Improvements in Automatic Electric Exchange.
Year: 1893

page_text: Date of Application, 8th June, 1893
Complete Specification Left, 8th Mar., 1894-Accepted, 8th June, 1894
PROVISIONAL SPECIFICATION.
Improvements in Automatic Electric Exchange.
I, ROBERT PIPPETTE of 31, Endymion Road, Brixton Hill, S.W. do hereby
declare the nature of this invention to be as follows:-
1. In Patent No. 16768, 1892, the adoption of moving connections and the use
of timers for effecting different operations in connection with automatic telephone
exchanges were described. In the present Specification I purpose describing their
application to electric exchange for any purpose, but especially with regard to
telephony. I shall describe a complete system of automatic electric telephone
exchange applicable to areas of any size.
2. To connect one point electrically with any one of several others, that is, by
conductors for the transmission of electric currents, it is usual to connect each
point by two or more conductors to a point called an exchange, where an attendant
is stationed to connect the various conductors as persons using the points require.
3. My invention briefly consists of apparatus by which a person at any one
point may, without the intervention of an attendant or operator at the exchange
cause the conductors of that point to be put into connection with the conductors
of any other point in connection with the exchange, so that electrical currents may
be transmitted from one to the other.
4. For this purpose each point is supplied with an apparatus for moving and
controlling by electricity a switching instrument in the exchange.
5. Each point is connected as usual to the exchange by two or more conductors.
6. One of these conductors may be replaced by the earth used in the common
manner as a return and it shall be considered as a conductor whatever its true
function may be. In the same manner wherever the earth is used in this Speci-
fication, a conductor insulated from it may be substituted.
7. The other conductor or conductors is or are the ordinary metallic conductors
such as linewires insulated in any ordinary manner from one another, and from the
earth between the point and the exchange, so that by using the earth the number
of wires required may be limited to one used for both controlling the switching
instrument and transmitting the required electric currents after the connection is
made.
8. The number of circuits to be obtained from any number of conductors 'using
N (N-1)
where N equals
any two at a time will be expressed by the formula 2
the number of conductors, including the earth if used.
9. The electric currents used for controlling and working the switching
instruments in the exchange, and for the general purposes of this invention, may
be derived from any convenient and suitable source and may be generated by
friction, chemical action, heat, magnetism, and induction from other currents; or
by any form of dynamic machine whereby energy is changed into electricity.
10. As before stated (3), the object of connecting the conductors of any two
points is for the transmission of electricity from one to the other. These currents
of electricity may be used for any purpose required. However generated, they
may be of anytension, quantity, and character; continuous or intermittent in either
direction, und ulating, varying in intensity and quantity, or both; alternating,
oscillating; or any combination, variation of combination and sequence of com-
bination, and variation of combination of these properties; except where they

page_text: would interfere with the working of the system. For the purpose of explaining
this invention, it will be supposed that the currents will be used for the purposes
of and for telephonic communication, but they may be used for any system of
telegraphic communication such as needle, Morse, A B C, sounder, type printing,
writing, automatic, bells, &c. or for the transmission of power, and for electric
lighting &r.
11. In the exchange, the wire or wires from each point pass to a switching
instrument special to and controlled by electricity from that point, by which a
person using that point can put his own wire or wires into connection with those
of any other point; and having finished his communication cause his own to be
disconnected from them and reset the switching instrument; and also at will to
cause another point's wires which may be in connection with his own to be
disconnected.
12. I shall first describe one modification according to this invention to present
a general view of its parts. Subsequently the other modifications will be explained
and more easily understood.
13. Each point connected by one linewire to the exchange. A magnet P M with
polarized armature permanently connected to the linewire.
In Fig. 1 is shown a diagram of the general connections at two points A and B,
and an exchange EX; the contacts denoted by the figures or numerals being
shown open.
14. Figs. 2 to 8 are contact diagrams of the circuits used in working this
modification for any one point and its switching instrument in the exchange.
This graphic method of showing the circuits and their changes will be used
throughout. The dots or small rings represent the contacts and parts of the
mechanism denoted by the numbers and letters above them. The lines joining
these rings represent conductors connecting the several parts.
The same letters or numerals refer to like parts of both A and B or any other
point.
15. Refer to point A, and the parts in the exchange in connection with it.
Fig. 1.
