Modems convert data from analog to digital and vice versa.

A modem whether it is a wireless modem, external or internal modem, are capable of more than converting analog data to digital data and vice versa. If supported, a modem can act as a telephone by allowing the user to make phone calls through their PC with the use of speakers and a microphone. This means that the modem is capable of switching from data mode, converting information, to voice mode, telephone usage. The modem can automatically answer the phone when the user is away if necessary. Also, many modems are able to send and receive faxes.