is FDM mainly used in analogue or digital technology? and why?
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Frequency-division multiplexing (FDM) is a form of signal multiplexing where multiple baseband signals are modulated on different frequency carrier waves and added together to create a composite signal.\n\nHistorically, telephone networks used FDM to carry several voice channels on a single physical circuit. In this, 12 voice channels would be modulated onto carriers spaced 4 kHz apart. The composite signal, occupying the frequency range 60 – 108 kHz, was known as a group. In turn, five groups could themselves be multiplexed by a similar method into a supergroup, containing 60 voice channels. There were even higher levels of multiplexing, and it became possible to send thousands of voice channels down a single circuit.\n\nModern telephone systems employ digital transmission, in which time-division multiplexing (TDM) is used instead of FDM.\n\nFDM can also be used to combine multiple signals before final modulation onto a carrier wave. In this case the carrier signals are referred to as subcarriers: an example is stereo FM transmission, where a 38 kHz subcarrier is used to separate the left-right difference signal from the central left-right sum channel, prior to the frequency modulation of the composite signal.\n\nWhere frequency division multiplexing is used as to allow multiple users to share a physical communications channel, it is called frequency-division multiple access (FDMA).\n\nFDMA is the traditional way of separating radio signals from different transmitters.\n\nThe analog of frequency division multiplexing in the optical domain is known as wavelength division multiplexing.\n\nContents [hide]\n1 Level 1 Diagram \n2 Level 2 Diagram \n3 Level 3 Diagram \n4 See also
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http://www.analogX.com
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Well... that's kind of a broad question, but here's the basics both signals. \n\nDigital Signal\n----------------------------\nA digital signal is like an electronic representation of bianary.  it has 2 states, high and low.  It depends on the logic being used (CMOS, TTL, or ECL), but the lows can run anywhere from -5.2 VDC in ECL Logic, and the highs up to +5.2VDC in TTL Logic.  in the o'scope, all you will see looks a little like:\n_-_--____--_--__--_--_____-__-----_       <==== where you can see definate highs and lows.\n\n__--__--__--__--__--__--__--__--__--__ <== A typical digital clocking signal, like in your computer\n\nAnalog Signal\n------------------------\nAn analog signal is like what you see in your windows media player when you turn on the o'scope visualisation (do it, it's a good example of an analog signal).  The pure definition of an analog signal is a variable signal that is continuous in both time and amplitude.  It could be a perfect Sine, triangle, square, or sawtooth Wave ( http://en.wikipedia.org/wiki/Image:Waveforms.png ), a straight DC level, or what you see in the Media Player Example.
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Truth be told in my experience most engineers don't use calculus very often.  An understanding of calculus is required to find derivations for most formulas that are used.  But in practical application most problems are solved making assumption that simplfy problems to simple algebra.  One application used in practice is definte intergration ussually using a spreadsheet.
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I don't understand why you want to start with a FM signal, and then need to revert back to a FM signal....?\nIf you already intend to use a fibre optic cable, then why not just send your digital signals from surface to ROV?  \nThese guys may have some handy stuff to achieve this:  http://www.esssales.com/ifo/fiberoptic-kits.html\nI can't think of an easy method of converting PWM signals into a FM radio signal.....
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Two reasons:\n1. Because it results in a finite spectrum result for a signal. Fourier Transform typically results in infinite spectrum result for a function (e.g if the function has C1 or C0 discontinuities e.g. square wave, triangular wave, ramp, sawtooth)\n\n2. FT assumes that signals are "stationary" and that their frequency-domain can be computed over infinite-time window and will not change. This is unrealistic - most real-world signals are not stationary in a window >10ms (e.g. speech, telecomms, EKG). WT computes its transform based on both a time- and frequency-window.\n\nAs to why you compute DWT rather than the direct Continuous (integral formulation) WT, it's for the same simple reason you generally use DFT instead of CFT - because it's mathematically tractable and lends itself to efficient digital computation (order(NlogN) time); also this formulation can be very efficiently parallelised whether in hardware or software esp. if N is a power of 2 e.g. 64,256,512,1024,... and people have developed these implementations very far (they're a standard toolbox feature or hardware IP).\n\nI don't know the theoretical links offhand but they should be trivial to find.
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They are both ways of putting information on a bigger pipe.\n\nFor modulation, you modulate a carrier frequency with a signal.\n\nMultiplexing involves taking multiple signals and placing them on the same baseband to carry them.\n\nThat isn't much of a similarity, though.  I guess the other one would be that you can have either digital or analog modulation and you can have either digital or analog (FDM) multiplexing.
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The frequency of 50 Hz is to low to modulate with digital, it can be done but would then be ULF.  You can use the 50 Hz transmission line as a digital line as long as the digital stream is not at a freq which is a multiple of the 50Hz then it can filtered out to leave only the digital information. This is a very basic answer Do Not play around with these voltages unless you know what you are doing. High Voltage can seriously damage your health, and equipment.
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Go for the Digitech.  They are quality products if they have the effects you want.
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I have used this long back, I don't know how good it is now\nhttp://www.analogx.com/contents/download/program/ssubmit.htm
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Orifice is most commonly used  for differential press. type \nElse venturi,Pitot tube/Delta tube,flow nozzles as per req.\n\nif accuracy is req. then\nmagnetic flow meter or most precise mass flow meters are prefered today\n\nat least i prefer it in industry where I'm working
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Radio has to do with sound waves and LASER has to do with light.  I suppose you could cobble up something using both technologies, but what is the point.  I mean fibre optics and radio signals have little in common other they can be used to transfer information.
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Laser is used to carry info through optical fibers.\n\nIn fiber optics, transmitters primarily consist of a laser and a modulator. The laser generates the light and the modulator changes the intensity of the laser light in order to couple the data to be transmitted. In effect, the modulator either blocks or passes the laser light depending upon the data signals being fed to it.\n\nThe lasers used in fiber optic communications are similar in many ways to those used at supermarkets and lecture halls. Both types are made in a similar fashion, using semiconductor materials much like the silicon used to make most electronic IC components. However, the one big difference between them is that communications lasers do not generate visible light, but rather infrared light.
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Yes. 'TextBridge' for example. The technology is still developing. Some software is more versatile than others in terms of the kind of graphics that can be converted -- file types; colors; etc.. Anything less than 99% accuracy is likely to be more trouble than it is worth. Even the best will need editing to correct errors. Be particularly careful of words which pass spell-check but make no grammatical sense.\n\nTextBridge was originally intended to be used in transferring office information from printed page to computer storage via scanner. The early versions do not do anything but black on white -- with scanner enhanced contrast: 99.9%. I am not up on the current limitations, but there is significant color ability available. Following some of the current free form graphic text is still likely to be iffy.
724551
Digital to digital conversion occurs when an analog system is used to convert between two digital signals.  The process involves first changing a digital signal to analog form, then the analog form is re-encoded digitally.  This process is often used to allow analog filtering techniques to be applied to digital signals.
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Analog and Digital systems just imply the type of modulation.\n\nFundamentally it doesn't matter what the carrier frequency is, so sharing bandwidth is okay .... the FCC may disagreed though.
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There is no difference.  Analog (voice) calls are digitized (sampled and quantized) the first time they hit a telco switch, usually within three miles of origin.  Everything through the network is digital.  They are converted back to analog at the local switch at the destination end -- again, within a few miles of the destination.\n\nFor transmission, calls are transmitted in 64k channels.  These are "stacked" on each other using time division mulitiplexing (TDM)and frequency division multiplexing (FDM).  T1, T3, and SONET are all built up through TDM and FDM to get the high-speed aggregate rates for long haul communications.