Computer network and the traditional telephone network and telegraph network what is the difference between the telephone network and telegraph network, since there is a telephone network and telegrap

Computer network and the traditional telephone network and telegraph network what is the difference between the telephone network and telegraph network, since there is a telephone network and telegraph network, then why get a computer network out! First of all, the telephone and telegraph networks as one, computer networks as one. The difference is that, first, the hardware base is not the same, you can observe them using the cable, telephone network using the line is relatively thin, there are 4 wires, computer networks use twisted pair of wires inside 8 wires. Second, the use of protocols are not the same (like the language used by human beings), the telephone network uses analog signals, converted to magnetic through ordinary electricity, the middle of the line exchange using the earliest use of artificial exchange (that is, the operator as seen on TV), and finally the use of electronic exchanges, the current cell phone more than the use of signaling No. 7. Computers use digital signals, transmitted via the tcp/ip protocol, and the exchange is not the same. So there is no replacement between the two, and of course VOIP is not in the discussion, but the two are slowly converging at the moment.