IMPROVEMENTS IN ELECTRIC TELEGRAPH SIGNAL OR ALARM APPARATUS
Year: 1872

page_text: LETTERS PATENT to Edward Augustine Calahan, of Brooklyn, New
York, United States of America, now of No. 8, Southampton
Buildings, London, Telegraphic Engineer, for the Invention of
COMPLETE SPECIFICATION filed by the said Edward Augustine
Calahan at the Office of the Commissioners of Patents, with his
Petition and Declaration, on the 20th May 1872, pursuant to the
9th Section of the Patent Law Amendment Act, 1852.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, EDWARD
AUGUSTINE CALAHAN, of Brooklyn, New York, United States of
America, now of No. 8, Southampton Buildings, London, Telegraphic
Engineer, send greeting.
WHEREAS I am in possession of an Invention for "IMPROVEMENTS IN
ELECTRIC TELEGRAPH SIGNAL OR ALARM APPARATUS," and have petitioned
Her Majesty to grant unto executors, administrators, and assigns,.

page_text: Her Royal Letters Patent for the same, and have made solemn Declara-
tion that I am the true and first Inventor thereof.
NOW KNOW YE, that I, the said Edward Augustine Calahan, do
hereby declare that the following Complete Specification under my hand
and seal fully describes and ascertains the nature of the said Invention,
and in what manner the same is to be performed, in and by the following
statement, reference being had to the accompanying Drawing forming a
part of this Specification: -
My Invention relates to simple but thoroughly efficient apparatus to
be placed in a telegraphic circuit for giving signals or alarms. It is
chiefly designed to afford a convenient and sure means for transmitting
arbitrary signals from hotels, banks, offices, private dwellings, and
other houses or buildings to a police station or other establishment to
notify to the same the need of assistance or attendance. It also pro-
vides in a simple and inexpensive manner for the protection of offices,
banks, houses, and other places from burglars during the absence
of the inmates, or at any time when the same are otherwise
unguarded.
The first part of my said Invention relates to a signalling instrument
so constructed that any number of such instruments may be placed in a
single line or circuit in connection with a single apparatus at the central
station, and each one when not being used will simply form part of the
line, offering no resistance to the passage of the current through the
same; and moreover the said instrument will not permit of two operators
using the line at the same time, each instrument showing whether the
line is clear or is occupied in the transmission of signals from any other
instrument in the circuit.
The second part of the said Invention relates to a contrivance whereby
the said instrument is connected with a local circuit which has a wire
extended to any desired part of the house or other building to be
guarded, and this wire on the entrance of a burglar or other person not
acquainted with its existence or arrangement will be broken, and will
cause the aforesaid instrument to operate and transmit to the police
station a series of signals, which will be continued and will entirely
prevent the use of the line for other instruments till these signals have
received attention.

page_text: In the accompanying Drawing I have shewn one of my improved
instruments and the manner of connecting the same with the main
circuit and with the aforesaid automatic contrivance, and I will now
proceed to describe the same.
Figure 2 is a front elevation; and Figure 3 is a side elevation of the
same.
Figure 4 is a side elevation of the said instrument, shewing it con-
nected with the automatic burglar alarm apparatus.
Figure 5 is a similar side elevation, illustrating a modification of the
said apparatus.
Like letters indicate the same parts throughout the Drawing.
The stand or base a of the instrument is constructed of cast iron or
other suitable material, and of any convenient form; 6 is a frame which
carries the clockwork as shewn, for operating the break wheels c, d.
This clockwork is wound up in the ordinary manner. e, f, are the break
springs; the spring e bears upon the perimeter of the wheel c and
spring upon the perimeter of the wheel d. These wheels when set in
motion produce the signals by the action of their notches upon the said
break springs. It is a part of my system that each house, office, or
other building in which these instruments are placed should be known
at the central station or establishment by a number or numbers. The
instrument shewn in the Drawing has two break wheels, and therefore
two numbers. The wheel c has five and two notches, which indicate 52.
The other wheel d has one notch less, and indicates 51. Therefore, when
either of these two signals are shewn at the central station the house or
other building whence they are sent will be indicated with unerring
precision. The springs e, f, are fixed to the frame bat e¹ and f¹, and
are insulated from the said frame by small blocks of hard india-rubber or
other suitable insulating material.
On the base a I place a switch 9 which is pivotted to the base at g',
and is insulated therefrom by a block of any insulating material. This
switch is enclosed between the two stops g², g³, which are also insulated
from the base a; the said switch is capable of movement from one to the

