Morse Code Symbology

https://www.electrical-symbols.com/electric-electronic-symbols/telegraphy-symbols.htm#morse_code_symbology

Símbolos de Motores Trifásicos

https://www.simbologia-electronica.com/simbolos-electricos-electronicos/simbolos-motores-electricos.htm#simbolos_motores_trifasicos

Telegraphy Symbols

The telegraph is an ancient system of transmission of messages over long distances, using a Morse code. Originally the medium used for the transmission of electrical impulses were cables and later through radio signals.

https://www.electrical-symbols.com/electric-electronic-symbols/telegraphy-symbols.htm