What are methods of signalling as per INTERCO or International Code of Signal ?

The methods of signaling which may be used are:

1. Flag signaling, the flags used being those shown inside the front cover.
2. Flashing light signaling, using the Morse symbols shown in Chapter 1.
3. Sound signaling, using the Morse symbols shown in Chapter 1.
4. Voice over a loud hailer.
5. Radiotelegraphy.
6. Radiotelephony.
7. Morse signaling by hand flags or arms.

Note :

Flag signaling

A set of signal flags consists of twenty-six alphabetical flags, ten numeral pennants, three substitutes, and the answering pennant. Detailed instructions for signaling by flags are given in Chapter 1,

The international flagbag consist of 40 flags: 26 alphabetical flags, 10 numeral pennants, 3 substitutes, and the ANSWER pennant.         

Flashing light and sound signaling.

The Morse symbols representing letters, numerals, etc., are expressed by dots and dashes which are signaled either singly or in combination. The dots and dashes and spaces between them should be made to bear the following ratio, one to another, as regards their duration:

1. A dot is taken as the unit;
2. A dash is equivalent to three units;
3. The space of time between any two elements of a symbol is equivalent to one unit; between two complete symbols it is equivalent to three units; and between two words or groups it is equivalent to seven units.

Voice over a loud hailer

Whenever possible plain language should be used but where a language difficulty exists groups from the International Code of Signals could be transmitted using the phonetic spelling tables.

Radiotelegraphy and radiotelephony

When radiotelegraphy or radiotelephony is used for the transmission of signals, operators should comply with the Radio Regulations of the International Telecommunication Union then in force.