From the British Admiralty's Handbook of Signalling, 1913.
10. When using the Morse Code, symbols are expressed by two elements called a "Dot" (or a "Short") and a "Dash" (or a "Long"), which are signalled either singly or in combination.
2. These two elements can be made in various ways. In visual signalling, by the motion of any single object which is made to appear and disappear for short and long periods of time, representing dots and dashes respectively. This method is illustrated in the flash of a Lamp, a Heliograph, or a Searchlight.
3. Flag Waving is an instance where the two elements are signalled by moving an object through small and large Arcs.
4. They can also be signalled by short and long blasts on the Whistle, Bugle, Fog-horn, or Syren.
5. In Telegraphy, these elements are recognised by short and long periods of silence between the clicks of a Sounder; or by short and long sounds emitted by a Buzzer.
6. The dots and dashes, and spaces between them, should be made to bear the following ratio one to another as regards their duration:-
A dot is taken as the unit, and a dash is equivalent to three units.
The space of time between any two elements of a symbol is equal to one unit, between two complete symbols is equal to a dash (or three units), and between two words or groups, two dashes (or six units).
Up to ordinary limits, whatever may be the rate of sending, accuracy in signally depends upon these rules being strictly adhered to.
7. In long-distance visual signalling, where the rate of signalling must necessarily be very slow on account of the apparatus usually employed under those conditions, no definite rate can be laid down; but while generally obeying these rules, it is best to erron the side of making the dots rather shorter in their proportion to the dashes, as it then makes the distinction between these elements plainer; otherwise, in very slow signalling, it is hard to appreciate their relative lengths, because they do not follow one another sufficiently quickly to show their distinction by comparison.
8. The following methods may be used for transmitting messages by the Morse Code:-
By Day:-
1. Flag-waving.
2. Heliograph.
3. Searchlight.
4. Sounder, Buzzer, and W/T.
By Night:-
1. Lamp.
2. Searchlight.
3. Sounder, Buzzer, and W/T.
In a Fog:-
1. Sound Signals.
2. Sounder, Buzzer, and W/T.
3. Searchlight.
9. Signals may be made either by using the groups of letters and signs in the Signal Books, or the communication may be made in plain language.
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