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NTC 360 Telecommunication Systems




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Telecommunications Systems
Paul Hartfield
June 14, 2010
Ricky Chow

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Telecommunications Systems
Technological advancements in telecommunications after the invention of telephone have
brought about significant changes in the way businesses communicate with clients. The need to
communicate with clients as well as have a connection between company regional branches and
their partners is crucial in telecommunications and efforts to ease communication.
Rotary and Dual Tone Multi-frequency (DTMF)
Rotary dial telephones generate a unique code, or series of electrical pulses as the dial
rotates back to position that corresponds to the number the person dials. A touch-tone telephone
generates tone signals known as dual tone multi-frequency when a person presses a button on
the telephone.
Wide Area Telecommunications Service (WATS) and leased lines
Wide Area Telecommunications Service (WATS) allows individuals to make outgoing and
incoming calls (OUTWATS and INWATS), or a combination of both services. INWATS is toll-
free dialing whereas OUTWATS is long distance dialing. Leased lines are telephone
connections; permanent fiber optic connections also known as dedicated lines and consist of a
telephone connection between two points set up by a telecommunications carrier.
Private Branch eXchange (PBX) and Centrex
Private branch exchange (PBX) is a business-oriented system located on the company’s
premise and is designed to provide efficient voice communications among company users. Calls
take place between users in the same company.
The layers of the International Standards Organization-Open Systems Interconnection (ISO-

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OSI) model
The OSI model defines the communication process into seven layers and has clear
characteristics as each layer is self-contained and implementation is independent. Therefore,
one layer can update without affecting the other layers.
Layer 7 – Application
The Application layer deals with application and end user processes. This layer is
application-specific and provides services typically associated with the application layer and
includes telnet, HTTP, FTP, TFTP, and SNMP.
Layer 6 – Presentation
The Presentation layer is responsible for formatting or presenting data into a compatible
form the Application layer can decipher. Sometimes called the syntax layer, formatting and
encryption of data is sent across the network, thus providing freedom from compatibility issues.
Layer 5 – Session
The Session layer is responsible for setting up, coordinating, and terminating conversations,
exchanges, and dialogs between applications at each end by assigning a session ID number to
each session keeping data streams separate. The Session layer deals with session and
connection coordination.
Layer 4 - Transport
The Transport layer is responsible for transition between the upper and lower layers of the
OSI model while managing end-to-end control and performs error checking. The Transport
layers main function is to ensure that complete data transfer exists. Data at the Transport layer
is known as a segment.
Layer 3 – Network

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