Means for Enabling Communication between the Driver and Guard and Passengers of a Railway Train to be Effected.
Year: 1899

page_text: Date of Application, 24th Aug., 1899
Complete Specification Left, 15th Dec., 1899-Accepted, 10th Feb.,
1900
PROVISIONAL SPECIFICATION.
Means for Enabling Communication between the Driver and Guard
and Passengers of a Railway Train to be Effected.
We, ARTHUR EDWIN LAMKIN, of 13, Blomfield Road, Uxbridge Road, London,
W., Electrician, and JOHN GEORGE LEMON, of 33, Palace Street, Buckingham
Gate, London, S.W., Hall Porter, do hereby declare the nature of this invention
to be as follows:-
-
The objects of our invention are to provide improved means of communication
between the driver and guard of railway trains and also between passengers in
such trains and both the driver and guard of the train whilst the train is
running; and to effect other purposes incidental to these main objects.
Our invention comprises means for establishing telephonic communication
between the guard and driver of a train independently of the passengers; means
whereby the guard can speak to the passengers in every compartment of the
train simultaneously, for such purposes as that of intimating the approach to a
station, or (for example if desired) for enabling a tourist conductor riding in
the guard's van to point out and describe to the passengers objects of interest
passed on the road; means whereby a passenger in any compartment can call
the attention of, and converse with, the guard, or guard and driver, and also
for enabling the guard to hear all sounds proceeding from the compartment
whence he is called (but from no other compartment of the train) so that he may
judge whether it is necessary to at once stop the train or not; means whereby a
visual signal is automatically exhibited outside the compartment of the passenger
calling; and means if desired, whereby the doors of that compartment are auto-
matically locked simultaneously with the transmission of the first alarm; and
the invention includes the provision of suitable couplings for the various electrical
conductors required, between adjacent vehicles of the train.
According to our invention the apparatus in the guard's van includes a bell
worked through a relay by a local cell normally in circuit with the main
battery in the same van. The bell is rung from any passenger compartment when
the circuit through the passenger's transmitter is closed by means of a switch
worked by a pull handle in the compartment, the bell when thus brought into
operation continuing to ring until cut out of circuit by the guard by means of a
switch which leaves the main battery in circuit with the calling passenger's pull
switch whereupon the guard by means of a double contact key completes the
circuit between his own receiving and transmitting apparatus and those in the
calling compartment.
The transmitting apparatus in each passenger's compartment comprises (say)
two microphones placed in opposite corners of the compartment and in circuit
with the primary winding of an induction coil in the circuit of whose secondary
winding is the receiver which is of the loud speaking type and is preferably
placed between two compartments with a trumpet mouth opening to each so as to
be available for both compartments. The guard's transmitter consists of a hand
microphone and his receiver is also of the loud speaking type, these being in
circuit respectively with the primary and secondary windings of an induction
انمم

page_text: The current sent through the calling passenger's transmitter by the drawing
out of his pull handle, passes to the guard's van through a wire which is common
to all the vehicles of the train and which branches to all the passenger's trans-
mitters, the circuit being closed only through that branch whose transmitter
by the action of the pull handle has been brought into use. On the depression
of the guard's double contact key this current passes through the guard's receiving
and transmitting apparatus and thence through a common return wire back to
the calling passenger's transmitter; the receiver in the calling compartment as
well as those in all the other compartments of the train being permanently
connected with a third common wire and actuated by induction through their
respective coils.
Should the guard desire to make.a. communication to the passengers, without
having received a call or alarm from any of them, he can speak to all the passenger
compartments simultaneously but the circuit mot being closed through any
passenger's transmitter the guard is unable to overhear any conversation between
the passengers. Similarly since only the calling passenger closes (by means of
his pull handle) the circuit through his own transmitter, the guard on receiving a
call or alarm from any passenger compartment can overhear what is going on in
that compartment alone.
The apparatus on the engine comprises a transmitter consisting of a hand
microphone in circuit with the primary winding of an induction coil in the circuit
of whose secondary winding is a loud speaking receiver. The driver is also
provided with a double contact key whereby he, is enabled when desirous of con-
versing with the guard.independently of the passengers, to cut out his own receiver
from the circuit of the common return wire and to cause the induced current
through his receiver to pass through the common wire upon which the passengers'
transmitters are branched. It follows therefore that while the driver and guard
are able to speak to one another and also to the passengers, and whilst anything
said by the guard to the passengers is heard on the engine, the driver and guard
by depressing their respective double contact keys can converse with-
out being overheard by the
no
passengers. The driver has
control
over the bell in the guard's van neither is a bell required on the engine.
any preconcerted signal made by merely clicking the key in either the guard's
van or the engine being rendered clearly audible to the official at the other end of
the train through the medium of the loud speaking receiver at that end.
