Modem

Modem is a part that converts the signal into the information signal (carrier) and ready for delivery and the part that separates the information signal (which contain data or messages) received from the carrier signal so that information can be well received. Modem is a two-way communication tool. Each remote communications devices typically use two-way section called "modem", such as VSAT, microwave radio, etc., but generally the term modem is better known as the hardware that is often used for communication on the computer.

Data from the computer in the form of a digital signal provided to the modem to be converted into an analog signal. Analog signals can be transmitted through several media, telecommunications such as telephone and radio.

Arriving at the destination modem, the analog signal is converted into digital signals back and sent to the computer. There are two types of modems are physical, ie an external modem and internal modem.

The types of modems
Modem 3GP
CDMA Modem
GSM Modem
Analog modem is a modem that converts analog signals into digital signals
ADSL Modem Cable Modem is a modem that receives data directly from service providers via cable TV
Source : www.wikipedia