IMPROVEMENTS IN ELECTRIC SIGNAL APPARATUS APPLICABLE FOR FIRE ALARMS TELEPHONE CALLS AND FOR LIKE USES
Year: 1884

page_text: We, HENRY ALFRED CHARLES SAUNDERS and ALFRED CHARLES BROWN both
of 66 Old Broad Street in the City of London do hereby declare the nature of
our Invention for "IMPROVEMENTS IN ELECTRIC SIGNAL APPARATUS APPLICABLE
FOR FIRE ALARMS TELEPHONE CALLS AND FOR LIKE USES" and in what manner
the same is to be performed to be particularly described and ascertained in and
by the following statement:-
This Invention has for its object improvements in electric signal apparatus
applicable for fire alarms telephone calls and for like uses..
It has long been known that many useful purposes of electric signalling can be
served, between two or more stations connected by a single line-wire by setting up
in the electric circuit at one or more stations a series or simultaneous number of
series, of pulsations or undulations of electric current, having definite and
isochronous rates; which currents flowing along the line are made to act electro-
magnetically on certain isochronous vibrating receivers placed in the circuit, with
the effect that only those particular vibrators out of a number in the circuit will
respond, whose individual rates of vibration correspond to one of the isochronous
rates of current pulsation or undulation being then produced in the line; and so
causing these vibrators to produce a signal either directly by their own simple
vibration, or indirectly by actuating certain devices locally connected to them.
The purpose of the present Specification is however to describe and claim
certain new special means and apparatus which we have devised for overcoming
certain defects contained in, and to render more practically workable the old
general method of electric signalling referred to above.
It has been known too that the vibrating bodies for the above mentioned purposes
may be either spring reeds, that is vibrators in which the governing power which
vibrates the mass, is almost exclusively the power of a spring, or gravity
pendulums in which the governing power is almost solely that of gravity.
Of these two classes of vibrators gravity pendulums are the most certain and
reliable in their action for the following and other reasons, (1), from the absolute
invariability of the controlling power (gravity), (2) from their being independent of
mass, and (3) from the simplicity of adjustment owing to the slow variation of rate
[Price Bd]

page_text: with length (as the square root only). Within the usual limits of practicable
space however it is impossible to get a very large range of rate of current impulses
with pure gravity pendulums, when only a single contact is made and broken per
beat, since the highest rate obtainable from them with certainty (that due to a
length of say only 1/2") equals only about 9 beats per second: while that due to a
pendulum of a foot length equals nearly two beats per second. From the slowness
of their practicable rates also, a comparatively long time is taken to determine
whether the pendulum when used as a receiver, is to accumulate or interfere, since
in every case the minimum number of current impulses necessary to certainly
distinguish the amplitude of the arc of oscillation of the accumulating vibrator
from that of the interfering ones, must be imparted to them before the signal can
be given. Where rapid signalling is required this of course becomes an important
item.
With spring reeds on the other hand the practicable range of rate is
enormously greater; varying from some thousands of beats per second as in the
high musical note producing reeds, down to rates, scarcely higher than that of
gravity pendulums, when the spring is very weak compared to the weight. From
the quick rates obtainable also, much more rapid signalling can be secured. In
consequence however of the comparatively larger amount of power required to
bend the necessarily stiffer spring of a moderate rate spring reed used as a receiver,
and having mass enough in its bob to render its rate certain the electro magnet must
be either put so close to the reed armature or else the current made so strong, that
when the armature is rigidly attached to, or indeed forms part of the mass of the
vibrator, in the usual way, such a large control is exercised over the reed, as to
endanger its being put into vibration by a rate of current pulsation considerably
different from the proper rate of the reed. More especially is this the case too
when the current is subject to any variation such as usually occurs in practice from
many causes. Where the vibrator is required to successively make a number of
different rates also, in order to form a transmitting apparatus, for opening and
closing electrical contacts in the rate of any desired one of the receiving vibrators;
it becomes very difficult in consequence of want of uniformity of springs, rapidity
of variation of rate with length, and for like reasons to obtain sufficient exactness,
with spring reeds.
