Improvements in or relating to Telephone Instruments.
Year: 1895

page_text: PROVISIONAL SPECIFICATION.
Improvements in or relating to Telephone Instruments.
I, THOMAS FREDERICK JOHN TRUSS, of 6, Pickering Road, New Brighton,
Cheshire, Electrician, do hereby declare the nature of the said invention to be as
follows:-
It is found that subscribers to telephone exchange systems frequently leave their
telephone receiver off the switch hook, as for instance when obtaining information
for the person by whom they have been called up, the receiver meanwhile hanging
by its cord from the instrument case. Sometimes the subscriber does not return to
the instrument and consequently the receiver may not be replaced on its hook until
a considerable amount of time has elapsed.
The result of this negligence is that during the time the receiver is off its hook
the subscribers battery is in circuit and running to waste, his signal bell being
meanwhile cut out of circuit, so that he cannot be signalled by the exchange.
If now the person who called up the subscriber becomes tired of waiting and
rings off, and another person asks the exchange to connect him with the subscriber
the exchange is unable to signal. him, his bell being cut out, necessitating the
despatch of a messenger to the subscriber's office.
All this entails dislocation of the exchange system and depreciation of batteries,
requiring increased supervision of instruments and extra work for the exchange
staff.
may
To obviate these objections I attach (under one method according to my
invention) the cord or insulated conductors of the receiver to the switch hook,
so that when the receiver is left hanging by its cord its weight will depress the
switch hook and so break the primary or battery circuit. The cord be
attached to the hook by a clip, or it may be knotted or provided with a stop and
passed through a hole in the hook, or be otherwise fastened thereto. From the
hook the insulated receiver conductors are continued to the usual terminals on the
instrument.
Instead of attaching the receiver cord to the switch hook ordinarily fitted to
telephone instruments, I may attach it to an additional switch hook, the function
of which is, firstly, to make and break the primary circuit, and secondly to short-
circuit the generator. The switch arm is provided with a knife edge metallic
piece adapted to make rubbing contact with two pairs of metallic springs
alternately, that is to say when the weight of the receiver is off the hook, and
the switch arm is in its upper position, its knife edge piece bridges the upper pair
of springs, which form part of the primary circuit, and when the weight of the
receiver is on the hook, and the switch arm is in its lower position, its knife
edge piece bridges the lower pair of springs which short-circuit the generator.
Therefore when the receiver is left hanging its weight will depress the additional
switch and break the primary circuit. At the same time the generator will be
short circuited through the lower pair of springs. If now anyone comes to the
instrument in the temporary. absence of the subscriber he cannot ring. off, the
generator being short circuited, and this serves as an indication to him that
the instrument is engaged, the exchange being meanwhile able to signal through
such short-circuit.

page_text: The ear piece of the receiver may be lined with india-rubber to prevent breakage
on falling against a wall.
Dated this 31st day of October 1895.
J. A. COUBROUGH,
Registered Patent Agent,
10 St. George's Crescent, Liverpool, Agent for the Applicant.
:
"
•
Improvements in or relating to Telephone Instruments.
I, THOMAS FREDERICK JOHN TRUSS, of "Pleasant View," Rake Lane,
Liscard, Cheshire, formerly of 6, Pickering Road, New Brighton, Cheshire,
Electrician do hereby declare the nature of the said invention and in what manner
the same is to be performed to be particularly described and ascertained in and by
the following statement :-
It is found that subscribers to telephone exchange systems frequently leave their
telephone receiver off the switch hook, as for instance when obtaining information
for the person by whom they have been called up, the receiver meanwhile hanging
by its cord from the instrument case. Sometimes the subscriber does not return to
the instrument and consequently the receiver may not be replaced on its hook until
"a considerable amount of time has elapsed.
The result of this negligence is that during the time the receiver is off its hook
the subscribers battery is in circuit and running to waste, his signal bell being
meanwhile cut out of circuit so that he cannot be signalled by the exchange.
If now the person who called up the subscriber becomes tired of waiting and
rings off, and another person asks the exchange to connect him with the subscriber
the exchange is unable to signal him, his bell being cut out, necessitating the
despatch of a messenger to the subscriber's office.
All this entails dislocation of the exchange system and depreciation of batteries,
requiring increased supervision of instruments and extra work for the exchange
staff.
To obviate these objections I attach (under one method according to my
invention) the cord or insulated conductors of the receiver to the switch hook,
so that when the receiver is left hanging by its cord its weight will depress the
switch hook and so break the primary or battery circuit. The cord may be
attached to the hook by a clip, or it may be knotted or provided with a stop and
passed through a hole in the hook, or be otherwise fastened thereto. From the
hook the insulated receiver conductors are continued to the usual terminals on the
instrument.
Instead of attaching the receiver cord to the switch hook ordinarily fitted to
telephone instruments, I may attach it to an additional switch book, the function
of which is, firstly, to make and break the primary circuit, and, secondly, to short-
circuit the generator. The switch arm is provided with a metallic piece adapted
to make contact with two pairs of metallic contacts alternately, that is to say when
.the weight of the receiver is off the hook, and the switch arm is in its upper
position, its metallic piece bridges the upper pair of contacts, which form part of
the primary circuit, and when the weight of the receiver is on the hook, and the
switch arm is in its lower position, its metallic piece bridges the lower pair of
contacts, the effect of which is to short-circuit the generator. Therefore when the
receiver is left hanging, its weight will depress the additional switch and break the
primary circuit. At the same time the generator will be short circuited through
the lower pair of contacts. If now anyone comes to the instrument in the
temporary absence of the subscriber he cannot ring-off, the generator being short-
circuited, and this serves as an indication to him that the instrument is engaged,

