Improvements in Multiple-switches for Telephone Exchanges.
Year: 1895

page_text: Date of Application,, 15th July, 1895--Accepted, 21st Sept., 1895
COMPLETE SPECIFICATION.
Improvements in Multiple-switches for Telephone Exchanges.
I, FRANZ STOCK, of 6-7 Zeughofstrasse, Berlin Germany, Engineer,, do hereby
declare the nature of this invention to be as follows:-
In the Specification of my application for Letters Patent dated 25 March 1895
No. 6171, I have described an arrangement of multiple-switch for double telephone
lines, in which the drawbacks attending the ordinary switches of that kind thereto.
fore employed, were obviated in a simple and certain manner.
In that arrangement the switching of the key-circuit from the main circuit, is
effected with the smallest possible amount of conducting material, and the
controlling devices can be easily and securely manipulated without necessitating
an increased use of connecting cables, whilst the form of the keys themselves is so
simple that any switchboard is readily capable of containing the number of keys
required for large services. In addition to these advantages of the aforesaid
apparatus, there is a further advantage, namely that the mode of influencing the
annunciator flaps is simple and certain, and does not interfere with the clearness of
transmission of the conversations.
My new multiple-switch, forming the subject of the present invention, is
illustrated diagrammatically in the accompanying drawing and consists in, an
arrangement or modification of the apparatus just referred to, and possesses, in
addition to the aforesaid advantages, the further one that the rising of the flaps is
effected automatically whereby the manipulation of the multiple-switch devices.is
still further facilitated and simplified, without the cost of construction being
thereby increased to any considerable extent.
With this object in view, the form of the keys K is the well known one ordinarily
employed in multiple switches for single lines, each of said keys consisting of two
metal parts & and bearing upon each other in an elastic or springy manner when
in a state of rest.
According to my present invention, however, each of the calling-up, keys A K
consists of three metal parts lih which are independent of one another and bear
upon one another elastically when in a state of rest, and which, are adapted to be
disengaged and insulated from, one another by the insertion of a plug into the key.
The arrangement of the flaps k and of the devices for operating the same, are
peculiar, namely:-Each flap k carries, as a counter-weight to the tablet for
indicating the number, a. part k¹ of soft iron of the shape of a segment of a circle
which serves to cause the flap, which is mounted to turn about the point x, to
assume a vertical position when the electro-magnet n is inactive. When however
the electro-magnet,n is energized by an electric current flowing through it, the iron
piece will be attracted, and the flap k caused to rotate through an angle of
about 90° around the point x, and when the core of the electro-magnet n is
de-magnetized, the flap k will move back again automatically into the vertical or
rest position. The energizing of the electro-magnet n can however take place
only on actuating a special relay R which is inserted in the main circuit and is
provided with electro-magnetic cores m and m¹ which, according to their condition,
attract or release the spring armature o, whereby the circuit passing from the
point through the contact p to the electro-magnet n, is closed or opened
respectively.

