communications

In the electronic world, it is the transfer of data and information from one location to another. "Data communications" or "datacom" refers to digital transmission. "Telecommunications" or "telecom" refers to voice or a mix of voice and data, both analog and digital. Although all long distance trunks are digital, and digital lines get closer to the end user all the time, there is still analog service into homes and offices.

"Networking" refers specifically to a local area network (LAN); however, a wide area network (WAN) is commonly called a telecom network.

The term "communications" may refer only to telecom-related subjects such as PBXs, modems, call centers and the like. However, the word is also a common English word such as in the "Analog Vs. Digital Communications" headline below. Thus, "communications" is used specifically in some cases and generically in others.

The Protocol
The way data communications systems "talk to" each other is defined in a set of standards called "protocols." Protocols work in a hierarchy starting at the top with the user's program and ending at the bottom with the plugs, sockets and electrical signals. See communications protocol and OSI.

Analog Vs. Digital Communications
Prior to the Internet, the world's largest communications system was the telephone network, a mix of analog and digital communications. The system, which used to be entirely analog transmitting only voice frequencies, is now almost entirely digital. The only analog part is the line between your telephone and a digital conversion point (digital loop carrier) within a mile or so of your house. Analog systems are error prone, because the electronic frequencies get mixed together with unwanted signals (noise) that are nearby.

Amplifiers Boost the Noise
In analog telephone networks, amplifiers were placed in the line every few miles to boost the signal, but they could not distinguish between signal and noise. Thus, the noise was amplified along with the signal. By the time the receiving person or machine got the signal, it may have been impossible to decipher.

Repeaters Regenerate
In a "digital" network, only two (binary) distinct frequencies or voltages are transmitted. Instead of amplifiers, repeaters are used, which analyze the incoming signal and regenerate a new outgoing signal. Any noise on the line is filtered out at the next repeater. When data are made up of only two signals (0 and 1), they can be more easily distinguished from the garble. Digital is simple.

The First Analog Communications

In 1876, Alexander Graham Bell sent the first electronic communications over a wire when he said, "Mr. Watson. Come here! I want you!" (Image courtesy of AT&T.)