IMPROVEMENTS ON SWITCHES AND APPARATUS FOR USE UPON TELEPHONE LINES
Year: 1880

page_text: LETTERS PATENT to Sydney Pitt, of Sutton, in the County of Surrey, for an
Invention of "IMPROVEMENTS ON SWITCHES AND APPARATUS FOR USE UPON
TELEPHONE LINES." A communication from abroad by Charles Darwin
Haskins, of New York City, in the County and State of New York, one of the
United States of America, Electrician.
COMPLETE SPECIFICATION filed by the said Sydney Pitt at the Office of
"
the Commissioners of Patents on the 23rd November 1880.
SYDNEY PITT, of Sutton, in the County of Surrey. IMPROVEMENTS ON
SWITCHES AND APPARATUS FOR USE UPON TELEPHONE LINES." A communication
from abroad by Charles Darwin Haskins, of New York City, in the County and
State of New York, one of the United States of America, Electrician.
This Invention relates to electric calls or signals especially adapted for use on
telephone circuits, though suitable for other purposes.
Its object is to enable signals to be exchanged between a central office and any
station on a given circuit without operating the signal or call bell of any other
station on the same circuit, and to provide a means by which persons at other
stations will be prevented from interrupting or overhearing a message which is
being sent by a person using a telephone at another station on the same circuit,
and to supply a method by which the operator at the central office of a telephone
exchange will be enabled to set the different instruments at a common starting
point.
In the accompanying Drawings,-
Figure 1 is a plan or top view of the receiving instrument; Figure 2, a similar
view partly in section on the line 2, 2, of Figure 3; Figure 3, a side elevation
thereof; Figure 4, an end elevation; Figures 5, 6, and 7 are detail views on an
enlarged scale of the unison stop and locking-out mechanism; Figures 8 and 9 are
detail views of the manner of pivoting the current changing armature on the
permanent magnet; Figure 10 is a diagram illustrating the working of the
improved system; Figure 11 is a diagram illustrating a modification thereof.
Referring to Figure 10, the letter U represents a galvanic battery with its poles
in connection with a suitable current, reversing switch V, and a cut out switch V₁;
S and S' are well known forms of circuit breaking keys; W is an ordinary call
[Ponian S31

page_text: bell. The letter Q designates the lever of a telephone switch curved inwardly at
its lower extremity, forming the projections q and q', and pivoted at x to the
frame X, the said frame at its lower extremity being bent to form a hook X¹
adapted to hold a telephone, the said lever and frame being of metal.
Rigidly attached to the lever Q are two metallic strips or contact springs Q¹
and Q, the spring Q¹ being insulated from the lever Q, and normally in contact
with segment R, spring Q making contact with segment R when lever Q is thrown
outward, as indicated by dotted lines.
The latter A designates a polarized electro magnet, similar in construction to
what is known as the Siemens' polarized relay magnet; B, B, being the coils
surrounding soft iron cores, and provided with inwardly extending soft iron poles
b and b¹; C is the permanent polarized magnet; and D is the soft iron armature
or tongue which plays between the poles b and b¹, and having its lower end fixed
to an arbor d, mounted in metallic bearings d' and d², arranged upon the permanent
magnet C, the said vibratory tongue having a prolongation D¹ of some non-
magnetic metal.
The letter E indicates a disc fixed to a sleeve F, which is mounted on a stud
projecting from the metallic plate G, and to this sleeve is fixed a ratchet wheel H;
the disc E has cut through it an aperture e, and said disc is so located as to be in
the path of the upper end of the vibratory tongue D' and a rearwardly projecting
pin D attached thereto, so that said tongue cannot make a full movement toward
the pole b¹, except when the aperture e of the disc coincides with the pin D³, so
that said pin can pass through it.
It will be thus observed that the disc E serves as a lock to prevent the tongue D
from making its full movement towards the pole b¹at all other times except when
said aperture and said pin are in coincidence, said disc being thus constituted a.
signal shunt lock as will presently appear.
To bring the aperture into or to remove it from coincidence with the pin D2,
the disk is turned by the operation of an impelling pawl upon the ratchet
wheel H, this impelling pawl being pivoted to the top of an arm i, the lower end
of which is fixed to a polarized stud armature I formed in the shape of a horseshoe,
and so pivoted to the arm J, projecting from the plate G, that its poles stand
directly in front of the soft iron poles b, b₁, of the polarized magnet A.
