IMPROVEMENTS IN FOG SIGNALS
Year: 1877

page_text: LETTERS PATENT to Peter Jensen, of Chancery Lane, London, for the Inven-
tion of "IMPROVEMENTS IN FOG SIGNALS." A communication from abroad by
Knut Ahlborg, of Stockholm, Sweden, late Steamship Captain, Member of the
Roval Commission on Unseaworthy Ships, now sitting at Stockholm.
Sealed the 18th April 1878, and dated the 22nd October 1877.
PROVISIONAL SPECIFICATION left by the said Peter Jensen at the Office
of the Commissioners of Patents on the 22nd October 1877.
PETER JENSEN, of Chancery Lane, London.
"IMPROVEMENTS IN FOG SIGNALS."
(A communication from abroad by Knut Ahlborg, of Stockholm, Sweden, late
Steamship Captain, Member of the Royal Commission on Unseaworthy Ships, now
sitting at Stockholm.)
The object of this Invention is to enable steamships in thick or misty weather to
give sound signals indicating the direction they are steering, and thereby preventing
collision with other vessels.
These signals are given by means of two steam whistles of different sound or tone,
all as herein-after described.
Two steam whistles of ordinary construction, but of different size, are by pre-
ference combined, the larger one giving a roaring sound, and the smaller one a shrill
whistling sound. The pipe leading from the steam boiler terminates in a three-way
cock provided with a handle and dial marked at one side with a letter corresponding
with the small whistle, and at the other side with a letter corresponding with the
large whistle. From the three-way cock elbow pipes lead to the whistles. By
alternately shifting the handle more or less times to the right or the left, different
signals are thus produced, the bandle being placed on the mark for giving a shrill
sound, and on the mark for giving a roaring sound. When the handle is in the
upright or middle position the steam is shut off.
For every signal both whistles are used in order to prevent mistakes because of

page_text: other steam whistles that might be used in the vicinity. At the same time an
"attention" signal may be given by this apparatus.
The course a steamer steers is in thick or misty weather indicated by two signals,
viz., an attention signal of about 7 or 8 seconds duration, and a thereupon imme-
diately following "course signal" may be rendered by one, two, or three sounds,
each lasting about 2 seconds, and following close upon each other.
For northerly and easterly course the attention signal is given by the shrill
whistle, and the course signal itself by the roaring whistle, or by both.
For southerly and westerly courses the attention signal is given by the roaring
whistle, and the course signal itself by the shrill whistle, or by both.
In order not to have to give too many or more complicated signals, it is con-
sidered enough to apply them to the eight chief points of the compass on a compass
dial. Such a compass dial, marked as just named, should be placed against the
apparatus at about the height of the signalman's eyes.
A steamer not going any of these courses should signal the one nearest to it,
always observing that if another vessel should be heard close by, the course should
be altered, so that the steamer really then steers the course signalled.
SPECIFICATION in pursuance of the conditions of the Letters Patent filed
by the said Peter Jensen in the Great Seal Patent Office on the 20th April
1878.
PETER JENSEN, of Chancery Lane, London. "IMPROVEMENTS IN FOG SIGNALS."
(A communication from abroad by Knut Ahlborg, of Stockholm, Sweden, late
Steamship Captain, Member of the Royal Commission on Unseaworthy Ships, now
sitting at Stockholm.)
The object of this Invention is to enable steamships in thick or misty weather to
give sound signals indicating the direction they are steering, and thereby prevent
collision with other vessels.
These signals are given by means of two steam whistles of different sounds or
tone, all as herein-after described.
Figure 1 of the accompanying Drawings is a plan of the apparatus as formed
suitable for this purpose; Figure 2, a front elevation; Figure 3, a side elevation;
and Figure 4, a section through a three-way cock forming part of the apparatus.
Two steam whistles O and I of ordinary construction, but of different size, are by
preference combined, the larger one O giving a roaring sound, and the smaller one I
a shrill whistling sound. The pipe A leading from the steam boiler terminates in a
three-way cock B (shewn in section at Figure 4); provided with a handle and dial F
marked at one side with a letter I corresponding with the small whistle, and at the
other side with a letter O corresponding with the large whistle O. From the three-
way cock elbow pipes D and E lead to the whistles. In the position of handle
shewn at Figures 2 and 4 the steam enters the pipe D, and when moved to the
opposite or right-hand position O; the steam enters the pipe E. By alternately
shifting the handle more or less times to the right or the left, different.signals are

page_text: thus produced, the handle being placed on the mark I for giving a shrill sound, and
on the mark O for giving a roaring sound. When the handle is in the upright or
middle position the steam is shut off.
For every signal both whistles are used in order to prevent mistakes because of
other steam whistles that might be used in the vicinity. At the same time an
"attention" signal may be given by this apparatus.
The course a steamer steers is in thick or misty weather indicated by two signals,
viz., an attention signal of about 7 or 8 seconds' duration, and a thereupon imme-
diately following "course signal" may be rendered by one, two, or three sounds,
each lasting about 2 seconds, and following close upon each other.
For northerly and easterly courses the attention signal is given by the shrill
whistle I, and the course signal itself by the roaring whistle, or by both.
For southerly and westerly courses the attention signal is given by the roaring
whistle O, and the course signal itself by the shrill whistle I, or by both.
In order not to have to give too many or more complicated signals, it is con-
sidered enough to apply them to the eight chief points of the compass, as shewn on
a compass dial at Figure 2, and as explained at Figure 5, which is an explanatory
table. Such a compass dial, marked as just named, should be placed against the
apparatus at about the height of the signalman's eyes.
A steamer not going any of these courses should signal the one nearest to it,
always observing that if another vessel should be heard close by, the course be
altered, so that the steamer then really steer the course signalled.
And having thus described and ascertained the nature of this Invention, I declare
that I claim as the Invention communicated to me, the application of two steam
whistles of different sounds combined and operated by three-way cock and handle,
or equivalent means, for indicating the steering course of ships.
In witness whereof, I, the said Peter Jensen, have hereunto set my hand and
seal, this Eighteenth day of April, in the year of our Lord One thousand
eight hundred and seventy-eight.