page_text: the exchange being meanwhile able to signal through such short-circuit.. The
additional switch is provided with a hook in order that the receiver may be hung,
upon it to indicate that the instrument is engaged.
I will now proceed to describe, with the aid of the accompanying, drawings, the
application of this invention to that type of receiving and transmitting instrument
in which the signalling circuit and the primary and secondary circuits are
respectively made and broken by a switch hook adapted to hold the receiver of
the instrument.
'
In Figure 1, A denotes the ordinary switch hook of the instrument, B is the
receiver whose conductors bb are connected to the terminals 6' 6. At present,.
if the receiver B is allowed to hang by its conductors its weight is supported by a
staple driven in the instrument case, and the hook A remains in its raised position,
thus completing the battery circuit. According to this invention I cause the
weight of the suspended receiver B to be borne, by the hook A (whereby, if the
receiver is left suspended, the battery circuit will be broken), and may accomplish
this as follows. pass the conductors bb (Figure 1) over the hook-forming a
bight and I secure them by a clip 2, which may be simply sprung onto the
conductors or its two sides may be rivetted. Or, I may form an eye in the
hook A (Figure 2) and I pass the conductors through it, a knot being formed or
a collar clipped on the conductors to prevent them from being drawn through the
eyc. In other cases I may forin a clip of thin sheet metal which may be bent
around the hook A (Figure 3) and secured by the conductors being passed
through an eye b formed by the clip. Or, I may connect the conductors to the
hook A. by a cord or stay in such a manner that when the receiver is left hanging
upon its conductors its weight will be borne by the hook A.
In Figure 4 is illustrated that part of my invention in which the conductors 6 of
a receiver B are attached to an additional switch hook C, which attachment may be
made according to either of the methods above described, the conductors 6 being
continued to the terminals b'. The functions of this hook are:-to break the
primary circuit of the instrument and to short-circuit or cut out the generator of
the instrument, at the same time providing or completing a circuit by means of
which the subscriber may be signalled by his exchange-all while the receiver is
off the ordinary switch hook A.
The switch hook C is pivotted at c and controlled by a spring e'. Upon the arm
of the hook is formed a bridge piece D, which by preference possesses, a knife-edge.
Such bridge piece D is adapted to make.rubbing contact alternately with two pairs
of contact springs E and F as the hook C rises and falls.
“ •
1.
Instead of contact springs E and F and bridge piéce D, I may employ mercurial
contacts arranged as shewn in Figure 5 (elevation) and Figure 6 (plan). In this
arrangement the contacts E consist of a metallic cup e containing mercury and a
metallic sleeve e surrounding a plunger e pivotted on the end of the hook C, which
plunger (of non-conducting material) is adapted-when the hook C is light-to
raise the level of mercury in the cup e so that it establishes a metallic contact
between the cup e and sleeve e¹. The contacts F consist of two cups of mercury ff,
into which the two ends of a metal rod dip when the hook C is weighted by the
receiver B.
The effect of thus bridging the contacts E and F will be understood upon.
reference to the diagrams, Figures 7 to 11, which will now be described.
Figure 7. A is the ordinary switch hook, adapted-as hereunder described-to
the requirements of this invention." B B are the receivers, the conductors of one of
them being attached to the additional book C, which hook is adapted to make
contact alternately with the contacts E and F. G is the generator, H the bell,
V line terminal, W earth terminal. X is the primary circuit and Z the secondary
circuit, of the induction coil Y. The switch hook A is specially arranged to
perform three functions, namely to establish a signalling circuit through the
contact a (as hitherto) when the hook is depressed; secondly to bridge a breach
in the primary circuit X by connecting the contacts x, x', with the insulated

