How is ISDN different than a regular phone line?
The way it all works has to do with the type of waveform an analog modem sends versus a digital modem waveform. An analog waveform might look something like this: But that can only happen in a perfect world. In the real world, an analog phone line will by nature, pick up a lot of static, or Electromagnetic Interference, the proper term. Once that line gets noise, the waveform looks a lot more like this: You can see that with the waveform distorted like that, it becomes much more difficult for the modems to determine what is really being transmitted. If a modem incorrectly receives part of that waveform, then it must be resent, slowing it down even further. If the noise gets too bad, then the modems might not be able to determine whats being sent at all, and terminate the connection completely. ISDN gets around this problem by sending a different type of waveform. An ISDN signal may look more like this: Thats a digital signal. There is no degree of variation; the signal is either up or
