It is the oldest form of symbols used for communication.

Its a device that converts human audio signals to an electronic signals which are transmitted via cables.

It use morse code transmitted messages through series of clicks and tones and light.

An individual must drain the water from the chosen semaphore to a certain height - leaving a code message base on the height of the water.

It is used to share their locations and to seek out assistance when they where in trouble or looking to be found.

It is an electronic communication sent and received by mobile phone.

It is a wireless telegraphy which developed the theory of electromagnetism.

It is the latest mode of communication in the digital era.