What system of dots and dashes was used to send telegraph messages?

Morse code is a telecommunications method that encodes text characters as standardized sequences of two different signal durations, called dots and dashes or dits and dahs. Morse code is named after Samuel Morse, one of the early developers of the system adopted for electrical telegraphy. In the 1890s, Morse code began to be used extensively for early radio communication before it was possible to transmit voice. In the late 19th and early 20th centuries, most high-speed international communication used Morse code on telegraph lines, undersea cables, and radio circuits.

Source: Wikipedia