When we study the history of telephone technology, a stepping stone was the invention of the telegraph. Sending electrical signals along a wire to transmit a message. However technologists failed to understand that they were utilizing only one of the properties of that electrical energy being transmitted along the wire (specifically adjusting the amplitude of the energy wave). When different properties of that energy were studied (such as frequency, waveform etc) different methods were developed to manipulate and utilize the properties of the energy to engineer better communication tools.

Engineers managed to abstract those properties from the electrical energy to create systems of symbols to transmit information for communication.