Improvements in Telephone Switch Board Mechanism.
Year: 1894

page_text: Date of Application, 16th July, 1894
Complete Specification Left, 16th Apr., 1895-Accepted, 1st June, 1895
PROVISIONAL SPECIFICATION.
Improvements in Telephone Switch Board Mechanism.
I, JOHN EDWARD KINGSBURY of 79 Coleman Street in the City of London,
Manager (a communication from The Western Electric Company of Chicago,
Illinois, United States of America) do hereby declare the nature of this invention
to be as follows:-
The invention relates to mechanism of telephone switch boards; more
particularly to the keys or switching mechanism and circuit connections
appropriate thereto furnished the operator for connecting her telephone with
the plug circuit and for calling subscribers, its objects being to reduce the number
of manipulations of keys required in making connection between subscribers and
to construct a compact and easily accessible form of key.
The improved key consists of a lever carrying a double wedge and switch
springs or levers controlled by the wedge in its different movements. One pair of
switch springs is arranged upon each side of the wedge; the members of each
pair are provided with suitably disposed contact pieces for controlling the various
circuits. The wedge tends to remain in a central or intermediate position between
the pairs of switch springs. In this position the operator's telephone is discon-
nected from the plug circuit, while the clearing out annunciator is connected in a
bridge between the different conductors of the plug circuit. When the wedge is
moved between one pair of switch springs, the operator's telephone is connected
in a bridge between the sides of the plug ciruit, the branch containing the clearing-
out annunciator is opened, and a local circuit including the restoring or resetting
magnet of the self restoring annunciator commonly employed is closed, replacing
this instrument in position to respond to a subsequent signal. The operator is thus
in position to communicate with a subscriber desiring connection. After the
required connection is established the wedge is held over in the opposite direction
and forced between the opposite switch springs, disconnecting all of the cord
circuit excepting the plug through which it is desired to signal, and connecting
the latter with the terminals of a generator of signalling current.
wedge is no longer held over in this position it is returned automatically to its
central or normal position, the telephone and signalling generator being disconnected
and the clearing-out annunciator being placed in condition to respond to the signal
for disconnection. Two push buttons may be adapted to act upon two opposite
arms of the lever to shift the lever from one position to the other, one push button
to shift the lever in one direction and the other to shift it in the opposite direction.
Or the lever arm carrying the double wedge may be extended beyond the fulcrum
on which the lever arm turns and this upward extension may be used for shifting
the lever arm into either one or other of its extreme positions.
When the
The invention is illustrated in the accompanying drawings. Of these :-
Figure represents a plan view of the improved key.
Figure 2 is a side elevation of the same, together with a portion of the frame
of the switchboard upon which the key is mounted.
Figure 3 is a longitudinal section of the key showing the construction of the
various parts.
Figure 4 is a view from beneath showing the disposition of the switch springs.
Figure 4 is an end view.

page_text: Figure 5 is a diagram representing the key with its circuit connections in a
plug circuit, the latter being in position of connecting two telephone lines upon a
switchboard.
The key shewn in Figures 1, 2, 3 and 4 consists of a frame a upon which
a lever is pivoted near the middle of its length in lugs a¹ a². Opposite the
extremities of the lever b, push buttons e and care provided, moving in
cylinders a³ a and bearing upon the corresponding extremities of the lever
through stems c. Near the middle of its length the lever b carries a short
cylinder acting as a double wedge. Two pairs of switch springs or levers de
and fg are arranged, one pair upon either side of the double wedge b' with their
curved free extremities presented to the wedge. These switch springs are fixed
at their rear extremities in blocks h and h, respectively, of insulating material
secured to the frame a. The switch spring d has a normal resting contact d¹ and
an alternate contact d with which it is adapted to make contact when the spring
is forced outward; these contact points are carried at the extremities of stiff
springs, also secured in the block. The switch spring e has no normal resting
contact but is provided with an alternate contact point ese carried in the same
manner. Parallel with the spring e an auxiliary spring i is arranged, insulated
from spring e but mechanically connected with it by a stud k of insulating material.
