First sight of communication The human need to communicate has motivated mankinds creativit Cave dwellers drew pictures on walls Smoke signals, drum rhythms passed messages Postal service: a system for physically transporting documents and other small packages Alexander Graham Bell: invented the telephone Data communication Data communications are the exchange of data between two devices via some form of transmission medium• The human need to communicate has motivated mankind’s creativity: – Cave dwellers drew pictures on walls. – Smoke signals, drum rhythms passed messages. – Postal service: a system for physically transporting documents and other small packages – Alexander Graham Bell: invented the telephone.  Data Communication: Data communications are the exchange of data between two devices via some form of transmission medium