Quick questions on The communication framework in HSC Information Processes and Technology

A communication system is often described by five parts: the source where the message originates, the transmitter that prepares and sends it, the transmission medium that carries the signal, the receiver that takes the signal in, and the destination where the message is used. The framework describes the functions that happen across these parts.

The data to send is generated, for example an email typed by a user or a record produced by a program.

Information is added so the message can be delivered and managed: the destination and source addresses, sequence numbers so packets can be reassembled in order, and control data that governs the exchange.

The organised, addressed data is turned into a signal the medium can carry, for example modulated onto a carrier or encoded as light pulses or radio waves.

The signal travels across the medium (cable, fibre or wireless) from transmitter toward receiver.

Sender and receiver must agree on timing so the receiver samples the signal at the right moments and knows where each unit of data begins and ends. Without synchronisation the bits cannot be read correctly.

The receiver checks whether the data arrived intact using methods such as parity bits, checksums or cyclic redundancy checks, and where the protocol allows, requests retransmission of corrupted data.

The receiver takes in the signal, converts it back to data, strips the control and addressing information, reassembles packets in sequence, and decodes the message into a form the destination can use.

The message is delivered to the destination application and ultimately displayed to the user, completing the journey.