A modem is a computer hardware device that converts digital data signals into modulated analog signals that can be transmitted over analog transmission media such as telephone or radio. The word "modem" is a portmanteau of "modulator-demodulator" because it modulates digital signals to analog signals and demodulates analog signals back to digital signals. The primary purpose of a modem is to transmit data through various communication channels, including telephone lines, cable lines, or wireless networks. Modems make it possible for established telecommunications media to support a wide variety of data communication, such as e-mail between personal computers, facsimile transmission between fax machines, or the downloading of audio-video files from a World Wide Web server to a home computer.
Modems can be used with almost any means of transmitting analog signals, from light-emitting diodes to radio. Most modems are "voiceband," which means they enable digital terminal equipment to communicate over telephone channels, which are designed around the narrow bandwidth requirements of the human voice. Cable modems, on the other hand, support the transmission of data over hybrid fiber-coaxial channels, which were originally designed to provide high-bandwidth television service.
A modem connects you to the Internet by interpreting signals from an Internet Service Provider (ISP) and typically, these signals are sent across coaxial cables or phone lines. While both a modem and a router help your devices connect to the internet, they have separate (and complementary) functions. A modem is a box that connects your home network to your internet service, while a router lets your devices talk to one another and use that internet connection.
