I must be really missing something, but here it goes. How does upgrading your Internet connection to DSL or a T1 line speed you up if the network infrastructure is still the same–low-bandwith telephone lines. Or, possibly more to the point, what are the physical elements that constitute this DSL’s and T1’s and how exactly do they manage to effect the aforementioned improvements on data transmission speeds?
the same copper wire is used (T1’s usually use 2 pairs) but the info is transmitted digitally (D) (along with ISDN) instead of analoge (A).
When you use a modem (standard phone service) the modem translates the signal from D to A.
The digital encoding is just more efficent. A T1 can encode 24 voice channels and there is talk of supassing that with voice over dsl.
But, aren’t telephne lines analogue? Isn’t that why you need a modem? If ISDN and T1 are digital, how can they transmit information through an analogue medium such as old telephone lines?
Also, how do you decode the data you requested when using these high-speed connections?
Sorry for all the questions; I’m realy confused. :rolleyes:
The wire isn’t inherently digital or analog. It’s just something current can flow through. It’s how you make use of that fact that matters. If you have DSL, there’s equiptment at the other end of the line prepared to handle digital signaling.
If there’s no such equiptment, all that’s at the other end is appropriate switching equiptment to connect you up, possibly through a number of intermediate switches (you call the lines between them “trunks”), to another telephone (or modem, or fax machine) via it’s line. The two devices then pass analog signals back and forth directly. Your dialup modem converts digital data into encoding that will work when switched as ordinary analog voice, then a modem at your ISP can translate that back into digital data.
Your DSL ISP will have something called a DSLAM (DSL Access Multiplexor) in your central office to accept the digital signals from your line, and connect you to the ISP’s network.
In fact, there a more stringent requirements on the quality of the line for acceptable use to carry digital signals, hence the concern about whether you have “clean copper” between your house and the CO, and exactly how far away you are - DSL won’t work over too long a distance.
If you want details about how the digital data is encoded into voltage levels on the line, and the sort of handshaking that goes on between your DSL modem and the DSLAM, I’m not competent to answer.
remember that your computer has copper wires all throughout at that produces a digital signal.
Then again what is really sent is a pulse of electricity that simulates a digital signal. There is some lag time going from 0 to 1.
The wire itself is just the conduit that the signal passes through the signal generator is what is digital or analoge
The bandwidth of a twisted pair (phone wire) is way above the 3 or 3.5 Khz that the phone company uses to transmit your voice. If you are using the voice channel of a regular phone, the bandwidth is not limited by the wires but by the phone company’s equipment. They give you 3 Khz because that’s all you need for voice but the wires can carry more. You could have several independent phone “lines” sharing a single physical twisted pair.
and as more people are getting multiple phone lines sometimes (a lot of times) there just isn’t enough copper pairs to go around. It is not uncommon for your home phone line to share copper with your neigbors.