What's the difference between telephone line and subscriber line?

Question

A book says a telephone line normally has a bandwidth of 3kHz and the highest bit rate for a telephone line is 34.860kbps(using shannon formula).
It also says the bandwidth of a subscriber line is 4kHz and the upper bit rate can be up to 56kbps(using a sophisticated modem to change the digital signal to analog).
I don't know why the upper bit rate is 56kbps.How to calculate it?

Answer 1

First you are mixing apples and oranges.



A true Modem uses a plain old telephone service line. PoTS

They download at speeds limited by the FCC to 53Kb/s. They upload at 33Kb/s <-- here's your Shannon Formula limit in practice.



A subscriber line is what DSL uses. Digital Subscriber Line.



The things people use for Cable, DSL, FiOS, or Satellite Internet access are not Modems. They do NOT MOdulate or DEModulate. That is the definition of MODEM, it must MOdulate and DEModulate, which is converting a digital signal to an analog one, and vice-versa. They are physical network bridges. They bridge a digital signal from Ethernet or USB; to Cable, DSL, or Satellite maintaining the digital format of the original signal.

Answer 2

Broadband can mean DSL, cable, fiber optic (such as T1/T3). If you are trying to compare DSL and wireless service such as Verizons or other similar service, you'll see a major difference with either DSL or cable. Wireless service can be as fast or much faster then a dial-up, depending on the service. It might be as good as 256kbps. If I can borrow the Verizon card from the sales team, I'll have to run a test on it to see how fast it is. Fiber is pretty expensive ($600+ a month per line). We have two T1's at work, one is for data, second is for voice, which is rated at 1.5 mbps versus some of the faster DSL and cable, which I've seen offered around the NE around 10mbps. Keep in mind that a T1 guarantees that bandwidth, where as with dsl and cable it will vary. And the upload of dsl and cable isnt comparable as a T1. Personally I prefer cable over dsl, this is while comparing the two in various places and companies in NM, CO, VT, NH, NC. It maintains its speed more consistantly and doesnt have the drops as the dsl does with incoming calls. BTW, to clarify another post, broadband also includes dial-up...

Answer 3

The telephone line which has a DSL as well, is connected to a Filter which filters out the DSL signal and sends it to the Computer/modem and the Telephone frequency to the Telephone set. Since human brain can detect 4Hz to 20 Hz, the frequency below 4 hz as detected by Filter is sent to the modem and all frequency bove 4hz to telephone line.



Important:- when we are surfing and get a call, we get disconnected and can login only when the phone is free...Change the filter...the small white colour box to which the phone line from outside is coming is connected.

Answer 4

the speeds of the internet are set by the fcc.

its got nothing to do with the physical limits of the copper.

if thats what your asking.