Improvements connected with Switch Boards for Telephonic Systems.
Year: 1890

page_text: Date of Application, 9th Sept., 1890
Complete Specification Left, 3rd June, 1891-Accepted, 11th July, 1891
PROVISIONAL SPECIFICATION.
Improvements connected with Switch Boards for Telephonic
Systems.
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 more particularly to accomplish multiple switching
throughout several boards at a telephonic exchange but is not limited thereto. We
will describe the arrangement in connection with three boards but it is to be under-
stood that the invention is not limited to that number. The outgoing wires are
connected to wires in two branches one leading to line through a bridge resistance
(which we will call 1) and the other to earth through a bridge resistance (which we
will call 2) and an unplugged resistance (which we will call 3) to earth the
connection with the annunciator coils being made with this branch between the
resistances 2 and 3.
If resistances 1 and 2 be made the same as each other and resistance 3 the same
as that of the line it follows that if the corresponding hole in the switch board be
plugged and a call is transmitted the current will divide equally between
resistances 1 and 2 one half of the current passing through resistances 2 and 3 to
earth and the other part of the current passing through resistance 1 to line the
pressure of current being equal at line and at between resistances 2 and 3 where
the annunciator coil connection is made so that there is no magnetism generated in
the clectro magnet of the annunciator and therefore the drop thereof is not
operated. The opposite of this occurs when a call is received the calling circuit of
the board being broken at the hole in the switch board the received current will
divide one part passing through the electro-magnet of the annunciator and to earth
charging the electro-magnet and throwing the annunciator drop. Suppose this to
be a call from No. 1 wire on the first board the operator will plug at the hole of
the board corresponding thereto, ring and speak in the usual manner. Suppose
No. 250 on the third board to be asked for, the operator then removes his speaking
plug from the said hole and inserts an extension plug. He then will communicate
through No. 250 on his board of the extension wire that is connected to the corre-
sponding number and to line through the third board. If the extension or line be
engaged the operator replies on No. 1 board that the line is engaged. If it be not
engaged he will ring up No. 250 and at once insert the extension plug in No. 250
of his board, connecting lines 1 and 250 together and by touching 1 or 250 hole
with his hand plug he ascertains if all is correct. This completes the operation of
switching. The ringing off may be as usual. Afterwards the operator removes
the extension plugs restoring the board to its normal condition.
Daind this 9th day of September 1890.

page_text: COMPLETE
SPECIFICATION.
Improvements connected with Switch Boards for Telephonic
Systems
We, HARRY THOMAS OGILATE FRASER Mechanical Engineer and JAMES
WALLACE BROws 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 more particularly to accomplish multiple switching
throughout severnl bonrils at a telephonic exchange but is not limited thereto. We
will describe an arrangement according to our invention in connection with three
boards but it is to be understood that the invention is not limited to that number.
The accompanying drawing represent this arrangement diagramatically AB
& Cindicating the tree switch boards and D the outgoing wires.
Each of the outgoing wires D) is connected at a to a wire having two branches e
and d the branche leading to line E through a bridge resistance the other
branch leading through bridge resistances Gand II to earth and the connection
with the annunciator coils I being unde with the branch dat between the
resistance (i and 11.
The resistances Fail G are made the same as each other and the resistance H
is the same as that of the line consequently it follows that if the hole K, in the
switch board corresponding to the annunciator magnet, be plugged and a call is
transmitted the current passing out by the wire D will divide at a equally between
the resistances F and one half of the current passing through the resistances G
and I to earth and the other part of the current passing through the resistance F
to line E the pressure of current being equal at where the branch e joins the
line and at between the resistances G and II where the annumeintor coil con-
nection is made with the branch d so that there is no magnetism generated in
the electro magnet I of the annunciator and therefore the drop thereof remains
in position.
The opposite of this occurs when a call is received the current entering the
board by the line (the calling circuit of the board being broken by the plug
being removed from the hole K) and dividing at one part thereof passing
through the electro-magnet I of the annunciator and thence by the resistance H
and branch d to earth thereby exciting the electro-magnet and releasing the
annunciator drop while the other part of the current passes to earth through the
wire c and d and resistances F G and H.
Suppose for example there be a call from a distant station on the line wire E
numbered and the caller desires to be put into communication with say No. 250
on line wire E Nod. 3. The operator having inserted his speaking plug in the
hole of the board corresponding to the annunciator of the caller, for example in
the hole K on the extension line 1 he rings and speaks to him in the usual
manner and having ascertained that he desires to be put on to 250 which is on
the third board C the operator removes his speaking plug from the hole K and
inserts therein one of the plugs of an extension or coupling plug the other plug
of the coupler being inserted in the hole K in the extension line (5) of the
board which extension is connected by line D' to the line E with which the
annunciator of No. 250 is connected.
If the extension wire or line (5) be engaged the operator replies to the distant
station on No. 1 line that the line 5 is engaged. If it be not engaged he will
ring up No. 250 and at once insert the extension or coupling plugs in the holes K
and K of his board thereby connecting the extension lines 1 and 5 together as
shown by dotted lines and then by touching the hole K or K with his hand plug
he cau ascertain if all is correct and thus complete the operation of switching.

page_text: The ringing off may be as usual after which the operator removes the extension
or coupling plug and restores the board to its normal condition.
From the foregoing it will be readily understood the mode of connecting any
two subscribers connected with multiple boards.
Having now particularly described and ascertained the nature of our said inven-
tion and the manner in which the same is to be performed we declare that what
we claim is:-
1st. In switch boards for telephone systems means for preventing the annunciators
being operated by an outgoing current the said means consisting in dividing the
outgoing currents and causing the divided currents to pass through proportioned
resistances arranged substantially as hereinbefore described so that the outgoing
current is balanced and the electro magnet connected therewith unaffected sub-
stantially as hereinbefore described.
2nd. The combination and arrangement of parts constituting improvements in
switch boards for telephonic systems whereby the annunciator drops are operated
by incoming currents but are unaffected by outgoing currents substantially as
hereinbefore described.
J. H. JOHNSON & Co.,
Agents.