Horns and whistles have long been a key means of communication between vessels. Important messages such as "I am passing on the starboard" can be sent with a single whistle blow and avoid collisions. A code of whistle blows were also used by one Red Hook tug boat captain, according to a 1903 newspaper article, to let his wife know that he would be home soon.

 Daily Sun, St John N.B, Wednesday, November 11, 1903. (From the New York Sun) Transcript of article:

 How Harbor Tugs Quickly Communicate with Each Other

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They Do it by Means of Their Steam Whistles According to a Well Established Code

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What the Blasts Mean

 A harbor tug was running along by the South Brooklyn shore not long ago.  When near Red Hook the captain blew two long and two short blasts on the tug’s whistle, and followed this by several short toots.

 “What does all that mean, captain?” asked a passenger.

 “That’s a signal to my wife that I’ll b home soon,” was the reply.

 “WE tugboat men have all sorts of signals,’ he continued, “and we can talk to each other by means of the whistle.  I always blow the way I just now did when the day’s work is over; and my wife hears it and gets ready for my home coming.”

 There is in every port in the United States a brotherhood of the American Association of Masters and Pilots of Steam Vessels.  This association is a secret order and anyone who holds an American master’s license can become a member.

 It is very like other orders, but it has its peculiarities.  There are about 10,000 members and by means of whistles a member can tell at once whether the master or pilot of another vessel is a member of the association and to what brotherhood he belongs. 

 These signals are not supposed to be known.  There is no published code but each member learns it and can use it whenever he thinks fit.

 A long blast followed by a short one on one vessel will ask the master of an approaching vessel if he a member of the association; and if he is he will answer by tooting one long blast followed by two short ones.  This will be enough introduction, and then by means of more tooting information can be given that may prove of great service.

 There is another signal that is well known, and whenever it is sounded, it is sure to answered.  It is one long blast, one short one, then another long one and another short one, and it is the distress signal.

 The members of the brotherhood are bound to help another member in distress and that signal may be heard in all parts of the world.  There are branches of the association in the Philippines, in Porto Rico, in Alaska, and in nearly every port on the coast and on the Great Lakes.

 Thee toots is always a salute, and sometimes after the saluted boat has acknowledged the compliment a short toot will be sounded, but this in not called for and is only at the whim of the captain.

 Tugs having a string of barges I tow, such as go out from this port to Boston, or up the Husdon river, or from Norfolk to this port, or to some eastern port, always have signals which are understood by those on the barges.  Each barge has its number and the captain will signal to it to get up anchor, pay out more hawser, shorten the hawser, set sail or take in sail or in fact do anything that may be wanted for the safe navigation of the barge.  These signals are distinct from the brotherhood signals, or from the signals that are universal, and were arranged by the international marine congress.

 Each line of ferry boats has its own code of signals.  Some oft these signals are ordered by the government.

 For instance, when a vessel is starting out from a pier it must sound a long blast on its whistle.  This is to notify vessels passing up and down the river that another is starting out of the slip.  If the captain of the ferry boat hears no answer he knows that his course is clear; and as soon as his boat can be seen from the river clear of the slop then he goes ahead and the regular signals apply.

 In the harbor like that of the port of New York, where there is so much traffic, collisions occur frequently.  Many times they are unavoidable, one vessel being crowded into another.  Often they are caused through mistaken signals.

 There are rules to govern the sailing vessels which have been drawn up by an international congress, and with these rules is a code of signals which captains of steam or sailing vessels must be familiar with; an by constant use they become almost second nature to the man at the wheel or the officer who is on the bridge.

 The broad rule which all captains must observe is to keep to the right.  That is what it means in the landsmen’s language, but to the sailor is ‘keep to starboard and pass another vessel on your port or left hand.’

 This rule, of course, applies chiefly when the vessels are I narrow channels; but when they have the whole big ocean to travel over, then it is not so generally observed, the idea being then to keep  clear of any other craft and avoid a collision.

 It often happens though that two vessels may be approaching almost head on, and each captain will be in doubt for a moment just which way to turn.  This doubt will be only momentary, however, for captains think and act quickly, and a short sharp blast from one of the whistles will sound out over the water.

 This blast I plain English will tell the captain or officer of the other vessel: ‘I am directing by course to starboard,’ or the right, and the man at the wheel of the vessel which gave the signal will roll his wheel over so that his vessel’s nose will turn to the right.

 As soon as the man in charge of the of the craft hears this signal he will answer generally by sounding a short toot on the whistle, and this means “Your signal is understood, I am directing my course to starboard.”  The wheel of his vessel is rolled over so that the boat’s nose turns to the starboard and the two vessels, if the signals have been given [in] time, will pass each other safely, each being on the port or left side of the other.

If the signal should be two short blast it would mean, “I am directing me course to port” and if this is understood on the other vessel the two boats will pass each other on the starboard side.

Sometimes it happens that when one captain has signaled that he is going to starboard the other captain will not agree to this and will answer with tow whistles and first captain will agree to the second signal and alter the course of his vessel accordingly.

 There is one more signal, but it is only used when vessels are getting close.   That is three short blasts and it means “My engines are going at full speed astern.”

 These rules have been put into a rhyme and the jingle is an easy way of familiarizing one’s self with the rules.   It is as follows:

 If one whistle you should blow

To starboard then your bow should go.

And speeding on across the tide

She’ll pas along her starboard side.

If two whistles you should blow

Why then to port your bow must go,

And if the space is far and wide

You’ll pass along her starboard side.

From three short blasts ‘tis yours to learn

That she is going full speed astern

If a captain should fail to understand the signal given by the approaching vessel he will sound at least four and probably several more short toots on the whistle on his own vessel.

 In fog, mist, falling snow or heavy rain storms vessels are to make all sorts of noises and a captain hearing these noises can tell at once what sort to of a vessel he is approaching awn what he must do to avoid a collision.  Every steam vessel must be provided with an efficient whistle or siren so place that the sound may not be intercepted by an obstruction and with an efficient fog horn to be sounded by mechanical means and with an efficient bell.

 When there is a fog a steamer must slow down its speed and must sound at intervals of not more than two minutes a prolonged blast on the whistle.  Those who have crossed the ocean and found fog on the Banks know how doleful the sound of that whistle is and how little sleep can be had so long as the fog lasts.

 If the vessel has been stopped but is not at anchor, every two minutes two prolonged blasts must be sounded with an interval of one second between them.  A prolonged blast means one of from four to six seconds duration.

 If a captain of an ocean steamer that is picking its way through the fog should hear two blast sound through the mist he would know that he is near some vessel that is simply drifting with the current.  If he should hear a bell rung rapidly for about five second every minute, he would know that he was near a vessel that was anchored.