When the armature I is attracted by the magnet the arm i and its pawl h cause
the ratchet wheel H to move one tooth at a time, a retractile spring i¹ with-
drawing the armature from the magnet when the influence of the latter ceases.
A stop h² projecting from the pawl h prevents the ratchet wheel moving more
than the length of one tooth each time, and a detent h' prevents a retrograde
movement. Some distance below its top the tongue D' has fixed to it an elastic
metallic arm K projecting rearwardly.
.
To a stud projecting from the plate G is fixed a block K¹ of insulating material,
and to the front face of this block is fixed a metallic plate k, the block K¹ and the
platek being so arranged that when the pin D2 of the tongue D¹ projects through
the aperture e of the disc E, the spring arm K will be carried toward the plate G
such a distance as to bring the tip or point of spring arm K in contact with said
insulating block, but when the tongue D' moves outward and the pin D² is with-
drawn from the aperture of the disc the tip of the arm K will press upon the end of
the metallic plate k. When the tip of this spring arm K rests upon the edge of
said plate k the signal bell is shunted out of the main circuit, but when said spring
arm is in contact with the insulating block K' the signal magnets will be shunted
into the main circuit, as will be hereinafter more particularly described, and thus
it will be seen that the arm K is the moveable portion of the signal shunt. As
before stated the disc E prevents the full movement of the tongue D toward pole b',
and consequently prevents the movement of the arm K from the brass plate k to
the insulating block K¹, except at such times as the aperture of the disc coincides
with the pin D of the tongue D¹, at all other times therefore the disc E locks
the signal bell shunt from being operated. It is thus a signal bell shunt lock,

page_text: Fixed to and turning with the sleeve F is a projection 7 and a pin m, triangular
in cross section, Figures 5, 6, and 7. In the path of the projection is a flat
spring L having a transverse rib ; said spring is fixed by a screw to an arm or
guard L, which projects at right angles from a stud L2 fixed to the plate G, but
electrically insulated therefrom by hard rubber sheath, the stud L² being in
metallic connection with the main line by wire 9.
Fixed to the tongue D' and projecting rearwardly is a rigid arm M having on
its extremity two vertical prolongations m¹ and m², Figures 5, 6, and 7, having
their opposite edges bevelled.
One terminal of the coils B, B, is connected with the line or ground wire 2, and
also to the switch lever Q; the other terminal is in metallic connection with the
metal plate G, to which the permanent magnet C is fixed in metallic contact.
One terminal of the call bell coils is connected to the plate G by wire 3, the
other terminal connecting to the plate k by wire 4, and to the metal segment R by
wire 5.
The telephone T is connected to the upper and lower contact plates of key S¹ by
wires 6 and 7, the upper plate of said key being also connected to segment R by
wire 8, the lever of key Si is in metallic connection with the main line 7, and with.
the insulated metallic spring Q¹ by branch wire 9.
The steel polarized armature I has its poles so arranged that an electrical current
through the coils B, B, having a polarity to cause the soft iron tongue D to move
toward the pole 6 will also cause the poles b, b¹, to attract said armature I, and
from this it follows that said armature will be repelled and fall back, with the
assistance of its retractile spring, when a current is passing through the coils B, B,
which will cause the tongue D to move toward pole b².
Each subscriber's station is provided with the apparatus consisting of the
shunting and locking instrument, an electrical bell and switch connected together.
and to the main line as described.
The aperture e of the disc E in each instrument is set in a different position with
relation to the pin D2 from that of all of the other instruments, so that at only one
instrument can the tongue D' perform its full movement toward pole 6' at a time,
and at none other of the stations will aperture e and the pin D2 coincide or be
in line.
For example, say that four vibrations of the arm i will cause pawl h to move
the ratchet wheel H four teeth, and bring aperture e opposite the pin D² at the
first station, it should require the movement of the ratchet a greater number of
teeth, say eight, to cause a similar coincidence at the second station, and so on.
