Improvements in Telephone Central-station Apparatus.
Year: 1888

page_text: CUM LEID DI BUIFICATION.
Improvements in Telephone Central-station Apparatus.
We, THEODORE NEWTON VAIL, of 190 Walnut Avenue, Boston, County of Suffolk,
State of Massachusetts, United States of America, Electrician, and JOHN ASHBY SEELY,
of 18 Cortlandt Street, New York, County of New York, State of New York, United
States of America, Electrical Engineer, do hereby declare the nature of our said
invention and in what manner the same is to be performed, to be particularly
described and ascertained in and by the following stateinent :-
Our invention is an improvement in certain details of construction of switch-boards
for use in telephone central stations. Such switch-boards consist of a series of
spring-jacks and the plugs designed for use in connection therewith. Spring-jacks
consist of two or more contact-points forming the terminals of a divided electrical
circuit, such contacts being normally held together by the force of springs upon which
one or both of said contacts are fixed. A spring-jack for use in a ground return
circuit has but two severable contact-points. A jack for use in a metallic return-
circuit has four such contact-points. A plug forming the terminal of a flexible connecting-
cord is used with these jacks, and such plug has one or two contact-points, according
as it is designed for use with a ground return or metallic circuit. These contact-
points are so formed and arranged as to force apart the spring-actuated points of the
jack, and when the plug is in position in the jack one-half the points of the jack are
open and the points of the plug are substituted for such open points, so that the
circuit entering the jack: is broken and connected to the plug and cord of which it
forms the terminal. These jacks are sometimes arranged with the plug-socket opening
upon a horizontal plane, and when so arranged dust, dirt, and fragments of insulating

page_text: material are liable to fall and lodge in the contact-points, thus causing a break
or opening in the circuit. To prevent this, we have constructed a spring-jack having
a dust-guard. This consists of a piece forming one contact-point placed between the
opening or plug-socket and the severable points of the jack in such a position as to
shed the dust and dirt, while it shields the contact-points from the evil effects of such
dust and dirt. It is preferably placed at an angle with the plane of the hole, opening,
or passage into the jack.
We arrange these jacks in position either in banks or singly, where they form parts
of the electrical circuit, and so that they may be readily removed for testing, cleaning,
or repairing. The electrical conductors usually come to the tables or boards in the
form of cables. These conductors are soldered to strips or pieces of metal, a series of
Each cable
such strips being firmly fixed in a portable block of insulating material.
may be attached to one, two, or more such portable blocks. Each block is shaped to
rest in a frame in such position as to bring the free ends of, the strips referred to into
registering position with the free terminals of the spring-jacks. The terminals of the
spring-jacks are fixed in a frame of insulating material in position to register with the
fixed electrical contacts forming the terminals of the circuits. Both these contacts
are corrugated or shaped so as to grip and hold together, while forming an electrical
contact which may be severed without the use of tools of any kind. By this arrange-
ment we avoid the soldering, of joints anywhere near the spring-jacks, and may easily
remove, replace, test, or repair any part. The jacks are placed in frames of insulating
material in banks of, say, eight or ten, and may be very expeditiously inserted and
removed. The plugs for these jacks forming the terminals of. flexible cords are
usually held in position with their bases resting upon fixed electrical contacts which
register with electrical contacts on the base of the plug. If a plug forms the terminal
of a double conductor-cord, there are two insulated contacts on its base, and if
we desire to have these two contacts rest upon two fixed contacts, respectively, and to
take up this same position whenever the plug is removed from a jack and allowed to seek
its normal position automatically under the influence of a weight operating as a "gravity
take-up" in a well-known manner, we must provide special means for securing this
result. For this purpose we have provided a cylindrical plug, one side of which
is flattened, and a plug-socket having a similar outline to the cross-section of the plug.
In this arrangement a plug can only reach its normal position when it is in the proper
relative position with respect to the socket and contact-points.
The accompanying drawings illustrate our invention.
