= Wireless telegraphy
{wiki}
Wireless telegraphy conveys discrete symbols without a connecting message wire. Here the mechanism is <radio communication>: keyed excitation produces <radio waves>, a receiving <antenna> drives a selective <electrical circuit>, and a detector produces a readable event. This makes a beautiful bridge between <resonance> and information: accumulating many appropriately timed small electrical disturbances can distinguish one transmission from another. Selectivity is finite, however; <resonance> alone cannot guarantee immunity to strong unwanted <signals> or <noise>.
The 1909 <Nobel Prize in Physics> recognized <Guglielmo Marconi> and <Karl Ferdinand Braun> for contributions to wireless telegraphy.<The Nobel Prize in Physics 1909 by Nobel Prize Outreach>[1909 award motivation and joint laureates]{ref} Their apparatus should be understood as a developing collection of systems. An early <coherer> receiver, a later tuned receiver and a modern <envelope detector> are different instruments.
\Image[/wireless-telegraphy-transmit-receive-chain.png]
{title=Functional transmit and receive chain for tuned spark wireless telegraphy}
{description=Original functional synthesis of <tuned spark wireless apparatus> and early <coherer> reception. Arrows show functional transfer; local <battery> <energy> powers recording.}
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