Understanding Signals and Communication: A Comprehensive Look
Understanding Signals and Communication
Key Competencies:
- LC: Linguistic communication
- MCST: Mathematical competence and basic competences in science and technology
- DC: Digital competence
- LL: Learning to learn
- SIE: Sense of initiative and entrepreneurship
- CAE: Cultural awareness and expression
- SCC: Social and civic competence
Analogue vs. Digital Signals
Analogue signals have an almost infinite number of values, such as frequency and amplitude. They are continuous signals which are similar (analogous) to the original information that produces them. For example, old-fashioned radios and phonographs used analogue technology.
Digital signals have individual, non-continuous values. They normally use a binary system of ones and zeros to represent numbers or digits. Nowadays, televisions, computers, and mobile phones use digital signals.
Analogue-to-Digital Conversion
Analogue-to-digital conversion uses many individual samples of analogue signals. For example, a scanner can make a digital image of a drawing by sampling the lines and colours in many places. If we want a very detailed, high-resolution image, the scanner must make a very large file with many digital samples. We can also make digital files of analogue audio signals. For example, when you talk on the telephone, it takes about 8,000 audio samples of your voice every second. Digital music recordings usually have 44,000 samples per second, and Blu-ray recorders take about 192,000 samples per second.
Periodic vs. Random Signals
Periodic signals are predictable because they follow a mathematical formula and repeat the same pattern again and again. They are often used to carry messages for telecommunications. Electromagnetic radiation is periodic.
Random signals are unpredictable. Human voices and musical recordings are examples of random signals.
Communication Basics
Communication is the transmission of information from one place or person to another. This process involves a transmitter, a medium, a message, and a receiver.
Bandwidth is the amount of information per second that a connection can transmit. Data transmission is measured in bits per second (bps). Audio and video transmissions are measured in hertz (Hz).
Types of Electromagnetic Waves and Their Uses
- Radio waves are used to transmit radio, television, and mobile phone signals. They are also used for wireless (Wi-Fi) systems and magnetic resonance scanners.
- Microwaves are used for communications and heating food. Microwaves are non-ionising, but they produce heat and they can affect the human nervous system.
- Infrared waves are emitted by materials with a temperature above absolute zero, which is 0 Kelvin or –273.15 °C. Television remote controls and night-vision goggles use infrared waves.
- Visible light is the electromagnetic radiation that the human eye can detect. Each colour of the rainbow corresponds to a different wavelength and frequency.
- Ultraviolet light is not visible to the human eye. This type of radiation has a lot of energy, and it can break the bonds between atoms. Ultraviolet light from the Sun can darken our skin, giving us a suntan. However, it can also cause sunburn and skin cancer. Most of the Sun’s ultraviolet light is absorbed by the ozone layer in the Earth’s atmosphere.
- X-rays can pass through most materials, so we use them to see inside closed objects, such as luggage at an airport, and to take x-ray photos for medical purposes. X-rays are a type of ionising radiation, so they are dangerous if we don’t take precautions.
- Gamma rays are very dangerous because they transmit a lot of energy. We use them in astronomy and in medicine. Gamma rays are used to diagnose and treat cancer and to sterilise medical instruments.