The modem[]
A modem is an electronic device that converts computer's digital information into analog carrier signals and vice versa. Computers use modems to communicate with each other a network. The eord modem derives from 'modulator-demodulator' that defines the function it performs. Modulation is the process of changing the form of the signal carrying the information. The demodulation process does the task extracting information from the signals that are modulated. (Modem function)
The first modem was invented to trasnmit data for the North American air defense during the 1950s.Modems were used to comunicate data over the public switched telephone network.
the Bell 103 by AT&T
In 1962, the commercial modem , the Bell 103, was manufactured by AT&T. The Bell 103 was also the first modem with full-duplex [transmission], frequency shift keying ([[1]] )and had a speed of 300 bits per seconds.
A computer sends information in the form of digital signals. But the information over the telephone lines needs to be tansmitted in the form of analog signals. To solve this problem, the functionality of modem comes into play. It convers the digial signals into analog signals. These analog signals are carried over the telephone lines. When these signals reach another computer, the analog signals are converted back to the digital form by its modem.
There are six types of modems :[]
-External Modem: this is a odem separeted from the system unit in the compute case;
-Internal Modem: an internal modem is a circuit board that can be added to the system unit of the computer;
-Standard Modems: most modems used today, these modems are usually operated by commands entered from a microcomputer keyboard;
-Intelligent Modems: also called , can acept new instructions and respond to the commands while transmitting data and information;
-Short-Haul Modems: are devices that transmit signals down the cable and they don-t require an external power source;
-Wireless Modem:transmit the data signals through the air instead of using a cable.