Morse code

Morse code represents characters as sequences of short and long elements, commonly called dots and dashes or dits and dahs. International Morse code can be conveyed by sound, light or other distinguishable signals. On amateur radio it is commonly sent using CW.

The basic duration is one dit. Standard spacing is essential: a receiver needs to distinguish elements, letters and words.

The character and word gaps are their total durations; they are not added on top of a separate one-unit element gap.

Using the PARIS reference word, including its following word gap, one standard word contains 50 dit units:

Dit duration in milliseconds = 1200 / speed_WPM

At 20 words per minute, a dit lasts 60 ms, a dah 180 ms and a word gap 420 ms. In Farnsworth timing, characters retain a relatively fast rhythm while gaps between characters and words are lengthened. Character speed and overall text speed are then different quantities.

In this table, a period is a dit and a hyphen is a dah. Spaces separate characters; they are not transmitted as additional elements.

CQ invites a general reply, DE introduces the sender, and K invites transmission. Procedural signals may join letters without the normal inter-character gap. For example, the end-of-work signal commonly written SK is sent as …-.-, rather than as two separately spaced letters.

The distress signal SOS is the continuous sequence …—…, with no letter gaps inside the signal. Its use differs from casually sending the three letters in a conversation.

Learning to recognise each character's rhythm helps avoid counting individual dots and dashes as speed increases.

• ITU-R M.1677-1: International Morse code.
• ARRL: A Standard for Morse Timing Using the Farnsworth Technique.