IMPROVEMENTS IN TELEGRAPHIC AND TELEPHONIC APPARATUS
Year: 1884

page_text: PROVISIONAL SPECIFICATION.
We DANIEL SINCLAIR, Electrical Engineer and JOHN LORIMER CORBETT, Watch-
maker, both of Glasgow, in the County of Lanark, do hereby declare the naturo
of our said Invention for "IMPROVEMENTS IN TELEGRAPHIC AND TELEPHONIC
APPARATUS," to be as follows:-
This Invention is a further development of the improvements in telegraphic and
telephonic apparatus described in the Specifications of Letters Patent N° 3380,
dated 7 July 1883, and No 5964, dated 31 December 1883.
The leading features of improvement in the present invention as distinguished
from those above referred to, are the substitution of clockwork mechanism for the
electro-magnets and ratchet devices formerly employed to actuate the contact-
making devices of the branch exchange instrument, which is used to place in
communication any two subscribers on the telegraphic or telephonic system; and
the imparting of an oscillatory or a to-and-fro movement in lieu of a rotatory
movement to the contact-making disc or crown wheel, so that such device may be
arranged in the form either of a straight bar or of a ring. The construction and
arrangement of various parts of the branch exchange instrument described in the
specifications above alluded to, are also suitably modified and simplified as will
hereinafter appear.
In one modification of our present invention the subscribers' wires are each led
to separate indicators forming part of the branch exchange instrument, but which,
instead of being placed radially round a common axis, are fitted in a row or rows
in front of a reciprocating notched bar, which replaces the rotating crown wheel
described in the Specification of Letters Patent No 5964 of 1883. On the drops
of the indicators are fitted projecting arms, which, in the normal position of rest of
the reciprocating bar, extend over inclined notches formed in the bar; and when any
subscriber rings up the exchange, the projecting arm on the corresponding indicator
drop falls into the notch, makes contact with the notched bar which is electrically
connected to the central exchange, and the exchange operator is thereby called.
At the same time the current passes through the notched bar to the coils of an
electro magnet similar to one of the subscribers indicators, the armature of which,
is fitted with an escapement device arranged, as hereinafter described, to set
free clockwork mechanism, which acts on the notched bar and traverses it in ono

page_text: .
direction to such an extent that the projecting arm on the indicator drop of the
subscriber who has rung up the exchange is pressed into the inclined notch to
remain in electrical contact with the notched bar, while the remaining notches are
no longer directly under the arms on the remaining subscribers' drops, but these
drops now rest on or lie over small pieces of vulcanite, or other insulating material
fitted at the side of the notches, so that these subscribers are cut off from electrical
contact with the notched bar and cannot for the time being ring up the exchange
or each other. The notched bar is also connected by a lever or equivalent device
to a rod or bar on the opposite side of the indicators, this rod or bar being
connected to earth or serving as an earth wire for the subscribers' lines through
the indicators; and the traversing movement of the notched bar traversos this
earth rod to a slight extent, and brings under the contact springs of each of the
indicators a vulcanite piece on the rod, whereby the earth connection is cut off, and
the subscribers so cut off, being unable to ring their call bells, understand that the
central exchange is engaged.
The connection between the central exchange and each subscriber on the branch
exchange is made through a finger or pointer on a spindle coming into contact with
one of a series of springs to which the subscribers' wires aro connocted. This
spindle is connected to the notched bar by means of a spring which is kept out of
contact by an insulating piece fitted on the bar while tho bar is in its normal
position, but which on the shifting of the bar by any subscriber ringing up the
exchange, bears directly on the bar and serves to conduct the current through the
bar from the exchange to the subscriber or vice versa; or a like means of com-
munication may be established by fitting in proximity to the end of the notched
bar a spring in connection with the central exchange, but with which the notchod
bar only makes contact after it has been shifted by a subscriber ringing up the
exchange. The object in each case of so connecting the notched bar to the exchange
line is that the exchange operator in ringing up a subscriber may not send a current
through the electro-magnet acting on the escapement device which frees the clock-
work and thereby move the notched bar.