E represents the earth return, M, a magneto to supply a continuous current at
will in either direction according to the direction of rotation. Contact 2 is
normally in connection with contact 3, the rotation of M automatically places it in
contact with 1.
16. Instead of M and contact 1, M with a closed circuit may be placed between
the bell B L and contact 2. The circuit of the armature of M being opened on
rotation when the current will pass to line.
17. BL, a bell capable of being rung by a continuous current or intermittent
current in the same direction. The ringing current may pass through a magnet
whose armature closes a local battery circuit in which the bell is placed. Alter-
nating currents may be used for ringing the ordinary magneto bell.
In this case a
key will have to be provided at the point to put the ringing circuit in connection
with another collector on the magneto axle. T, represents in one letter, the
telephone, transmitter and battery, induction coils and contacts. 3 is normally in
contact with 2, the unhooking of the telephone will break this connection and make
it touch 4.
18. The above arrangement of the parts between contact 5 and the earth is not
essential to the invention and may consist of any telephone outfit, as long as some
adequate source of electricity is provided, whose direction can be changed at will
and also a bell, buzzer or other audible or visible signalling arrangement for
attracting attention, that can be actuated by the said current.
19. 7, a key contact normally kept by a spring in contact with 5, but may be
depressed and brought into contact with 6. Contacts 5. 6. and 7 really form the
three contacts of a Morse key, which may be used in their place.
BY, a battery of sufficient power to work the magnets of the switching
instrument S in the exchange. L, the linewire connecting A with E X.

page_text: 20. In the exchange, passes to the switching instruments, special to A.
It contains P M, an electro magnet with polarized armature, making and breaking
certain contacts, 8 with 9, and 12 with 13. 12 and 13 not shown in Fig. 1 are the
terminal contacts of the resetting circuit of the switching instrument S. In this
case PM is permanently connected with L (13).
SR M, an electro magnet working a relay closing and opening the local switching
circuit LSC of S. For LSC see ALSC and BLS C Fig. 35.
C, a moving contact special to A. There may be more than one.
BR, the contact bar special to A.
21. Point B, and every other point in connection with the exchange, is supplied
with similar parts as above described for A.
The office of S is to provide a means; under the control of a person at the point
to which it is allotted of putting the moving contact C of that point in connection
with the bar BR of any other point; through which connection, communication is
established between the two points, and of parting the connections and resetting S
when required.
22. Fig. 2 shows the permanent connections of the parts before mentioned.
Fig. 3 shows the contacts normally connected when point A is ready to receive a
call or to switch.
23. Switching, ringing, speaking, and resetting. Suppose point A wishes to speak
to point B whose number is for instance 316. By depressing key 7, A closes the
circuit shown in Fig. 4, thus sending a current from BY to the exchange called a
switching current, first three times, then once, and six times allowing
a small
interval of time to elapse between each group of currents. Then the switching
instrument S automatically makes the connections in the exchange shown in Fig. 5.
A's contact C is now in connection with B's bar B R, and A's bar BR is
earthed.
24. Either B's bar is earthed from a similar cause, or B is ready to receive a
call, and his connections are as shown for A in Fig. 3. If the latter, then a
current from A's magneto M, called a ringing current, in the same direction as the
switching current will pass from point A to B's instrument S whence it may partly
pass, through B's SRM to earth, and partly to B through PM. The current
through B's S R M may move B's S, but that through B's P M throws over its
armature, resets B's S if moved, and cuts SRM out of circuit with the earth
through contact 9. Then the whole of A's ringing current passes on to B ringing
his bell B L. This circuit is shown in Fig. 6. Fig. 7 shows the speaking circuit.
25. When finished, A disconnects the wire and resets S, by sending a current
called the resetting current in the opposite direction to the switching or ringing
currents from the magneto M, through the circuit shown in Fig. 6 to B. Because
this current is in the same direction as B's switching current, it throws the arma-
ture of B's P M back into its original position reestablishing contact 9.
Part of
the resetting current passes as before (24) through SRM to earth and moves B's
instrument S. At the same time, the armature of A's P M has been thrown over
joining contacts 12 and 13 of the resetting circuit, thus resetting
or use, the armature of P M being automatically thrown back
position. It only remains for B to reset his own instrument S.
sending his resetting current through his instrument. Both instruments and lines
are now in their normal condition, with contacts as shown in Fig. 3.
for another call
into its original
This is done by
26. Had B's bar BR been earthed when A rang through, A. would have
received no answer and would reset his instrument as described (25).
