Information Technology Reference
In-Depth Information
Figure 6.1
Medium (4)
Elements of a
Telecommunications System
Telecommunications devices relay
signals between computer systems
and transmission media.
Telecommunications
device (5)
Signal (2)
Signal (2)
Medium (4)
Telecommunications
device (3)
Sending computer
system and
equipment (1)
Receiving computer
system and
equipment (6)
Medium (4)
Signal (2)
headquarters in Geneva, Switzerland. The international standards produced by the ITU are
known as Recommendations and carry a high degree of formal international recognition.
Communications between two people can occur synchronously or asynchronously. With
synchronous communications
, the receiver gets the message instantaneously, when it is sent.
Voice and phone communications are examples of synchronous communications. With
asynchronous communications
, the receiver gets the message after some delay—sometimes
hours or days after the message is sent. Sending a letter through the post office or e-mail over
the Internet are examples of asynchronous communications. Both types of communications
are important in business.
Using telecommunications can help businesses solve problems, coordinate activities, and
capitalize on opportunities. To use telecommunications effectively, you must carefully
analyze telecommunications media and devices.
synchronous communications
A form of communications where
the receiver gets the message
instantaneously, when it is sent.
asynchronous communications
A form of communications where
the receiver gets the message after
some delay—sometimes hours or
days after the message is sent.
Telecommunications technology
enables business people to
communicate with coworkers and
clients from remote locations.
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Basic Telecommunications Channel Characteristics
The transmission medium carries messages from the source of the message to its receivers.
A transmission medium can be divided into one or more telecommunications channels, each
capable of carrying a message. Telecommunications channels can be classified as simplex,
half-duplex, or full-duplex.
A
simplex channel
can transmit data in only one direction and is seldom used for business
telecommunications. Doorbells and the radio operate using a simplex channel. A
half-duplex
channel
can transmit data in either direction, but not simultaneously. For example, A can
begin transmitting to B over a half-duplex line, but B must wait until A is finished to transmit
back to A. Personal computers are usually connected to a remote computer over a half-duplex
channel. A
full-duplex channel
permits data transmission in both directions at the same time,
so a full-duplex channel is like two simplex channels. Private leased lines or two standard
phone lines are required for full-duplex transmission.
simplex channel
A communications channel that can
transmit data in only one direction.
half-duplex channel
A communications channel that can
transmit data in either direction, but
not simultaneously.
full-duplex channel
A communications channel that
permits data transmission in both
directions at the same time, so a
full-duplex channel is like two sim-
plex channels.
