What is the detailed process of communication between two computers through MODEM and public telephone switching network? Solve it

Computer communication through telephone switching network is realized by modem (commonly known as cat). Modem is a kind of computer hardware, which can translate computer digital signals into analog signals that can be transmitted along ordinary telephone lines. These analog signals can be received by another modem at the other end of the line and translated into a language that the computer can understand.

For example, when communicating, computer A sends information to computer B. First, the computer sends a digital signal that the computer can recognize through the network card. When it passes through the modem, it is converted into an analog signal and transmitted through the telephone line. When it is about to arrive at computer B, it first passes through the modem of computer B, and then it is demodulated into a digital signal. Therefore, computer B can recognize this signal and communicate successfully.

There is also a commonly used modem that converts digital signals into optical signals (commonly known as optical cats) and then transmits them through optical fibers, which is faster and more efficient.