Key ideas

• People need different methods of communication because conditions change. Sometimes words are not possible, safe, fast enough, or understandable at a distance.
• Signs, signals, and codes help people communicate across noise, distance, darkness, language barriers, emergencies, and special situations.
• Different methods may be visual, sound-based, written, tactile, or symbolic.

Examples over time

• Ancient people used symbols, markings, drums, fires, and flags to communicate.
• Military, maritime, and rescue systems helped develop more organized signals.
• Technologies like telegraphy, Morse code, radio, and digital messaging expanded how codes and signals could be used.
• Modern communication still depends on symbols and codes, from traffic signs to computer encryption.