Figure 1 is a cross-section of a switch-board on line 11, Fig. 2; and Fig. 2 is a
plan view of a section of the switch-board. Fig. 3 shows the cabled conductors
having terminals fixed in portable insulating-blocks.
In Fig. I are shown two spring-jacks consisting of severable points c c², held together
by spring-pressure. F is a plug socket or passage from the surface of the board B,
which is horizontally disposed. G is a dust-guard; also forming an electrical contact-
point for one contact, p, of the jack-plug P. It is located between the passage F and
contact-points c c¹. Dust, dirt, and fragments falling through F are shed off and caused
to fall below the points c c', thus avoiding evil effects thereof. In these spring-jacks
there are four severable contacts c c¹ and four free terminals like m. There are also a
series of fixed terminals, t, in insulating-block T in position to register and electrically,
connect with terminals m, and the meeting points of both m and t are so formed as to
lock together and make good electrical contact. The conductors are soldered to the
terminals at the point n, Fig. 3. There is a space between board B and portable
insulating-blocks T for the passage of the hand and to facilitate changes.
U is a bar or division, of which there are several, forming a frame for the portable
insulating-blocks T. The conductors w of cable W are "fanned out" and soldered
to strips t t at n n. These terminals t are fixed in the portable insulating-blocks T in
position.to make contact with terminals m of the spring-jack.
The two conductors i, and j, passing through flexible cords C, terminate in plugs P,
having two electrical contacts, 1 and 2, at their base. There are also fixed contacts 3
and 4, with which it is desirable that contacts 1 and 2 should connect at all times
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page_text: when plug P is in its normal position, said plug being returned to its normal
position by the gravity take-up w, as well understood. Now, in order that these
plugs when released and automatically returned to their normal position by weight wo
may always assume the same position, we provide a guide or passage having an
eccentric geometrical formation, and we form the plug to correspond. We have
chosen to make the guide circular, with a chord subtending a few degrees of
the circle removed, as shown at s in Fig. 2. The cross-section of the plug is of
similar outline and the entrance to the plug-socket is slightly flaring, as shown
in Fig. 1, so that the plug, acting under the force of weight w and approaching
socket F out of position, will right itself and sink into its normal position in proper
position to unite contacts 1 and 2 with 3 and 4 respectively and uniformly.
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 :-
1. A spring-jack consisting of two or more severable contact-points, an opening
or passage to such points for the insertion of a jack-plug, and a shield or dust-
guard constructed of suitable material to shed or deflect falling dust or dirt,
movably supported between the mouth of the opening or passage and the severable
contact-points, substantially as herein before described.
2. In a spring-jack, the combination of two or more severable contact-points,
an opening or passage to such points forming a plug-socket, and a shield or dust-
guard forming an electrical contact for the said plug, all arranged substantially as
hereinbefore described.
3. A switch-board consisting of a frame or support two series of blocks of insu-
lating material fitting into said frame or support, located in two parallel planes, a
series of electrical instruments composing the operative mechanism of a switch-
board, such as spring jacks, having free terminals located in one series of blocks,
one or more in each block, a series of electrical contacts having free terminals
located in the second series of blocks in position to register with the terminals
of the first series, and a series of electrical conductors connected to the second.
series of contacts, one conductor for each contact, substantially as hereinbefore
described.
4. The combination, in a switch-board, of two or more insulated electrical contacts
located in a plug-socket having an eccentric geometrical outline or formation, a
switch-plug of similar geometrical outline or formation, having one or more insu-
lated electrical contacts in position to register with the first-named contacts when
said plug is in its normal position, and means for automatically returning such
plug to its normal position when free to move, substantially as hereinbefore
described.
.
5. A switch-board composed of a frame or support, one or more electrical instru-
ments located in said frame having two or more tree terminals, one or more portable
blocks or sections of insulating material fitting into said frame, two or more
conducting sections fixed in said blocks, their free terminals in position to register
with the free terminals of the said electrical instruments, and wires or conductors
connected to said conducting sections, substantially as hereinbefore described.
Dated this 26th day of September 1888.
THEODORE NEWTON VAIL.
JOHN ASHBY SEELY.