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Core 3: Communication Systems

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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.

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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.

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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 arent 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 VPNs or Virtual Private Networks. A VPN uses the internet to allow external access to an organisations Intranet.

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Teleconferencing is a multi-location, multi- person 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.

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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.

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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).

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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.

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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.

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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.

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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.

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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 customers 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

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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

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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.

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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.

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4. Electronic Mail MIME (Multipurpose Internet Mail Extensions Mime is the protocol used to code non- textual 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.

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Financial transactions that occur over an electronic network are all examples of electronic commerce. In this section we will explore ATMs, EFTPOS and Internet Banking.

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ATMs 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 customers card, and a keypad used to input the customers 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.

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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 dont 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.

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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).

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Come to page 300 of the text