To overcome then the above mentioned defects of spring reeds used as receivers
while retaining their greater speed and range of rate and to combine with them
as transmitters the certainly acting and easily adjustable variable rate gravity
pendulum, so as to obtain the advantages of both with the defects of neither, and
thereby to produce a very certain and efficient electric signal, capable of application
to many purposes (some of which are mentioned later on) is the object of the
present Invention.
Our improved apparatus then designed to fulfil the above mentioned conditions
is as follows.
Where it is required that an operator shall be able to adjust his transmitting
vibrator, to the rate of any one of the receiving vibrators in the circuit, we retain
for the transmitting vibrator the gravity pendulum making more than one contact
per beat, as described in the Patent granted to us in the year 1883 N° 2020.
The number of contacts made and broken per beat as the pendulum oscillates is
there represented as two, and this will often be sufficient but the number can be
multiplied indefinitely, where high rates for receivers are required. This may be
done by extending out a light spring arm from the transmitting pendulum rod
preferably near its point of suspension, and causing the free end of the spring arm
to bear on, and rub over as the pendulum oscillates, an arc composed of alternating
pieces of electrical conducting, and insultating materials (say brass and ivory) all
the conducting pieces being connected together so as to form one electrode of the
transmitter while the pendulum rod forms the other electrode, the number of such
puces is that requisite to make the desired number of contacts and insulations per
beat of the pendulum. This method of course requires that the amplitude of the

page_text: arc of oscillation of the pendulum be kept practically constant throughout the
signal; but this can be easily arranged by simply making the bob sufficiently
heavy.
Where however the operator at a particular station only requires to cause the
same one particular receiver, of a number in the circuit to respond for every call,
we give him a spring reed transmitter (as represented in Figures 1 and described
below). The spring in this instrument is not rigidly fixed at either end but is
attached at the free end of a pendulous rod by which the electric contacts are
made and broken. Only one contact is made per beat, and the bobs are fixed so
as individually to make the same number of beats per second as the particular
receiver required to respond. This arrangement is somewhat simpl-r than the
gravity pendulum and it is accurate where the transmitting vibrator is always
confined to one rate.
The details of this transmitting reed are as follows,-
a Figures 1 is a bracket fixe i to a base board and carrying a light spring to
which is attached a moderately long rigid brass rod c having a small platinum
plate fixed on one side, and towards its lower end as shewn. The side-movement
of this rod, which is allowed by the spring at the top bending, is controlled at its
bottom end within very narrow limits by two adjusting screws d and e screwed
into the insulated brass bracket f also fixed to the same base board. The screw d
has a piece of ivory or other hard insulating material fixed into its point so that it
never makes an electrical contact with the rod c although it forms a mechanical stop
therefor. The screw c however is tipped with platinum, and makes electrical as
well as mechanical contact once per beat with the platinumn plate fixed on the side
of the rod c. The free reed proper is fixed to the bottom of the rod c, and consists
of a spring to which is attached a rod on which the bob h can slide for
adjustment. The strength of the spring and weight of the bob are so chosen as to
permit of the desired rate being obtained as well as a sufficient period of vibration.
The exact adjustment can then be made by sliding the bob up or down as required,
and it can then be fixed firmly by the set screw as shown. Or the bob may be
attached directly to the spring g; but it is more convenient to use an intervening
rod.
The rod c then makes a very firm contact once per beat with the screw e; and
so opens and closes in the rate of the reed the electrical connection between the
brackets a and f which form the two electrodes of the transmitter, and which can
be connected with a source of electricity and with the line circuit in any ordinary
well understood way.
It will be found that the rate of this transmitter is
practically uniform for all amplitudes from the maximum down to very small
ones; which would not be the case where the spring y extended right up to the
bracket a.
