Communication is a process whereby information is enclosed in a package, channelled and imparted by a sender to a receiver via a medium; the receiver decodes the message and gives feedback. Key terms: Data (raw facts before processing), Signal (electric or electromagnetic encoding of data), Signaling (propagation of signals across a channel), Transmission (sending data by means of signals).
Five basic components of a communication system: Data Source (creates data for transmission), Transmitter (encodes data), Communication channel (the connecting medium), Receiver (decodes data back to original), and Destination. Example: when John calls Peter, John is the data source, his phone is the transmitter, the telephone cable/microwave is the channel, Peter’s phone is the receiver, and Peter is the destination.
Communication Channels
- Simplex Mode: signals travel in only one direction, e.g. radio/TV broadcasting, computer to printer.
- Half Duplex Mode: signals travel both ways, but only one way at a time, e.g. a police walkie-talkie.
- Full Duplex Mode: signals travel both ways simultaneously, e.g. the telephone.
Data Transmission Modes
Digital vs. Analogue: digital transmission is the physical transfer of a bit stream over a channel such as copper wire or fibre; analogue communication transfers a continuously varying signal, either as pulses (baseband) or continuously varying waveforms (passband), using a modulation method.
Asynchronous vs. Synchronous: asynchronous transmission exchanges data without requiring an immediate response, with a gap between data marked by start/end bits – slower and cheaper, but more flexible. Synchronous transmission sends data in blocks or frames with no gaps – faster and costlier, used to confirm operations in real time.
Serial vs. Parallel: serial transmission uses a single line, sending bits one by one – slower but practical over long distances (e.g. USB devices). Parallel transmission uses multiple lines (usually 8 or a multiple) to send several bits at once – faster, but costlier and prone to cross-talk over distance, so it’s mainly used for short connections like a printer cable.
