Modem Terminology Overview
Modem Terminology Overview - Page
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SPOT 14.4
SPOT 14.4 User's Guide
User's Guide
38GDE00001SCF - Issue 4 (11/96)
38GDE00001SCF - Issue 4 (11/96)
How Does a Modem Work ?
How Does a Modem Work ?
Unlike a computer, the telephone network was designed to respond to the
human voice. To carry voice signals over long and sometimes complex
routes, the telephone network contains a multitude of amplifiers,
repeaters and filters designed to maximise signal quality. Unfortunately
these are not designed to handle digital signals - hence the need for a
modem.
A modem converts the digital signals produced by your computer into
audible tones suitable for telephone transmission. Different tones
represent a digital high (a 1 bit) and digital low (a 0 bit). For two way
communication, the modem must also convert the audible tones received
from the telephone line back into digital signals that your computer can
understand. In electronic terms, the process of changing digital signals
into audible tones is called MODulation. The process of changing audible
tones into digital signals is called DEModulation. From these two terms
we get the name MODEM.
Hardware Naming Conventions
Hardware Naming Conventions
In communications 'tech-speak', the computer is the Data Terminal
Equipment (DTE). This term comes from large installations where
several terminals connected to a mainframe computer. The Modem is the
Data Communications Equipment (DCE).
Say for example you call the office from home. Your PC and modem
would be known as the
Originating
Data Terminal Equipment. The
equipment in the office is the
Answering
Data Terminal Equipment.
These definitions still hold true even when you receive data from the
office in response to your call. On the other hand if the office computer
were to call you at home, then it would be the Originating DTE and yours
would be the Answering DTE. At the moment these terms may seem
unnecessary, but they are important when you have to select certain
operating modes and data protocols.