Communication and Media Technology
Forms of media affect and saturate every aspect of our daily lives. Media spreads information and advertising messages, documents world affairs as well as private events, and serves recreational purposes.
Modern technology has made this more convenient than ever.
Technology – fixed-line telephone Networks
Thanks to the digitization of the telephone system, calling has become much more convenient in the last few years. Numerous new services have also become available.
Today, most fixed-line systems include fiber-optic network cables that link different individual cities or geographic areas. However, individual customer connections, also known as the “last mile,” still usually consist of the original double copper wire that connects them to the telephone company’s local exchange.
When a user picks up or activates the telephone receiver, it forms an electrical circuit to the local ex- change. Dialing a phone number sends two combined tones for each digit to the exchange office, initiating the process that connects the telephone call.
Telephone exchanges
Exchanges are the individual nodes in the telephone network. The local exchange is responsible for managing customers’ connections. When a user makes a call, the local exchange is the first point of contact. The person being called is often not directly connected to the same local exchange, therefore the phone call may be routed over various higher-level centers to reach their local exchange.
Main centers function as connection points between distant networks, routing calls from one network to those of other domestic telephone providers. International phone calls are routed through international gateways.
With the introduction of computer technology into telephone networks, separate channels were established for voice and signal data. The data carried by the signal network includes the phone number being called and the local exchange of the call recipient, in addition to connection and disconnection information for the voice channel.
ISDN
ISDN, or Integrated Services Digital Network, is an international standard for digital communications networks. With traditional analog landlines, the voice signal is not digitized until it reaches the local exchange. ISDN digitizes the entire connection, starting at the telephone or other device.
In addition, several channels can be used at the same time within one connection, allowing users to make phone calls, surf the Internet, or send a fax at the same exact time. ISDN also offers numerous convenient features for its users, such as caller identification, call forwarding, and the management of multiple callers simultaneously.
DIGITIZING VOICE SIGNALS
To digitize a voice signal, a converter samples the sound signal several thousand times per second. Each value is represented as a binary series of ones and zeros, easily processed by computers.
In this way, many telephone conversations and accompanying data signals can be transmitted almost simultaneously over a single line.
BASICS
WIRELESS TELEPHONES consist of a mobile unit and a base station. The mobile unit maintains a radio link with the base station, which is connected to the local telephone network.
EARLY FIXED-LINE telephone networks used only copper wires for all connections.