Transcript Communication Systems

Core 3: Communication Systems
We are going to look at the following…
• Teleconferencing Systems
• Messaging Systems
• Electronic Commerce Systems
But before we do that there are a number of large
wide area networks used to transmit data on the
above systems that need to be clarified.
Internet
The internet is a worldwide packet
switched public network based on the
internet protocol where all data moves
between nodes within IP datagrams. The
internet is designed for asynchronous
(emails etc) and synchronous (webcam
etc) purposes.
Public Switched Telephone Network
(PSTN)
PSTN is a network that carried traditional
telephone connections throughout the
world. It establishes a synchronous
connection between individual clients in a
circuit. Internet service providers often
lease out PSTN connections rather than
establish their own infrastructure.
Intranet and Extranet
An intranet is a private network maintained by a
company or government organisation and is based on
the Internet protocol (IP). Optical fibres are often used in
intranets because the short distances aren’t too
expensive to cover with cables. WAN stands for private
Wide Area Network.
Extranets are an extension of an intranet and allow
customers and other users outside the organisation. For
this reason the extranet MUST be secure.
Both Intranets and Extranets can also include VPN’s or
Virtual Private Networks. A VPN uses the internet to
allow external access to an organisations Intranet.
We are going to look at the following…
• Teleconferencing Systems
• Messaging Systems
• Electronic Commerce Systems
Teleconferencing is a multi-location, multiperson conference where audio, video
and/or other data is communicated in real
time to all participants.
There are two examples of this from page
262 – 271 of the text.
For one of the two
examples in the text create
single page document that
includes the Information
System diagram (see right)
as well as a list of
advantages /disadvantages
below the diagram.
This should fit on a single
A4 page.
Distance Education System


Environment – ABC University,
lecturer, local students, servers for
video transfer, remote students
and their PCs and internet
connections.
Purpose – Enable remote students
equal learning opportunities,
reduce work for lecturers, allow
remote students to connect via the
IT they have in their home, allow
for minimal disruption within the
lecture (webcam etc should be
used discretely).
Distance Education System



Data/Information – Participant
audio, Participant video stream,
application software for running
conference or sharing documents
during conference, text chat
program, IP addresses, PIN
numbers.
Participants – Lecturers, local
students, remote students.
IT – Purpose built audio, video,
web teleconferencing room
including PCs, displays,
projectors, cameras, microphones.
Distance Education System


Information Processes – Audio and
video are collected, audio and video
are transferred through internet,
servers process, information is
received and displayed.
Advantages/Disadvantages –
Remotes students do not need any
special IT, Video streams are
automatically adjusted to fit remote
students internet specs, PTSN provides
reliable audio connection for all
participants, remote students with
poor internet connections may
experience video lag, home telephone
of remote student may be tied up
during extensive telecom calls.
We are going to look at the following…
• Teleconferencing Systems
• Messaging Systems
• Electronic Commerce Systems
1. Traditional Phone and Fax

Telephones are largely similar to the way that
they were when first created 100 years ago. Old
phones used to use pulse dialling and were
connected through copper wires that were
manually changed by an operator. Now phones
use tone dialling and the copper wire is changed
using electronic switching, which is automatic.
There is also a use of analogue AND digital
transmission rather than analogue only. The PSTN
includes more digital mediums and less use of
copper wire now.
1. Traditional Phone and Fax
 Fax
machines are similar to telephones.
These days they use a digital signal of
compressed bits to describe an image
collected by light sensors. The receiver
then recreates the image and uses an
inkjet or laser printer to reproduce it.
2. Voicemail and Phone Information Services

Voice mail used to be a timed analogue recording
that was stored on a tape. Now it is a digital version
that records after having given the outgoing message
after a certain number of rings. The digital file is
stored in the customer’s voice mailbox. The customer
can then ring the voicemail and have the recording
played back to them. Voice mail can also be used as
a decision tree; for example “Press 1 to access junior
school. Press 2 to access the front office.” Etc.
Come to page 279 of the text…
3. Voice over Internet Protocol (VoIP)
 Voice
Over Internet Protocol (VOIP) uses
the internet to transfer individual digital
recordings that are strung together to sound
like a conversation. It uses IP addresses and
the internet rather than PSTN. It is also
different because it provides an interface
for the connection.
Come to page 283 – 284…
4. Electronic Mail


During email the message is composed of two
broad components – the envelope and the
contents.
Envelope: The envelope contains the
information required to transfer the message to
its destination, much like a physical envelope.
The envelope data is examined and used by
SMTP servers to relay messages to other SMTP
servers and ultimately their destination.
4. Electronic Mail
 Email
Contents: The contents contains the
actual message data together with various
header fields used to specify sender,
receiver, date/time, subject and also
relationship of this message to other related
messages.
Page 285 – 287 of the text outlines all of the
possible header fields attached in the contents
of an email.
4. Electronic Mail
MIME (Multipurpose Internet Mail Extensions
 Mime
is the protocol used to code nontextual data and attachments into ASCII so
that it can be transmitted within email
messages. MIME is used to code HTML
email messages, image files, video files and
any other type of file attached and
transmitted via email.
We are going to look at the following…
• Teleconferencing Systems
• Messaging Systems
• Electronic Commerce Systems
Financial transactions that occur over an
electronic network are all examples of
electronic commerce.
In this section we will explore – ATM’s,
EFTPOS and Internet Banking.
ATM’s or Automatic Teller Machines

ATMs are used to withdraw money from a bank
account. The collection devices include a magnetic
stripe reader that collects magnetic information from
the back of the customer’s card, and a keypad used
to input the customer’s PIN. Display includes an LCD
screen and a receipt printer. Cash dispensers
include a safe that contains drawers for each
denomination of bank note and another drawer for
bills that are rejected. ATMs are connected to their
respective bank using a dedicated phone line or an
Ethernet connection.
EFTPOS or Electronic Funds Transfer at point of sale


EFTPOS machines are similar to ATMs in that they
use a card and PIN to access a bank account and
make a transfer. However, they are different in that
they can only charge money on an account rather
than withdraw money, also they don’t deal with cash.
They are connected to the banks through a
dedicated phone line on the PSTN.
EFTPOS organises the transfer of cash from one
institute to another by verifying the account and then
making a withdrawal from the bank, and a deposit in
the receiving institute.
Internet Banking

Internet banking allows bank customers to pay
bills, transfer money between accounts and
perform carious other functions from the comfort
of their home or office. It is more cost effective
than face-to-face banking and is also available
24/7. Uses user ID and password. Connects
directly to the banks web server using a URL with
https. Https shows that it is a http with SSL (secure
sockets layer) or TLS (Transport Layer Security).
Come to page 300 of the text…