Back to the topics list

Information Technologies and Instrumentation: Appropriately designed technologies (e.g., radio, television, cell-phones, wired and wireless computer networks) make it possible to detect and interpret many types of signals that cannot be sensed directly. Designers of such devices must understand both the signal and its interactions with matter. Many modern communication devices use digitized signals (sent as wave pulses) as a more reliable way to encode and transmit information.

Information Technologies and Instrumentation: How Waves Carry Our Messages 📡

Imagine you’re texting a friend, watching a YouTube video, or listening to your favorite song on wireless earbuds. None of that is magic. It all depends on something invisible moving around you all the time: waves that carry information. Designers and engineers build special devices that can send, catch, and understand these waves—even when our own senses cannot detect them directly.

These devices include radios, TVs, smartphones, Wi‑Fi routers, and even the sensors in weather satellites. They all rely on the science of waves, signals, and how those signals interact with matter (like air, metal, buildings, and our bodies).

To understand how this works, we need to explore what waves are, how we turn information into signals, and why digital signals are so important in modern technology.

The idea of signals traveling as waves is introduced with a simple example in [Figure 1], where you see how sound and radio waves spread outward from a source.

What Is a Wave?

A wave is a disturbance that carries energy and information from one place to another, usually without moving matter permanently from one place to another.

Think of a sports stadium “wave.” People stand up and sit down again. The people do not move around the stadium, but the wave of motion does. That moving pattern is like a wave carrying energy and information (“stand now!”) around the stadium.

Many communication technologies use electromagnetic waves, such as:

• Radio waves (radio, Wi‑Fi, Bluetooth)
• Microwaves (Wi‑Fi, cell phones, satellite links)
• Visible light (fiber‑optic cables, remote controls with LEDs)

All electromagnetic waves travel through empty space at the same speed: the speed of light, usually written in formulas as \(c = 3.0 \times 10^8 \, \textrm{m/s}\). That is about 300,000,000 meters per second. ⚡

Properties of Waves Used for Communication

To build information technologies, designers must understand the properties of waves, such as:

• Wavelength – the distance between two crests (tops) of a wave.
• Frequency – how many crests pass a point each second.
• Amplitude – how “tall” the wave is (related to energy or loudness for sound).

Frequency is measured in hertz (Hz), which means “per second.” If a radio station broadcasts at 100 million hertz, that is 100 megahertz, or \(100 \times 10^6 \, \textrm{Hz}\).

Frequency and wavelength are connected by a simple relationship: \(v = f\lambda\), where \(v\) is the wave speed, \(f\) is the frequency, and \(\lambda\) is the wavelength. For electromagnetic waves in a vacuum, the wave speed is \(c\), the speed of light, so \(c = f\lambda\). You can see how this relationship is used in designing different parts of the electromagnetic spectrum in [Figure 2].

From Information to Signal: What Is a Signal?

A signal is a pattern that represents information. The information might be:

• A person’s voice in a phone call
• Video for a TV show or a livestream
• Text messages, emails, or game data
• Sensor readings, like temperature or heart rate

To send this information far away, we have to:

1. Capture it (for example, with a microphone for sound).
2. Encode it into a signal (turn it into changes in a wave).
3. Transmit the wave (send it through wires, air, or space).
4. Receive it with an antenna or sensor.
5. Decode it back into something we can sense (sound, image, text).

This whole chain is what modern information technologies are designed to do.

Analog vs Digital Signals

There are two main kinds of signals used in communication technologies: analogue and digital.

Analog signal:

• Changes smoothly and continuously.
• Can take any value within a range.
• Example: the exact shape of your sound wave when you talk into a simple microphone.

Digital signal:

• Has only a few clear values, usually two: 0 and 1.
• Information is stored and sent as patterns of these 0s and 1s, called bits.
• Example: the data inside your phone, computer, or on a USB drive.

Most modern devices use digitized signals. That means real-world information (like your voice) is converted into many tiny numbers (0s and 1s) that can be sent as bits.

