What is a Modem?

The name modem evolves from the term Modulator-Demodulator. It is a device that modulates an analog carrier signal to encode digital information, and also demodulates such a carrier signal to decode the transmitted information.

It is the device used for connecting and accessing the internet in the domestic sphere.

History of Modems

The first types of modems ever used were the ones used by The United States Air Force for communication between radar stations, air bases ad command centers. They worked on a simple phone line system (the twisted copper wires). The idea for using modems was derived by the telegraph system.

The early modems were called voice band modems, which worked on the binary system. The voice band modem used to turn the digital 1s and 0s of a personal computer into sounds that can be transmitted over the telephone lines of Plain Old Telephone Systems (POTS), and once received on the other side, it converted those 1s and 0s back into a form used by a USB, Ethernet, serial, or network connection.

The first commercial modem was the Smart Modem, which was launched by US Robotics in 1981. It was a modem with the capacity to send/receive data at 300 bits per second. It was attached to a small controller that let the computer send commands to it and enable it to operate the phone line. The command set included instructions for picking up and hanging up the phone, dialing numbers, and answering calls, and this made it the first modem that had a number of functions that we see today, i.e., making and receiving calls, faxes et al.
Present day modems

The modems used these days are classified into two types: Fixed line modems and radio modems.

The fixed line modems are the most used ones, due to their commercial availability and they are also very pocket friendly. Under the fixed line modems we have Dial-up modems, Broadband modems and USB modems.

The radio modems include WiFi and WiMax technology modems.

Fixed Line modems

The dial-up modem is one of the most widely used modems in the world. It usually works at speeds varying between 33 kbps and 56 kbps. It uses a phone line connection to access the internet. It connects to the PC using either a serial, parallel or USB connection if it is an external modem, and is attached to the motherboard if it is an internal one. It connects to the phone line using a RJ-11 jack. It connects by dialing a number to the service provider, and hence a connection is established. It is slow and depends on the availability of the network and congestion. The billing is also done just as a phone call is, that is on the basis of the pulse of the telephone.

The USB/PCI laptop modems are dial up modems for more portability, and are used mostly for laptops, but are compatible with desktops also. It is best suited for travelers and professionals who need access to internet at all times. They work on a microwave/mobile network technology, the same that cellular phones use (CDMA or GSM). They also dial a number to the service provider but the difference is that they use a cellular network instead of a landline. A USB modem operates either through USB port or PCI slot.

The broadband connection is the most popular form of connectivity due to its high speed. The speed ranges from 128kbps to 2mbps, which is suitable downloading multimedia. They are more secure than dial ups as they support firewalls and other security measures. They work either on a RJ 45 jack or a USB port. Many broadband modems include the functions of a router (ethernet/WiFi), which enables the user to setup a small home network too. It is much more economical as compared to dial ups as it does not work on the pulse system and hence is not fully dependent on phone line.

Major Service Providers of Broadband connections

BSNL/MTNL
Tata Telecom
Reliance Communications
Bharti AirTel

Major Modem Brands

Motorola (Better for radio modems)
Beetel (provided with all major service providers as the default modem)
Logitech

What to look for when buying a modem

Compatibility with the motherboard (in case of internal modem)
Speed of connection
Connectivity with the Motherboard (in case of external modem, serial, parallel, USB, Firewire, RJ45, RJ11)
Portability and network availability, in the case of USB modems.