The drawing out of the pull handle in any passenger compartment serves also
to exhibit a visual signal by projecting outwardly an electric lamp normally
housed within (say) the side wall of the carriage, said lamp when so projected
automatically establishing its own circuit through suitable contacts, so as to
be rendered visible under all circumstances. The drawing out of the pull handle
may also if desired serve to effect, through suitable mechanical or electro-
mechanical means the locking of the doors of the compartment, the doors being
thereafter capable of being unlocked from outside only. In any case the pull
handle would be provided with means for preventing its return to normal position
when once pulled out, except by the guard or other authorized person.
Suitable provision would be made for coupling together the electrical con-
ductors between adjacent vehicles in the train, and in cases where the vehicles
are provided with automatic mechanical coupling devices the necessary electrical
connections for the conductors would preferably be combined with such automatic
coupling devices.
It will be obvious that the above described means of communication between
driver and guard might be employed in the case of other than passenger trains.
1 1800
A. M. & WM. CLARK,
Chartered Patent Agents, 53, Chancery Lane, London.

page_text: Means for Enabling Communication between the Driver and Guard
and Passengers of a Railway Train to be Effected.
We, ARTHUR EDWIN LAMKIN, of 13, Blomfield Road, Uxbridge Road, London,
W., Electrician, and JOHN GEORGE LEMON, of 33, Palace Street, Buckingham
Gate, London, S.W., Hall Porter, 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 manner :-
.*! 1
The object of our invention is to provide railway trains with improved means
of electrical telephonic inter-communication whereby the passengers on a train
may communicate with the officials in charge of the train and whereby such
officials travelling in different vehicles of the train may communicate with one
another, whether the train be running or at rest; and the invention comprises
means for establishing telephonic inter-communication between the rear or
principal guard and the driver and the front guard of a train, independently of
the passengers; means whereby the guard is enabled to speak to the passengers
in every compartment of the train simultaneously, for such purposes as that of
intimating the approach to a station or (for example if desired) whereby a tourist-
conductor riding in the guard's van can indicate and describe to the passengers
objects of interest passed on the road; and means whereby a passenger in any
compartment can call the attention of and, if desired, converse with the guard,
and whereby the guard can hear all sounds proceeding from the compartment
whence he is called (but from no other compartment of the train) so that he may
judge whether it is necessary to visit that compartment, or to stop the train.
The invention will be described with special reference to the different electrical
and telephonic connections required for the purposes just enumerated, which are
assumed to be typical; but it will be obvious that the scope of the connections and
their mode of arrangement may be varied, as for example by affording the driver
of the train the same facilities for being called and for communicating tele-
phonically with the passengers, as are herein specified in the case of the principal
guard of the train; the general principles of the system of inter-communication
remaining however the same in all cases.
In the accompanying drawings forming part of this specification Figure 1
represents diagrammatically a railway train provided with our improved system
of telephonic inter-communication; the train comprising a locomotive and tender A
a forward brake compartment B a single passenger compartment (such as for example
a saloon or coupé) C, a carriage with two adjoining passenger compartments D D¹,
and a rear guard's van E, all the parts of the. apparatus being shewn as in their
normal or inactive position. Three main conducting wires or leads 1, 2, 3,
run the whole length of the train, suitable means of coupling up and uncoupling
the leads between adjacent vehicles being provided so that all vehicles fitted with
our apparatus are thus rendered interchangeable. These three leads 1, 2, and 3
serve respectively the purposes of an outfeed main, a common return and a private
return wire, the transmitting and receiving instruments and switches in the
several vehicles and compartments of the train, the main battery, and the relay
which controls the call bell in the rear or principal guard's van, all as hereafter
described, being so connected to two or more of said leads that the outfeed main
and common return wires are normally available for the direct transmission of
communications from the rear or principal guard's van to every compartment
of the train simultaneously; that officials can at will converse independently
of the passengers by transferring their own transmitters and receivers from the

page_text: circuit of the common return to that of the private return wire; that any
passenger by merely drawing out a pull-handle may close the circuit through his
bell relay, his own transmitter, and the private return wire and so call and
establish telephonic inter-communication with the rear or principal guard and
enable said guard to hear all sounds in the compartment whence the call pro-
ceeds, but in no other compartment
The compartments of the train occupied by the officials, viz. the cab of the
engine A, the forward brake B, and the rear van E, are each provided with a loud-
speaking telephone receiver (rA, B, E, respectively) which is normally in
circuit with leads 1 and 2 but may be transferred at will from the circuit of lead 2
to that of lead 3 and of the main battery b by means of a double contact key.
