Improvements in or connected with Telephonic Switching Apparatus.
Year: 1890

page_text: Date of Application, 9th Sept., 1890
Complete Specification Left, 3rd June, 1891-Accepted, 11th July, 1891
PROVISIONAL SPECIFICATION.
Improvements in or connected with Telephonic Switching
Apparatus.
We, HARRY THOMAS OGILVIE FRASER, Mechanical Engineer, and JAMES
WALLACE BROWN, Electrical Engineer, both of 109 Farringdon Road, in the
City of London, do hereby declare the nature of this invention to be as
follows:-
The object of this invention is to provide in connection with telephonic switching
apparatus means whereby whilst the annunciator is operated in the ordinary way
when a call is made to the exchange the annunciator does not fall when the operator
at the exchange communicates with the distant station and the invention further
enables switching to be conveniently effected in a more ready and expeditious
manner than hitherto.
According to this invention the electro-magnets of the annunciator are wound
differentially and so connected that a transmitted current will divide equally one
half passing through the electro-magnet in one direction to earth and the other half
through the electro-magnet in the opposite direction to line so that then the cores
of the electro-magnets will not be inagnetized and therefore the line circuit can be
rung through without causing the annunciator drop to fall. When however a
current or signal is received the current will not be divided at the electro-magnet
but will pass through to earth in the ordinary manuer magnetizing the core of the
electro-magnet and causing the drop of the annunciator to fall. The earth circuit
is never broken so that springs or other mechanical arrangement of circuit closing
on the back of the board can be dispensed with. The usual number of metal bushi
plug holes may be provided and each metal bush be in connection with the point of
division of the circuit of the corresponding electro-magnet. In addition we may
have extensions or extension blocks fitted preferably on the table. There is also
an extra bushed hole for testing. The usual transmitter and generator or battery
may be attached to the board. The receiving telephone is preferably so arranged
that it can be worn on the head.
In order to expedite the operations of the person at the exchange there is
provided a hand switch which by simple pressure of the hand can be made to
complete a circuit for speaking to, or ringing the bell at, a distant station as desired.
A convenient arrangement consists of a handle made in parts of ebonite or like
material so connected that when in one position they open out from each other so
as to complete one circuit and can be pressed together or one part in or towards
the other so as to complete the other circuit. A metal plug is fixed to one part to
which is connected a spring bearing on an insulated contact piece and to the other
part is fixed an insulated contact stud, the plug extending out from the two parts.
The contacts are made in the following manner:-A. convenient length of two wire
insulated core is introduced into the device. One of these wires is connected to
the contact piece on one part and the other to the contact stud on the other part,
the other end of the wire that is connected to the said insulated piece gives contact
through the receiver, secondary coil of the transmitter and to earth. The wire
that is connected to the stud gives contact through the generator and to earth (or
the connections may be the reverse of this).
When this hand switch is held by the operator when he touches with the plug
one of the metal bushings it puts in circuit the transmitting and receiving apparatus
but if he slightly contracts his hand it causes the switch to close breaking the
contact before made and making contact with the other contacts so as to bring the
generator in circuit so that the bell can be rung. By relaxing the pressure on
the switch whilst still retained in the hand the normal condition is restored and

page_text: thus the operator can with one hand do the work which hitherto has required two
hands because as the hand is passed over the board it can pick up plugs from any-
where and so the act of ringing speaking and plugging becomes practically one
operation and the other hand is left free to perform other duties. All the boards
in the switch room can be constructed and arranged as above described. As an
example we will suppose that there are three, the plan of connecting the boards
together by their extensions will be as follows: No. 1 board will have its No. 1 line
wire connected by means of the No. 1 bush and extension wire to the correspondingly
numbered bushing on the No. 1 extension block of No. 2 table and continued in the
same order throughout the series of switch boards in the room, the same order of
connecting being common for all the lines brought to the switch board. No. 2 switch
board will have its line wire bushing connected to its own correspondingly numbered
bushing of No. 2 extension block on No. 1 table and in the same order throughout;
this order of connecting will be continued for any number of boards there may be
in the room and the arrangement of plugs and cords will be very simple that is two
plugs connected one at each end of a cord the cord passing through the table and
weighted. With this system it is not necessary to have a large number of plugs
one half as many more than are employed on the board as hitherto arranged should
be sufficient for all extensions. The mode of operating the board is as follows:-
No. 1 board receives a call through No. 1 line the operator having the hand switch
plug in his hand and in the act of passing the hand over the board to answer the
call he picks up with that hand any disengaged plug. He may either insert the
plug that he has taken up and by the simple act of touching his hand switch plug
to the metal of the plug that he has inserted ring back or if preferable he may first
touch the bushing with the hand switch plug and afterwards insert the other plug.
There is not much loss of time either way as both plugs are in one hand and in
position the call may be for No. 250 the operator kuowing that number to be in one
sot of his extensions he leaves No. 1 plugged and in passing to No. 230 on his
extension he picks up the companion plug touches the bushing of No. 250 with
his hand switch plug, rings, and then inserts the other plug, this operation extends
the line wire that enters No. I board through the board and line that has the
corresponding number but in the act of calling or ringing the drops of either board
are not thrown but at any moment the operator can determine if communication is
established by simply touching with his hand switch plug the engaged line plugs.
The same is the case if an extension is engaged. Supposing that No. 1 board las
No. 75 of that board plugged to the extension No. 250 which may be the number
of the line on No. 3 board and that line No. 220 calls on No. 3 board requesting
communication with No. 75 the operator at once touches the extension bushing No. 75
on his board instantly finds that that wire is engaged and he does not interrupt but
replies back to the call, that the line is engaged.
It will be readily understood that by this system it is within the power of any
one operator to concentrate all the lines that may enter a central exchange and
make it possible to operate the same from one board.
Dated this 9th day of September 1890.
J. H. JOHNSON & CO.,
Agents.
COMPLETE SPECIFICATION.
Improvements in or connected with Telephonic Switching
Apparatus.
We, HARRY THOMAS OGILVIE FRASER, Mechanical Engineer and JAMES 5
WALLACE BROWN Electrical Engineer both of 109 Farringdon Road in the City
of London 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 :-
The object of this invention is to provide in connection with telephonic switching 5

