CSN200 Introduction to Telecommunications, Winter 2000 Lecture_02
Communication Concepts

Data Transmission Modes:
There are three ways in which data can flow in a circuit: one way only, one way at a time or both
directions simultaneously.
Simplex Data can flow in only one direction. Examples are radio, TV, computer to printers,
public address systems or any other unidirectional transmission.
Half-Duplex Data flows in only one direction at a time. It is sometimes called two-way
alternate. Communication occurs in one direction and then the line is “turned
around” and information flows in the other direction. CB radio is half-duplex.
Full Duplex Data flows in both directions at the same time. Most modem connections today
transmit full duplex increasing efficiency with data flowing on the same pair of
wires in both directions simultaneously.

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CSN200 Introduction to Telecommunications, Fall 1999 Lecture_02
Parallel vs. Serial Transmission:

Parallel:
In parallel transmission all bits in a single character are transmitted simultaneously.
Data travels in parallel (simultaneously) within a PC over the data bus (bundle of data lines).

• Point-to-point Network: A Point-to-point Network is one in which exactly two stations
are connected. It may be dial connection or a leased line.
• Costly and faster.

Multidrop: (or Multipoint)
• Describes a telephone line configuration in which a single transmission facility is shared
by several end stations.
• Also called shared circuit.
• Multidrop line: Line or circuit interconnecting several stations. Also called multipoint
line.
• Only one station can send or receive at any time, all others must wait.
• Cheaper and slower.
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