Telephone Attachment. Page: 3 of 5
2 sheets, 3 p. : ill. ; 23 cm.View a full description of this patent.
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UNITED STATESPATENT OFFICE,
CHARLES B. MITCHELL, OF FRANKLIN, TEXAS, ASSIGNOR OF ONE-FOURTH TO HAM-
MET B. HURT AND ONE-FOURTH TO JAMES W. McCRARY, OF FRANKLIN, TEXAS.
TELEPHONE ATTACHMENT.941,086. . Specification of
Application filed February1
To all whom it may concern:
Be it known that I, CHARLES B. MITCHELL,
a citizen of the United States, residing at
Franklin, in the county of Robertson arid
5 State of Texas, have invented a new and use-
ful Telephone Attachment, of which the fol-
lowing is a specification.
This invention has reference to improve-
ments in telephone systems and more partic-
10 ularly to multi-party line systems whereby a
subscriber is enabled to call up any other sub-
scriber on the line and then hold the line
against interference or eavesdropping on the
part of other subscribers. In addition to
15 these features the present invention.includes
a means whereby subscribers in the zone in-
cluded in a conversation between two sub-
scribers and also other subscribers outside of
this zone on either side thereof have the sig-
20 nal circuit intact so that the fact that there
may be an active zone between two sub-
scribers or between any subscriber and a cen-
tral station will not interfere with the send-
ing of signals to such central station or be-
25 tween subscribers outside the active zone or.
to the subscribers using the telephone within
the active zone.
The invention will be best understood from
a consideration of the following detail de-
30 scription taken in connection with the accom-
panying drawings, forming a part of this
specification, in which drawings,
Figure 1 is a diagram of a single local sta-
tion on a multi-party line showing the appli-
35 cation of the invention hereto. Fig. 2 is a
face view or elevation of the improved at.-
tachment designed to be applied to ordinary
telephone units whereby the said telephone
unit may be modified to carry out the pur-
40 poses of the present invention. Fig. 3 is a
similar view to Fig. 2 except that parts are
shown in section and also in a different posi-
tion, than Fig. 2. Fig. 4 is a central vertical
section through the attachment with parts
45 shown in elevation.
Referring first to Figs. 2, 3 and 4 there is
shown a frame 1 which may or may not be
inclosed in a suitable casing or form part of
a suitable casing depending upon whether
50 the attachment is to be phced inside the call
box of an ordinary telephone unit, or
whether it is to be placed exterior thereto.
Assuming that the supporting structure 1 is
in the form of a rectangular frame such as1c
Letters Patent. Patented Nov. 23, 1909.
9, 1909. Serial No. 478,841.
illustrated in Figs. 2, 3 and 4 there are pro- 55
vided two cross bars 2-3, spaced apart in
the direction of the thickness of the frame. 1
and located intermediately between the top
and bottom of said frame. Journaled in the
bars 2 and 3 at the middle portion thereof is 60
a short shaft 4 extending beyond the cross
bar 2 a suitable distance and there provided
with a hand wheel 5 which may be in the
form of a milled head or may be replaced by
a suitable crank if so desired. On the hand 65
wheel 5 there is a pointer or indicator 6.
The shaft 4 between the bars 2 and 3car-
ries a cam member 7, the purpose of which
will hereinafter appear and this shaft at any
appropriate point, say beyond the cross bar 70
3 may carry a crank 8 to the outer end of
which is fast a stud 9 and to this stud there
is secured one end of a spring 10 the other
end of which may be made fast to a stud 11
on the frame 1. Stop pins 12 on the cross 75
bar 3 limit the movement of the shaft 4 by
engaging the crank 8 at the two extremes of
its rotative movement about the longitudinal
axis of the shaft 4.
Fast to the frame 1 are two binding posts 80
13, or other means for the connection of con-
ductors. From the binding posts there ex-
tend to the interior of the frame 1 and be-
tween the cross bars 2 and 3 two spring
arms or members 14 having their ends 85
closely adjacent to the end of the frame 1
remote from the binding posts 13. At an
intermediate point in that end of the frame
1 remote from the binding posts 13 there is
secured a post or stud 15 projecting into the 90
frame 1 but at the outer end thereof being
formed into a binding post for the reception
of a terminal end of a conductor, or being
provided with suitable means for the attach-
ment of the conductor. On each side-of the 95
stud 15 are other studs 16-17, spaced from
the stud 15. The frame 1 is commonly made
of insulating material but if made of con-
ducting material then the studs 15, 16 and
17 will be insulated therefrom in any appro- 100
priate manner.
The free end of each spring strip 14 is
appropriately bent or otherwise shaped as
indicated at 18 for engagement with the cen-
tral stud 15 which at this point is flattened '05
to insure good electrical contact between the
stud 15 and the portion 18 of the spring.
strip -. The extreme end of each strip 14
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Mitchell, Charles B. Telephone Attachment., patent, November 23, 1909; [Washington D.C.]. (https://texashistory.unt.edu/ark:/67531/metapth508234/m1/3/: accessed July 18, 2024), University of North Texas Libraries, The Portal to Texas History, https://texashistory.unt.edu.; crediting UNT Libraries Government Documents Department.