The free extremity of the spring i is bent round in the form of a hook, and a
contact point is provided to register with the inwardly projecting extremity. The
tension or resiliency of the spring i is so adjusted, with relation to that of spring e,
that it is normally pressed inward and away from the contact point i; but when
relieved of the pressure of spring e, it is adapted to move outward and thus to bear
upon the contact. The switch springs and g are each provided with resting
contacts and g, and with alternate contact points and g², respectively;
similarly secured to the extremities of the stiff springs.
On account of the pressure of the springs defy, the wedge will be held
normally in a central or intermediate position between the springs. When the
button is depressed, the wedge is forced between the switch springs de throwing
these apart. The spring d is thus separated from its resting contact d and closed
upon its anvil ; the spring e is closed upon its anvil e, while the spring i is
permitted to bear upon its contact : The range of movement or throw of the
lever b is so adjusted that the curved extremities of springs d and e pass beyond
the thickest portion of the wedge and are permitted to close on its other faces,
thus preventing its return, whereby the circuit connections thus established are
permitted to remain until the position of the key is forcibly altered.
When now
the button is depressed, the wedge is first returned to its normal central position,
permitting the switch springs d and e to regain their normal positions; then, in the
further movement of the wedge, it enters between switch springs fand g separating
these from their respective resting contacts and forcing them outward against their
alternate contact points. The wedge is not however permitted to enter sufficiently
far between these springs to be held by them (a projection on b preventing it) but
is returned by their pressure upon its inclined surfaces to the central position.
Referring now to the diagram (Figure 5) showing the circuit connections of the
key, its various functions in connection with the plug circuit may be traced.
In this diagram 7 and represent double connecting plugs of the usual type,
each having a tip adapted to register with the line spring of a spring jack, and a
sleeve to make connection with the thimble or ring of the same.
.
The plug is used in answering a call or signal for connection, and the plug
for completing the connection with the line called for, the former being ordinarily
designated the "answering" plug, and the latter the "testing" plug. The tip of
the plug is connected by conductor 1 with the switch spring d, the sleeve of the
same plug by conductor 2, with the switch spring e. The tip and sleeve of the
plug are united with the switch springs fand 9 respectively through conductors 3
and 4. The conductor 1 is connected with the resting contact f' and conductor 2
with resting contact g¹ through wires 5 and 6 respectively. The contact anvils d³ e*

page_text: constitute the terminals of the operator's telephone m. A self restoring clearing-
out annunciator n having a main or operating magnet n' and a restoring magnet n
is connected in a bridge between the conductors 1 and 2, one side of the magnet n¹
being connected directly through wire 7 with conductor 2 and the other terminal
being connected through wire 8, with the resting contact d' and thus with the
switch spring d. The restoring magnet n³ is in a normally open local circuit with
a grounded battery o, one terminal of the maguet being connected by conductor 9,
with switch spring i whose contact anvil is grounded. The contact pieces f
and g constitute terminals of a generator p of signalling current. A ringing key q
is connected in the conductors extending to the telephone m, the circuit being
normally continuous through the key; when the plunger of the key is depressed,
forcing its switch springs 'g' outward the circuit to the telephone is disconnected
and the generator p of signaling current is connected in place thereof, thus trans-
mitting a signaling current to both of the connected lines.
Two telephone lines are shewn, extending from substations r¹ and connected
with the usual spring-jacks upon a multiple switchboard at the telephone central
station. Thus the station r is connected through line wires 12 and 13 with spring-
jacks S and S' and with an individual annunciator t. A subscriber, as for example
at station r, desiring to have his line connected with another, signals the central
office by rotating his calling generator u, whose generated current operates the
annunciator t, causing it to display its signal. The attendant operator at the
switchboard V, at which the line annunciator t and the spring jack S¹ are located,
seeing this indication inserts the plug into the spring-jack..