27. If another point, say B, sends his ringing current through A's bar, the same
changes take place in A's instrument S as described for B's instrument S when A
rang B up (24). In this case the ringing circuit shown in Fig. 8, is established.
28. The switching instruments. In Fig. 10. is shown the exchange switching
instrument. S. It contains all the parts special to any one point mounted on a base
plate BA so arranged, that the over-all thickness of the instrument shall be as
small as possible, say 1 incl.

page_text: 29. LT, the terminal to which the line L is connected; E T, the earth terminal.
BRT, the terminal to which the bar BR is connected; CT, the moving
contact C terminal, BT-BT 2, the two terminals of the battery BY 2 working
the local switching circuit. RT and RT 2, two terminals of the resetting
circuit.
Its armature ARM is
30. SRM is the switching relay electro magnet.
supported by the spring S P, insulated from SR M. The distance of AR M from
the poles of SRM is regulated by the set screw S C. ARM carries a
contact KT, which strikes against the contact KT2, and completes the local
switching circuit.
31. PM, an electro magnet, before shown in Fig. 1, with polarized armature ;
the poles PL and PL2 are placed between the poles of the polarized
armature A R M 2 as shown in Fig. 19.
32. The armature AR M 2 is made up of two permanent magnets M 2 and M 3
fixed on the axle AL by the screws SC2 SC3 entering the collar C L fixed on
the axle AL. Their opposite poles are opposed. PLN indicates the north pole,
and PLS the south pole of each magnet M 2 and M 3.
33. See Figs. 10 and 14. AL is carried by support SPT and the yoke Y K
of P M, and carries the arm A M and cross arm A M 2. The cross section of AL,
Fig. 15, will show that the arms are inclined to one another, so that they may be
nearer the bridges but not so much as to touch BRG 3 at the same time.
34. AL also carries the arm A. M 3 parallel to the centre line of A RM 2.
Upon A M 3 screws the adjustable weight W T, of such mass, that when it passes
the centre of A L to either side, it shall overbalance the turning moments of the
bridges BRG, BRG 2 and BRG 3 when opposed to it, and cause ARM 2 to
remain in the position it has been placed by PM. Thus when A R M 2 is turned
towards the base plate BA, AM will turn the bridge BR G3 in the same
direction; when inclined from BA, A M 2 will turn BRG and BRG 2 in a like
direction.
The normal position of AR M 2 is when it is turned or inclined towards BA, as
shown in Fig. 14. A current passing through PM. in the direction of the
switching current from B Y, will keep AR M in its normal position; a current in
the reverse direction, such as a resetting current or ringing current from B will
throw A R M over to the other side.
35. Riding loosely on A L, are three collars CL2 CL3 CL4. Two CL2
and CL3 are connected by the insulating bar BR 2. Through the latter pass
the bridges BRG and BKG 2. Collar CL4 with a similar insulating bar holds
bridge BRG 3. A M 4 and A M 5 are two arms fitted to BR 2 and CL 4
respectively.
36. BRG and BRG 2 are shown in Figs. 17 and 18.
BRG is fitted with the
needles N 9, N 8, N 11, and N 10, of which N 8 is the longest, N 11 next in length,
and N 9, N 10 the least; BRG 2 is fitted with the needles N 11 E just behind N 11,
and NE; N 11 E being the same length as N 8; NE like N 10.
37. BRG 3 is shown in Fig. 16 and is fitted with the needles N 12, N 13; of
which N 12 is the longer.
38. All the needles are placed over cups of the same number namely C 9, C 8, C' 11,
C 10, CE, C 12, C 13; N 11 and N 11 E dipping into the same cup C 11.
39. The details of the cups are shown in Fig. 22. The cup, say C8, is made of
some insulating material, or a metal with which mercury will not amalgamate., In
the bottom, is fitted a ferrule FL, with an internal screw. This screws on the
screw SC4 passing through the insulating shelf SH, and is fitted with two
clamping nuts NT and NT 2. The height of the cup can be adjusted by the
ferrule FL.