In addition to the series of springs connected to the subscribers wires is a spring
at a point in the path of the finger which is used as a zero point, and this spring is
connected to earth. When the finger on the spindle is in contact with the earth
spring, the electrical connection between the spindle and the notched bar is broken
by an insulating piece on the spindle which for the time being breaks the contact
with the spring connected to the notched bar. The spindle is rotated to such an
extent as to bring the finger in contact with the spring connected to any one of the
subscribers on the exchange, by means of clockwork and an escapement brought
into action by a rolay when a current is sent along the main wire (the spindle
being on a branch of the wire or connected to the central exchange by a
separate wire) or by means of electro-magnets and ratchet devices such as are
described in the Specifications of Letters Patent herein before referred to as appliod
for placing the central exchange in communication with any individual subscriber.
The finger or pointer is also employed to make a momentary contact between two
springs or a spring and a fixed metallic piece, and thereby to close the circuit
through a local battery and through the electro-magnet which acts on the escape-
ment device controlling the action of the clockwork employed for actuating the
notched bar; and when this electro magnet is thus momentarily brought into
action, the escapement device is attracted and releases the clockwork, so that it
again traverses the notched bar, but this time in the reverse direction, by which
means the arm on the subscriber's indicator drop is raised out of the inclined notch
into which it fell when the exchange was called, and all the notches are brought
immediately under the projecting arms on the indicator drops. This motion of the
notched bar is accompanied by a like motion of the earth rod, which on being
traversed brings every subscriber's line in connection with the earth wire, so that
any subscriber may ring, and the same cycle of operations be repented.

page_text: The clockwork employed is of ordinary construction and may be actuated by a
spring or weight. The function of the one set of clock work is simply to traverse
the notched bar, while that of the second clockwork mechanism is to operate the
spindle carrying the contact-making finger, the time and extent of action being
controlled by an escapement device in each case fitted on or connected to the
armature of an electro-magnet. This device, in the case of the first clockwork,
consists of a forked bar forming a continuation of the armature and embracing
between its forked end a disc or wheel of the clockwork mechanism, on which are
fitted two or more pairs of studs. The studs bear on the end of the forked bar,
which serves then to keep the clock work out of action; but when the armature is
attracted by reason of a current traversing the coils of the electro-magnet, the end
of the forked bar is moved out of the way of tho stud bearing on it for the time
being, and the disc is impelled round by the spring of the clock work. By the time
the next stud comes round, (when there are only two in the circumference of the
disc), the armature has been released and the forked end bars the way to further
notion of the clockwork; or if the action of the electro-magnet should not be
sufliciently rapid, the disc is stopped by the corresponding stud on its opposite face
coming in contact with the opposito prong of the forked bar. Rapidity of action
of the electro-magnet is however provided for by connecting its coils to the recip-
rocating notched bar from which it receives the current, through a spring bearing
on the bar, and by fitting a strip of insulating material on the bar in such a position
that, as soon as the traverse of the notched bar. begins, it brings the insulating strip
under the spring and cuts off the electrical connection with the coils of the electro-
magnet, so that the armature is only acted on momentarily. Any ordinary escape-
ment device may be used in lieu of that described, but the forin described has the
advantage that, by placing the studs or pins at unequal intervals round the disc of
the clockwork, the extent of traverso of the notched bar may be greater at one
movement than at the succeeding movement. By so arranging the escapement,
the notched bar is traversed in the one direction to such an extent only as will
remove the notches from under the arms on the subscribers' indicator drops, and at
the succeeding movement it is traversed to such an extent as to bring the arm
which is in the notch, quite out of it and over the bar, so that it may raise the
drop into the catch on its armature, and traversed partly back until the arins on
the indicator drops are fairly over the notches. The return movement of the
notched bar from the position which it assumes after a subscriber calls up the
exchange, is effected as already mentioned by the operator at the central exchange,
who sends as many currents as may be requisite to bring the pointer round to the
position in which it presses together or makes contact between the springs which
close the local battery circuit through the coils of the electro-magnet actuating the
escapement device, which releases the clockwork mechanism acting on the notched
bar. When, as is preferred, the contact-making pointer spindle is actuated by
clock work, such clockwork is put into action by an escapement which allows the
clockwork to turn the spindle only to the extent of bringing the pointer out of
contact with the spring connected to one subscriber's wire and into contact with
the next in succession. If there are ten subscribers on the branch exchange, there
will be ten springs ranged radially round the spindle, but the circle will be divided
into cloven spaces, one space being allowed for the zero point, which is represonted
by a spring to earth and by the contact-making springs which close the circuit
through the local battery and electro-magnet controlling the first set of clockwork.
