IMPROVEMENTS IN TELEPHONIC APPARATUS
Year: 1882

page_text: "
LETTERS PATENT to Francis Raymond Welles of Antwerp in the Kingdom of
Belgium for an invention of "IMPROVEMENTS IN TELEPHONIC APPARATUS
A communication from Charles E. Scribuer and William R. Patterson Loth
of Chicago Illinois United States of America
COMPLETE SPECIFICATION left by the said Francis Raymond Welies at
the Office of the Commissioners of Patents on the 15th August 1882.
"
FRANCIS RAYMOND WELLES of Antwerp in the Kingdom of Belgium "IMPROVE-
MENTS IN TELEPHONIC APPARATUS a communication from Charles E. Scribner
and William R. Patterson both of Chicago Illinois United States of America
This Invention has for its object improvements in telephonic apparatus; and
relates in the first place to that system of inter-communication known as the
telephone exchange or central office system.
Figure 1 indicates the arrangement of the circuits and shows partly in elevation
and partly in section some of the apparatus at the central office.
The improvement shown in Figure 1 may be used where complete metallic
circuits are connected with multiple switch boards at the central office. Two
subscribers stations S' and S2 are indicated each provided with the usual telephone
outfit and each connected with a switch of each of the multiple boards at the
central office. 1, 2 and 3 are switches belonging to the subscriber S'; they are on
three separate switch boards at each of which there are attendants, for it is
supposed that the subscribers are too numerous to be attended to at a single switch
board.
4, 5 and 6 are the switches on the same three boards belonging to the
subscribers S. The switches 1 and 4, are on one board; 2 and 5 on another and 3
and 6 on a third.
The normal circuit-that is the circuit when not connected for conversation-of
each of the subscribers may be traced as follows:-From S' by line a through
spring or lever u and contact point of switch 1, of the first board, and thence to

page_text: the spring of switch 2, of the second board and to the spring of switch 3, of the
third board and thence through the calling annunciator b and through test-
keys c, d, e and thence by the return wire a¹ to S¹.
In like manner the circuit of S2 may be traced over the same switch boards:
that is to say-by line f through switches 4, 5 and 6 of said first second and
third boards respectively to annunciator g and thence through the keys h, i, k and
by return wire f¹ to S².
The circuits through the central office as thus described are the same as
heretofore used, except that I have provided return circuits a¹ and f¹ instead of
grounding the lines.
In switch 1, a plug is shown to be inserted, and there is a similar plug in
switch 4, but this is not the normal position.
Let us suppose the plugs removed from switches 1 and 4 and that an operator
at one of the boards, for example the second board, desires to call up S¹. This he
does by pressing the plug n against the spring or lever w of the key d.
At the test keys the circuit is normally closed by contact between the lever w
and screw head x of the said test keys. The plug n is provided with two contact
pieces, one a central point and the other a ring upon the exterior and these are
coupled respectively with the poles of the battery o as shown. When the plug is
pressed against the test key the lever w of the key is carried away from contact
with the screw and brought into contact with a stud y connected with the
wire m thus shunting the electro-magnet of annunciator b. The metallic collar of
the plug first forms contact with the lever of the test key and the circuit of the
battery is completed when the central contact point of the plug touches the
screw head of the test key. The lever is also connected with the wire m and the
annunciator magnet is thus shunted when the battery is looped into the line for
calling so that the annunciator is not thrown down by the calling battery.
The operator at the second board by pressing the plug n against the test-key as
shown, loops in the calling battery o and bell p thus sending a current through
the electro magnet of the bell at station S¹. The ringing of the bell p notifies the
operator that the line is not in use at either of the other boards, while at the same
time the subscribers bell at S' announces the call. In case line a belonging to
subscriber S¹ should be in use, being connected say as shown at switch 1 the
portion of the circuit of line a including the test keys will be open at the switch
so that the circuit of the calling battery will remain open though the plug n were
connected with the test-key d as shown.
Under these conditions the bell p will not ring and the operator will thus know
that the line of S¹ was in use or connected at one of the other boards.
Any two of the metallic circuits may be formed into one for conversation by
inserting the double pointed terminal plugs of a double flexible conducting cord
in the switches respectively of said circuits upon either of the multiple boards.
The springs or levers w of switches 1, 2 etc are insulated from the metal frames
by hard rubber and the plugs at the ends of the double conducting cords have
double points. Thus the central portion q which is intended to make contact with
the spring of the switch is insulated from the portion r which is intended to
make contact with the metal frame of the switch into which it fits. This insulation
is effected by means of the rubber sleeve s. When the plug is insulated as shown
the lever of the switch u is lifted from the contact point so that the line a is cut
off from the test keys c d e and directed through the central point of the plug and
thence through a strand of the conducting cord to the central point of the ther
terminal plug whence the circuit may be traced through the line f to the second
subscriber through his instruments and back by the return line f'. The wire z
connects with the frames of the switches 4, 5 and 6 which are connected through
the plugs with the frames of the switches 1, 2 and 3. The line t connects the
frames of the switches 1, 2, 3 directly with the return circuit a¹.
The improvements also relate to the transmitting arrangement and to the
receiver