40. The cups contain mercury to the required level. The needles N 8, N 11 E, N 12
dip into their respective cups in all positions of the bridges. Through the weight
of their respective sides, the bridges BRG and BRG 2 tend to turn towards
cup C 8, and bridge B R G 3 towards cup C 13. With reference to the bridges B RG

page_text: and BRG 2, when in the lowest or first position turned towards cup C 8, all the
cups C 9, C8, C 11 are connected; when B R G and BRG 2 are turned a little
towards C 10 so as to come into the second position, C8 and C 11 are joined;
when BRG and BRG 2 are in the highest or third position, cups C8 and C 10 are
joined and C 11 is connected to C E. This is due to the lengths of the needles.
The same may be effected when the bridges have needles of equal lengths by
raising and lowering the level of the mercury in the cups.
41. Fig. 9 is a diagram showing how the cups are joined for each position of the
bridges, cups C 12. C 13. excepted. The firm line shows the cups joined in the
first position of the bridges; the lines with two and three dots between the dashes,
the cups joined in the second and third positions of the bridges respectively. The
centre dotted line shows the axle upon which the bridges turn.
42. Above the cups will be seen the arm A M 6. This can assume three
positions as shown in Figs. 20 aud 21, namely P1, P2, P3. A M 6 carries a
stirrup STP limiting the movement of A M 4. When A M 6 is in the first
position P1 bridge BRG 3 cannot be turned towards cup C 13 since the arm A. M 5
is kept back by A M 6. A M4 can move within the limits of the stirrup ST P.
Normally it will assume the position shown in Fig. 21, owing to the bridges BRG
and BRG 2 taking up their first position by reason of their tendency to turn
towards cup C8 (40).
43. If a current in the same direction as A's resetting current pass through P M
it will throw the armature AR M 2 over from its normal position and turn the
bridges BRG BRG 2 towards C 10 thus bringing them into the second position
that is with cups C 8 and C 11 only joined (40).
44. If through any cause the switching instrument S is moved, A M 6 will be
brought into the second position P 2, and the bridge BRG 3 is free to fall on the
arm A M of the axle A L. If A R M 2 be now turned from its normal position
as above described (43) A M will allow BRG 3 to join cups C 12 and C 13, closing
the resetting circuit, and A M 2 will turn BRG BRG 2 to take up their second
position as above. When the instrument S is reset A M 6 will be brought with a
jerk into its first position P 1, and the bridge BRG 3 striking the arm A M 2
would by its momentum carry AR M 2 back into its normal position, BRG,
BRG 2 at the same time falling back into their first position. This is what occurs
when S is reset after a conversation.
45. But suppose a ringing current to enter A's BR from some other point B as
before shown (27) part will pass through P M and part through SR M. The part
through P M would throw A R M 2 over and bring BRG and BRG into the
second position, cutting out S R M. The part through SRM may have moved
A's instrument S, when A M 6 will take up its second position P 2, and allow B RG3
to close the resetting circuit and reset S, and would finally jerk back the
armature A R M 2 into its nornial position as shown (44). This has taken up the
fraction of a second of time. B naturally rings for two or three seconds and
the whole of the current passing through PM to A will keep A R M 2 still
thrown, over, so that although AM 6 is now brought back into the first position P' 1,
AR M 2 will keep BRG and B RG2 in their second position.
46. Whenever the switching instrument S has brought A's moving contact C
into connection with required bar BR, it automatically moves A M 6 into the
third position P 3, the stirrup brings BRG and BRG 2 into their third position
(40), thus joining cups C8 and C10, the armature AR M 2 remaining in the
normal position..
47. When it is required to disconnect and reset S, A's resetting current being
contrary in direction to the switching current will throw AR M 2 over and join
cps.C12 and C 13 closing the resetting circuit. The arm A M 6 and the bridges
are brought back into the normal positions as described in paragraph 44.
48. A table to show at a glance the cups connected by each position of A RM 2
and A M 6. The lines joining the cups denote those connected.

page_text: Position of A M 6.
P 1.
A R M 2 in its normal
position.
C 12 C9—C8—C11
A R M 2 thrown over.
C12 C9 C8-C11
C 13
C 10 CE
C 13
C 10 CE
P 2.
C12 C9-C8-C11
C12 C9 C8-C11
C 13.
CIO CE
C13
C10 CE
P 3.
C 12 C9 C8 CII
C 13
C 13
C.12 C9 C8 C 11
CE
49. S M is the switching electro magnet in the local switching circuit. Its
armature AR M 3 is carried by spring S P 2. A RM 3 carries a fitting F.T.