page_text: metallic plate 2, when the hook is light; and thirdly to complete the secondary
circuit Z by establishing metallic contact between the contact z and the lead z¹
through the metal of the hook, also when the hook is light. In this figure the
switch hook A is represented as weighed down by the receiver resting on it; the
instrument is thus in cendition to be signalled by the exchange over the circuit
shewn in heavy lines.
Figure 8. Both the hooks A and C are light, the receiver being held by the
subscriber. A speaking circuit is thus established as shewn in heavy lines.
Figure 9. This is the "engaged" condition, i.e., the receiver B is assumed to
to be hanging, by its conductors, upon the hook C, which is therefore depressed,
the hook A being light. As the hook C is depressed it no longer bridges the
contacts E, consequently the battery circuit X is broken; and, by bridging the
contacts F short circuits the generator G over the leads F1, F2. Entering at
the line terminal V a signalling current splits, one portion passing over the lead V',
hook C, contacts F, lead F1 and through the bell H to earth W, the other portion
passing over the lead V2 and secondary circuit Z to earth W, the resistances of
both paths being approximately equal. The condition of the instrument therefore
when the receiver B is left hanging on the hook C is this the battery circuit is
broken at the contacts E, the generator is short circuited through F, F1, F2, whilst
at the same time a signalling circuit is open from the exchange end only. Under
these conditions a subscriber may leave his receiver hanging by its conductors
upon the additional hook C, either inadvertently or in order to indicate that the
instrument is engaged, without exhausting his battery and at the same time
rendering it possible for the exchange to signal him.
In the diagrams, Figures 10 and 11, I show another method of arranging the
electrical connections of a telephone instrument provided with the additional switch
hook of my invention, which method differs from that before described in that the
lead is connected to one of the contacts F instead of to the hook C. The effect
of this modification in the "engaged" position, i.e. when the receiver B is hanging
by its conductors on the hook C (Figure 10) is that the exchange may ring over
the lead V, contacts F and lead F', bell H, to earth W, as shewn in heavy lines.
If now someone approaches the instrument in the subscribers absence and-without
noticing the hanging receiver-attempts to ring by depressing the switch hook A
by hand, and turning the generator handle, the generator is short circuited through
the lead F, hook A, leads V2 and V₁, contacts F and lead F¹, as shewn in heavy
lines, Figure 11.
In order to protect the receivers of telephone instruments from damage by falling
against a wall or the like (at present a very common occurrence) I provide them
with rings of india rubber or other yielding material, J, as shewn in Figures 1 and 4.
These rings of yielding material may be laid in a groove formed in each end of
the receiver, or in the ear-piece only; or the rings may have a flat inner surface so
as to rest on the exterior of the receiver, or may be moulded to correspond with
the conformation of such exterior surface.
Although I have in the above description described only two methods of applying
the additional switch hook of my invention to a telephone instrument, whereby
when the receiver is left hanging thereon the battery circuit is broken, the
generator short circuited or cut out, and a circuit provided for the receipt of a
signal from the exchange, I would have it understood that such methods of
connecting up the parts will be varied to suit varying requirements, and I do not
restrict myself to the particular arrangements of leads herein described and
illustrated.
Having now particularly described and ascertained the nature of this inven-
tion and in what manner the same is to be performed, I declare that what I
claim is :-
1. For the purpose of breaking the battery circuit of a telephonic instrument of

page_text: receiver thereof is left hanging by its conductors, attaching such conductors to
the switch hook of the instrument as herein described with reference to Figures 1
to 3 of the drawings.
2. The employment in a telephonic instrument of the type herein specified, of an
additional switch hook, to which the conductors of the receiver (or one of the
receivers) of the instrument are attached, the function of said switch book being.
to break the battery circuit, to short circuit the generator of such instrument, and.
to provide a circuit for the receipt of a signal by such instrument, when the weight
of the receiver is borne by said hook, substantially as and for the purposes herein.
described.
3. In a telephonic instrument of the type herein specified, the combination of an.
additional switch hook C to which the conductors of the receiver (or one of the.
receivers) of the instrument, are attached, with two pairs of contacts E and F, the
contacts E forming part of the battery circuit of said instrument, and the contacts F
forming part of a circuit by which the generator of said instrument is short circuited
and by which a signal may be received by said instrument, when the hook is
depressed by the weight of said receiver, arranged and operating in the manner
and for the purposes herein described with reference to the drawings hereto.
annexed.
4. Providing the receiver or each of the receivers of a telephonic instrument.
with protecting pieces' or rings of india rubber or other yielding material,
substantially as and for the purpose herein specified.
TL tone
J. A. COUBROUGH,
Registered Patent Agent (Qual. by Exam.),
10, St. George's Crescent, Liverpool, Agent for the Applicant..