(kA, B, kE, respectively) in each of the officials' compartments A, B, and E.
Each of these compartments is also provided with a microphone transmitter
(mA, mB, mE, respectively) preferably of a type adapted to be held in the hand
when in use so as, when lifted off its supports, to cause a local circuit to be closed
through a small battery (nA, nB, nE, respectively) and through the primary
winding of an induction coil (A, B, E, respectively) whose secondary winding
can be thrown into the circuit of the corresponding receiver. In the cases of
the driver and front guard the secondary winding is normally isolated and is
thrown into the circuit of the corresponding receiver rA or B by the depression
of key kA or kB as the case may be; but in the case of the rear or principal guard
his receiver E is permanently in circuit with the secondary winding of his
induction coil E.
Each passenger compartment is fitted with a number of microphone transmitters
(a pair being shewn in each compartment) which are fixed in opposite corners
or elsewhere about the compartment so as to be adapted to collect and transmit
sounds emanating from every part of the compartiment. Each pair or set of
such passenger transmitters (tC, D, D¹, respectively) is permanently in circuit
on the one hand with lead 2 and on the other with lead 3 through the primary
winding of an induction coil (cC, cD, or cD¹) whose secondary winding (normally
isolated) is thrown into the circuit of the corresponding loud-speaking receiver
(SC or sD) in consequence of the pulling out of his handle (hC, AD, or D¹) by a
passenger who desires to call the attention of the guard. The receiver sC in the
isolated compartment C has a single trumpet mouth, but for the sake of simplicity
and economy a single receiver SD) is fitted between the two adjacent compart-
ments D D', this receiver having a double trumpet mouth (as indicated) so as to
speak into both compartments simultaneously. All the receivers in the passenger
compartments are connected unalterably to leads 1 and 2.
The various transmitters and receivers throughout the system are arranged in
multiple arc (i.e. are on shunt circuits to the lines 1, 2, 3) so as to be capable of
being worked independently of one another; this arrangement permitting the
various vehicles composing a train to be transposed relatively to one another
without affecting the inter-communication between them.
The pull handle (hC, hD, or hD¹, respectively) which is provided in each
passenger compartment and which when drawn out effects the calling of the
rear guard, and enables the latter to hear all sounds in that particular compart-
ment, is illustrated on a larger scale in Figures 2, 3, and 4 which represent
diagrammatically the handle and its connections in three positions, the normal
position being shewn in Figure 2 and the active or drawn-out position in Figure 3,
whilst Figure 4 shews the position of the parts when the calling passenger, having
finished his conversation with the guard, has pushed back the handle as far as it
will go, in readiness to make a subsequent call if necessary.
The pull handle mechanism (of which the only part accessible to the passengers
is the external knob h of the handle itself) comprises a rod d capable of sliding in
guides e e and retained (against accidental displacement) in either of its three
positions by means of a spring jumper f engaging with one or other of three
notches in the bar. A spring finger a carried by bar d maintains contact in all

page_text: a
positions of the pull handle h with a long contact strip 30 which is connected
directly to lead 1. In the first and third positions of the handle the finger
establishes electrical connection between strip 30 and a shorter strip 31, and in
the second position of the handle establishes connection between strip 30 and
another shorter strip 32; the strip 31 being connected directly to the receiver
in the same compartment whilst strip 32 is connected to this receiver through
the secondary winding of the induction coil whose primary winding is as already
A second spring
stated in the circuit of the corresponding set of transmitters.
finger carried by bar d establishes, in the second position of the pull handle,
electrical connection between two contacts 33 and 34, the former being con-
nected directly to lead 3, and the latter to lead 2 through the primary winding
of the induction coil in the same compartment and through the corresponding
set of transmitters. The establishment of connection between contacts 33 and 34
causes the rear gard to be rung up by the passenger desiring to call.