Digital signals are often sent as pulses (bursts) of a wave—like short and long flashes of light in a fiber‑optic cable, or on and off changes in voltage in a wire.

Why Digital Signals Are So Powerful 💡

Digital signals have several advantages for information transfer:

1. They are easier to clean up. Noise from the environment can change analogue signals in confusing ways. With digital signals, as long as the signal is “close enough” to 0 or 1, the receiver can correct small errors and still read the bit correctly.
2. They are easier to store and copy. You can save digital data on memory chips or hard drives and copy it again and again with almost no loss in quality.
3. They are more secure and flexible. It is easier to encrypt (lock) digital data for privacy and to compress it to save space and time.

This is why your music streaming, social media, and online gaming all depend on digital signals.

How Devices Detect Signals We Cannot Sense Directly

Our senses are limited. For example:

• Our ears hear only certain sound frequencies.
• Our eyes see only visible light, not radio waves or X‑rays.
• We cannot feel tiny changes in magnetic fields or infrared radiation.

Engineers create instruments and detectors that can sense these invisible signals. Then, the device converts them into forms we can understand—like sound, pictures, or numbers on a screen.

Some key examples:

• Radio receiver – detects radio waves and turns them into sound.
• Television or streaming device – detects complex digital signals and turns them into images and sound.
• Cell phone – uses antennas and chips that detect specific microwave frequencies used by your mobile network.
• Wi‑Fi adapter – detects and sends radio waves around 2.4 GHz or 5 GHz.
• Infrared remote control – uses invisible infrared light pulses to give commands to a TV or game console.

In all these cases, the designers must understand:

• The type of wave (radio, microwave, infrared, etc.).
• How that wave interacts with matter (absorbed, reflected, passing through).
• How to encode and decode information using that wave.

The path that signals follow in a common digital communication system is laid out in [Figure 3], showing how messages move from a sender to a receiver through several steps of encoding and decoding.

How Signals Interact with Matter

When waves meet matter (like buildings, trees, air, or your hand), several things can happen:

• Reflection – the wave bounces off (like a mirror reflects light).
• Absorption – the material takes in the energy of the wave, often turning it into heat.
• Transmission – the wave passes through (like light through glass).
• Scattering – the wave spreads out in many directions after hitting small particles.

Designers of communication technologies must carefully choose frequencies and materials based on these interactions.

Some examples:

• Wi‑Fi and cell‑phone signals need to pass through walls, so they use radio and microwave frequencies that can move through many building materials but are still safe for humans.
• Fiber‑optic cables use light waves that reflect inside the glass core so they stay trapped and can travel very far with low loss.
• Satellite TV uses microwaves that can travel through the atmosphere but may be blocked by heavy rain or storms.

Did you know? 🌍 Weather radar uses microwaves that reflect off raindrops so meteorologists can “see” storms even at night or through thick clouds.

Examples of Modern Communication Technologies

1. Radio and Broadcast TV

Radio stations convert sound (music, voices) into an electrical signal. This electrical signal is used to modulate (change) a radio wave. There are two common ways to modulate a radio wave:

• AM (Amplitude Modulation) – changes the amplitude (height) of the carrier wave to match the sound signal.
• FM (Frequency Modulation) – changes the frequency (spacing) of the carrier wave to match the sound signal.

Your radio has a tuner that selects which station (which frequency) to listen to, then a demodulator that extracts the original sound from the wave.

2. Cell Phones 📱

Cell phones use digital signals. Your voice is picked up by a microphone and turned into an analogue electrical signal. Then:

1. An analog‑to‑digital converter (ADC) samples that signal many times per second and turns it into numbers (bits).
2. These bits are encoded and compressed (to use less data).
3. The phone’s antenna turns the digital signal into radio waves at special cell‑phone frequencies.
4. Nearby cell towers receive the waves, process them, and pass the information into the phone network or the internet.
5. On the other side, another phone does the reverse process, turning bits back into sound through its speaker.

