Modem is a device that modulates an analog signal to encode into the digital signals and also demodulates it to transmit the information. Modems can be used over any means of transmitting analog signals, from light emitting diodes to radio. The most familiar example is a voice band modem that turns the digital data of a personal computer into modulated electrical signals in the voice frequency range of a telephone channel. These signals can be transmitted over telephone lines and demodulated by another modem at the receiver side to recover the digital data. The modems are of various types.
- Internal Modem:
Internal Modem is the device installed in the desktop or laptop computer to communicate over a network with other connected computers. These are cheaper than external modems as they do not requirea power supply or a chassis. There are two types of internal modems: dial-up and WiFi® (wireless). Dial up works on the telephone cables and requires a network access phone number and log on credentials to make a connection and WiFi modem comments to the network without filling these credentials
- External Modem:
External modems are the simplest type of the modem to install this kind of modem you didn’t open the computer. The telephone line plugs into a socket on the rear panel of the modem. As external modems have their own power supply you can turn off the modem quickly to break the connection. The examples of these modems are the DSL modems which are used in the broadband connections.
- PC Card Modem:
These modems, designed for portable computers, are the size of a credit card and fit into the PC Card slot on notebook and handheld computers. These modems are removed when the modem is not needed. Except for their size, PC Card modems are like a combination of external and internal modems. These devices are plugged directly into an external slot in the portable computer. So no cable is required other than the telephone line connection. The cards are powered by the computer, which is fine unless the computer is battery-operated. Running a PC Card modem while the portable computer is operating on battery power drastically decreases the life of your batteries.