It is preferable that the key should be left with the button c' (Figures 2 and 3)
in its depressed position, the operator's telephone being thus already connected
with the conductors 1 and 2. In this position of the key the bridge containing
the clearing-out annunciator n, is open at the contact point d. It will be understood
that the necessity for this arrangement arises from the fact that each operator has
a considerable number of pairs of plugs under her charge, with several or all
of which her telephone may be connected at the same time; in which case, if each
clearing-out annunciator were left permanently connected with its plug circuit, the
telephone would be shunted by such a number of annunciators in parallel that its
efficiency would be materially impaired. At the same time the local circuit
including the restoring magnet n of the clearing-out annunciator is closed at the
contacts ii, whereby this annunciator, if it has been previously operated and left
with its indicator exposed, would be reset to its normal position ready for a
disconnection signal.
Hence having inserted the plug into the spring jack of the subscriber calling,
the operator finds herself already in position to communicate with the subscriber to
receive his order. This being done, she proceeds to test the line called for, in the
usual way, by applying the tip of plug to the test ring or thimble of the
nearest spring jack of the line. If the line be free, no effect is produced in
the telephone by this test; but if the line were in use, a plug would be already
inserted in a spring jack of the line, where the test ring w would be connected
through a battery to earth at the spring jack where such connection was made.
Then a current would be created through the path to the test ring w, thence to the
tip of plug , through conductor 3, switch spring f, resting contact fi through
wire 5 to spring d, thence to anvil d, thence to the operator's telephone, and
through one-half of its magnet coil to earth. A click would thus be produced in
the operator's telephone which would indicate to her that the line was in use.
"
Having found the line to the station called for, as station r', to be free, the
operator inserts the plug fully into the spring jack S. She then depresses the
button c of the key, whereby the wedge 6 is forced between switch springs fy,.
disconnecting the conductors 5 and 6 and the remainder of the plug circuit, and
looping the calling generator p into circuit with the plug . A signalling current
is thus transmitted to the station. As soon as the operator releases the button c,
the wedge is returned to its central position by the pressure of the springs f¨ y-

page_text: The connections are thus restored to their former condition, excepting that the
telephone is disconnected from the circuit of the plugs, the bridge containing the
clearing out annunciator n is completed, and the local or restoring circuit is again
opened.
C
When the subscribers have finished their conversation, either or both may send
a clearing-out signal, which will operate the clearing-out annunciator n. It is cus-
tomary for the operator having received a clearing-out signal to bring her telephone
again into the circuit, in order to discover whether another connection is desired by
either party. The operator does this by depressing the button c', thus returning
the entire apparatus to its first condition. If she desires to again disconnect her
telephone, she accomplishes this by depressing the button c until the wedge b has
reached the central or normal position between the switch springs, but not
sufficiently far to enter between the switch spring ƒ g. This is easily done, since
a greatly increased resistance to the pressure upon button c is experienced at the
moment the wedge enters between springs fg. If, however, it be not necessary to
disconnect the telephone, the operator may leave the key in the former position
and may remove the connecting plugs from the spring jacks into which they
are inserted. The entire plug circuit and the key are now in position for immediate
use in answering another call.
с
If it be necessary at any time for the operator to signal to other than the
subscriber called for, this would be done by depressing the button of key.q by
which signalling current would be sent to both substations.
Thus with the improved key the operator is enabled to control the circuit
connections of all her different appliances for speaking and signalling, in the
performance of ordinary work, in two motions for each connection; the first
being to depress button c in order to signal to the answering subscriber and at
the same time to disconnect the telephone, and the other being to depress the
button after receiving the clearing-out signal.
Instead of fitting the key with two push buttons three may be used as shown
in Fig. 6. The pins of the push buttons which operate lever b are in this case
supplied with stops or shoulders which limit their motion. By pressing upon the
button the wedge b' is forced between springs d and e and retained in that
position until returned to its middle position by pressure on the push button c'.
By pressure upon the button c the double wedge is moved from the middle position
to the right so as to bring it between the springs and g. The locking of the
wedge in this position does not occur. As soon as the pressure on the button c is
removed the springs and g by pressure upon the faces of the wedge return the
latter to its middle position.
