I understand all the protocols and whatnot, but at the physical level, how on Earth can a piece of metal conduct, say, this message that I'm typing to a server from which you can all access it?
Likewise, with VoiP or with regular phones, how is one's voice transmitted through a piece of metal back and forth from one end to another, especially considering that thousands of people may be placing a phone call in a certain region every minute?
Thanks a lot
Likewise, with VoiP or with regular phones, how is one's voice transmitted through a piece of metal back and forth from one end to another, especially considering that thousands of people may be placing a phone call in a certain region every minute?
Thanks a lot
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1. Convert photo, video, or audio to analog voltages, through a 'transducer' or 'sensor'
2. Convert analog voltages into a binary (digital) patterns of 1 and 0 in a 'sampler'
3. Once you've collected enough binary data, add extra binary info (overhead) to indicate addresses, and other protocol.
4. Over time, transmit a single bit, followed by the next bit, by either putting +15 or -15 volts on a serial cable, or some other voltage (+5, 0) into another circuit, depending on your chosen physical interface.
5. To bundle more than one signal, you need to pass each signal into it's own 'modulator'. Just like AM or FM radio, by putting each signal in it's own unique "frequency" range, more than one station can share the airwaves, (or the copper wire) without interfering. This is called "frequency division multiplexing"
6. Instead of FDM (#5), you can coordinate stations, so that each station is allowed a certain amount of time. Then a different station gets a turn. This is called "Time Division Multiplexing". If the timing windows are fast enough, and the data or info is slow enough, you can switch rapidly between stations, and still carry multiple messages on the same copper.
7. At the other end, reassemble in reverse order.
2. Convert analog voltages into a binary (digital) patterns of 1 and 0 in a 'sampler'
3. Once you've collected enough binary data, add extra binary info (overhead) to indicate addresses, and other protocol.
4. Over time, transmit a single bit, followed by the next bit, by either putting +15 or -15 volts on a serial cable, or some other voltage (+5, 0) into another circuit, depending on your chosen physical interface.
5. To bundle more than one signal, you need to pass each signal into it's own 'modulator'. Just like AM or FM radio, by putting each signal in it's own unique "frequency" range, more than one station can share the airwaves, (or the copper wire) without interfering. This is called "frequency division multiplexing"
6. Instead of FDM (#5), you can coordinate stations, so that each station is allowed a certain amount of time. Then a different station gets a turn. This is called "Time Division Multiplexing". If the timing windows are fast enough, and the data or info is slow enough, you can switch rapidly between stations, and still carry multiple messages on the same copper.
7. At the other end, reassemble in reverse order.
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digital multiplexing.The Concept of multiplexing goes back to the 19th century when they figured out how to send many messages at once in multiple directions on a single telegraph wire. There are various ways of doing it - Time slicing, Frequency differentials, and when amped up on high capacity line with digital signals and algorithms, multiplexing can be done on a massive scale.
In essence there are as many 'channels' on a wire as there are ways to figure out how to identify and separate a channel. We understand frequency separation. But in the digital age you can identify and pick out a signal based on any algorithm you can come up with. Obviously there is diminishing returns - the more you have separate signals the more overhead you need to identify and separate those signals. Capacity is in theory limitless, but speed becomes a problem if you only get a piece of your message every few minutes or so.
http://en.wikipedia.org/wiki/Multiplexin…
In essence there are as many 'channels' on a wire as there are ways to figure out how to identify and separate a channel. We understand frequency separation. But in the digital age you can identify and pick out a signal based on any algorithm you can come up with. Obviously there is diminishing returns - the more you have separate signals the more overhead you need to identify and separate those signals. Capacity is in theory limitless, but speed becomes a problem if you only get a piece of your message every few minutes or so.
http://en.wikipedia.org/wiki/Multiplexin…