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DESCRIPTION Analogue is usually thought of in an electrical context, but Mechanical , Pneumatic , Hydraulic , and other systems may also use analogue signals. The word "analogue" implies an Analogy between Cause and Effect , Voltage in and voltage out, Current in and current out, Sound in and sound out. Analogue circuits do not involve quantisation of information into digital format. Whatever the original quantity, whether sound, light, pressure, temperature, or an exceeded limit, the source signal information being handled by the circuit remains continuous from end to end. ANALOGUE SIGNALS An analogue signal uses some property of the medium to convey the signal's information. For example, an Aneroid Barometer uses Angular position as the signal to convey Pressure information. Electric ally, the property most commonly used is voltage followed closely by Frequency , current, and charge. Any information may be conveyed by an analogue signal, often such a signal is a measured response to changes in physical phenomena, such as sound, light, temperature, position, or pressure, and is achieved using a Transducer . In an analogue sound recording, the variation in pressure of a sound striking a microphone creates a corresponding variation in the current passing through it or voltage across it. An increase in the volume or amplitude of the sound causes the fluctuation of the current or voltage to increase proportionally while keeping the same Waveform or shape and electrical analogue. DISADVANTAGE OF ANALOGUE SIGNALLING The primary disadvantage of analogue signalling is that any system has Noise , that is random disturbances or variations in it. As the signal is copied and re-copied, or transmitted over long distances, these random variations become dominant and lead to signal degradation. Electrically these losses are lessened by Shielding , good connections, and several cable types such as Coax and Twisted Pair and using low noise amplifiers. The effects of random noise can make signal loss and distortion impossible to recover, since amplifying the signal to recover attenuated parts of the signal often generates more noise and amplifies the noise as well. Another method of conveying an analogue signal is to use involves altering the amplitude of a sinusoidal voltage waveform by the source information, Frequency Modulation changes the frequency. Other techniques, such as changing the phase of the base signal do also work. Sources: Some of an earlier version of this article was originally taken from Federal Standard 1037C in support of MIL-STD-188. SEE ALSO
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