Design and Implementation of DSL-Based Access Solutions

The World of Analog

Earlier applications that used analog modem involved text-based applications. These applications were mainly used by corporations who had a need for employees or vendors to access and use a corporate database. Digital bits and bytes from the PC applications are converted into analog waves by analog modems. Those analog waves then are transmitted through a Public Switched Telephone Network (PSTN). These waves are received by another modem, which in turn converts these signals into digital bits and bytes that the far-end (receiving) computer can understand. Figure 1-1 illustrates how the signals are converted from one PC to another from digital to analog and then back again to digital.

Figure 1-1. Signal Conversion Between ...