The rod R D slides through two holes in F T and is kept in the position shown by
a spiral spring SP 3, the lower end bearing on FT, and the upper end against the
nut N T3. RD carries the movable hook H K. To HK, one end of the
cord CD is fastened, the other passing round the grooved wheel NL. On
the same axle is the toothed wheel T W held in position by the detent D T.
50. In connection with the moving hook HK the timer TR may be now
.described. When A RM 3 is attracted, the fitting FT strikes against the end of
the rod RD 2. To the other end of RD2 is fastened a cord CD 2 passing round
the axle AL 2. Passing round AL 2 in the opposite direction to CD2 is another
cord CD 3 fastened to the spring SP 4. Fixed on the axle A L 2 is an arm A. M 7
carrying a pallet PT mounted on a spring. At the back of AM 7 is a stud or
projection $T, engaging with grooved collar CL5, fastened on the rod RD 3.
The pallet PT 2 is mounted on a spring S P 5 fastened to the end of R D 3.
SP 5 has a step or bend near pallet PT 2. The escapement wheel E W rides
loosely on AL 2. The escapement ES engages with the teeth of E W.
adjustable pendulum P 4 regulates the time of the vibrations of E S.
The
51. On armature AR M3 being attracted by S M, the rod RD 2 is pushed
back, C D 2 turns the axle AL 2 in opposition to the spring S P 4.
At the same
time A M7 is turned. The stud S T at the back of AM 7 moves RD 3 with it
for a short distance retracting the pallet PT 2. When the step in S P 5 strikes
against the fitting FT 2, it raises PT 2 out of the way of T W. A M 7 continuing
to turn leaves the collar CL 5, and comes to rest at some point, and at the same
time the pallet PT slips over the teeth of EW.
52. The current ceasing in SM, AR M 3 springs back. SP4 gives up the
force stored in it and now turns AL 2 in the opposite direction. Pallet PT
engages with the teeth of E W and turns it and puts the escapement ES in motion.
This allows AL 2 to turn at a set rate. When A M7 reaches the collar C L5
it pushes it forward, and pallet PT 2 will engage with a tooth of T W and turn
it à distance of one tooth.
53. If A R M 3 remains inattracted until detent DT slip over the next tooth,
the hook H K will be lowered.
If it is attracted before PT 2 reaches T W, the hook H K will not be lowered.
Thus HK will not be lowered until a certain interval of time has elapsed since
ARM 3 was last attracted.
54. HK engages with three other hooks HK2 HK3 and HK 5 on the
levers LV, LV 2, LV 3. A view of the levers L V LV2 and LV 3 towards S M
is shown in Fig. 23 and the opposite side in Fig. 24.
55. Lever LV turns on pin P N, levers L V 2 LV 3 on pin P N 2.

page_text: 56. Lever L V is again shown in Fig. 26. Its parts are the hook H K 2, the-
detent DT2 and the arm A M 8 carrying a pallet PT3 on a spring S P 6.
Lever LV2 is again shown in Fig. 25. Its parts are the hooks H K 3, H K 4,.
and tail T L.
Lever LV 3 is again shown in Fig. 27. Its parts are the hook HK 5, the-
detent D T 3, and tail T L 2.
When at rest the three hooks H K 2, HK 3, H K 5 are in a straight line.
57. BR, BR are metal bars fixed to the body of the switchboard S B, and.
insulated from one another. Each BR is special to some point, and is connected
to the BRT of that particular point's switching instrument.
58. For cleaning, SB is made movable and is fitted with a metal tongue TG
at top and bottom, fitting in a metal groove GR, screwed to the frame.
rails FR.
59. The switchboards S B are made in convenient lengths to serve a convenient.
number of instruments, like bars of each group of switchboards being connected
in series or parallel.
60. There is any convenient number of bars BR on each board, and also on
both faces of a board. In this case, there are 100 bars on each face of each board,.
and as many boards as may be required. Two are shown in Fig. 10.
61. Parallel to the faces of bars and ixed by the ears R to FR, FR, are the
metal guides G, of the section and form shown in Fig. 28. All those guides on.
the faces of all the boards SB belonging to one switching instrument are
electrically connected in series or multiple branch to the terminal CT of that.
instrument.
62. Along these guides G slide the moving contacts C. Each consists of the
weight W T2, secured by the clips CP to the guides G, as shown in Fig. 28..
