Modems . A Basic Question

[shiju joseph]

What is the exact reason the digital signals can't be sent via telephone lines?

I am looking for an exact reason

thanks in advance
shiju

white

[herbieII]

In one word...bandwidth

Roger L. McElfresh

[Shahzad]

In simple words it is the bandwidth.
Why? because Digital signals require more bandwidth to travel (infect unlimited bandwidth) and telephone lines have bandwidth of 4kHz. Every media has its own charactestic bandwith, the most high bandwidth is of-course supported by optical fibers.
Why digital signals need more bandwidth? because it consists of pulses and pulses are composed of infinit harmonics: the fourier transform!

Shahzad

[joseph shiju]

Dear Shahzad

Thanks a lot for a clear answer.If so what happens when we use ISDN.What sort of
sampling makes it possible that data goes digitally itself. Please find enough time to send me a
detailed replay. my mail id is shijujoseph@excite.com

thanks
shiju

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