Why do you need a router and a "cat" to install broadband?

Cat is to realize the coupling of different signals. For example, telephone line cat realizes analog-to-digital and digital-to-analog conversion, that is, analog signals are converted into digital signals, and digital signals are converted into analog signals. Computers are digital signals, while analog signals are transmitted over telephone lines. The modulus is called the modulation coefficient, and the modulus-> number is demodulated, so the cat is commonly known as Modem in Chinese. Similarly, the power cat is the modulation and demodulation of two kinds of electric signals, and the light cat is the modulation and demodulation of photoelectric signals. Basically, as long as you use the last mile technology, you must use a cat to access it. As for the home router, it is a device that simply integrates NAT and 4-port switch, which can realize a broadband account and everyone can enjoy the function of surfing the Internet. If you don't use a broadband router, you can only use a computer to surf the Internet, and deeper technology can be enjoyed. I hope we don't discuss it here.