3. Wi‑Fi Networks

A Wi‑Fi router connects to the internet and uses radio waves to send data to your devices. The signals are digital, using complex patterns of changes in amplitude, phase, or frequency of the radio wave to represent bits. Your laptop or console has a Wi‑Fi chip and antenna that detect these patterns, decode the bits, and turn them into images, text, or game actions on your screen.

4. Fiber‑Optic Communication

Many long‑distance internet connections use fiber‑optic cables. These are thin strands of glass that guide light. Inside the cable:

• Lasers or LEDs turn digital bits into flashes of light—light on might be 1, light off might be 0.
• The light bounces down the cable by internal reflection.
• At the other end, detectors see the flashes and turn them back into electrical digital signals.

This system can send huge amounts of data very quickly with low energy loss.

Digitizing Sound: A Simple Numerical Example

To see how a real‑world signal becomes digital, consider voice recording:

1. Suppose a microphone produces an analogue voltage between 0 and 5 volts depending on sound loudness.
2. An ADC samples this every tiny fraction of a second and rounds the voltage to the nearest allowed level.
3. If it uses 3 bits at each sample, that means there are \(2^3 = 8\) possible levels (from 0 to 7).
4. So the voltage range 0–5 volts is divided into 8 steps. A reading of about 2.5 volts might be encoded as 100 in binary (which equals 4 in decimal), for example.

Now the sound is stored as a sequence of bits like 100, 011, 101, and so on. These bits can be sent through the internet, saved on a device, or processed with software.

Why Understanding Waves and Matter Matters for Designers

When engineers create new devices, they must answer questions like:

• What wave type and frequency should we use?
• How far does the signal need to travel?
• What materials will it pass through (air, walls, water)?
• How much noise (unwanted signals) will be around?
• How can we encode information so it is reliable and secure?

For example:

• Bluetooth is designed for short‑range communication through air and around people, so it uses low‑power radio waves that work well over a few meters.
• GPS satellites use specific radio frequencies that can pass through the atmosphere and still be detected accurately on the ground.
• Medical imaging devices (like MRI and X‑ray machines) use waves that interact with the human body in special ways to build images of bones and organs.

These choices all depend on the science of waves and their interactions with matter.

Real‑World Applications and Examples 🔬

1. Weather Monitoring

Weather satellites use sensors that detect infrared radiation and microwaves from clouds and the Earth’s surface. These signals are turned into digital data and sent to ground stations, where computers decode and display them as weather maps.

2. Earthquake Detection

Seismometers detect tiny vibrations in the ground (seismic waves) that humans cannot feel. The vibrations are converted into electrical signals, then digitized so scientists can analyze them and send warnings.

3. Space Communication

Spacecraft send digital radio signals across millions or even billions of kilometers. Because the signals are weak and noisy by the time they reach Earth, scientists use powerful antennas and error‑correcting codes to recover the data.

4. Medical Sensors

Devices like heart rate monitors and pulse oximeters detect signals from the body—electrical signals from the heart or changes in light passing through your finger. These are turned into digital numbers that can be displayed, stored, or sent wirelessly.

A Simple At‑Home Experiment with Waves

Materials:

• String or rope (about 2–3 meters)
• A friend or a solid doorknob

Steps:

1. Tie one end of the rope to a doorknob or have a friend hold it tightly.
2. Hold the other end and quickly move your hand up and down once to make a single pulse.
3. Watch the pulse travel down the rope, reflect at the end, and come back.

What you observe:

• The pulse is like a single bit of information traveling through a medium.
• The rope itself does not move along the whole length; only the disturbance moves.
• This is similar to how waves carry energy and information in communication systems.

Key Ideas to Remember ⭐

Waves are at the heart of modern communication technologies. Devices like radios, TVs, cell phones, and computer networks depend on understanding how waves carry signals, how those signals interact with matter, and how to encode information reliably—especially using digital bits. These ideas allow us to send texts, stream videos, explore space, and monitor our planet using invisible signals all around us. 🎉