It is obvious that the improved key is capable of many modifications in detail of
construction or to adapt it to different circuits, and to effect other and different
permutatious.
Dated this 11th day of July 1894
J. E. KINGSBURY.
Improvements in Telephone Switch Board Mechanism.
I, JOHN EDWARD KINGSBURY, of 79 Coleman Street, in the City of London,
Manager, (a communication from The Western Electric Company of Chicago,
Illinois, United States of America) 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 invention relates to mechanism of telephone switch-boards, more particularly
to the keys or switching mechanism and circuit connectious appropriate thereto
furnished the operator for connecting her telephone with the plug circuit and for

page_text: calling subscribers, its objects being to reduce the number of manipulations of keys
required in making connection between subscribers, and to construct a compact and
easily accessible form of key.
The improved key consists of a lever carrying a double wedge and switch springs
or levers controlled by the wedge in its different movements. One pair of switch
springs is arranged upon each side of the wedge; the members of each pair are
provided with suitably disposed contact pieces for controlling the various circuits.
The wedge tends to remain in a central or intermediate position between the pairs
of switch springs. In this position the operator's telephone is disconnected from
the plug circuit, while the clearing out annunciator is connected in a bridge between
the different conductors of the plug circuit. When the wedge is moved between
one pair of switch springs, the operator's telephone is connected in a bridge
between the sides of the plug circuit, the branch containing the clearing out
annunciator is opened, and a local circuit including the restoring or resetting
magnet of the self restoring annunciator commonly employed is closed, replacing
this instrument in position to respond to a subsequent signal. The operator is thus
in position to communicate with a subscriber desiring connection. After the
required connection is established, the wedge is held over in the opposite direction
and forced between the opposite switch springs, disconnecting all of the cord
circuit excepting the plug through which it is desired to signal, and connecting the
latter with the terminals of a generator of signalling current. When the wedge is
no longer held over in this position it is returned automatically to its central or
normal position, the telephone and signalling generator being disconnected and the
clearing out annunciator being placed in condition to respond to the signal for
disconnection.
Two push buttons may he adapted to act upon two opposite arms of the lever to
shift the lever from one position to the other, one push button to shift the lever in
one direction and the other to shift it in the opposite direction. Or the lever arm
carrying the double wedge may be extended beyond the fulcrum on which the lever
arm turns and this upward extension may be used for shifting the lever arm into
either one or other of its extreme positions.
The invention is illustrated in the drawings Figures 1 to 6 left with the
Provisional Specification, and in Figure 7. Of these
Figure 1 represents a plan view of the improved key.
Figure 2 is a side elevation of the same, together with a portion of the frame of
the switchboard upon which the key is mounted.
Figure 3 is a longitudinal section of the key showing the construction of the
various parts.
Figure 4 is a view from beneath showing the disposition of the switch springs.
Figure 4 is an end view.
Figure 5 is a diagram representing the key with its circuit connections in a
plug circuit, the latter being in position of connecting two telephone lines upon a
switchboard.
с
which a
The key shown in Figures 1, 2, 3 and 4 consists of a frame a upon
lever bis pivotted near the middle of its length in lugs al a³. Opposite the
extremities of the lever b, push buttons e and e' are provided, moving in cylinders a³ a
and bearing upon the corresponding extremities of the lever through stems c² c'.
Near the middle of its length the lever b carries a short cylinder ¹ acting as a
double wedge. Two pairs of switch springs or levers de and fg are arranged, one
pair upon either side of the double wedge b' with their curved free extremities
presented to the wedge. These switch springs are fixed at their rear extremities in
blocks and h, respectively, of insulating material secured to the frame a. The
switch spring d has a normal resting contact d¹ and an alternate contact d³ with
which it is adapted to make contact when the spring is forced outward; these
contact points are carried at the extremities of stiff springs, also secured in the
block. The switch spring e has no normal resting contact but is provided with
an alternate contact poiutee carried in the same manner. Parallel with the

page_text: spring e an auxiliary spring i is arranged, insulated from spring e but mechanically
connected with it by a stud k of insulating material. The free extremity of the
spring i is bent round in the form of a hook, and a contact point is provided to
register with the inwardly projecting extremity. The tension or resiliency of the
spring is so adjusted, with relation to that of spring e, that it is normally pressed
inward and away from the contact point ; but when relieved of the pressure of
spring e, it is adapted to move outward and thus to bear upon the contact ¹. The
switch springs f and g are each provided with resting contacts and g', and with
alternate contact points f2 and 2, respectively, similarly secured to the extremities
of the stiff springs.
