Basic Elements of a Communication System
Data communication is used to send a message from a sender to a receiver.through a medium.

1. The sender (source) - creates the messages to be transmitted
2. The medium that carries the message
3. The receiver (sink) - receives the message

Examples

• Ramith listens to a song on the radio.
• Naveen watch cricket on TV.
• Ruwan males a phone call to Malinda.
• Yohan sends a SMS to Raveen
• Harsha sends an email to Chamara..
• A tap on the mobile icon starts an app.
• A Graphic card sends a video signal to a Monitor. 
• Processor fetches data from memory.

Data : information sent
Signals : Electric or electromagnetic encoding of data.
Signaling : Propagation of signals across a communication medium.
Transmission : Communication of data by the processing of signals.

Data Communication Modes (Simplex , Half Duplex)