio (SNR). As the signal is transmitted, copied, or processed, the unavoidable noise introduced in the signal path will accumulate as a generation loss , progressively and irreversibly degrading the SNR, until in extreme cases, the signal can be overwhelmed. Noise can show up as hiss and intermodulation distortion in audio signals, or snow in video signals . Generation loss
77-414: The voltage , current , or frequency of the signal may be varied to represent the information. Any information may be conveyed by an analog signal; such a signal may be a measured response to changes in a physical variable, such as sound , light , temperature , position, or pressure . The physical variable is converted to an analog signal by a transducer . For example, sound striking the diaphragm of
88-507: The central traffic control, base stations which are located along the railway lines, and mobile station located in the trains. The system is further connected to the internal railway telephone network, where it functions like a regular telephone. Scanet is also connected to the automatic train control system. However, several lines lack the system, including the Arendal Line , the Flåm Line ,
99-426: The direction information passes through them: Passive transducers require an external power source to operate, which is called an excitation signal. The signal is modulated by the sensor to produce an output signal. For example, a thermistor does not generate any electrical signal, but by passing an electric current through it, its resistance can be measured by detecting variations in the current or voltage across
110-449: The representation and adds quantization error . The term analog signal usually refers to electrical signals; however, mechanical , pneumatic , hydraulic , and other systems may also convey or be considered analog signals. An analog signal uses some property of the medium to convey the signal's information. For example, an aneroid barometer uses rotary position as the signal to convey pressure information. In an electrical signal,
121-611: Was being planned terminated by Telenor . Scanet was replaced by Global System for Mobile Communications – Railway (GSM-R) in 2007. The system, delivered by Nokia Siemens Networks , was on time and on budget, and made Norway one of the first countries to fully implement the system throughout Europe. After GSM-R was fully implemented on 1 November, Scanet was gradually closed. The new system has been characterized as simpler to use and giving better audio quality than Scanet. Analog signal An analog signal ( American English ) or analogue signal ( British and Commonwealth English )
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