The extent of motion of the contact-making pointer will then be one-eleventh part
of a revolution at a time, but the number of steps made by the pointer will be
determined by the number of currents or impulses transmitted by the operator at
the central exchange.
Instead of the notched reciprocating bar being made straight as described,
it may obviously be made bent in the form of a circular hoop, in which case
the subscribers' indicators will be ranged radially round it, and an oscillatory

page_text: motion in every respect similar to the reciprocating motion of the straight bar, will
be imparted to the circular bar by means of the clockwork.
In either form the apparatus described is as well adapted for use in transmitting
telegraphic messages as for telephonic work; but when employed in connection
with a number of telegraphic stations connected to a central station by a single
wire, as a means of communicating a message to an individual station while cutting
off the remaining stations, it will be unnecessary to provide the second clockwork
arrangement used in the case of a telephonic branch exchange.

page_text: COMPLETE SPECIFICATION.
We, DANIEL SINCLAIR, Electrical Engineer, and JOHN LORIMER CORBETT,
Watchmaker, both of Glasgow, in the county of Lanark, do hereby declare the
nature of our said Invention for "IMPROVEMENTS IN TELEGRAPHIC AND TELEPIIONIC
APPARATUS" and in what manner the same is to be performed to be particularly
described and ascertained in and by the following statement:-
This Invention is a further development of the improvements in telegraphic and
telephonic apparatus described in Specifications of Letters Patent No 3380, dated
7 July 1883, and No 5964, dated 31 December 1883.
The leading features of improvement in the present Invention as distinguished
from those above referred to, are the substitution of clockwork mechanism for the
electro-magnets and ratchet devices formerly employed to actuate the contact
making devices of the branch exchange instrument which is used to place in
communication any two subscribers on the telegraphic or telephonic system; and
the imparting of an oscillatory or a to-and-fro movement in lieu of a rotatory
movement to the contact making disc or crown wheel, so that such device may be
arranged in the form either of a straight bar or of a ring.
The construction and arrangement of various parts of the branch exchange
instrument, described in the Specifications above alluded to, are also suitably
modified and simplified as will hereinafter appear.
In one modification of our present Invention which is illustrated in elevation
and in plan in Figures 1 and 2 of the accompanying drawings, the subscribers
wires w are each led to separate indicators A forming part of the branch exchange
instrument, but which, instead of being placed radially round a central axis, are
fitted in a row or rows in front of a reciprocating notched bar B, which replaces
the rotating crown wheel described in the Specification of Letters Patent No 5964
of 1883. On the drops a of the indicators, are fitted projecting arms a', which in
the normal position of rest of the reciprocating bar B, extend over inclined
notches formed in the bar, and when any subscriber rings up the exchange, tho
projecting arm a' on the corresponding indicator drop a falls into the notch b,
makes contact with the notched bar B which is electrically connected to the central
exchange, and the exchange operator is thereby called. The connection between
the central exchange and the bar B is made through the trunk wire W, the coils of
a relay electro magnet R, the wire W¹, and the terminal and spring C bearing on
the bar B. At the same time the current passes through the notched bar B, by a
spring D and the wire W to the coils of an electro magnet E similar to one of the
subscribers indicators the armature E' of which is fitted with an escapement
device F arranged as hereinafter described to set free clockwork mechanism F
which acts through a lever G on the notched bar B and traverses it in ono
direction to such an extent that the projecting arm a' on the indicator drop a uf
the subscriber who has rung up the exchange is pressed into the inclined notch b to
remain in electrical contact with the notched bar B, while the remaining notches b
are no longer directly under the arms on the remaining subscribers' drops a, but
these drops now rest on or lie over small pieces b¹ of vulcanite or other insulating

page_text: material fitted at the side of the notches, so that these subscribers are cut off from
electrical contact with the notched bar and cannot for the time being ring up the
exchange or each other. The notched bar B is also connected by a lever Hor
equivalent device to a rod or bar I on the opposite side of the indicators A, this
rod or bar I being connected to earth by the wire W³, or serving as an earth wire
for the subscribers lines through the indicators; and the traversing movement of
the notched bar traverses this earth rod I to a slight extent and brings under the
contact springs A¹ of each of the indicators a vulcanite piece i on the rod I whereby
the earth connection is cut off, and the subscribers being unable to ring their call
bells, understand that the central exchange is engaged.
