5.13. Modem network types

A modem is a device that provides the ability to exchange information between computers using the telephone network. During the communication session, both computers using a modem must be connected to a telephone line.

Faxmodems have a special scheme allowing exchange of information not only between computers, but also between computers and facsimile devices. Faxmodems are able to work in two modes: modem mode and fax modem mode, and also exchange fax messages. In this and in another case, the individual elements of work are in some respects similar, the capabilities of each mode and the technology for working with them differ significantly.

Using a modem allows you to make the following network information technology and information services.

1. Direct connection. This is the simplest way to connect two computers and organize the exchange of information between them without intermediaries and additional payment. If the hourly pay system for telephone calls is not applied, then work by modem within the local telephone network is free of charge. When a modem connection has been established using a cellular or long-distance connection, the payment is made according to the time-based tariff set for this type of communication. Direct communication is provided by special switching programs.

After the connection between the computers is established, the switching programs allow you to immediately transfer files between them. When direct switching is used, you can transfer any type of file or text information directly typed on the keyboard. The type of document that is transmitted or received during the transmission of messages may either coincide or differ depending on the transmission method used.

2. Communication with the bulletin board (BBS). In this case, a connection is made to a computer or local network in which there is a database and special software that implements the query language, searches the database for the necessary information and copies it to the subscriber’s computer. Within the local telephone network, the services of these information systems are provided to all users and are free of charge. To work with the BBS, you can use switching programs and special software that is read from the BBS itself after the first access to it using a switching program. In addition to copying files, some BBS offer additional features - address correspondence between its subscribers or posting messages addressed to a specific group of subscribers or all BBS subscribers.

3. Remote access. This is one of the ways to connect to a single computer or local office network. After this connection, the remote computer acquires the status of a full-fledged workstation of this network, and the modem simultaneously performs the functions of a network card.

4. Connect to global networks. Global is a network of computers distributed throughout the world, which provides information and other types of services on a commercial basis. Connection to the global network is carried out after connecting to a computer or local network via a modem of an intermediary - provider. Sites are called powerful information nodes, which are computers or local networks of providers connected by high-speed channels to nodes of other providers around the world and collectively forming a global network. The most famous global network is the Internet. The provider provides services on a commercial basis, and to obtain them you must first conclude a contract.