An Improved Switch Board.
Year: 1892

page_text: Date of Application, 21st July, 1892
Complete Specification Left, 14th Apr., 1893-Accepted, 20th May, 1893
PROVISIONAL SPECIFICATION.
An Improved Switch Board.
Sir CHARLES STEWART FORBES, Baronet, 28 Queen's Gate Terrace, London,
S.W. East India Agent, do hereby declare the nature of this invention to be as
follows:-
:-
My invention consists in an improved switch board for effecting communication
between telephone users; It is designed more particularly for short lines and for
domestic hotel or factory use but is also applicable to small exchange systems.
The construction and application is as follows:-The speaking circuits are connected
to a set of terminals placed on one side of the board, separate bell circuits being
connected to an independent set of terminals preferably placed on the opposite side.
Connection is made from the speaking wire of each user through a cut out indicator,.
and plugs suspended by a flexible cord with a common plug plate which connects
with the line terminal of the telephone and switch mounted on the board.
When the telephone is on the hook the attendants bell is in circuit, but it is cut.
out upon lifting the telephone to speak. Mounted upon the same board is a switch
whereby the bell of any user may be connected to a push included in the battery
circuit common to both the speaking and beli circuits. In a convenient position.
upon the board is a galvanometer or other indicating instrument connected to two
plug plates which serve to couple up a local battery and include the same in the
circuit of any two users whose respective plugs are inserted therein.
The cycle of operations is as follows:
1
The plugs forming the extremities of each users wire are always after use
replaced in the common plug plate so that any user may call the attendant and
give the number of the user he wishes to speak to. The switching is effected as
follows:-
The attendant first by means of the bell switch calls up the number asked for and
after getting his attention, removes the two plugs representing the caller and called,
and places them in the plug plates connecting the galvanometer and local battery.
Conversation can now be carried on without fear of interruption and as the
instruments employed for speaking are so constructed as that the current flows
through the microphone, magnet coils and line wire the galvanometer or equivalent
instrument replacing it indicates by its deflection that the line is in use.
Upon
either party putting his telephone upon the hook the deflection or other pre-
arranged signal ceases, and the attendant then replaces the plugs in the main circuit
plug plate.
The galvanometer may be replaced by a self-setting indicator if desired.
The galvanometer or like indicating instrument may be dispensed with if the
indicators in the general circuit are polarized and the connecting parts upon the
switch board altered to suit. This arrangement also permits several pairs of users
to be connected at the same time.
The battery employed to operate the call bells may be replaced by a magneto
generator if desired.
T511002

page_text: COMPLETE SPECIFICATION.
An Improved Switch Board.
Sir CHARLES STEWART FORBES Baronet 28 Queens Gate Terrace London
S.W. East India Agent, 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 consists in an improved switch board for effecting communication
between telephone users: It is designed more particularly for short lines and for
domestic hotel or factory use but is also applicable to small exchange systems.
The construction and application is as follows:-
The speaking circuits are connected to a set of terminals placed on one side of
the board, separate bell circuits being connected to an independent set of terminals
preferably placed on the opposite side.
Connection is made from the speaking wire of each user through a cut-out
indicator, and plugs suspended by a flexible cord with a common plug plate which
connects with the line terminal of the telephone and switch mounted on the board.
When the telephone is on the hook, the attendants bell is in circuit, but it is cut out
upon lifting the telephone to speak. Mounted upon the same board is a switch
whereby the bell of any user may be connected to a push included in the battery
circuit common to both the speaking and bell circuits. In a convenient position
upon the board is a galvanometer or other indicating instrument connected to two
plug plates which serve to couple up a local battery and include the same in the
circuit of any two users whose respective plugs are inserted therein.
The cycle of operations is as follows:-
The plugs forming the extremities of each users wire are always after use replaced
in the cominon plug plate; so that any user may call the attendant and give the
number of the user he wishes to speak to. The switching is effected as follows:-
The attendant first by means of the bell switch calls up the number asked for
and after getting his attention, removes the two plugs representing the caller and
called, and places them in the plates connecting the galvanometer and local
battery.
Conversation can now be carried on without fear of interruption and as the
instruments employed for speaking are so constructed as that the current flows
through the microphone, magnet coils, and line wire, the galvanometer or equivalent
instrument replacing it indicates by its deflection that the line is in use.
Upon either party putting his telephone upon the hook the deflection or other
pre-arranged signal ceases, and the attendant then replaces the plugs in the main
circuit plug plate.
The galvanometer may be replaced by a self setting indicator if desired.
The galvanometer or like indicating instrument may be dispensed with if the
indicators in the general circuit are polarized and the connecting parts upon the
switch board altered to suit.
The battery employed to operate the call bells may be replaced by a magneto-
generator if desired.
To enable my invention to be better understood 1 will now describe the same
more particularly by means of the accompanying drawings in which
Fig. 1. is a general view of my invention.
Fig. 2. is a side elevation of same.
Fig. 3. is a front view of modification.
In the drawings A. is a board formed of any suitable wood or other material.
Secured thereto and depending upon the number of circuits, are a series of binding
screws. In the case now described the switch board is arranged for six separate
circuits. The speaking circuits are connected to a set of terminals lettered a, to f,
shewn to the left of the board near the top, the bell circuits being connected to a
distinct set of terminals lettered a', to f', to the right hand, the line wire of each