The connection between the central exchange and each subscriber on the branch
exchange is made through a finger or pointer ; on a spindle J coming into contact
with one of a series of springs K to which the subscribers wires ware connected.
The spindle J is rotated to such au extent as to bring the finger j in contact with
the spring K connected to any one of the subscribers on tho exchange by means of
clockwork M and an escapement M¹ operated directly by an electro-magnet M²
brought into action by the relay R when a current is sent along the main wire (tho
spindle being on a branch W of the wire or connected to the central exchange by
a separate wire) or by means of electro-magnets and ratchet devices such as are
described in the Specifications of Letters Patent hereinbefore referred to as applied
for placing the central exchange in communication with any individual subscriber.
The finger or pointer j is also employed to make a momentary contact between
two springs or a spring L and a fixed metallic piece L', and thereby to close the
circuit X through a local battery and through the electro-magnet E which acts on
the escapement device F controlling the action of the clockwork F employed for
actuating the notched bar B; and when this electro-magnet is thus momentarily
brought into action the escapement device F¹ is attracted and releases the
clockwork F so that it again traverses the notched bar, but this time in the
reverse direction, by which means the arm a¹ on the subscribers indicator drop a
is raised out of the inclined notch 6 into which it fell when the exchange was
called, and all the notches b are brought immediately under the projecting arms a¹.
of the indicator drops a. This motion of the notched bar B is accompanied by a
like motion of the earth rod I, which on being traversed brings every subscribers'
line w in connection with the earth wire so that any subscriber may ring and the
same cycle of operations be repeated.
The clockwork F and M employed is of ordinary construction and may be
actuated by a spring or weight. The function of the one set of clockwork F is
simply to traverse the notched bar, while that of the second clock work mechanism M
is to operate the spindle J carrying the contact making finger j, the time and
extent of action being controlled by an escapement device ( and M') in each case,
fitted on or connected to the armature of an electro-magnet. This device in the
case of the first clockwork consists of a forked bar F forming a continuation of
the armature E¹, and embracing between its forked end a disc or wheel F of the
clockwork mechanism on which are fitted two or more pairs of studs f. The
studs f bear on the end of the forked bar F¹ which serves then to keep the clock-
work out of action; but when the armature E¹ is attracted by reason of a current
traversing the coils of the electro-magnet E, the end of the forked bar F¹ is moved
out of the way of the stud f bearing on it for the time being and the disc is
impelled round by the spring of the clockwork. By the time the next stud f
comes round (when there are only two in the circumference of the disc) the
armature has been released and the forked end F¹ bars the way to further notion
of the clockwork, or if the action of the electro-magnet should not be sufficiently
rapid, the disc is stopped by a corresponding stud on its opposite face coming in
contact with the opposite prong of the forked bar. Any ordinary escapement
device may be used in lieu of that described, but the form described has the
advantage that by placing the studs or pins fat unequal intervals round the disc
of the clockwork, as shown, the extent of traverse of the notched bar may be.

page_text: greater at one movement than at the succeeding movement. By so arranging the
escapement F the notched bar B is traversed in the one direction to such an
extent only as will remove the notches from under the arms at the subscriber's
indicator drops, and at the succeeding movement it is traversed to such an extent
as to bring the arm a¹ which is in the notch b quite out of it and over the bar B
Bo that it may raise the drop a into the batch on its armature and be traversed
partly back until the arms a' on the indicator drops a are fairly over the
notches b.