The foregoing description of the various connections established by means of
the pull handle h, applies without exception to all single or isolated passenger
compartments such as C, and to one member (such as D¹) of each pair of
In the case
associated passenger compartments served by a single receiver.
however, of the second member (such as D) of a pair of associated compartments,
the contact 31 and its connection is not required, the corresponding parts in the
adjacent compartment serving for both compartments alike.
The pull handle h can at all times be drawn out to its fullest extent, that is
to say to the second or active position (shewn in Figure 3) in which the calling
of the rear guard is effected, but can be pushed back by a passenger as far only
as the third position shewn in Figure 4, the connections established in this
position being however the same as those established in the first or normal
position of the handle, so that any number of calls can be made from the same
compartment; the partial projection of the knob when in the third position
serving as a tell-tale or indicator whereby the guard, on making a round of
inspection of the train, is notified of the compartment from which he has received
a call. The handle is prevented from being completely restored to normal position
by a passenger, by such means as the spring-pressed detent 35, which is in-
accessible by passengers but can be lifted (so as to allow of the complete return of
the handle) by the guard who alone is provided with a key giving access to the
interior of the casing containing the mechanism.
No battery is required in any passenger compartment, the one main battery b
required in the system being situated in the guard's van E where it is per-
mently connected on the one hand to lead 3 and on the other to a switch w
whereby the relay controlling the circuit of the call bell, may be thrown into,
or out of operation. This bell, which is the only bell required in connection
with the system, is of the trembler type, and is situated in the rear or prin-
cipal guard's van E. It is caused to ring by the local circuit through the bell
battery y being closed in consequence of the movement of the armature z¹ of the
electro-magnetic relay when the latter, which is normally in the circuit of the
main battery b, is excited by a current from that battery.
We will now proceed to describe the mode of effecting inter-communication
between the various compartments of the train.
1. Inter-communication between officials, viz:-
(a) between rear guard and driver.
(b) between rear guard and front guard.
(c) between driver and front guard.
(a) Should the rear or principal guard in the van E desire to speak with the
driver, he first throws over the switch w so as to cut out the relay z from the
circuit of the main battery b (thus preventing the bell from being rung) and
5 then taps his double contact key AE a certain number of times according to a
pre-arranged code of signals whereby the officials in charge of the train are
enabled to indicate which member of the train-staff is wanted. The current

page_text: emissions constituting the "call" signal thus sent by the rear guard will be
transmitted from E by wire 4, 5, battery b, switch w, wire 6, 7, 8, to lead 2
thence by branch 9, (in the engine cab A), the driver's double contact key kA
and wire 10 to the driver's receiver rA, returning by wire 11, lead 1, branch 12
(in van E), guard's receiver rE, the secondary winding of his induction coil E,
and wire 13 to key E. The receivers being of the loud-speaking type the sounds
produced by the tapping of key kE will be rendered plainly audible in the engine
cab. It will be seen by an inspection of the diagram that the same signal will
also be audible in all the other compartments of the train, since all the receivers
throughout the train are connected to leads 1 and 2 through which are sent the
currents constituting the call" under consideration, but as will be explained
hereafter, no passenger can overhear the actual conversation subsequently carried
ou by the officials. The rear guard having sent the code signal calling the driver,
keeps his key kE pressed down permanently until the close of the conversation,
the speaking circuit being completed by the driver pressing (and likewise
holding down permanently) his key kA, thus closing the circuit of his receiver
through the secondary winding of his own induction coil iA, thence through the
branch 14, 15, lead 3, branch 16 (in the guard's van E), and wire 4 to key kE.
66
It is of course understood that in order to converse, the guard and driver must
take up their respective transmitters mA and mE, thus closing the local circuit
through the transmitters and bringing the corresponding induction coils A
and into operation.
The driver by depressing key kA as already mentioned, will have cut his
receiver A out of the circuit of lead 2 so that the conversation between the driver
and the rear guard cannot be overheard by the passengers, since the passengers'
receivers sC and sD are unalterably connected to leads 1 and 2 alone. At the con-
clusion of the conversation the rear guard, after releasing his key kE, returns
switch to normal position.