On account of the pressure of the springs defg, the wedge will be held
normally in a central or intermediate position between the springs. When the
button c¹ is depressed, the wedge is forced between the switch springs de, throwing
these apart. The spring d is thus separated from its resting contact d¹ and closed!
upon its anvil &; the spring e is closed upon its anvil, while the spring i is
permitted to bear upon its contact . The range of movement or throw of the
lever is so adjusted that the curved extremities of springs d and e pass beyond
the thickest portion of the wedge and are permitted to close on its other faces,
thus preventing its. return, whereby the circuit connections thus established are
permitted to remain until the position of the key is forcibly altered. When now
the button c is depressed, the wedge is first returned to its normal central position,
permitting the switch springs d and e to regain their normal positions; then, in the
further movement of the wedge, it enters between switch springs fand,
g, separating
these from their respective resting contacts and forcing them outward against
their alternate contact points. The wedge is not, however, permitted to enter
sufficiently far between these springs to be held by them (a projection on
venting it), but is returned by their pressure upon its inclined surfaces to the
central position.
pre-
Referring now to the diagram (Figure 5) showing the circuit connections of the
key, its various functions in connection with the plug circuit may be traced.
In this diagram and represent double connecting plugs of the usual type,
each having a tip adapted to register with the line spring of a spring jack, and a
sleeve to make connection with the thimble or ring of the same.
I
The plug is used in answering a call or signal for connection, and the plug
for completing the connection with the line called for, the former being ordinarily
designated the "answering" plug, and the latter the "testing" plug. The tip of
the plug is connected by conductor I with the switch spring d, the sleeve of the
same plug, by conductor 2, with the switch spring e. The tip and sleeve of the
plug are united with the switch springs fand g respectively, through conductors 3
and 4. The conductor 1 is connected with the resting contact", and conductor 2
with resting contact g', through wires 5 and 6, respectively. The contact anvils d'e³
constitute the terminals of the operator's telephone m. A self-restoring clearing-
out annunciator n having a main or operating magnet n' and a restoring magnet n'
is connected in a bridge, between the conductors 1 and 2, one side of the magnet n¹
being connected directly through wire 7 with conductor 2, and the other terminal
being connected through wire 8 with the resting contact d', and thus with the
switch spring d. The restoring magnet is in a normally open local circuit with
a grounded battery o, one terminal of the magnet being connected by conductor 9
with switch spring i, whose contact anvil is grounded. The contact pieces f*
and g constitute terminals of a generator p of signalling current. A ringing key q
is connected in the conductors extending to the telephone m, the circuit being
normally continuous through the key; when the plunger of the key is depressed,
forcing its switch springs gq2 outward, the circuit to the telephone is disconnected,
and the generator p of signalling current is connected in place thereof, thus
transmitting a signalling current to both of the connected lines.
Two telephone lines are shown, extending from substations rr and connected
with the usual springjacks upon a multiple switchboard at the telephone central

page_text: station. Thus the station is connected through line wires 12 and 13 with
springjacks S and S' and with an individual annunciator t. A subscriber, as for
example at station r, desiring to have his line connected with another, signals the
central office by rotating his calling generator u, whose generated current operates
the annunciator t, causing it to display its signal. The attendant operator at the
switchboard e, at which the line annunciator t and the springjacks' are located,
seeing this indication, inserts the plug into the springjack.