The return movement of the notched bar, from the position which it assumes
after a subscriber calls up the exchange is effected, as already mentioned, by the.
operator at the central exchange who sends as many currents as may be requisito
to bring the pointer; round to the position in which it presses together or makes
contact between the springs L L' which close the local battery circuit X through
the coils of the electro-magnet E actuating the escapement device which releases
the clockwork mechanism Facting on the notched bar B. When it is preferred the
contact making pointer spindle J is actuated by clockwork, such clockwork M is
put into action by an escapement M' which allows the clock work to turn the
spindle only to the extent of bringing the pointer out of contact with the spring K
connected to one subscriber's wire and into contact with the next in succession.
If, as shown, there are six subscribers on the branch exchange there will be six
springs K ranged radially round the spindle J, but the circle will be divided into
seven spaces, one space being allowed for the zero point, which is represented by
the contact making springs L L which close the circuit X through the local
battery and electro-magnet E controlling the first set of clock work. The extent
of motion of the contact making pointer will then be one seventh part of the
revolution at a time, but the number of steps made by the pointer will be doter-
mined by the number of currents or impulses transmitted by the operator at tho
central exchange.
In the arrangement described, the mode of operating to effect communication
from the central exchange operator to any subscriber is as follows. The exchango
operator sends a battery current or other continuous current through the trunk
wire W through the coils of the relay electro-magnet R to the reciprocating bar B,
which is electrically connected by the spring D through the electro magnet E and
thence to earth. In its passage the current closes the armature R¹ of the relay,
and thereby closes the local buttery circuit X and effects by means of the clock-
work M one forward step of the pointer j, from zero to the first spring K connected
to.the subscribers wire w. At the same time by acting on the armature E¹ of the
electro magnet E the clock work F effects a movement of the reciprocating bar B,
cuts off the connection from the subscribers to earth and also the electro magnet E
acting on the clockwork F. The succeeding current sent by the exchange operator
passing through the relay R closes the local circuit as before to act on the pointer
spindle J, and finds its earth through the subscribers spring K and wire w with
which the pointer is in contact. Each succeeding current acts in like manner
until the pointer rests on the spring K of the subscriber wanted. The exchange
operator is then in direct communication with the subscriber.
When the con-
versation is at an end the exchange operator continues to send battery currents
until the pointer reaches zero. In making its last step to zero the pointer presses
the spring to make contact and closes the local battery circuit X through the
electro-magnet acting on the clockwork F and thereby moves the reciprocating bar
back to its normal position, when the subscribers will all be connected to earth,
and the exchange trunk line will find its earth through the relay R, bar B, spring D
and electro-magnet E.
Instead of the notched reciprocating bar being made straight as described, it may
obviously be made bent in the form of a circular hoop in which case the subscriber's
indicators will be ranged radially round it and an oscillatory motion in every
respect similar to the reciprocating motion of the straight bar will be imparted to
the circular bar by means of the clockwork.

page_text: In either form the apparatus described is as well adapted for use in transmitting
telegraphic messages as for telephonic work, but when employed.in connection with
a.number of telegraphic stations connected to a central station by a single wiro
as a means of communicating a messago to an individual station while cutting off
the remaining station it will be necessary to provide the second clockwork
arrangement used in the case of a telophonic branch oxchange.
Having now particularly described and ascertained the nature of our said
invention and in what manner the same is to be performed, wo declare that what
we claim is
First. The improvements in telegraphic and tolephonic apparatus substantially
as herein described.
Second. The improved automatic branch exchange instrument herein described
and illustrated.
Third. The arrangement in a branch exchange instrument of the reciprocating or
Oscillating notched bar B operated automatically for connecting and disconnecting
the central operator and the subscribers to the branch substantially as herein
described.
Fourth. The clockwork mechanism in combination with an electro magnet and
escapement arranged to impel the spindle (J) carrying the contact-making pointor
substantially as herein set forth.
Fifth. The clockwork mechanism in combination with an electro-magnet and
escapement arranged to operate the notched bar B through which communication
is made between the central exchange and the subscribers to the branch exchange
substantially as herein set forth.