Improvements in Portable Telephones, applicable also for Testing Purposes.
Year: 1899

page_text: Date of Application, 24th Jan., 1899
Complete Specification Left, 26th July, 1899-Accepted, 23rd Dec., 1899
Improvements in Portable Telephones, applicable also for Testing
Purposes.
We, HENRY FIELD BLACKWELL, Junior, Superintendent of Fire Alarms, and
MAUDE ALICE BLACKWELL, both of 99, East Sist Street, New York City, United
States of America, do hereby declare the nature of this invention to be as
follows:-
This invention has for its object to provide a telephone of small and compact
form that may be readily carried in the pocket, and adapted to be attached to a
fire alarm system or circuit without impairing or cutting out the circuit for fire
alarm purposes, and is designed to facilitate operations of the fire department
and its officers in the execution of their various duties, by superseding the
existing system of telegraphing code signals and Morse characters.
The transmitter is mounted in a casing which is provided with a swing door
and a bail by which it may be supported on the inner door of a street fire alarm
box, the said casing also containing a battery having spring connections or
contacts with the primary circuit of an induction coil, and a condenser. The
receiver casing contains a coil, steel core and the diaphragm, the coil being sur-
rounded by a steel thimble which is in magnetic connection with the core.
The
ear piece may be in the form of a bent tube so as to be adapted to be inserted in
the ear to shut out external sounds.
A switch is arranged within the receiver consisting of a spring arm adapted
to be pushed into engagement with a contact point by a push button. The switch
is located in a primary circuit, and when it is desired to leave the instrument in
circuit and not in use, by releasing the button, the spring will move to its open
position so that there can be no waste of the battery. To the secondary circuit
is connected a jack plug consisting of a central pin surrounded by a sleeve of
insulating material, separating the pin from the outer conducting sleeve. A
socket for receiving the jack plug is arranged within each fire alarm plug, and has
two connections, one of which has connection with the main fire alarm line, and the
other leads to the ground. These connections are normally open, but when the
jack plug is inserted in the socket, to place the secondary circuit in the telephone
in electrical connection with the fire alarm circuit and with the ground, through
the condenser without placing a ground on the wire, one wire of the secondary
leads to the outer shell of the jack plug and the other wire leads to. the inner-pin
of the jack plug.
In operation when it is desired to telephone to headquarters or to any other
place on the line, the jack plug is to be inserted in the socket and the instrument
hung upon the inner door of the fire alarm box; then by placing the receiver to
the ear and closing the switch the circuit is complete, so that conversation may be
had through the telephone.
While we have described the instrument as particularly adapted for the use of
the fire department. it is to be understood that it will also be useful as an instru-

page_text: ment of accuracy in making capacity determination, and the other tests for
locating faults in underground constructions or overhead work, by being used in
place of a galvanometer, as at present.
Dated this 24th day of January 1899.
A. M. & WM. CLARK,
Chartered Patent Agents, 53, Chancery Lane, London.
COMPLETE SPECIFICATION.
Improvements in Portable Telephones, applicable also for Testing
Purposes.
We, HENRY FIELD BLACKWELL, Junior, Superintendent of Fire Alarms, and
MAUDE ALICE BLACKWELL, both of 99, East 81st Street, New York City, United
States of America, do hereby declare the nature of this invention and in what
manner the same is to be performed, to be particularly described and ascertained
in and by the following statement:-
This invention relates to improvements in telephones, and it has for its object
to provide a telephone of small and compact form that may be readily carried in
the pocket, and adapted to be attached to a fire alarm system or circuit without
impairing or cutting out the circuit for fire alarm purposes and is designed to
facilitate operations of the fire department and its officers. in the execution of
their various duties, by superseding the existing system of telegraphing code
signals and Morse characters.
We will describe a telephone embodying our invention, and then point out the
novel features in the appended claims.
Reference is to be had to the accompanying drawings forming a part of this
specification, in which similar characters of reference indicate corresponding
parts in all the figures.
Figure 1 is a front elevation of a telephone embodying our invention and
showing the same as attached to a fire alarin box;
Figure 2 is a front elevation of the telephone, drawn on a larger scale than
that in Figure 1;
Figure 3 is a longitudinal section of a receiver employed; and
Figure 4 is a diagrammatic view illustrating, the circuits.
The telephone comprises a casing 1, provided with a swinging door 2, and
having a bail 3 adapted to be supported upon the inner door 4 of a fire alarm
box 5. Arranged within the casing is the diaphragm 6, for the transmitter, and
also a battery 7 preferably of the dry type, having spring connections or contacts
with the primary circuit. Also arranged within the casing is a condenser 8, and
an induction coil comprising the primary 9 and the secondary 10. The primary
of the circuit is contained entirely in the case of the telephone, excepting where
the wire loops pass out into the receiver through the receiver core 11.
The receiver comprises a casing 12 within which is the coil 13, the steel core 14,
and the diaphragm 15. The coil 13 and core are surrounded by a steel thimble 16
which is in magnetic connection with the core 14. Connected to the diaphragm
end of the receiver is an ear piece 17, here shown in the form of a bent tube, whose
end is intended to be placed within the ear, so that the operator will not be
disturbed by other sounds on the street.
"
A switch is arranged within the receiver, and consists of a spring arm 18
adapted to be pushed into engagement with the contact point 19, and extended
outward from the spring 18 is a push button 20. The switch, of course is located
in a primary circuit, and when it is desired to leave the instrument in circuit and

page_text: not in use, by releasing the button 20, the spring 18 will move to its open
position, so that there can be no waste of the battery.
Having connection with the secondary circuit is a jack plug 21, consisting of a
central pin surrounded by a sleeve of insulating material, separating the pin from
the outer conducting sleeve. A socket 22 for receiving the jack plug is arranged
within each fire alarm plug, and has two connections, one of which indicated at 23,
has connection with the main fire alarm line 24, and the other 25 leads to the
ground. These connections are normally open, but when the jack plug is inserted
in the socket to place the secondary circuit in the telephone in electrical connection
with the fire alarm circuit and with the ground, through the condenser 8, without
placing a ground on the wire, one wire 26 of the secondary leads to the outer
shell of the jack plug 21 and the other wire 27 leads to the inner pin of the
jack plug.
In operation, when it is desired to telephone to headquarters or to any other
place on the line, the jack plug is to be inserted in the socket 22 and the instru-
ment hung upon the inner door of the fire alarm box, as plainly indicated in
Figure 1 then by placing the receiver to the ear and closing the switch the
circuit is complete, so that conversation may be had through the telephone.
While we have described the instrument as particularly adapted for the use of
the fire department it is to be understood that it will also be useful as an instru-
ment of accuracy in making capacity determination and the other tests for loca-
ting faults in underground constructions or overhead work, by being used in
place of a galvanometer as at present.
Having now particularly described and ascertained the nature of the said
invention, and in what manner the same is to be performed we declare that what
we claim is:-
1. The metal thimble arranged in the casing and surrounding the receiver coil
and engaging with the coil core.
2. A switch in the receiver for controlling the primary of the induction coil
and the transmitter battery.
3. The portable telephone having a bail provided with a hook portion for
suspending it from the top of a fire alarm box door.
Dated this 26th day of July 1899.
A. M. & WM. CLARK,
Chartered Patent Agents, 53, Chancery Lane, London.