Introduction to Data Communications
4. Data Communications
 

4. Data Communications

Data Communications is the transfer of data or information between a source and a receiver. The source transmits the data and the receiver receives it. The actual generation of the information is not part of Data Communications nor is the resulting action of the information at the receiver. Data Communication is interested in the transfer of data, the method of transfer and the preservation of the data during the transfer process.

In Local Area Networks, we are interested in "connectivity", connecting computers together to share resources. Even though the computers can have different disk operating systems, languages, cabling and locations, they still can communicate to one another and share resources.

The purpose of Data Communications is to provide the rules and regulations that allow computers with different disk operating systems, languages, cabling and locations to share resources. The rules and regulations are called protocols and standards in Data Communications.

5. Why Telecommunications?

What does networking have to do with telephones?
Telephones and networking work hand in hand. The telecommunications industry has been gradually integrating with the computer industry and the computer industry has been gradually integrating with the telecommunications industry. The common goal is to join distantly located Local Area Networks into Metropolitan and Wide Area Networks (MANs and WANs).

5a. Voice Channels

First thing that comes to mind is telephone systems and the phone at home. Talking to someone on the phone uses Voice Channels. This doesn't seem to have much to do with Networks!

We do use voice channels for modem communications to connect to BBSs (Bulletin Board Services) or to connect to the Internet. We also use voice channels to connect LANs using remote access. Due to the bandwidth limits on the Voice Channel, the data transfer rate is relatively slow.

Voice Channel: Dial-up connection through a modem using standard telephone lines. Typical Voice Channel communication rates are: 300, 1200, 2400, 9600, 14.4k, 19.2k, 28.8k, 33.6k and 56 kbps (bits per second).

5b. Data Channels

Data channels are dedicated lines for communicating digitized voice and data. At the end of 1996, there was a major milestone where more data was communicated in North America's telecommunications system than voice.