What are the similarities of Modulation and Multiplexing?
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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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rf modulator.\nhttp://www.radioshack.com/search/index.jsp?kwCatId=&kw=rf%20modulator
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Because one of the main reasons of modulation is to shift a signal from one frequency band to another. Multiplication by a sinusoidal does this shifting directly because multiplication by a sinusoid in time domain is equivalent to a shift in frequency domain, this is one of the properties of fourier transform. Any other periodic signal other than a sinusoid will, in addition to the shift you want, introduce other "waste" or rubbish components at other frequency bands which may harm your system or someone else's. Got the point?
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Hi. All de-codable signals modulate something. Amplitude or signal strength, frequency, or phase. In FSK, two frequencies are chosen and the signal changes from one to the other. This change, or shift, is used to carry the signal. Hence FSK. Found this which may help. : http://www.answers.com/main/ntquery?s=frequency%20shift%20keying&gwp=16
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there will stretching to the string, and the amplitude and frequency will be tranmitted....but the cycles wont be at light speed...so they wont allow for instantaneous communication.  Now if the cable was fiberoptic...and pulses were transmitted...hmm
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From a data transmission standpoint, fiber optic performance is limited by attenuation and dispersion.  Attenuation is the loss of signal strength over distance; dispersion is the loss bandwidth due to the degradation of signal waveforms.
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the information is quantized, that is, it is assigned some voltage values and then it is modulated, for that modulation there are several techniques with different frequencies intervales. in the case of cable, the channel that is used to send the information is the optical fiber, so u use a transductor from voltage to light and then at the receiver u have a transducter that does the opposite. the receiver is usually the nearest cable station to ur house, so, actually the optical fiber doesn't go to your house, i'll bet u have a coaxial cable that goes up to the decoder. if u don't have a decoder (actually i'm not from the U.S. so i don't  really know if the system is the same, but it must be a lot alike) the cable goes directly to your tv, it means it wasn't codified and it is easier for your neighbors to steal your cable system. and then your tv has a system to convert this voltage signal to the images u see, and that's about it!
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Modulator Demodulator.\nWhich means that the signal is converted both to and from computer language (binary) and sounds.
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should be able send signals with minimum (atenuations)loss of signals;\nshould have a high transmission speed-Bandwith;\nAccessibility and reparable;\nproduces what enters from the begining at the end;
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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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Cheap receivers are possible.  Take AM radio, for example.  It is very wasteful of bandwidth compared to a digital transmission.  However, you can receive AM with a simple envelope detector.  You can receive AM with a "crystal radio"  constructed with only a diode, a coil, a capacitor, and a pair of headphones.
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None really - thats why digital signalling has taken over, now we have the technology. A analogue signal attenuates over distance and if you amplify it you also amplify the noise and interference. Digital signals also attenuate but can be repeated, which leaves the unwanted part of the signal behind.
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PCM (Pulse Code Modulation) is a common method of storing and transmitting uncompressed digital audio. Since it is a generic format, it can be read by most audio applications—similar to the way a plain text file can be read by any word-processing program. PCM is used by Audio CDs and digital audio tapes (DATs). PCM is also a very common format for AIFF and WAV files.\n\nDolby Digital (Formerly AC-3)\nDolby Digital is a very high quality audio encoding and noise reduction system that is the audio component of High Definition Television (HDTV) and digital broadcast TV (DTV). It is also used in DVDs, laser discs, digital cable and direct broadcast satellite (DBS) systems.
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multiplexor\nIn communications, a device that merges several low-speed signals into one high-speed transmission and vice versa.\n\nmul·ti·plex \n\nRelating to, having, or consisting of multiple elements or parts: “the whole complex and multiplex detail of the noble science of dinner” (Thomas Love Peacock).\nRelating to or being a system of simultaneous communication of two or more messages on the same wire or radio channel.
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Even I'm searching for the same.\nwell you can find some on searching with yahoo as -- "data communications".
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I think the previous answer is geared towards channel allocation and not bit rate vs bandwidth.  I will try to clarify the issue.\n\nFirst, you must understand how FM works and how a digital signal converts to FSK (frequency shift keying).  Therefore I will use a simple example.\n\nEach bit takes up some frequency.  For example, the bit '1' could take up 5 Hz carrier frequency on the bandwidth spectrum and '0' could take up 6 Hz on the bandwidth spectrum.  Therfore, there is a seperation of 1 Hz between bits.  \n\nIf I send a '1' followed by a '0' then on a meter I should see 5 Hz freqency and then a 6 Hz frequency back to back.  We could speed this up to infinity and therefore have these 2 frequencies transmitting all data at infinite speeds.\n\nIn the real world however, a '1' may fall around the 5 Hz frequency but not exactly on it.  It may be about 5 Hz.  Why around 5 Hz and not exactly on it everytime?  Because in the real world we have noise in transmission lines.  Noise can distort the frequency causing it to be a little less than 5 Hz or a little more than 5 Hz.  Imagine if the '1' bit is transmitted but on the receiving end it ends up receieved as 5.5 Hz.  What happens now?  It's not quite 5 Hz and it's not quite 6 Hz.  Noise caused it to move 0.5 Hz away from 5 Hz.  It is in the middle of 5 Hz and 6 Hz.\n\nNow the receiving end has to decide if this is '1' or '0'.  What are the odds the receiving end gets it right?  By slowing down the speed the 1s and 0s that are transmitted , you can hold steady the 5Hz or 6 Hz for that bit.  The faster you go, the less accurate the bit will fall exactly where it should on the frequency.\n\nSo, what are some possible solutions?  Well, you can slow the frequency down or make the frequency seperation larger.  For example, make a '1' be 5 Hz and make '0' be 10 Hz.  Now you have 5 Hz seperation between bits instead of 1 Hz seperation.  Now if the frequency of 5.5 Hz is received, the receiving end can determine that this should have been 5 Hz.  It's highly unlikely it was originally transmitted at 10 Hz.  Therefore, the receiving end detects a '1'.  \n\nBut what have you lost by doing this increase in frequency seperation?  You have taken up more bandwidth.  Every cable has only so much bandwidth and if you have several channels on a cable all transmitting at the same time, you need to limit the amount of bandwidth each channel takes up or you will run out.\n\nSo, therefore, since most companies don't want to backdown on speed to the consumer (you), then they upgrade their technology (i.e. cables) to higher bandwidth cables such as fiber optic cables.\n\nI hope this helped.  Others, please feel free to expand on this topic.  I've only discussed FSK modulation.  Other techniques such as PSK, ASK, QPSK, bit stuffing, NRZI, CRC, and FEC codes can improve bit rate over channels.\n\nYou can read more about bandwidth limits.  Shannon and Hartley came up with a theorem which still holds today and is used quite extensively.  I even know someone who worked with Shannon at Bell Labs back in the day.  Shannon's theorem is C = BW*log2(1+S/N) where C is the channel capacity in bits per second,  BW is bandwidth, S is the signal power and N is the noise power.\n\nWF\nTelecom Engineer
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sender , message , channel , receiver