It is preferable that the key should be left with the button e' (Figures 2 and 3)
in its depressed position, the operator's telephone being thus already connected
with the conductors 1 and 2. In this position of the key, the bridge containing the
clearing out annunciator », is open at the contact point d'. It will be understood
that the necessity for this arrangement arises from the fact that each operator has
a considerable number of pairs of plugs under her charge, with several or all of
which her telephone may be connected at the same time; in which case, if each
clearing out annunciator were left permanently connected with its plug circuit, the
telephone would be shunted by such a number of annunciators in parallel that its
efficiency would be materially impaired. At the same time the local circuit
including the restoring magnet of the clearing out annunciator is closed at the
contacts, whereby this annunciator, if it has been previously operated and left
with its indicator exposed, would be reset to its normal position ready for a.
disconnection signal.
Hence having inserted the plug into the springjack of the subscriber calling,
the operator finds herself already in position to communicate with the subscriber
to receive his order. This being done, she proceeds to test the line called for, in
the usual way, by applying the tip of plug to the test ring or thimble w of the
nearest springjack of the line. If the line be free, no effect is produced in the
telephone by this test; but if the line were in use, a plug would be already inserted
in a springjack of the line, where the test ring w would be connected through a
battery to earth at the spring jack where such connection was made. Then a
current would be created through the path to the test ring w, thence to the tip of
plug, through conductor 3, switch spring, resting contact f¹ through wire 5 to
spring d, thence to anvil d, thence to the operator's telephone, and through one half
of its magnet coil to earth. A click would thus be produced in the operator's
telephone which would indicate to her that the line was in use.
Having found the line to the station called for, as station r¹, to be free, th
operator inserts the plug fully into the spring-jack S. She then depresses the
button of the key, whereby the wedge is forced between switch springs/g,
disconnecting the conductors 5 and 6 and the remainder of the plug circuit, and
looping the calling generator p into circuit with the plug . A signalling current
is thus transmitted to the station . As soon as the operator releases the button c,
the wedge is returned to its central position by the pressure of the springs fy.
The connections are thus restored to their former condition, excepting that the
telephone is disconnected from the circuit of the plugs, the bridge containing the
clearing out annunciator n is completed, and the local or restoring circuit is again
opened.
When the subscribers have finished their conversation, either or both may send a
clearing-out signal, which will operate the clearing-out annunciator n. It is
customary for the operator having received a clearing out signal to bring her
telephone again into the circuit, in order to discover whether another connection is
desired by either party. The operator does this by depressing the button e', thus
returning the entire apparatus to its first condition. If she desires to again
disconnect her telephone, she accomplishes this by depressing the button c until the
wedge b has reached the central or normal position between the switch springs, but
not sufficiently far to enter between the switch spring ƒ g. This is easily done,
since a greatly increased resistance to the pressure upon button c is experienced at
the moment the wedge enters between springs fg. If, however, it be not necessary
to disconnect the telephone, the operator may leave the key in the former position

page_text: .
and may remove the connecting plugs from the spring jacks into which they are
inserted. The entire plug circuit and the key are now in position for immediate use
in answering another call.
If it be necessary at any time for the operator to signal to other than the
subscriber called for, this would be done by depressing the button of key 7 by which
signalling current would be sent to both substations.
Thus with the improved key the operator is enabled to control the circuit
connections of all her different appliances for speaking and signalling, in the
performance of ordinary work, in two motions for each connection; the first being
to depress button c in order to signal to the answering subscriber and at the
same time to disconnect the telephone, and the other being to depress the button c¹
after receiving the clearing-out signal.
Instead of fitting the key with two push buttons three may be used as shown in
Figure 6. The pins of the push buttons which operate lever b are in this case
supplied with stops or shoulders which limit their motion. By pressing upon the
button c the wedge is forced between springs d and e and retained in that position
until returned to its middle position by pressure on the push button c¹. By pressure
upon the button the double wedge is moved from the middle position to the
right so as to bring it between the springs fand g. The locking of the wedge in
this position does not occur. As soon as the pressure on the button is removed
the springs and g by pressure upon the faces of the wedge return the latter to its
middle position.