The description just given pre-supposes the rear guard to be the caller; should
the driver however wish to call the rear guard, he presses down a key A a certain
number of times according to the pre-arranged code of signals, thus bridging
wires 15 and 9 and sending a corresponding succession of currents through wire 15
lead 3, branch 16 (in the guard's van E) wire 5, battery b, switch w, relay z
(causing the bell a to ring a number of times corresponding to the signal sent),
wires 17, 7, 8, lead 2, and branch 9, back to key A. The rear guard on hearing
the bell give the particular signal by which he himself is specially designated,
moves switch w so as to cut out relay and stop the bell when, by pressing down
key kE and taking up his transmitter mE he is enabled to converse, the speaking
circuit being completed (to the exclusion, of the passengers as before explained)
by the driver releasing key vA, and as before, depressing key kA.
(b) Inter-communication between the rear guard and front guard is effected in
the same way as between the rear guard and driver, the instruments provided in
the front brake compartment being similar to those in the engine cab.
(c) If the driver desires to call the front guard he depresses key -A a certain
number of times according to the pre-arranged code, thus closing as many times
the circuit from key -A, through wire 9, lead 2, branch 8 (in van E) wire 7, 17,
relay, (consequently causing the bell to be rung an equal number of times)
switch w, battery b, wires 5, 16, lead 3, and branch 15 (in cab A) back to key A.
The signal rung out by the bell will be disregarded by the rear-guard, whilst
the tapping of key A will be heard telephonically in the forward brake B
(as well as in the various passenger compartments) by reason of a portion of the
current passing from key -A through wire 9, key kA, wire 10, receiver rA,
wire 11, lead 1. branch 12 (in the rear van E) receiver rE, the secondary
winding of induction coil E, wire 13, and key kE, from the normal contact
of which it rejoins the current passing in wires 8 and 7 as already described.
The front guard on hearing the signal by which he himself is designated, presses
and holds down his key kB, the driver at the same time releasing key vA and

page_text: pressing and holding down key kA, when, on taking up their respective trans-
mitters ma, and mB, the driver and front guard are enabled to converse in
private, the induced speaking current passing by way of the secondary winding
of the induction coil A, key kA wire 10, receiver rA, wire 11, lead 1, branch 18
(in forward brake B) receiver rB, wire 19, key kB the secondary winding of
induction coil B, wire 21, 22, lead 3, branch 15 (in cab A) and wire 14 to the
secondary winding of induction coil iA.
It will be seen that no other receiver circuit whereof leads 2 and 3 form part is
open, and that consequently the conversation between the driver and front guard
is not liable to be overheard.
In the event of the front guard desiring to call the driver, the procedure
is similar to that just described with reference to the driver calling the front
guard and therefore requires no detailed explanation.
II. Inter-communication between rear guard and passengers, enabling
(a) rear guard to speak to entire train.
(b) rear guard to receive a call from any passenger compartment.
(c) rear guard to overhear all sounds in calling compartment alone.
(d) rear guard to hold conversation with passengers in calling compartment.
(a) The rear or principal guard is enabled to speak to all the compartments of
the train simultaneously, by merely taking up his transmitter mE, the induced
speaking current passing from the secondary winding of his induction coil ¿E,
through his own receiver rE and wire 12, to lead 1. The current thence reaches
the receivers in the passenger compartments as follows:-In the single com-
partment the current passes through branch 40, contact strip 30, spring
finger aC (which is in its first or normal position), contact strip 31 and wire 41
to the receiver sC whence it passes by wire 42 to lead 2. In the associated
compartments D and D' the current passes through branch 43, contact strip 30,
spring finger al¹ (which is in its first or normal position) contact strip 31,
and wire 44 to the double-mouthed receiver sD, whence it passes by wire 45
to lead 2. The current in all cases returns by lead 2, branch 8 (in van E), key kE
and wire 13, to the secondary winding of the induction coil E.
Although the rear guard would not usually employ this public method of
communication directly with the driver and forward guard, it is to be observed
that these latter officials will hear all the rear guard's remarks to the passengres,
the speaking current passing in the case of the driver, from lead 1, by branch 11,
to the driver's receiver rA and thence by wire 10, key A and wire 9, to lead 2;
whilst in the case of the forward guard the current passes from lead 1 by branch 18
to the forward guard's receiver B and thence by wire 19, key kB and wire 20,
to lead 2; the current in both cases returning to the induction coil E as already
described.