The impulse for starting these transmitting reeds as in the case of the gravity
pendulum transmitters, may be given to them either directly by hand or through
the medium of any mechanical combination: and they will then continue to
vibrate ainply long enough for most purposes of signalling. Where a length of
time of vibration is required greater than that which can be obtained by increasing
the weight of the bob however, special means such as clockwork, or an electro-
motor etc. must be applied to continue the vibration.
For receivers we use apparatus also somewhat similar to those described in the
Specification of the above mentioned Patent N° 2020 of 1883; the new feature
being that we now use spring reeds, instead of gravity pendulums and we render
these receiving vibrators practically unaffected by variations in the electric current
or in strength of the electro-magnetic field by the separation of the armature from
forming part of the mass of the free-reed or vibrator and connecting it therewith
only through the flexible reed or spring so that the mass of the bob may be
capable of movement separate froin the armature and to a great extent.
independently of it-also by controlling the motion of the armature between fixed
stops, so that it can never move more than a certain pre-determined distance.

page_text: Our improved receiver is represented in Figures 2. It consists of an electro
magnet fixed to a base board and having an armature k. Where the rate of the
vibrator is not required to much exceed say 300 double beats per minute, this
armature is simply pivotted to the electromagnet frame at the top, and inclined
slightly to the vertical line, as shewn, so that gravity tends to draw it back against
the adjustable screw back stop l. Where this rate is required to be much exceeded
however the top of the armature is attached to the electro magnet frame by a
piece of spring instead of a pivot, and which spring tends to force the armature
back against the back stop . The apparatus will then work in any position. The
spring reed proper is then attached to the bottom of the armature, the point of
attachment or root of the free reed proper being the point n.
the
The reed consists simply of a spring m fixed in any ordinary way to the bottom
of the armature, (we prefer to fix it by slitting the armature, letting in the spring
as shewn, and then fixing it by rivetting or soldering or both). This spring carries
a bob o which is clamped either to the spring itself or to a rod firmly attached
thereto, as shewn. The rate of the reed can be adjusted by varying the distance
of the bob from the point n, and it can then be securely fixed by the set screw,
rate being thereafter invariable. The motion of the armature being then limited
to a very small extent by the pole of the electro magnet i on the one side and the
adjustable screw back stop on the other side, no one current, however strong it be,
can cause the free reed to move through an abnormally long distance; as has
always been heretofore the case, when the current has been allowed to act electro-
magnetically, directly on the free vibrating mass of the reed. Our improved
receivers are therefore practically insusceptible to variations of current, providing
only that it be sufficiently strong to attract the armatures at all. Since also our
armatures are by this means kept very close indeed to the poles of the electro
magnets the apparatus is extremely sensitive, and will work with far less current
than that required in the ordinary way; where the electro magnets have necessarily
to be placed a comparatively long way off the reed armatures.
In order that an electromagnetic vibrator may interfere properly, and remain
nearly at rest while a succession of currents, not in the rate of the vibrator, are
being sent through the coils thereof; it is evidently required too that the average
strength of all the accellerating impulses shall be equal to that of all the retarding
ones; and it is also evident that this condition can never be properly fulfilled
while the armature forms part of the mass vibrating under the control of the
spring in consequence of the want of uniformity of the magnetic field in which
the armature moves; the reed being more controlled by the electro magnetic pull
when towards the magnet than when it is farther away from it. Attempts have
been made to reduce this evil by placing the electro magnet farther away from the
reed; but this of course involves an enormous loss of sensibility, and does not even
then entirely cure the evil. By detaching the armature from the mass vibrated by
the spring and limiting the motion of the armature to a very short distance
between fixed stops, it will be seen, that the above difficulty is entirely obviated;
since, the point of attachment of the reed is always moved through the same short
distance for every current.