The operator at the central office by means of the key S can send over the main
line the proper number of electrical impulses to cause the disc at any desired
station to move to bring its aperture to a proper position to receive the pin D³, the
current being of the proper polarity to cause the tongue D to rest against the
pole b, thus the pin D2 will not engage with the discs at any station, but when
the polarity is reversed the tongue D will complete the full movement toward the
pole b¹ at the station where the aperture e and pin D² coincide.
Coincident with this movement of the tongue D the elastic metallic arm K will
be carried rearward, so that contact between it and plate / will be broken, and the
end of said arm K will rest upon the end of insulating block K¹. The direction
of the current passing from the main line will now be by way of wire 7, branch
wire 9, metallic spring Q', wire 5-4, call bell coils, wire 3, coils B, B, wire 2, to
main line or ground; the call bell coils being now in the main line circuit each
separate impulse of the current causes the armature of the call bell to be attracted
and the proper signal can now be sent.
The call having been, answered the subscriber removes the telephone from the
supporting hook X', thereby throwing the switch lever Qinto the position shown
by dotted lines, Figure 10, and thus breaking contact between the spring Q' fixed
to said lever and forming part of the circuit of the polarized relay and the metallic
segment R. This movement of the switch lever causes the main line current to

page_text: pass through the telephone outside of the coils of the polarized relay, by wire 1,
key S¹, wires 6 and 7, and telephone T, wire 8, segment R, spring Q, to wire 2,
consequently subsequent electrical currents sent over the main line will not energise
the coils of the polarized relay until the telephone has been replaced upon its
supporting hook and the spring Qis again in contact with segment R.
In all the other stations the aperture e will be out of coincidence with the pin D³,
and in consequence the vibratory tongue D will hold its arm K so that it makes
contact with the end of metallic plate k, and in each of these uncalled stations the
main line current will flow by the shortest route via the wires 1, 9, spring Q¹,
segment R, wires 5, 4, metallic block k, spring K, tongue D, arbor d, frame G, 1
coils B, B, wire 2, to line or ground, thus avoiding the electric bell circuit, said bell
remaining unrung. By keeping a memorandum at the central office the operator
will know how many impulses are necessary to place the instrument at any station
in a position to permit a call to be made, and the call should be sounded by a
current of the same polarity as that required to move tongue D toward pole b', in
order that said tongue may be maintained in proper position to keep the bell
circuit switched into the main line.
When the line is not in use the battery current should be left on with a polarity
to cause the tongue D to move toward pole b¹, so that armature I will be released
or repelled from the poles 6 and 61, as before explained, and, consequently, when
from any station a call is made for the central office none of the other instruments
in the circuit will be affected..
I will now describe that part of the Invention which relates to the prevention of
interruptions, or of overhearing of messages passing between two or more
subscribers at different stations.
In the telephone exchange apparatus in general use this is accomplished by
"grounding" the main line at each station when the telephone is taken from its
hook or lever for use; this is done either automatically or by hand, a lever adapted
to "ground" either the incoming or outgoing wire being moved to the proper
position; thus, when any two stations are using the line, a person at an inter-
mediate station will interrupt the conversation by innocently or maliciously lifting
the telephone from its supporting hook or lever. I avoid this source of trouble by
dispensing with the earth wire at sub stations, and by means of shunting and
locking apparatus at each station, cutting out every telephone that is not being
used.
At each station the telephone rests normally in the hook ✗¹ of the switch, the
telephone being then in a branch circuit, as shown. A subscriber desiring to call
the central office removes the telephone from its hook, and thus moves the switch
lever Qand the metallic springs fixed to it to a position indicated by the dotted
lines; the telephone is now in the main circuit, excluding the polarized relay
magnet, the circuit to which has been broken by the movement of the switch lever Q.
The subscriber next ascertains whether the line is in use, and if, upon
manipulating the key S', the telephone remains silent the line is being used, but
if the line is clear the telephone gives forth a sound at each movement of the key.
Central office locks or short circuits out all other stations but those
communicating.
The subscriber having communicated with the central office, and having been put
in communication with a subscriber at another station on the same or on another
circuit, the operator at the central office arranges to prevent any interruption by
other stations on the circuit now in use.