It is obvious that the improved key is capable of many modifications in detail of
construction, as for example the lever may as shewn at Figure 7 be operated by an
_arm extending upwards from it; the key may also be modified to adapt it to
aifferent circuits and to effect other and different permutations.
Having now particularly described and ascertained the nature of my said
invention and in what manner the same is to be performed I declare that what I
claim is :-
1. In telephone switch board mechanism the combination of the two plugs, the
flexible conductors passing from one to the other, the double wedge and the two
sets of contact springs and connections interposed in the length of the conductors so
disposed that when the wedge is moved between the contact springs of one set and
one of the plugs is inserted into the spring jack terminal of any subscriber's line
from which a call has been received the attendant's telephone is brought into circuit
with that line and when the wedge is moved between the contact springs
of the other set and the other plug is inserted into the spring jack terminal of any
other subscriber's line that the first subscriber wishes to communicate with the
attendant's calling generator is put into circuit with this line and when the double
wedge is moved into its central position the lines of the two subscribers are
connected together and a bridge circuit established through a clearing out
annunciator.
2. A key for telephone switch boards consisting of a double wedge movable from
its middle position in two directions and which wedge actuates two groups of switch
springs which springs in the three positions of the double wedge produce the
necessary changes in circuit of the various apparatus.
3. The combination with two sets of symmetrically disposed switch springs of a
double wedge between the adjacent free ends of the springs the wedge being
normally free from both pairs of switch springs and means for forcing the wedge
between either pair of switch springs to alter their positions substantially as
described.
4. The combination with a rocking lever of a double wedge carried by the lever
symmetrically placed switch springs upon opposite sides of the double wedge, each
face of the wedge being adapted to enter between one pair of switch springs and
contact anvils and circuit connection for the switch springs substantially as
described.

page_text: 5. The combination with two sets of symmetrically disposed switch springs of a
double wedge mounted upon a rocking lever between the presented ends of the
switch springs the wedge being normally free from both sets of springs but capable
of being forced by the lever between either set, and when forced by the lever
between one set retained from returning to its normal central position but not
retained when forced between the other set so that it returns to its normal position
when the operator ceases to hold the lever over.
6. The combination with two sets of symmetrically disposed switch springs of a
double wedge mounted upon a rocking lever between the presented ends of the
switch springs-the wedge being normally free from both sets of springs but capable
of being forced by the lever between either set, the range of movement of the
wedge in one direction being so adjusted that it is held by the corresponding pair of
springs and prevented from returning to its normal central position, whilst the range
of movement in the opposite direction is so adjusted that the wedge is not held by
the springs but returns to its normal central position when the lever is free.
7. In an operator's key, the combination with two sets of symmetrically disposed
switch springs, of a double wedge adapted to be forced between either set of springs,.
double plugs each having its two parts connected with the different members of oue
set of switch springs, the resting contacts of one pair of springs being connected
with the two parts of the other plug, and the alternate contacts of the same switch
springs being connected with the terminals of a calling generator, the alternate
contacts of the other pair of switch springs constituting the terminals of an operator's
telephone, whereby when the wedge is moved in one direction one plug is disconnected
from the other and connected with a calling generator, and when the wedge is
moved in the other direction the telephone is connected in a bridge between the
different conductors uniting the plugs, substantially as described.
8. The combination with two pairs of symmetrically disposed switch springs, of a
double wedge between the presented extremities of the two pairs of springs, normally
free from both pairs, two press buttons, one adapted to more the wedge in one
direction the other in the other direction, a double connecting plug having its parts.
connected with the members of each pair of switch springs, alternate contact points.
constituting the terminals of a telephone, for one pair of switch springs, the wedge
being adapted to be held between this pair of springs when thrust between them to
press them outward, alternate contacts for the other pair of switch springs
constituting the terminals of a calling generator, the wedge being adapted to be
returned to its central position by the pressure of the corresponding springs upon
when it is thrust between them, substantially as described.
it
9. The combination of switch board mechanism substantially as herein before.
described and illustrated in the drawings annexed.
Dated this 11th dox of A 1905
J. E. KINGSBURY.