Modem
The modem is a hardware device that allows computers or routers to receive and send information over a cable or telephone line. When sending a signal, the device modulates by converting digital data to an analog audio signal. Then it transmits the sound over a telephone line and demodulates the audio by converting it to digital sound. Some companies may use the modem to send and receive a fax or act as an auto-answering machine. With the modem, computers can gain internet connectivity using telephone lines.
