Are the modem and the codec functional inverses (i.e., could an inverted modem function as a codec............

Question

Are the modem and the codec functional inverses (i.e., could an inverted modem function as a codec, or vice versa)?

Answer 1

You really have 2 questions here... yes, they're functional inverses, but no, you couldn't reverse one to do the other's job. Let me explain.

Consider the difference... A modem converts binary digital signals into analog for transmission over the voice network and then back into a digital binary signal at the other end. A codec is the functional inverse, it's for coding analog data into digital form for transmission and then decoding it back into analog at the receiving end.

So here's a way to rephrase your question: could you use the "demodulator" portion of a modem and replace it with the "coder" portion of a codec and have the same output? Basically, no. The demodulator takes in an analog sine wave (from the modulator on the transmit side) and outputs discrete digital signals based on what is samples. With a coder, this is not the case, because it starts with a random signal (one that is not modulated in any way) and generates a digital signal by sampling that. The coder is the first step and the demodulator is the 2nd step.

Hope that helps.

PS: I can tell from the question, studying from Tanenbaum, eh? Great text :-)

Answer 2

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Answer 3

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