(b) A passenger desiring to call the rear guard has merely to draw out his pull
handle to its full extent, when the bell in the van E is set ringing until
stopped by the guard. The drawing out of handle has for effect to close
the corresponding circuit through battery b, the current passing in every case
from lead 2, by branch 8, wires 7 and 17, relay (whose armature being
attracted closes the local circuit of battery y causing bella to ring) switch w,
battery b, wires 5 and 16 to lead 3. In the case of compartment C the current
passes from lead 2 to lead 3 by way of branch wire 46, transmitter C, wire 47,
second transmitter C, wire 48, the primary winding of the induction coil C,
wire 49, contact strip 34, spring finger C. contact strip 33, and wire 50. In the
case of both compartments 1) and D₁ the course of the current is similar being
from branch 51 to 55 in the former case and from branch 56 to 60 in the latter.
(c) The rear guard having received the call from a passenger compartment
(for example compartment C) moves switch so as to cut the bell out of circuit
and is at once enabled to hear all sounds in the compartment in question. Such
sounds are transmitted telephonically by induced current through the circuit of
the guard's receiver, the current in the primary circuit passing from battery b

page_text: through switch w, wires 6, 7, 8, to lead 2, thence by branch 40 (in compartment
the first transmitter tC wire 47, second transmitter C, wire 48, the primary wind-
ing of induction coil cC, wire 49, contact strip 34, spring finger jC, contact strip 33,
wire 50, to lead 3, and thence by branch 16 and wire 5 back to battery b. The
induced current passes from the secondary winding of induction coil cC, by
wire 61, contact strip 32, spring finger aC, contact strip 30 and wire 40 to lead 1,
thence by branch 12 (in van E), to the rear guard's receiver rE, returning by the
secondary winding of his induction coil ¿E, wire 13, key kE and wire 8, to lead 2,
thence by branch 42 (in compartment C), receiver sC, and wires 41 and 62 to
the secondary winding coil cC. The current by which the rear guard is thus enabled
to hear sounds in any passenger compartment being in every case an induced cur-
rent dependent upon the primary current through a circuit which is closed only
when the handle h is drawn out to its full extent, it follows that the guard can over-
hear sounds in that passenger compartment alone from which he has received a
call, so that complete privacy is ensured in the case of every other passenger
compartment.
(d) The rear guard in order to speak to the calling passenger, must of course
take up
his transmitter mE, thus exciting the primary winding of his own
induction coil E which acts by induction upon all the receiver circuits through-
out the train, these circuits being unalterably connected, as already explained,
to leads 1 and 2, in whose circuit the secondary winding of the coil E remains
for the time being. It follows that the conversation betwen the rear guard and
the calling passenger will be audible to all in the train, but this is of no moment,
as such conversations are likely to be always brief and not of a private nature.
The arrangement already described whereby the calling passenger is enabled
to restore the connections to the normal condition existing previously to his
making the call, whilst permitting any passenger to communicate repeatedly
with the guard, prevents the latter from being needlessly interrupted in the
discharge of his regular duties as he might otherwise be each time he happened
to be rung up for (say) some trivial reason, owing to its being necessary for the
guard to visit the calling compartment in order to restore the pull handle to
normal position; any subsequent call from the same compartment being effected
by the drawing out of the pull handle, as before, to the second position. The
same arrangement has the further advantage of preventing the guard, after the
pull handle has been returned to the third position, from overhearing any con-
versation subsequently carried on in the compartment whence the call emanated.
It is to be observed that the rear guard must keep switch w constantly in
position to allow of the bell a being rung, except when he himself is calling or
engaged in conversation, and to this end switch w may be arranged to be
actuated by a push button or similar device adapted when pressed to cut out
relay and to be returned by a spring to normal position when the pressure is
released.
In order to enable any portion of the apparatus requiring repair, to be readily
replaced without specially skilled assistance, each instrument (such as a trans-
mitter, receiver, battery, or the like) throughout the train would be made com-
plete in itself and provided with spring plug couplings whereby electrical con-
nection with the proper wire conductors (which would be fixed permanently in
the several vehicles) would be automatically broken or re-established on the
removal or replacement of the instrument, so that an imperfect instrument can
be removed by any unskilled person, such as the guard of the train, and at once
replaced by a perfect instrument taken from a stock of such parts which would
be constantly maintained at the principal stations on the railway.
