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New Jersey Scuba Diving

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New Jersey Scuba Diving

Nautical Signaling Systems

Alpha-Numeric Signal Flags

In this modern age of radio, these signal flags are a quaint anachronism that is no longer used, although they were once very important in ship-to-shore and ship-to-ship communications. Each flag stands for both a letter value and a shorthand message. The letters are expressed here in the modern international phonetic alphabet, in which A-B-C would be spoken Alpha-Bravo-Charlie (see below).

The letter and number values could be used in groups to spell out messages, or a single flag could be used to convey a message, such as the familiar blue-and-white diver-down flag - Alpha. You may notice that the red-and-white "diver down" flag is missing. That is because it is not one of the official signal flags, although it is accepted and required in the United States, where it must be flown along with the blue and white Alpha flag from any vessel engaged in diving.

The bright colors and highly contrasting patterns of the flags allowed them to be read over great distances at sea. Naval commanders in the seventeenth and eighteenth centuries used flag signaling to coordinate actions among ships during battle. Special codes such as "attack at will" or "fall in astern" could be pre-arranged for the whole fleet. During major battles, smaller vessels, often frigates, were kept outside the fray to act as repeaters, duplicating the admiral's signals aboard the flag ship, which might be otherwise be obscured from the rest of the squadron by smoke. Signal flags were ultimately replaced by Morse code light signals and radio.

signal flag
Alpha
Diver Down - Keep Clear
or Speed Trial
( when moving )
signal flag
Juliet
I Am On Fire
Keep Clear
signal flag
Romeo
( no meaning )
signal flag
Bravo
Dangerous Cargo
( Explosives )
signal flag
Kilo
Stop Instantly
signal flag
Sierra
Engines Going
Full Astern
signal flag
Charlie
Yes
signal flag
Lima
Desire to
Communicate
signal flag
Tango
Keep Clear
Do Not pass
signal flag
Delta
Keep Clear
Maneuvering with Difficulty
signal flag
Mike
I Am Stopped
Doctor On-board
signal flag
Uniform
Standing
into Danger
signal flag
Echo
Altering Course
to Starboard
signal flag
November
No
signal flag
Victor
Require Assistance
( not distress )
signal flag
Foxtrot
Disabled
Please Communicate
signal flag
Oscar
Man Overboard
signal flag
Whiskey
I Require
Medical Assistance
signal flag
Golf
Pilot Required
signal flag
Papa
I Am About to Sail
Need a Pilot
signal flag
X-ray
Stop Your
Intentions
signal flag
Hotel
Pilot on Board
signal flag
Quebec
Quarantine
Request Pratique *
signal flag
Yankee
Dragging Anchor
or Carrying Mail
signal flag
India
Altering Course
to Port


* A pratique is a clearance granted to a vessel to proceed into port after compliance with health regulations or quarantine.
signal flag
Zulu
I Require a Tug
( shore communications )
signal flag
One

signal flag
Two

signal flag
Three

signal flag
Zero
signal flag
Four

signal flag
Five

signal flag
Six
signal flag
Seven

signal flag
Eight

signal flag
Nine
( spoken: niner )

signal flag
Answer
End of Message
Decimal Point
signal flag
First Repeater
Repeat First Flag
signal flag
Second Repeater
Repeat Second Flag
signal flag
Third Repeater
Repeat Third Flag


Semaphore

The semaphore flag signaling system is an alphabet signaling system based on the waving of a pair of hand-held flags in a particular pattern. The flags are usually square, red and yellow, divided diagonally with the red portion in the upper hoist.

The flags are held, arms extended, in various positions representing each of the letters of the alphabet. The pattern resembles a clock face divided into eight positions: up, down, out, high, low, for each of the left and right hands. Six letters require a hand to be brought across the body so that both flags are on the same side. The entire sequence is shown below.

One way to visualize the semaphore alphabet is in terms of circles. In the first circle, the letters A to C are made with the right arm, and E to G with the left, and D with either as convenient. In the second circle, the right arm is kept still at the letter A position and the left arm makes the movements; similarly in the remaining circles, the right arm remains fixed while the left arm moves. The arms are kept straight when changing from one position to another. Semaphore was more a land-based system that signal flags.

First
Circle
Seventh
Circle
signal flag
A / 1
Second
Circle
signal flag
[ rest ]
signal flag
[ error ]
signal flag
Z
signal flag
B / 2
signal flag
H / 8
Third
Circle
belongs
next to
X
below
signal flag
C / 3
signal flag
I / 9
signal flag
O
Fourth
Circle
signal flag
D / 4
signal flag
K / 0
signal flag
P
signal flag
T
Fifth
Circle
signal flag
E / 5
signal flag
L
signal flag
Q
signal flag
U
signal flag
[ numeric ]
Sixth
Circle
signal flag
F / 6
signal flag
M
signal flag
R
signal flag
Y
signal flag
J
signal flag
W
signal flag
G / 7
signal flag
N
signal flag
S
signal flag
[ annul ]
signal flag
V
signal flag
X

Note that J is out of order, as are V, W, X, and Y. The intention seems to be to promote Y and [annul] to better spots in the sequence, and demote the relatively unimportant letters. Z is in order at the end of the sequence, but is shown out of place here because of formatting constraints - it belongs at the lower right next to X. The J signal was also used as the [alphabetic] symbol. Positions having both flags in the same direction are not used. Semaphore has been replaced by radio communications, except perhaps in the Boy Scouts.


