in which the current activates a telegraph sounder that makes a click; communication on this type of system relies on sending clicks in coded rhythmic patterns. The archetype of this category was the Morse system and the code associated with it, both invented by Samuel Morse in 1838. In 1865, the Morse system became the standard for international communication, using a modified form of Morse's code that had been developed for German railways.

Electrical telegraphs