It has been already stated that previous to ringing the call bell at a station the
tongue D was caused to move towards the pole b¹, and force pin D² against disc E by
a reversal of this main line current, so that at all but the called station the pin D2
rested against the face of disc E, and at only the called stations did the tongue D¹
make a full movement and carry the pin D2 into the aperture e; therefore, before
proceeding to arrange the apparatus to prevent interruptions from uncalled stations
on the same circuits, it is necessary that the tongue D' should be returned to its

page_text: normal position, and thereby prevent the pin D³ from being carried into the
aperture e at the uncalled stations.
This is accomplished by the operator at the central office who reverses the main
line battery, which restores the current to its original polarity; thus the tongue D'
and with it the pin D2 is drawn towards pole b at all of the uncalled stations, and
at the called stations where the telephone is being used the tongue D' is not
withdrawn, as has been hereinbefore explained.
The projection fixed to sleeve F is in metallic connection with the plate G,
the said plate being in metallic connection with one terminal of the coils B, B, the
other terminal of said coils connecting with the outgoing main line 2.
The ribof the spring L and the bar or guard L¹ being in metallic connection
with the stud L³, said stud being in metallic connection with the incoming main
line, it follows that when the projection is in metallic contact with the rib l'a
new and short path is open for the main line current by wire 10, stud L², guard L¹,
spring L, projection 7, sleeve F, plate G, coils B, B, wire 2, to main line or ground.
The operator at the central office knowing the position of the projection 7 by
manipulating the key S, he will send the proper number of electrical impulses to
move the ratchet wheel H by a step by step movement, thus turning the sleeve F
until the rib and projection 7 are in contact at every station not using the
the telephone, thus making at these stations a short path for the main line current,
as herein before described, consequently the act of taking the telephone from
its hook, or the breaking of contact at key S will not interrupt the main line.
It will be understood that at the stations using the telephone the circuit leading
to the polarized relay which actuates the locking mechanism has been broken, as
has been hereinbefore explained, and that the currents sent over the main line for
the purpose of shunting the telephone out of circuit at stations not using it will not
energise the said polarized relay at stations which have been put into com-
munication; the pin D2 of the tongue D' will therefore remain in the apertures of
the discs at the communicating stations, and prevent said discs from turning to bring
projection of their sleeves F in contact with the ribs, which would shunt the
telephone out of circuit. The tongue D' and its pin D² thus lock the telephone
shunt, or, at least, its moveable part, which is the sleeve F, having this projection l,
which will be unlocked when the telephones are replaced upon their hooks, as will
be understood from the foregoing description.
When the subscribers have finished their communication the operator at the
central office restores the apparatus to its normal condition by sounding one or
more electrical impulses, thus causing the ratchet to move forward, whereupon.
contact between land l' is broken.
When the subscribers have finished using the line it is desirable to bring the
different apparatus to a common starting point. I accomplish this by means of a
unison stop, which I will now describe, referring particularly to Figure 7.
When the vibratory tongue D is in its normal position near the pole 6 the
vertical projection m³ of the arm M fixed to the said tongue is brought into the
path of the pin m once in a full revolution of the ratchet wheel H, the pin m and
projection m¹ are brought in contact, as shown in 1st position, and the movement
of the pin m then ceases. After the necessary number of electrical pulsations have
been sent from the central office to cause the pin m and projection m' to make
contact in the apparatus of all the stations, the operator reverses the direction of
the current, thus causing the tongue D to move towards the pole b¹; this move-
ment breaks contact between pin m and projection m³, after which the bevelled
edge of projection m² is brought against the oblique face of pin m, forcing said pin
aside and out of the path of m', as shown in 2nd position, when the operator
reverses the current, and the tongue D returns to its normal position, leaving the
pin and projections as shown in 3rd position. In lieu of the circuiting breaking key
at the central office I may use an ordinary transmitter similar to that used in con-
nection with a dial telegraph, having a circuit wheel turned by clock work or a

page_text: crank and suitable gearing, and an indicating pointer moving over a dial marked
with the numerals and the words "unison" and "cut out."
Figure 11 illustrates a modification of the Invention in connection with an
ordinary call system, dispensing with the shunting, locking, and unison mechanism.
