Telecommunications Pocket Reference
Pull Telecom Answers from Your Pocket!
TABLE OF CONTENTS Telecommunications Pocket Reference
Chapter 1: Digital Transmission Fundamentals
Before talking about specific technologies, we need to first understand the fundamentals of digital transmission. When we speak about protocols, we talk about parameters, fields, and various values within these fields as if they were plain text. However, what is actually transmitted over wire, through airwaves, and through computer circuitry is nothing more than electrical current (or optical, depending on the medium). Transmission is the lowest form of communications within a network.
1.1 Analog to Digital
All transmissions within a network must be converted from binary code to electrical or optical signals. All information, including the information appended by protocols, must be sent at this lowest form of transmission. In some cases, additional information is appended at this layer to facilitate timing and error control.
1.1.1 ASCII and EBCDIC
Characters must be converted into binary numbers so that they can be converted into electrical current or optical transmission. There are two standards used for representing just plain text, without any formatting. It is important to understand that these standards are not used for the text that is generated by modern-day word processors or desktop publishing systems. When text is word processed, additional information must be provided by the source so that the receiver knows how the text is to look (italics, bold, underlined, specific fonts, etc.). This formatting is not represented in these two standards, but in proprietary formats handled at the upper layers of protocols. Applications receive envelopes of data that include binary information regarding the formatting of...
Copyright The McGraw-Hill Companies, Inc. 2000 under license agreement with Books24x7