page_text: apparatus means whereby whilst the annunciator is operated in the ordinary way
when a call is made to the exchange the annunciator does not fall when the
operator at the exchange communicates with the distant station and the invention
further enables switching to be conveniently effected in a more ready and
expeditious manner than hitherto.
According to this invention the electro-magnets of the annunciators are wound
differentially and so connected that a transmitted current will divide equally one
half passing through the electro-magnet in one direction to earth and the other
half through the electro-magnet in the opposite direction to line so that then the
cores of the electro-magnets will not be magnetized and therefore the line circuit
can be rung through without causing the annunciator drop to fall. When however
a current or signal is received the current will not be divided at the electro-magnet
but will pass through to earth in the ordinary manner magnetizing the core of the
electro-magnet and causing the drop of the annunciator to fall. The earth circuit
is never broken so that springs or other mechanical arrangement of circuit closing
on the back of the board can be dispensed with. The usual number of metal
bushed plug holes may be provided and each metal bush be in connection with the
point of division of the circuit of the corresponding electro-magnet and in addition
we have extensions for coupling up the boards. There are also provided extra
bushed holes for testing. The usual transmitter and generator or battery may be
attached to the board. The receiving telephone is preferably so arranged that it
can be worn on the head.
In order to expedite the operations of the person at the exchange there is
provided a hand switch which by simple pressure of the hand can be made to
complete a circuit for speaking to, or ringing the bell at, a distant station as
desired.
In order that our invention may be well understood we will describe the same
with reference to the accompanying drawings
Figure 1 of which represents diagrammatically a multiple switch board with our
improvements applied thereto and
Figures 2 and 3 are sectional views of our improved hand switch and its
connections.
Referring to Figure 1 A B and C represent three boards combined but it is to
be understood we do not restrict ourselves to this number. The various numbers
or lines in connection with the bushings on one board are connected to the other
boards by means of extensions 1, 2, 3, 4, 5, 6 and so on. As will be seen the
board A. has its No. 1 line wire connected by means of the bush B' and extension
wire 1 to the corresponding bushing B' on the No. 1 extension line of the board B
and is continued in the same order throughout the series of switch boards the same
order of connecting being common for all the lines brought to the switch boards.
The switch board B has its line wire bushing B connected to its correspondingly
numbered bushing of extension line 2 on board A and in the same order throughout
the series of boards this order of connecting being continued for any number of
boards there may be in the room. The arrangement of plugs and cords for coupling
may be that ordinarily in use and consisting of two plugs connected one at each end
of a cord the cord passing through the table and weighted, the coupling being
effected in the manner hereinafter described.
Our improved hand switch as shewn in Figures 2 and 3 consists of a handle
made, of ebonite or other suitable material, in two parts a, b, hinged or otherwise
connected together as at c so as to be capable of opening out or separating from
each other and of being closed or pressed together by the hand.
When the parts
are separated a circuit (say the speaking circuit) is completed and when the parts
are pressed together or towards each other this circuit is broken and another circuit
(say the ringing circuit) is completed. A metal plug d is fixed to the part a to
which is connected a spring e bearing on an insulated contact piece fand to the
other part 6 is fixed an insulated contact stud g. The plug d extends out from the