page_text: A separate battery B-preferably composed of accumulators-which may be
common to the whole of the exchange, that is to say to all the switch-boards,
supplies the current required for energizing the electro-magnet n. A portion B
of this battery B serves at the same time to energize the telephone T when
ascertaining if the desired line or circuit in the office is free.
The system of calling up illustrated diagrammatically in the drawing, is the
ordinary two-cord system, but the lever switch U has in addition, a special contact y
which is closed when the operator or official wishes to ask the calling up subscriber
which connection he requires.
The ringing-off flap S K has also an automatic arrangement and differs from the
subscribers flap in that in the former case the flap falls by gravity and is raised by
magnetic attraction, whilst in the latter case the action is just the reverse.
The method of working is as follows:-
P
which is
On calling up in the circuit L, the calling up currents pass through the lead a,
point 1, the electro-magnet m¹, of the relay R, the springs ii and h and back along
the lead b. The relay R attracts its armature o and closes the contact
otherwise open in the rest position. The circuit of the battery B is thus closed,
and a current passes from B through n, p, armature o, electro-magnet m, point 2,
springs, the contacts of the keys K, point 3, and back to B. This
current causes the armature o to remain attracted and the contact p to remain
closed. The flap k will therefore remain in its depressed position, which is at an
angle of 90° from its rest position. This condition of things remains even when the
calling up current has ceased to act, because the electro-magnet m is attracted at
the same time as n, and, in consequence of the action of the current coming from
the battery B, holds the armature o of the relay R until the circuit established
through the contact p is broken at some point. This takes place when the plug S
is inserted into the calling up key A K, the springs li and has already stated,
then becoming separated, and the circuit broken. When this takes place, the core
of the electro-magnet n is de-magnetized and the flap k allowed by the peculiar
construction hercinbefore described, to move back automatically by gravity into
the rest position.
To ascertain whether the desired connection or line is in use or not, I proceed in
the well-known manner, which is described in my said former application for
Letters Patent No. 6171 of A.D. 1895. If the line is free, then on placing the
plug S against a key-sleeve c a current will pass through the telephone T which will
be indicated by the well-known crackling sound. If there is no crackling sound
then this is a certain sign that the line is otherwise occupied or broken.
The course of the current, when the testing plug S, is placed against a key-
sleeve c, is as follows when the line is unoccupied. The current passes from the
branch battery B' to the telephone T over the lever-switch U, point 6, battery
key BT to the head of the plug S, through the key-sleeve c, to the controlling
circuit that connects the keys, through point 4 and electro-magnet m' point 5,
thence through the whole series or row of keys to point 3, and back to the other
pole of the battery B¹. The telephone allows of hearing the crackling sound.
When connection has been established between two lines, the relay R of the
calling-up subscriber is cut out of circuit. But the relay R₁ of the called-up
subscriber is still included as a bridge in the loop line.
When the ringing-off sign is given, this relay comes into operation, but the
corresponding subscriber's flap cannot be caused to fall, because the circuit
including the battery B is broken in the plugged key. Consequently only the
ringing-off flap S K is disengaged and caused to fall.
The arrangement herein before described allows of arranging the flaps either
below or above the subscribers keys, which is a feature of considerable practical
importance. Also the relays R or R' may be arranged in any desired
conveniently accessible part of the switch-board.
or
My improved construction of multiple switches can be employed in conjunction
with single lines with earth return.

page_text: Having now particularly described and ascertained the nature of the said inven-
tion and in what manner the same is to be performed I declare that what I
claim is :-
"
1. A multiple-switch for a telephone exchange in which the automatic rising of
an annunciator flap k, which has a constant tendency to fall back into the "rest
position by the action of gravity, is effected by ineans of a relay R which is
connected with the telephone circuit and is adapted to close and open a circuit
including a battery and the winding of an electro-magnet n controlling the said
annunciator flap, substantially as herein described.
2. In a multiple switch of the kind specified in the preceding claim, a calling-up
key A K consisting of three metal pieces lih which bear elastically upon one
another when in the rest position, and become insulated from one another on the
insertion between them of a plug, substantially as herein described.
3. A multiple switch of the kind specified in the Claim 1, in which a relay R is
provided with a pivoted armature o adapted to keep the circuit through the
winding of the electro-magnet n controlling an annunciator flap k, the winding of an
electro-magnet m of the relay, and a battery B, closed after the calling-up current
has ceased, and until a plug is inserted in a key, whereupon the said circuit is
interrupted and the armature o and the flap k permitted to return automatically
into the rest position, substantially as herein described.
4. In a multiple switch of the kind specified in Claim 1, a flap k mounted to
turn about a pivot a and so constructed that it will be moved into its operative
position when its controlling electro-magnet n is energized, and will be caused to
return automatically into its rest or inoperative position by the action of gravity
when the said electro-magnet is de-magnetized, substantially as herein described.
5. The combination of parts constituting the improved multiple switch herein-
before described with reference to and shown in the drawings annexed.
Dated this 15th day of July 1895.
For the Applicant,
W. LLOYD WISE,
46 Lincoln's Inn Fields, London, W.C., Chartered Patent Agent.