The cores of the magnet B, B, have right angled soft iron prolongations b, b¹, with
a vibratory polarized. armature Y playing between said prolongations, the said
tongue being pivoted at its lower extremity to and in metallic connection with
the metallic plate G; this plate may be a permanent magnet. The extremity of
the vibratory tongue Y is provided with platina contact points y, y', which are
brought alternately in contact with the contact screws z, z¹, suitably mounted on
insulated standards Z, Z¹, as the tongue Y is vibrated between the poles b, b².
From the contact screw a wire 11 leads to the signal bell coils W, thence to the
segment R. The contact point z¹ is connected to the insulated contact spring Q¹
by line 12, the said spring being connected to the line 2. One terminal of the
coils B, B, is in metallic connection with the plate G. by wire 13, the other
terminal of said coils is connected to the line wire 1 by wire 14.
1
The operation is as follows:-As shown in the Drawing, the vibratory
armature Y is towards b, making contact at points y', ¹, thus making a short route
for the main line current by the way of wire 2, 12, vibrating tongue Y, plate G,
coils B, B, wire 14, to line 1, the call bell circuit being open as shown.
In its normal condition the vibratory tongue Y is toward the pole b, the
points y, z, being in contact; in this position of the tongue the call bell W is in the
main line circuit ready to respond to electrical impulses.
If, after putting two stations in communication, it is desired to prevent other
stations from overhearing or interrupting them the operator at the central office,
by reversing the direction of the main line current, causes the tongue Y to move
toward pole piece b' at all stations excepting at those using the line; the said tongue
now makes contact at points Y¹, Z', thereby making a short route for the main
line current outside of the bell and telephone.
The detached call bell W can be dispensed with by placing the gong over the
coils B, B, and fixing a second armature in front of the poles b, b', the lever of said
armature being prolonged, and having a hammer fixed to its extremity, and
adapted to ring the gong, as shown in dotted lines.
Any other electric apparatus may be used in connection with the shunting,
locking, and unison instruments, besides electrical bells where there are a series of
such apparatus in a circuit, and it is desired to operate them singly.
I claim,
First. In a series of telephones upon the same main circuit connected with a
central station, the combination with each of the telephones of a shunt or cut-out
operated by a current over the main circuit, and a locking device for each of said
shunts or cut-outs independently operated for locking by a current in one direction
over said main circuit, and for unlocking by a reversed current, whereby any
given number of telephones may be placed in communication, and all the other
telephones may be cut out of the circuit by an operator at the central station
except those at stations where the shunt or circuit is locked.
Second. The combination with the telephone and signal at each station of a
telephone shunt operated by a series of pulsations of the same polarity and shunt
lock and a signal shunt and shunt lock, operated independently of each other by
means of reversed currents, whereby the operator at the central station may call
any given station, and place it in communication with any other without actuating a
the signals of any but these two stations, and then shunt out of circuit the call
bell, telephone, and break key at the remaining stations.
Third. The combination with the vibratory tongue D, operated by reversals of
the main line current, of the unison stop controlled by said vibratory tongue, and
the call bell shunt, operated also by said tongue, and controlled by a current
over the main line, substantially as described.

page_text: Fourth. The combination with the vibratory tongue D, operated by reversals of
the current, of the unison devices controlled by said tongue, and the telephone
shunt and its operating devices controlled by a current over the main line,
substantially as described.
Fifth. The combination with a single polarized magnet of the vibratory tongue
armature, the unison devices, and call bell shunt controlled by said tongue, and
the telephone shunt and the devices operated by said magnet for actuating said
stop and telephone shunt, substantially as described.
Sixth. The combination with the telephone switch lever Q carrying the spring
arm Q, insulated therefrom, and the spring Q in electrical contact therewith, of
the metal segment R, having its ends so arranged that when the switch lever is
in its normal position one of said ends will be in contact with spring arm Q',
and the telephone switched out of the main circuit, and when the said lever is
swung outward the other end of said segment will be in contact with arm Q³,
and the telephone switched into the main circuit, substantially as described.
Seventh. The improvements in switches and apparatus for use upon telephono
lines, substantially as described and illustrated by the Drawings annexed.
In witness whereof, I, the said Sydney Pitt, have hereunto set my hand and
seal, this Sixteenth day of November, in the year of our Lord One thousand
eight hundred and eighty.
SYDNEY PITT. (L.S.)