The impulses given to the reed being therefore, always very near equal, a much
closer approximation to the proper rate of the reed, may be sent, as current
impulses, through its coils, without causing it to vibrate beyond a given amplitude
than has heretofore been possible. We are therefore enabled to get a much larger
number of receivers for a given range of rate, as well as a much greater certainty
in action than heretofore, and we can also use with much greater reliability
currents, subject to the many variations arising in practice.
The combination of one or other of the transmitting vibrators above described
with the above mentioned improved spring reed receiver then makes a first rate
electric signal for accomplishing either of the following objects, viz. To enable an
operator at any one out station of a series of stations connected by one line wire to

page_text: call the attention of the terminal or main station, and intimate to that statin the
number of the out station for the time being so calling, such an arrangement
constitutes an efficient fire alarm, or 2.-To enable an operator at any one of a
number of stations in series on one line wire, to call the attention of any other
station or stations without disturbing the remainder, as required for a telephone or
telegraph individual call, or 3. To enable an operator at any one of a number of
stations in series on one line wire, to signal any one of a number of pre-arranged
conventional signals to one or other of the distant stations, as required for a
messenger or police call, or railway train describer. It is evident that. in either of
these cases the signals may be made by the simple vibration of one or more of the
receiving vibrators, out of a number in the same circuit; or, by the action of relays
or devices locally actuated by the vibrating receivers.
For fire alarms we arrange a transmitting reed similar to Figure 1 in a box with
a device such that on pulling a knob the reed is put into vibration. A number of
these boxes are then arranged at various positions in the streets or places to be
protected; and connected by a single line wire in such way that the electrical
circuit runs through a number of the transmitting vibrators in series. The
transmitters are normally held over to their contact closed side, by a lever which
is moved away when the knob is pulled. The circuit passes through the coils of a
set of corresponding reed receivers, as described above, placed at the fire station
together with a battery. The circuit is completed by either an earth connection at
each end, or by a return wire. The receiving reeds then each carry a flag or disc
bearing a number or signal corresponding to that of the box which contains the
similar rate transmitting reed and so serve to shew by their individual vibration,
the particular point from which a call is being sent. Or the receiving vibrators
may be actuated by a local battery controlled by a relay whose coils are placed in
the line circuit so as to respond to the pulsations of current produced by any of
the transmitting vibrators. A bell may also be arranged to be rung at the fire
station on the starting of any of the transmitting vibrators, by a local current
controlled by a relay in the ordinary way.
For telephone or telegraph signalling we arrange the apparatus exactly as
described in our Patent No 2020 of 1883, except that we now use higher rate
spring reed receivers as described above, in place of the gravity pendulum receivers
therein described.
For messenger or police calls, we give the operator a gravity transmitting
pendulum as above described, so that it can be set to make and break contacts in
the rate of any of the receiving vibrators, placed in the same circuit. The receivers
carry flags or discs bearing on them the names or conventional signals desired to be
sent; the same signals are marked on the scale behind the transmitting pendulumı
at each transinitting station at the proper position for making the corresponding
rates of current impulses.
Having now particularly described and ascertained the nature of our said
Invention and in what manner the same is to be performed we declare that what
we claim is-
First. A receiver consisting of a spring and a mass vibrating under the control
of the spring when actuated by an electro magnet and armature such armature
moving independently of the mass but in so doing imparting impulses thereto
substantially as described.
the
Second. A receiver consisting of a spring and a mass vibrating under
control of the spring, the said spring being connected with the armature of an
electro magnet which under the influence of the magnet is moved to and fro
independently of the mass over a short distance limited by stops substantially as
described
Third. A receiver consisting of an electro magnet and armature and a spring
fixed to the said armature and carrying at its free end a vibrating mass substantially
as described.

page_text: Fourth. A transmitter consisting of a contact making rod or part and a spring
fixed to the said rod or part and carrying at its free end a vibrating mass
substantially as described.
Fifth. The combination in a signalling apparatus of a gravity pendulum
transmitter and spring reed receivers substantially as described.
Dated
7111
7000