page_text: part a convenient distance for making contact with the plug holes in the switch
board. The contacts are made in the following manner:
A convenient length of two-wire insulated cord is attached to the switch one of
which wires is connected to the contact piece on the part a of the switch and
the other wire i is connected to the contact stud 7 on the other part b. The
opposite end of the wire is connected to the generator and to earth, and the
other wire i directs the current through the receiver and the secondary coil of
the transmitter m to earth (or the comicetious may be the reverse of this). When
this hand switch is held by the operator and he touches with the plug one of the
metal bushings in the switch board it puts in cirenit the transmitter mand
receiver but if he contracts his hand so as to close the parts a and b of the switch
sufficiently to cause the study to come into contact with the springe and force it
out of contact with the piece the receiver and transmitter is cut out of circuit and
the generator & brought into circuit so that a distant hell can be rung. Upon
relaxing the pressure on the switch whilst still retained in the hand the normal
condition is restored and thus the operator can with one hand do the work which
hitherto has required two hands be use as he passes the hand holding the switch
over the switch and he can pick up with it a plug from any part of the board and
so the act of ringing, speaking and plugging can be done with one hand while the
other ham is left free to perform other duties.
The following is an example of the nude of operating the board. Suppose the
board A receives a call through line ("the operator having the hand switch plug
in his hand, he in the art of passing the hand over the board to answer the call
pick up with that hand any disengaged plug. He may either insert in the bushing
corresponding to the annumeiator of the caller's wire for example B' of the board A
the plug that he has taken up, and then by simply touching the metal of this plug
with the plug of the hand switch may ring back, or if preferable he may first
tonch the bushing with the hand switch plug d and afterwards insert the other
plug. There is no loss of time either way as both plugs are in the same hand.
The calling current entering the board A from the line C passes through the
anuneiator coils in the direction indiented by arrows 1 to earth and causing the
amnunciator flap to fall. Suppose the call to be for No. 200 the operator knowing
that number to he in one set of his extensions say 5. he leaves the bushing B
plugged, and in passing his hand to the bushing B³ in connection with No. 250 on
this extension (5) he picks up the companion plug to that inserted in B and
touches with his hand switch plug d the bushing 13 thus ringing the bell of 250's
apparatus. He then inserts the other plug of the coupling in the bushing B³
thereby connecting the bushings B and B as shown by dotted line on the hoard A.
This operation extends the line wire that enters the board A. to and through the
hoard and line that has the corresponding number 250 say for example the board C,
but in the act of calling, or ringing, neither of the annunciator drops or flaps on the
boards A and are released as the outgoing current is divided at one part going
in the direction indicated by arrows 2 to the line (* in connection with the board C,
and the other part of the current passing through the reverse windings of the
annunciator coils to earth as indicated by arrows 3. The operator can readily
ascertain whether or not the communication is established by simply touching with
his hand switch plug d either of the plugs in the bushings B' and 'B'. Supposing
that the board A has No. 75 connected with it and that this number on the board is
plugged to the extension to No. 250 which may be on the line 5 on the board C
and suppose that No. 220 calls on board C requesting communication with No. 75,
the operator at board C at once touches with his hand switch plug the extension
bushing of No. 75 on his board thereby instantly ascertaining that that wire is
engaged, he does not therefore interrupt but replies back to the call No. 220 that
the line is engaged. It will be readily understood that by this system it is within
the power of any one operator to concentrate all the lines that may enter a central
exchange and make it possible to operate the same from one board.

page_text: It is found in practice that a saving of about 30 per cent. of wires is obtained, as
compared with the telephonic switch boards hitherto in use, and as the earth circuit
is never broken the usual mechanical arrangements for opening and closing this
circuit is dispensed with.
Having now particularly described and ascertained the nature of our said inven-
tion and in what manner the same is to be performed we declare that what we
claim is :-
1st. In telephonic switching apparatus, differentially wound electric coils for
operating the annunciators the connections of the windings of the coils with the
leads being so arranged that incoming currents will pass through the coils and
actuate the annunciators but outgoing currents are divided so that part only passes
through the coils to earth, the other part going to the line whereby the
annunciators of the sending switch board remain unaffected substantially as herein-
before described.
2nd. In telephonic switching apparatus, differentially wound electric coils for
operating the annunciators the connections of the windings with the lends and with
earth being so arranged that while incoming currents operate the annunciators the
annunciators of the sending switch board are unaffected by outgoing currents, and
the earth circuit remains unbroken substantially as herein before described.
3rd. For use with telephonic switch boards, a hand switch by means of which by
simple pressure of the hand a circuit may be completed for speaking to or giving a
signal at a distant station substantially as herein before described.
4th. A handswitch made in parts capable of being moved away from and towards
each other while held in the hand, and provided with contacts for completing
different circuits according to the positions of the parts relatively to each other
substantially as herein before described.
5th. The combination of parts constituting the improved hand switch sub-
stantially as herein before described and illustrated in Figures 2 and 3 of the
accompanying drawings.
Dated the 3rd day of June 1891.
J. H. JOHNSON & Co.,
Agents.