Computer Hardware

To exchange a few words between computers over superior distances the best unconventional was to use the in attendance laid down telephone network, which spans across the whole country. This network can only broadcast analog signals, so normally a device called modem is used to communicate between two computers. The term modem combines the words modulator and demodulator. Simply, the modem modulator circuit exchanges binary data into tones. At the other end of the transmission line the demodulator circuit translates the tones back into binary data. By this technique, a couple of modems can send digital information over elongated, distances. The modems agree to personal computers to communicate with mainframes and each other. Modem authorizes any two devices to exchange a few words over a single pair of dedicated wires or the switched telephone network using a serial data communication protocol. The switched network comprises all the telephone; any individual can arrive at any one by dialing a number dialing a number. The switched telephone network is not only connected by wires, but it in addition uses microwave and satellite transmissions. This means it cannot be used to throw binary data limited of first converting the data to tones, since these are ac-coupled circuits.