Telegraph key

A telegraph key—also called a clacker, tapper, or morse key—is a specialized electrical switch that a trained operator uses to send text messages in Morse code over a telegraphy system. These keys work with both landline (wire) telegraphy and radio (wireless) telegraphy. By pressing the key, the operator creates electrical pulses (or, in modern continuous wave radio, unmodulated radio waves) of two distinct lengths: short pulses known as dots or dits, and longer pulses called dashes or dahs. These pulses combine to form the letters and characters of the message. The first telegraph key was created by Alfred Vail, a colleague of Samuel Morse. Over time, the technology evolved and improved, leading to a variety of key designs. The straight key is the familiar telegraph key seen in many period films and TV shows. It consists of a simple bar with a knob on top and an electrical contact beneath. Pressing the bar down against spring tension closes an electric circuit. American keys traditionally had short, flat-topped knobs and narrow, often curved bars, while European keys had tall, ball-shaped knobs and thick bars. This difference appears to be purely cultural and a matter of training, yet users of each style are fiercely partisan. Straight keys have been made in countless variations for over 150 years in many countries, and they are avidly collected. American railroad telegraphy keys also included a shorting bar, required for the American-style wiring that connected the circuit through a station when the operator was not sending. This shorting switch was necessary because North American railroad telegraph systems supplied signal power from batteries at one or both ends of a line, rather than each station having its own battery bank (common in Europe). The shorting bar completed the electrical path to the next station and all following ones, allowing their sounders to respond to signals from the central office. While sometimes included in later keys for tradition, the shorting bar is unnecessary for radio telegraphy, except as a convenience to produce a steady signal for tuning a transmitter—otherwise, operators might resort to placing a book on the key to free both hands.