page_text: and
other of these stops, but they are so formed that it can never be entirely
free or clear of both of them. The main wire or circuit which is indi-
cated by the line 1 is connected to the pivot pin g¹ of this switch,
the aforesaid stops g³, g³, are connected to the springs e, f, by the wires
2, 3; the wire 2 connecting the stop g² to the spring e, and the wire 3
connecting the stop g³ to the spring f.
On the face of the break wheel c is a stud c¹; this stud is arranged
to be held by the lever h, which is connected to the finger key h¹ whose
fulcrum or pivot is at h², the said pivot being insulated from the base a.
This key is connected by the wire 4 to the contact stud i, and the latter
is normally in contact with the shunt key j. This pin and key are both
insulated from the base, and the said key by the wire 5 is connected to
the main line or circuit 1, as clearly shown in Figure 2. Or instead of
connecting this finger key to the contact stud i as above described; I
may arrange a small spring to bear upon the stud c¹ when the said stud
is held by the key, this spring being connected to the contact stud by a
wire, and the finger key and lever then acting only as a stopping and
releasing device. ³ is a spring for returning the key h¹ after each
depression; and h are insulating stops.
In the base a I form a box or receptacle a¹, in which I place an
electro-magnet k, which is connected to the connecting post by the
wire 6 and to the main line 1. kis the armature of the said magnet.
The armature lever is pivotted at ³ in the box a¹, and its upper end
works in a slot in the bar k³, which is provided with stop pins k* to
regulate the movement of the said armature.
When any instrument in the circuit is not being used and during the
transmission of signals from another instrument in the circuit, the
current obeying the law by which it is caused to take the shortest or
most direct path, passes from the main line through the switch and
through one or other of the wires 2, 3, spring e or f, and wheel c or
wheels c, d, to the lever h, and thence through the wire 4, the contact
studi, shunt key j, and wire 5, to the other end of the main line wire 1.
But when signals are being sent by this instrument, the short or direct
connection between the two ends of the main line being broken by
raising the lever h out of contact with the break wheel, the current
flowing from the main line to that one of the said break wheels with
which the switch is put in connection, passes through the instrument to
the connecting post 7, which is not insulated, and thence through the

page_text: be pulled away from the magnet by the spring 9 or by a weight, and will
depress the finger key, thereby releasing the break wheel and putting the
instrument in action.
In order that this release of the armature may be accomplished auto-
matically, and in such a manner that a burglar or other unauthorized
person entering the premises may effect the release of the instrument
unconsciously, I use a very fine and almost invisible wire for connecting
the battery and magnet, and carry the same in a circuitous manner
around the building. Consequently, the burglar cannot enter the
premises or move from one part to the other thereof without coming in
contact with this wire, which being so fine is broken by the slightest
movement or pressure. The finger key h' which holds the instrument
being thereby withdrawn and held out of contact with the break wheel,
the instrument is immediately put in operation and transmits a rapid
succession of signals to the station or receiving house. And this
repetition of signals coupled with the fact that the line is closed by
them against all other instruments necessitates prompt attention, and
the capture of the burglar is ensured by his own act before he has any
knowledge of such a possibility.
The apparatus shewn in Figure 5 is in construction similar or nearly so
to that in Figure 4, but the action is reversed, that is to say, in Figure 5
the normal position of the armature lever m² is that of separation from
the magnet m, in which position it is kept by the spring ³; and the
said magnet by drawing down the armature lever m³ depresses the finger
key h¹, and releases the instrument.
With the instrument shewn in Figure 4 the local wire or circuit is so
made that the breaking of the wire as aforesaid destroys the connec-
tion between the battery and magnet, and the cessation of the current
deprives the magnet of its power, and it therefore drops the armature
with the result above described. But with the instrument shewn in
Figure 5 the local circuit is so arranged that so long as the wire is
unbroken the circuit is complete without the magnet which is connected
indirectly to the said circuit. But when the wire is broken by the
burglar the direct circuit is destroyed, and then the current passes
through the magnet, causing the same to pull down the armature m¹
and finger key h', thereby releasing the instrument which operates
continuously, as above described, till the signals have received attention.

page_text: Having thus fully described the said Invention and the manner of
performing the same, I wish it understood that I claim,—
First. An electric telegraph signal or alarm instrument provided with
an electro-magnet, and so constructed and connected with the main line
or circuit that the current is made to pass through the said magnet in
giving a signal and for ascertaining the condition of the line, and the
said magnet is excluded from or cut out of the circuit after each signal.
Second. A number of such instruments connected to a single wire
which forms the main line or circuit, and which is also connected with
any suitable signal or alarm apparatus at a central station or receiving
house for the purpose set forth.
Third. The switch and its stops connected to the break springs and
acting through them in combination with break wheels which are
rotated by clockwork, and are so formed that each wheel in one
revolution gives a distinct arbitrary signal as herein set forth.
Fourth. The finger key and its lever in combination with a stud or
other stop on the break wheel for holding the same, and either
completing the main circuit by itself through the shunt key, or arranged
in combination with a spring for so completing the circuit and excluding
or cutting out the magnet, as herein set forth.
Fifth. The electro-magnet placed in a box or receptacle formed in the
base a or otherwise conveniently arranged, and so connected with the
main line or circuit that the same is completed through the said magnet
when the more direct circuit is broken by the depression of the finger
key or shunt key, as herein set forth.
Sixth. In an electric telegraph signal or alarm instrument the switch
and its stops, the springs, the break wheels with their actuating clock-
work, the stop lever and key, the magnet and shunt key, and other parts,
with their wire connections arranged to act in combination together in
the main line or circuit, as herein set forth.
Seventh. The combination with the aforesaid instrument of the
apparatus shown in Figure 4 or Figure 5, which is so constructed and
connected to the finger key of the said instrument and with a local
circuit that when the wire of the latter is broken the armature of the
5 said apparatus will depress the said finger key, and thereby effect the

page_text: automatic transmission of signals from the said instrument, as herein
set forth.
In witness whereof, I, the said Edward Augustine Calahan, have
hereunto set my hand and seal, this Fifteenth day of May, in
the year of our Lord One thousand eight hundred and seventy-
two.
Witness,
EDWARD E. JACKSON.
EDW³. A. CALAHAN. (L.S.)