page_text: These improvements are illustrated by Figure 2. The receiver is shown in
transverse section.
The improvement in the transmitting arrangements admit of one battery serving
for several subscribers stations.
The battery is applied by a Wheatstone Bridge or balance. The coils of the
transmitting telephone form a side or sides of the bridge and the primary of one
induction coil forms the cross connection. The secondary is in the line circuit,
A and C represent the stations of two subscribers.
•
At station À I have shown two transmitters a¹ and 6 placed respectively in
opposite arms of the Wheatstone bridge or balance and so arranged as to be acted
upon at the same time by the same sounds.
The mouth piece c¹ is common to the transmitters a¹ b. The other arins of the
bridge are balanced by means of resistance coils d', e, so that; normally there may
be no effective current through, the primary of the induction coil f¹ which is
included in the cross wire of the bridge.
The telephone line gl passes through the secondary of the induction coil.
The transmitters a¹ and b¹ are placed in close proximity so that their diaphragms
will vibrate synchronically when acted upon by the same sounds.
The resistance in each of the opposite arms of the bridge is thus varied with
the vibrations of the diaphragms and undulatory currents are thus sent from the
battery through the primary coil in the cross wire and corresponding currents
are induced in the main telephone line g¹. By the use of a Wheatstone balance at
each station the same battery may be used for several stations.
Thus the second station C is also connected with the battery h.
The battery may be located at the central office or wherever may be most
convenient.
A single transmitter may be used in one arm of the bridge and the three other
arms may be balanced by means of resistance coils.
Experiments indicate however that the effective current in the cross wire is
much increased by the use of two transmitters as shown in the opposite arms or
branches as compared with the current, when only one transmitter is used in one
of the arms of the bridge.
The receiving telephone & is of novel construction its coils are in a local battery-
circuit and the current is rendered undulatory by induction. This telephone is
designed to be used as an operators telephone. This telephone although it works
best as a receiver operates successfully also as a transmitter. I prefer to place an
ordinary transmitter or microphone. in circuit with telephone k².
In the section shown of the telephone k, m¹ is the iron diaphragm and n' is the
soft iron core surrounded by the coil o¹; Binding posts p, q, are provided in the
bed pieces is a battery placed in the circuit of the coil o'. This coil should
be of about four or five ohms resistance.
t is an induction coil consisting of two windings; the winding or coil u' which
is included in the circuit of the battery, should be of low resistance, preferably of
about one half of an ohm, while the other winding V₁ which is included in the
circuit of the telephone line g' should be of comparatively high resistance, preferably
of about (150) one hundred and fifty ohms.
When undulatory currents are excited in the line passing through the high
resistance winding V₁ like undulatory currents are reproduced by induction in the
low resistance winding u².
The induced currents find circuit through the coil o' of the telephone.
The magnetic tension of core n' is thus varied and the diaphragm m³ is caused
to vibrate.
Telephone
as thus constructed may be worn by the operator as a head
telephone without fatigue.
The Invention also relates to that class of telephone transmitters in which the
contacts consists of a metallic point supported by a spring and a carbon piece at
the free end of a loaded yielding support.

page_text: The improvement consists in an adjustable stop, preferably of soft rubber placed
on the side of the weighted support of the carbon opposite the metallic point and
so adjusted as not to interfere with the vibration of the electrodes, yet so near as
to keep the loaded carbon piece from moving far enough away to break contact
with the metallic point.
Figure 3 shows the ordinary microphone provided with the improvement.
The diaphragm a¹ is placed upon the frame 611 as heretofore. The battery
circuit of lines is closed through the electrodes e, f, in the usual manner.
Speaking against the diaphragm varies the resistance of the battery circuit at
the point of contact of the metallic point ell and the carbon piece f".
Loud sounds close to the diaphragm would drive the carbon piece so far back as
to break the circuit; this is prevented by the cushion gl.
The cushion g¹¹ is supported and adjusted by the screw ¿". A hole is bored in
the end of the screw to receive the soft rubber cushion.
The stop should be adjusted so as to touch or nearly touch the piece h². Hard
rubber may be used with good results instead of the soft rubber or but less
advantageously the end of the screw itself may be employed to prevent the
carbon piece being driven back so far as to break contact.
Having thus described the nature of the said Invention and the manner of
performing the same I would it understood that I claim :-
First. The arrangement of telephone circuits substantially as described in respect
to Figure 1 of the annexed drawings.
Second. The switches and connecting plugs constructed and operating together
substantially as described in respect to Figure 1 of the annexed drawings.
Third. The test keys and calling plugs constructed and operating together
substantially as described in respect to Figure 1 of the annexed drawings.
Fourth. The Wheatstone bridge or balance transmitting arrangement substantially
as described in respect to Figure 2 of the annexed drawings.
Fifth. The receiving arrangement, consisting of the telephone ², containing
the electro magnet n¹, o', of which the coils o¹, are in a local circuit including the
battery s¹ and also one of the windings of an induction coil t¹, the other winding
being in the line circuit, substantially as described in respect to figure 2 of the
annexed drawings.
Sixth. The combination with a microphone transmitting telephone of an
adjustable stop ", either with or without a cushion piece g¹¹, to prevent loss of
contact when the instrument is influenced by loud sounds, substantially as described
in respect to Figure 3 of the annexed drawings.
In witness whereof I the said Francis Raymond Welles have hereunto set my
hand and seal this first day of August in the year of our Lord One
thousand eight hundred and eighty two.
F. R. WELLES (L.S.)