Normal radio traffic is done by talking to another station via a microphone. In some cases the radio signal may be weak or be affected by radio interference, and it may be difficult to hear one other. In this case you can transfer individual letters in a message using telegraphy or Morse code. Each letter is encoded with a number of short and long tones. For example, A is written as a short and a long tone, and B is written as a long and three short tones. You create the tones by pressing a "telegraph key". The tones are heard very well through the interference and are easy to interpret.
Here you can see how each letter is encoded. Try sending a telegraphy character using the telegraph keys on the table. You can also listen to the characters by pressing and holding the buttons on the small light gray plastic box. Try to hear which letters are being sent.
Modern technology has created other systems for transmitting radio messages in difficult and disturbed conditions. Morse telegraphy has thus become increasingly rare, but was an important means of communication during the 19th Century.
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