CS is the contact spring, screwed to WT2, and presses lightly on the faces of
the bars B R. The upper part of WT 2 is fitted with a ring R G, and adjustable.
coupling CP 2, containing an internal right and left handed screw. To R'G is..
fastened the cord CD4, for raising and lowering the contact C. Fig. 11 shows
the arrangement of the contacts of different points side by side on the faces of the
bars B R.
63. The cords CD are wound upon the reels R L. The reels R L have hollow
axles A L 3 revolving in the bearings B G.
64. On one end of each axle AL 3 is shown a disk D.
views of D. A portion of the edge of D is cut away at P 5.
Fig. 29 shows two
On the back of D.
is the spring S P7. The most important part of SP 7 is the projection P J raised
above the surface of D.
65. A L4 is a long axle passing through the hollow axles AL 3, supported on.
suitable bearings. Two of these bearings are shown at BG2 and BG 3..
AL4 is provided with the arms A M 9 revolving just in front of the disk D.
It.
66. Each reel RL tends to turn by reason of the contact weight WT 2.
is detained by lever L V 4 forced by the spiral spring S P 8 on the pin P N 3.
into P 5 of the disk D, and presses the spring S P 7 and its projection PJ back
to the face of the disk.
If LV 4 he moved out of P 5, R L will be turned by the weight W T 2 until
the PJ of the spring S P7 strikes the arm A M 9 of the axle A L 4, when the
further descent of contact C will be governed by the movement of AL 4.
67. A L 5 is an axle supported on suitable bearings B G4, BG 5, BG 6. The
escapement wheel E W 2 is fixed on one end of A L5 which carries a collar C L 6.
To CL 6 one end of the spiral spring SP 9 is fastened, the other end being.
fastened to B (4. AL 5 can move in two directions; lengthways and axially
both in opposition to the spring S P 9. On A L5 are the radial arms A. M 10
arranged at equal angular distances from one another, so that for each position
of AL 5, only one of the arms A M 10 will be opposite one of the levers L V 4.
68. E W 2 is turned one tooth at a time by the spring pallet PT3 of
lever LV, this against the spring S P 9, and is prevented from returning by the-

page_text: detent DT4. Having brought the required arm A M 10 opposite the required
lever LV 4, the lever LV 2 is pulled by HK. The hook HK4 draws Ę W 2
and the axle A L 5 lengthways, and the latter is prevented from returning by the
notch NH in detent DT 4. The other end of LV 4 is drawn out of the P 5 in
which it was. PJ is pushed forward by the spring S P 7, and the reel R L is free
to drop on the arm A M 9, which now carries the whole of the weight of the
contact C.
69. We now return to A L 4. It is fitted with a pilot reel PRL carrying
the pilot weight PW. In front of PRL is an escapement wheel E W 3, shown
in elevation in Fig. 30. One of its teeth is replaced by a pin P N 4.
70. Riding loosely on AL 4 between E W 3 and the bearing BG 2, is an
arm A M 11 carrying the escapement ES 2 shown in elevation and plan in Fig. 32.
ES2 has two pallets PT4 PT5 and vibrates on the centre screw SC 5. ST2 is
a stud by which the arm A M 11 is held by the escapement ES 3. AM 12 is an
arm by which the tail T L 2 of lever L V 3 lifts ES2 and allows one tooth at a
time to escape.
71. The bearing BG 2 carries the escapement ES 3, shown in elevation and
plan in Fig. 31. It vibrates on the axle A L 6 between the bearings BG7
and BG 8. Its two pallets are PT 6 and PT7, and it has an arm A M 13 by
which the tail T L of the lever L V 2 raises it, and allows the stud ST 2 to pass,
when axle A L4 and E W 3 will make a complete revolution carrying E S2 with
them.
72. The axle A L4 is square for the remainder of its length. On this part, the
grooved collar CL 7 slides carrying the bevel toothed wheel B W. This is pushed
backwards and forwards by the forked end of the spring SP 10. SP 10 is
A RM 4 is
attached to the armature ARM 4 of the winding magnet W M.
supported by the spring S P 11.
73. To reset the switching instrument, B W is brought into contact with B W 2
on the axle A L 7. BW 2 being turned, A L 4 raises the pilot weight P W and
the contact C used. The cord PCD of the pilot weight is provided with an
adjustable stop STP2. This is raised on the cord and strikes against the
fork FK of the resetting rod RD 4, and raises the lever L V 5 moving about the
pin P N 5. Various pins PN 6, P N 7 on LV 5 raise the detent DT releasing
the hook HK which returns to its first position, raises detent DT 4, and the
arm A M 14 to detent DT 2. The latter operation opens the resetting circuit and
replaces the bridges.