In order to permit of telephonic conversation being carried on with ease not-
withstanding the vibration and consequent noise inseparable from a train in
motion, every transmitter and receiver, or other portion of the apparatus liable
to transmit such vibrations or sounds would be loaded with lead or otherwise
and suspended from indiarubber springs and further protected against con-
.

page_text: cussion by means of indiarubber buffers; and the aperture of each transmitter
and receiver would be covered with a wire gauze screen for the purpose of pre-
venting damage by mischievously-disposed persons.
In cases where the vehicles are provided with automatic mechanical coupling
devices the necessary electrical couplings for the leads 1, 2, and 3 would pre-
ferably he combined with such automatic coupling devices.
It will be obvious that the above described means of communication between
driver and guard might be employed in the case of other than passenger trains.
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. Means whereby the passengers on a railway train may communicate tele-
phonically with the officials in charge of the train and whereby such officials
may communicate telephonically with each other whether the train be running
or at rest, said means consisting of three electrical conductors extending through-
out the train and serving as an outfeed main, a common. return and a private
return wire respectively; a hand microphone transmitter in each compartment
that is appropriated to the use of officials; microphone transmitters in each
passenger compartment; telephonic receivers in every compartment; a main
battery, a trembler bell apparatus, and an electro-magnetic relay controlling its
action, contained in the rear or principal guard's van; all said instruments or
apparatus being so connected with two or more of the said conductors under the
control of suitable switches that the outfeed main and common return wires are
normally available for the direct transmission of telephonic communications
from the rear or principal guard's van to every compartment of the train simul-
taneously; that officials desiring to converse may do so independently of the
passengers by transferring their transmitting and receiving instruments from
the circuit of the common return to that of the private return wire; and that any
passenger may, by drawing out a pull handle in his own compartment, manipu-
late a switch which closes the circuit through the bell relay, his own transmitter,
and the private return wire, and so cause the rear or principal guard to be rung
up. establish telephonic inter-communication with said guard, and enable said
guard to hear all sounds in the compartment whence such call has emanated but
in no other compartment, substantially as specified.
2. In apparatus for enabling electrical telephonic inter-communication to be
effected between the guard and passengers of a railway train whether the train
be running or at rest; the combination with three electrical conductors extending
throughout the train and serving as an outfeed main, a common return and a
private return wire respectively, of telephonic transmitting and receiving instru-
ments located in each passenger compartment and in the guard's van, and a
main battery, a trembler bell apparatus, and an electro-magnetic relay con-
trolling said bell apparatus located in said guard's van, all of the said instru-
ments, battery, bell apparatus, and relay being so connected to two or more of
the said three conductors under the control of suitable switches that the outfeed
main and common return wires are normally available for the direct transmission
of telephonic communications from the guard's van to every passenger com-
partment simultaneously; and that any passenger can by drawing out a pull
handle in his own compartment, manipulate a switch which closes the circuit
through the bell relay, his own transmitter, and the private return wire, and
so cause the guard to be rung up, establish telephonic inter-communication with
said guard, and enable said guard to hear all sounds in the compartment whence
such call has emanated but in no other compartment, substantially as specified.
3. In apparatus whereby the passengers on a railway train may communicate
telephonically with the officials in charge of the train and whereby such officials
may communicate telephonically with one another, whether the train be running
or at rest, the combination with three electrical conductors extending throughout

page_text: the train and serving as an outfeed main, a common return and a private return
wire respectively, of telephonic receiving and transmitting instruments located
in each compartment of the train, and a main battery, a trembler bell apparatus,
and an electro-magnet relay controlling said bell apparatus located on one of
the compartments appropriated to the use of officials, all of the said instruments
battery, bell apparatus, and relay being so connected to two or more of the said
three conductors under the control of suitable switches that telephonic inter-
communication may be established at will between any two or between all of
the compartments appropriated to officials without the conversation transmitted
by such lines of communication being overheard by persons travelling in the
passenger compartments of the train substantially as specified.
4. In a system of telephonic apparatus as described for enabling the passengers
on a railway train to communicate with the officials in charge of the train, provid-
ing two adjoining passenger compartments with a single telephonic receiver so
formed and connected as to serve for both compartments in common, substantially
as specified.
1511 1
T
1 - 1000
A. M. & WM. CLARK,
Chartered Patent Agents, 53, Chancery Lane, London.