Morse Code

The earliest telecommunications device - the telegraph - was not capable of transmitting much more than noise. But even noise can be used to encode useful information, and so the Morse code signaling system was developed. Morse code consists of sequences of long and short bursts of static, or later, tones, commonly known as dots and dashes. When ships ( and airplanes ) were first equipped with radios, these were not much better than telegraph, incapable of transmitting voice, and so used Morse code.

Unlike signal flags and semaphore, which are strictly visual systems, Morse code is extremely flexible and can be used with many different transmission mechanisms. It can be sent down a wire, or alternatively transmitted on the radio, or even by sound. Morse code can also be transmitted visually by means of flashing lights. This is still used today when ship-to-ship communications with radio silence are desired. Many modern radio navigation beacons transmit three-letter identification codes in Morse which can be monitored by audio to ascertain that the correct beacon has been tuned in the receiver. So unlike the previous two signaling systems, Morse code is far from dead.

A
B
C
D
E
F
G
H
I
J
K
L
M
. -
-. . .
- . -.
- . .
.
. . -.
- - .
. . . .
. .
. - - -
- . -
. - . .
- -
N
O
P
Q
R
S
T
U
V
W
X
Y
Z
- .
- - -
. - -.
- - . -
. - .
. . .
-
. . -
. . . -
. - -
- . . -
- . - -
- - . .
0
1
2
3
4
5
6
7
8
9
Full Stop
Comma
Query
- - - - -
. - - - -
. . - - -
. . . - -
. . . . -
. . . . .
- . . . .
- - . . .
- - - . .
- - - - .
. - . - . -
- - . . - -
. . - - . .

Notice how the most-used letters ( a e i m n t ) have the simplest encodings, to speed transmission and reduce errors. All numbers consist of 5 bits, and punctuation is 6 bits.

... -.-. ..- -... .-


Storm Warning Flags

These flags are flown at inlets, marinas, Coast Guard stations, and other port locations to indicate hazardous weather conditions. The meaning depends on whether the flags are flown singly or in pairs.

Gale Flag

Small Craft Warning
Winds up to 38 mph


Gale Flag

Gale Flag

Gale Warning
Winds 39-54 mph
Hurricane flag

Full Gale Warning
Winds 55-73 mph


Hurricane flag

Hurricane flag

Hurricane Warning
Winds 74 mph +

Unfortunately, there is no standardization in beach warning flags. Different colors indicate safe or hazardous surf, no swimming, no surfing, undertows, jellyfish, pollution, and other conditions, but the pattern varies from place to place.


Shipping Line Ensigns

Clyde-Mallory Lines flag
The Clyde Lines flag that would
have flown from the Delaware

Clyde-Mallory Lines flag
Clyde-Mallory Lines flag, a combination of
designs after the merger of the two companies.
This pennant would have flown on the Mohawk.


Phonetic Alphabet

The phonetic alphabet was derived from previous US military alphabets, such as the Army's:

Able
Baker
Charlie
Dog
Easy
Fox
George
How
Item
Jig
King
Love
Mike
Nan
Oboe
Peter
Queen
Roger
Sugar
Tare
Uncle
Victor
William
X-ray
Yoke
Zebra

The Navy and Air Corps substituted: Affirm, Hypo, Inter, Negat, Option, and Prep. Numbers are spoken as usual, except for nine, which becomes "niner". The whole thing was standardized after World War II, but you may still run across the old forms in war films and histories. The modern phonetic alphabet is heavily used in aviation and marine radio communications:

Alpha
Bravo
Charlie
Delta
Echo
Foxtrot
Golf
Hotel
India
Juliet
Kilo
Lima
Mike
November
Oscar
Papa
Quebec
Romeo
Sierra
Tango
Uniform
Victor
Whiskey
X-ray
Yankee
Zulu


So what does all this have to do with scuba diving? Not much, I guess, but I think it is interesting from a historical perspective, and it makes a nice colorful web page. I especially like the little semaphore guys waving their flags around. Your final exam is at right.

signal flag
November
signal flag
Charlie

Vessel in Distress

... --- ...


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Disclaimer:

I make no claim as to the accuracy, validity, or appropriateness of any information found in this website. I will not be responsible for the consequences of any action that is based upon information found here. Scuba diving is an adventure sport, and as always, you alone are responsible for your own safety and well being.

Copyright © 1996-2016 Rich Galiano
unless otherwise noted

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