Understanding Communication Technology: Signals, Media, and Networks

Fundamentals of Communication Systems

A communication system consists of a transmitter and a receiver that exchange information through a channel using coded messages (language). The communication channel is used to route messages from the sender to the receiver. Communication can be carried out through various means, including:

• Electronic Media: Radio, Television (TV), etc.
• Format: Written or Oral.

Transmission Media: Guided and Unguided

A means of transmission is defined as a physical support upon which one or more channels of transmission can carry data. These media are categorized as:

• Guided Media (Wired): Copper or cable transmission (e.g., Twisted Pair, Coaxial Cable).
• Unguided Media (Wireless): Air or vacuum, used in wireless communication.

Communication Links

Communication links are classified based on the number of participants:

• Point-to-Point Links: Used when there is a single communicant at each end.
• Multipoint Links: Used if there are several communicants at one or both alternating ends of the channel.

Signal Characteristics and Types

Key Signal Characteristics

Signals are defined by several measurable characteristics:

• Bandwidth: The maximum value of the signal, often measured in millivolts (mV).
• Period: The length of a cycle, measured in seconds.
• Frequency: The number of cycles repeated per second, measured in Hertz (Hz).
• Frequency Spectrum: The range of frequencies contained within a signal.

Analog and Digital Signals

Signals can be broadly classified into two types:

Analog Signals

A sinusoidal signal corresponds to a graph that shows a single, pure frequency. A random signal corresponds to the superposition of many frequencies. Analog signals continuously vary in volume, light intensity, or other physical properties.

Digital Signals

Digital signals operate by switching between discrete states (e.g., open/closed switch, on/off light bulb).

Wired Communication Technologies

Common guided transmission media include:

• Twisted Pair Cable: Consists of two copper wires twisted together.
• Coaxial Cable: Features a copper inner conductor, an insulator, and a copper mesh shielding layer designed to protect against external electrical interference.
• Fiber Optic Cable: Provides high bandwidth, greater lightness, and faster transmission with less interference. It is made of pure crystal (glass) or plastic shielding.

Wireless Communication Components and Systems

Antenna Technology

The antenna is the device responsible for converting electrical signals that travel in waveform into pulsed electromagnetic waves, and vice versa, allowing information to be transmitted wirelessly.

Communications Satellites

A communications satellite is essentially a repeater placed in orbit. Its behavior is similar to a mirror that reflects the data sent from a ground station to a terminal installed in the territory to which the satellite provides coverage.

Mobile Telephony

Mobile telephony, also called mobile phones, basically consists of two parts:

1. A communications network (or mobile network).
2. Terminals (or mobile phones) that allow access to that network.

Television Technology

Television is a system for transmitting and receiving moving images and sound from a distance. This transmission can be carried by radio waves or specialized cable television networks. The receiver of the signal is the television set itself. The word "television" is a hybrid of the Greek word "tele" (distance) and the Latin "visio" (vision).

Effects of Radiation Exposure

The effects of radiation may be acute, appearing a short time after exposure to radiation, or chronic, which often appear many years after receiving exposure.