page_text: user is connected to a binding screw and thence through a cut-out indicator 2, the
outgoing wire from which consists of a flexible cord terminating in a split or taper
plug, these plugs are lettered a¹¹ to " and when the board is out of use are inserted
in plug holes in the common plug plate 3, which serves to connect the line terminal
of the users telephone t', with the attendants telephone t, mounted upon the board.
The form of telephone I prefer to employ being of the type described in my
Specification of Letters Patent No. 10,466 June 1st 1892, consisting of a double
tympan with receiving tube operating the switch lever and a microphone included
in the line circuit. This however may be replaced by an ordinary telephone
preferably wound to low resistance coupled in series with a microphone. When
the users ear tube, is upon the hook at the end of switch lever, the circuit is
broken, since the bent arm of the lever, rests against the idle stop m. The
attendants telephone, upon the board is fitted with a bell terminal contact 4,
which replaces the idle stop m, in the users instrument, and when not in use for
speaking, the ear tube r, by its weight brings the bent end of the lever against
this stop 4.
Upon the caller raising the ear tube, the lever, makes contact with line
contact n, thereby placing the battery B in circuit, and the attendants bell 5 rings,
the indicator 2, shewing the letter or number of the caller. Upon the attendant
raising the ear tube r, to reply the bell 5 is cut out and his own telephone placed in
the battery circuit. Upon the board is a switch s, having as many contact points
as there are circuits.
By turning the levers, the attendant is enabled to connect by a separate
wire, see dotted lines, the bell 5 of each caller to a push P, which is included in
the main battery circuit.B, common to the speaking and bell circuits. In a suitable
position upon the board is mounted an ordinary low resistance galvanometer G;
having two plug blocks g, g, whereby a local battery L may be included in the
circuit of any two callers whose respective plugs may be inserted therein.
The cycle of operations is as follows:-
The plugs a, to, which form the extremities of each callers wire, are always
after use replaced in their respective plug holes in the plug block 3, so that each
one may be able to call the attendant and give the number or letter of any other
caller he may wish to speak to. For instance I have shewn in the drawing
that c, wishes to speak to d. The attendant having received his instructions
from c, places the switch levers, upon the contact d, and presses the button P,
thereby ringing the bell marked 5, over instrument d. Having informed d,
that c, wishes to speak, he then places the plugs ", and ", in the blocks g. 9;
thereby breaking the main line circuit and placing the galvanometer G, in series
with the local battery L, and the telephones c, d. c and d can now converse
without fear of interruption and since the current from the battery L, causes a
deflection upon the galvanometer G, the attendant is advised that the electrical
connection is complete. When either--or dreplace the ear tube upon
the hook the circuit is broken and the needle of the galvanometer returns to
zero. The attendant now replaces the plugs c" and in the common plug
block.
If desired the bell switch may be replaced by a series of ordinary pushes
having the same effect. The form of plugs I prefer to employ will be seen
from and which are removed from the plug plate 3, for this purpose.
I have also in Fig. 2, in order to more clearly shew the switch lever s,
placed the same in the downward instead of the horizontal position shewn in
Fig. 1.
In the modification shewn in Fig. 3 the plugs and plug block are dispensed
with and replaced with a series of switch levers . Connection is made from
cach indicator to the pivot e, on which each switch lever ", turns. Beneath
the outer end of switch are three contact studs, y,, those to the left hand
are all coupled together and connected to one side of the coil of galvanometer G,
the outgoing wire from which is connected to one pole of the local battery L, by a

page_text: -wire 20, the opposite pole is connected by wire ', with the right hand terminals;
which are all connected together. Taking the case previously described wherein
wishes to speak to d. c, having called up the attendant, d is informed of his
wishes. The switch at the end of wire e is then turned so as to make contact with
stude and switch d, to contact, whereby the main battery B is cut out and the
local battery L thrown in, e can now converse with d without fear of inter-
ruption, the needle of the galvanometer by its deflection shewing the attendant
that the line is properly connected.
When either party breaks the circuit by replacing the ear tube », or the
telephone replacing same, upon the hook at the end of switch lever ', the needle
returns to zero and the switch levers are brought to the central contact y,
thereby putting each caller into the attendants bell circuit.
The indicators I prefer to employ in the switch boards described are so con-
structed, as that in falling the resistance of the coils is cut out, they may however
be of any form suited to low resistance circuits. The galvanometer may also be
replaced by a self setting or balanced indicator. The battery employed to operate
the users call bells may be replaced by a magneto-generator if desired, the
bells shewn being replaced by those of the ordinary magneto pattern having an
independent return wire.
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 a switch board for telephones working in series with the microphones, the
particular combination and arrangement of parts whereby any two users are
enabled to privately converse upon a separate local circuit, the attendant being
automatically advised of such circuit being in use or otherwise, in the way and
manner described.
2. The combination in or with a switch board for telephones operating in series
with microphones, of a private speaking circuit and attendants and users speaking
and call circuit operated in the way, by the means and in the manner described.
3. In a switch board for controlling telephones connected in series with a
microphone, the combination of a plug plate 3, and plugs a to operating the
main battery circuit B and the plugs a to f" and plates g, g, for placing any two
subscribers in the local battery circuit L, with the galvanometer G for indicating
the through connection and completion of the conversation in the way and manner
described.
Dated April 14th 1893
FRANCIS M. ROGERS,
Agent.