Old signal or morse key, used in fishing vessels. A signal key is a electromechanical device to make electrical pulses, normally for Morse code. This serves an electrical contact as soon as the key is pressed downward. On release, a spring presses the key up and the contact is disconnected. In this way a series of electric pulses is made in the rhythm of operating the signal key. In Morse code short and long pulses are used. The signal key was usually served by a operator, who was specially trained to be able to quickly transmit and decipher Morse code. After Telegraph had become obsolete via Morse, the signal also became a rarer appearance. However, many signal keys are still in use by radio amateurs.