What is communications technology?
Communications technology covers every way we make and share messages with tools: printing, photography, graphic design, audio, video, animation, websites, radio, TV and networks.
The communication system
- Source: where the message starts (a person, a camera, a microphone).
- Transmitter / encoder: changes the message into a signal (electrical, radio, light).
- Channel: the path (cable, optical fibre, air, satellite).
- Receiver / decoder: turns the signal back into a message.
- Destination: the person or device that gets it.
Noise is anything that spoils the signal: static, a weak Wi-Fi signal, a blurred photo. Feedback is the reply that tells the sender the message arrived.
Design elements and principles
Good media use elements (line, shape, colour, texture, space, type) and principles (balance, contrast, emphasis, alignment, repetition, unity). Creative techniques include the rule of thirds, camera angles, lighting and storytelling.
Signals, waves and the science behind them
Radio, Wi-Fi, mobile signals and light are electromagnetic waves. They travel at c = 3 × 108 m/s. Sound is a different wave: it needs air and travels at about 343 m/s.
- Frequency (f): waves per second, in hertz (Hz).
- Wavelength (λ): length of one wave, in metres.
- Amplitude: height of the wave; in sound it means loudness.
They are linked by λ = c ÷ f. FM radio at 100 MHz has λ = 3 m.
Analog and digital
An analog signal changes smoothly, like a real sound wave. A digital signal is a list of numbers (0s and 1s). We turn analog into digital by sampling (measuring many times a second) and quantising (rounding each sample to a level set by the bit depth). Digital copies do not lose quality and can be compressed.
Light and colour
Screens mix red, green and blue light (RGB, additive). Printers mix cyan, magenta, yellow and black ink (CMYK, subtractive).
Formulas and calculations
- Image size (bytes) = width × height × bit depth ÷ 8
- Audio size (bytes) = sample rate × bit depth × channels × time ÷ 8
- Bit rate (bit/s) = file size in bits ÷ time
- Download time = file size ÷ connection speed
- Aspect ratio = width : height (16:9 for HD video)
- Print size (inches) = pixels ÷ PPI (300 PPI for good print)
Units: 1 byte = 8 bits; 1 kB = 1000 B; 1 MB = 1000 kB (some software uses 1024).
Equipment and software
Devices
- Camera: lens, sensor, shutter speed (motion blur), aperture or f-number (light and background blur), ISO (sensitivity), white balance.
- Microphone: dynamic (tough, for loud sound) or condenser (sensitive, for voice); pick-up pattern such as cardioid.
- Lights: three-point lighting (key, fill, back).
- Printer, scanner, mixer, audio interface, router.
Software
Raster image editors (photos), vector drawing apps (logos), page layout, audio editors, video editors, 3D and animation tools, web editors and content management systems. Choose software by the output you need.
Process and production skills
- Pre-production: brief, audience, research, script, storyboard, schedule, budget.
- Production: set up equipment safely, check levels and focus, shoot or record.
- Post-production: edit, colour correct, mix sound, add titles, export in the right format.
- Distribution: publish, print or broadcast; get feedback.
Conventions and rules
Follow file-naming and folder rules, back up, use the 180-degree rule in video, keep text readable, give credit, respect copyright and privacy, and get consent before filming people.
Try it: measure your phone photo
Open a photo's details on a phone. Note width and height in pixels. Work out width × height × 24 ÷ 8 to get the uncompressed size, then compare it with the real file size. The real file is much smaller because JPEG compression removes detail you hardly see. Then play with the sliders in the last 3D step.
Key formulas and definitions
- λ = c ÷ f (c = 3 × 10⁸ m/s)
- Image size (B) = width × height × bit depth ÷ 8
- Audio size (B) = sample rate × bit depth × channels × seconds ÷ 8
- Bit rate = bits ÷ seconds
- Download time = file size (bits) ÷ speed (bit/s)
- 1 byte = 8 bits; 1 MB = 1 000 000 B
Worked examples
1. An FM station broadcasts at 100 MHz. Find the wavelength.
λ = c ÷ f = 3 × 10⁸ ÷ 1 × 10⁸ = 3 m.
2. Wi-Fi uses 2.4 GHz. What is its wavelength?
λ = 3 × 10⁸ ÷ 2.4 × 10⁹ = 0.125 m = 12.5 cm.
3. Find the uncompressed size of a 1920 × 1080 image with 24-bit colour.
Pixels = 1920 × 1080 = 2 073 600. Bits = 2 073 600 × 24 = 49 766 400. Bytes = ÷ 8 = 6 220 800 B ≈ 6.2 MB.
4. Find the size of 60 s of CD-quality stereo audio (44 100 Hz, 16 bit, 2 channels).
44 100 × 16 × 2 × 60 = 84 672 000 bits. ÷ 8 = 10 584 000 B ≈ 10.6 MB.
5. A 50 MB video is downloaded on a 20 Mbit/s connection. How long does it take?
50 MB = 50 × 8 = 400 Mbit. Time = 400 ÷ 20 = 20 s.
6. A photo is 3000 × 2400 pixels. How big can it print at 300 PPI?
3000 ÷ 300 = 10 inches; 2400 ÷ 300 = 8 inches. So 10 × 8 inches (about 25 × 20 cm).
Common mistakes
- Forgetting to divide by 8 to change bits into bytes.
- Mixing MHz and Hz in λ = c ÷ f. Change 100 MHz to 1 × 10⁸ Hz first.
- Thinking digital is always better. Low sample rate or low bit depth sounds worse than good analog.
- Using RGB colours for print without converting to CMYK, so printed colours look dull.