What I found out about telegrams:

Telegrams were sent by an electrical telegraph person or telegrapher using Morse code, telegraphers or telegraphist were an operation to use Morse code to communicate. 

The telegrams were made in the 1830s and 1840s by Samuel Morse. Telegrams were sent by a submarine telegraph  cables. In the United States, Western Union shut down its telegraph service in 2006. At the time, the company reported that only about 20,000 telegrams were sent in the previous year. Telegraphs were used to send  letters to people in olddays.