Improvements in Electric Signalling.
Year: 1891

page_text: Date of Application, 20th Oct., 1891
Complete Specification Left, 20th July, 1892-4ccepted, 3rd Sept., 1892
PROVISIONAL SPECIFICATION.
Improvements in Electric Signalling.
ALAN ARCHIBALD CAMPBELL SWINTON 66 Victoria Street London S.W.
Engineer do hereby declare the nature of this invention to be as follows:-
My invention relates to improvements in electric signalling, & affords a means
whereby, alternating electric currents, such as are now supplied for electric lighting
& other purposes, may be utilised for operating telephone call bells, house bells, &
similar signals, thus obviating the necessity for the primary batteries or magneto
generators at present commonly employed for this purpose.
According to my invention, such batteries or generators are replaced by a
transformer or induction coil through the primary wire, of which the alternating
current supplied, is caused to circulate, the secondary wire being electrically
connected to the distant bell or signal.
By suitably proportioning the windings of the coil, the voltage of the current
can be raised or lowered as may be found convenient, and by separating the primary
& secondary wires, by means of asbestos, or other unimflamable insulating substance,
the two may be kept quite distinct, so that all danger due to a direct connection
between the electric supply & the signalling circuits is avoided.
Electric bells or signals, of any convenient type, may be employed, but polarised
bells may preferably be used, modified if necessary, so as to make the natural
period of the swing of the hammer, sufficiently rapid to enable it to respond to the
alternations of the current.
The push-button or operating key is inserted in either the primary or secondary
circuit of the transformer, or arranged to connect or disconnect both at once, and
when employed on telephone lines it may be made double pole, so as to brake all
connection between the supply mains and the transformer, this preventing any
disturbance in the telephone due to statical or other induction.
In cases where signalling is done from both ends of the line, the push buttons
may be arranged to cut out or short circuit the bell at the transmitting end & the
secondary of the induction coil at the receiving end.
For safety, the primary of the coil may be connected to the supply mains
through cut out fuses, and a resistance may also be inserted with a like object.
Where an induction coil is already used in connection with the telephone
transmitter, the same coil may be employed for signalling, a tertiary coil of
wire being preferably added for this purpose and connected as required to the
electric supply.
Dated this 19th day of October 1891.
A. A. C. SWINTON.
COMPLETE SPECIFICATION.
Improvements in Electric Signalling.
ALAN ARCHIBALD CAMPBELL SWINTON 66 Victoria Street Westminster
Engineer, 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 :-
My invention relates to improvements in electric signalling, and affords a means
whereby alternating electric currents, such as are now supplied for electric lighting
and other purposes, may be utilised for operating telephone call bells, house bells,

page_text: and similar signals, thus obviating the necessity for the primary batteries or
magneto generators at present commonly employed for this purpose.
According to my invention such batteries or generators are replaced by a trans-
former or induction coil through the primary wire of which the alternating current
supplied is caused to circulate, the secondary wire being electrically connected to
the distant bell or signal which is then operated by the electric currents induced
in the said coil.
By suitably proportioning the windings of the coil, the voltage of the current
can be raised or lowered as may be found suitable for the resistance of the bell or
signal and of the line, and by separating the primary and secondary wires by means
of asbestos or other non-inflamable insulating substance the two may be kept quite
distinct, so that any danger or inconvenience due to a direct connection between
the electric supply and the signalling circuit is avoided.
Electric bells or signals of any suitable type may be employed, but polarised
bells of the type now ordinarily used for telephonic calls are preferably employed,
these being modified if necessary so as to make the natural period of the swing of
the hammer sufficiently rapid to enable it to respond to the alternations of the
electric current used. Drop indicators of the ordinary or any suitable pattern may
also be operated. The push-button or operating key is inserted in either the
primary or secondary circuit (preferably the former) of the coil, and when employed
on telephone lines it is preferably made double pole, so as to break all connection
between the supply mains and the coil, this being advisable to prevent disturbances
in the telephone due to electro-static or other induction.
Induction coils of any suitable type may be employed, with either open or closed
magnetic circuits.
Fig. I shows diagramatically a convenient arrangement of the apparatus,
AA are wires connected to the electric supply. These by means of the double
pole key, K which may be of any convenient construction, are when required
connected with the extremities P. P₁ of the primary wire of the induction coil C.
S. S are the ends of the secondary wires of the coil. B is the bell or signal
and E represents the earth or return circuit. In the figure, two complete
stations are shown connected by a line wire, and arranged so that the pressing of
the key at either station rings both bells. Should it be undesirable that the bell
at the operating end should ring, the arrangement may be modified by the addition
of contacts to the key which will short circuit the bell at the operating station,
when the key at that station is depressed.
As shown in Fig. II a similar device may be used to short circuit the secondary
coil at the receiving end, the key when in its normal position bearing against two
contacts which are connected to the ends of the secondary wire. Where an induc-
tion coil is already used in connection with the telephone transmitter, the same
coil may be employed for signalling, the voltage of the supply current being reduced
by a suitable resistance to suit the resistance of the primary, or the arrangement
as shown in Fig. III may be employed. In this case a tertiary coil of wire TT
of suitable length is wound over the secondary and connected by means of the
key K with the supply mains. When the key is depressed and the circuit
established, the current flowing in this tertiary coil will induce currents in the
secondary, which flowing to line and earth will ring the bell, otherwise, when the
key is in its normal position, the primary P. P¹ is used in the ordinary manner, in
connection with a battery D, and a microphone M for inducing telephonic electric
currents in the secondary, and thus operating the distant telephone.
As shown in this figure an automatic switch hook H of ordinary construction
may be employed for switching on the telephone receiver R or the bell B
respectively, as may be required in the usual manner. As will readily be under-
stood a similar arrangement of switch hook may also be employed in connection
with the other arrangements hereinbefore mentioned.
For safety
a cut out consisting of a short length fusible wire may be inserted in
the circuit between the supply mains and the key; and where the electric pressure

page_text: in the supply mains exceeds that required it may be reduced to the proper
amount by means of a suitable resistance or choking coil introduced in the primary
circuit.
Having now particularly described and ascertained the nature of my said inven-
tion, and in what manner the same is to be performed, I declare that what I
claim is.
(1) In electric signalling apparatus the employment of an induction coil or
transformer whereby the alternating electric-currents supplied for electric lighting
and other purposes may be used for operating electric bells or signals substantially
as set forth.
(2) In combination with the above the use of a double pole push button or
key whereby all connection with the supply mains is cut off for the purpose set
forth.
(3) The several arrangements of electrical signalling apparatus, substantially
as described with special reference to the accompanying drawings.
Dated this 18th day of July 1892
A. A. C. SWINTON.