74. A L 7 runs by a given number of the switching instruments, carrying_a
bevel toothed wheel B W 2 for each. A L 7 is turned by the winding motor W M R,
set in motion by the starting electro magnet SM3 in series with W M and the
battery BY 3. SM 3 is only supposed to release or start the motor W MR,
which is worked by some other motive power such as steam gas electricity weights
or springs.
75. See Fig. 33. AL 8 is an axle turning in the
has the arms A M 14, A M 15 and A M 16. A M 16
connecting rod RD 5 to AM 17; A M 6 and A M 17
the short axle AL 9 so that A M 6 is governed by the
76. There are three stages in the movement of AL 8.
rests on detent DT 2, then A M 6 and STP are in the
and 21.
bearings B G 9, BG 10, and
is connected by pins and a
(see Fig. 21) are fixed on
movement of A M 14.
In the first position A M 14
first position P 1, Figs. 20
to the
77. On lever LV being pulled by hook HK, AM 14 drops on
detent DT 3 of lever LV 3 and AM 6 and STP come into their second
position P 2.
78. When lever LV 3 is pulled by hook H K, A M 14 drops down and AM 15
rests on the spring S P 5 of the timer as SP5 moves to the right A M 15 escapes
and drops allowing A M6 and STP to reach their third position P3. On
resetting the instrument S, the lever L V 5 raises A M 14 again to detent DT 2. (73).
79. Now I will describe the use of the instrument. In Fig. 34 is shown a

page_text: diagram of the contacts and circuits for any two points A and B. The
batteries BY 2 and B Y 3 and the magnet S M 3 being used in common by all the
switching instruments. The contacts are shown open.
80. Upon inspection of Fig. 34 and contact diagram Fig. 35, A and B's local
switching circuits ALSC and BLSC are seen to comprise KT, BT, BY 2,
BT 2, SM, and KT2, and that A and B's local resetting circuits ARC
and BRC comprise C 12, RT, SM 3, BY 3, RT 2, W M and C 13. With the
exception of BY 2, BY 3 and S M 3, these parts denoted by the letters included
by the lines AS and B S belong to A and B's switching instruments respectively.
81. Fig. 35 shows the permanent connections of the various parts from A's earth
to B's earth. Fig. 36 shows the normal connections when A and B are set to
r.ceive a call or to switch.
82. As before (23) I will suppose that A wishes to speak to B whose number
is 316. Taking key 7 A presses it three times. Each time a current is sent
from BY through the switching circuit shown in Fig. 37 and the magnets P M
and S R M are excited. The armature ARM 2 of PM remains in its normal
position and keeps the bridges BRG BRG 2 and B RG3 in the first position,
and the armature AR M of S R M completes the local switching circuit ALSC
by which magnet S M is excited, and armature AR M 3 attracted. Hook H K
pulls lever LV which first drops A M 14 on the detent DT3, thus bringing A. M 6
into the second position P 2, and turns the escapement wheel EW 2 three teeth by
pallet PT 3. This brings the third arm A M 10 opposite the end of the third
lever L V 4 of the third reel R L. At the same time the armature A R M 3 has
moved the timer T R as described in Section 51.
83. After these three currents have passed a small interval of time is allowed to
elapse when the pallet PT 2 of the timer T R will lower the hook H K from HK 2
to HK 3.
84. On pressing key 7 again once, the same circuits are completed and H K pulls
lever LV 2. This first draws axle A L 5 forward, and the third arm AM 10
raises the third lever L V 4 from the disk D of the third reel R L, and allows the
spring SP7 to push the projection PJ forward; RL being free, turns by the
weight W T 2 and rests on the third arm A M 9 of axle A L 4. At the same time
the tail TL of lever LV 2 raises the escapement E S3, and allows the stud ST 2
to pass, thus letting ES2, EW 3 and the axle AL4 to make a complete
revolution and the third contact C is lowered a distance equal to ten bars but does
not reach the bars.
Every time key 7 is pressed C is lowered a distance equal to ten bars, and had
it been pressed three times C would have reached the twentieth bar.
As before hook H K is lowered down to hook H K 5 by TR.
85. On pressing key 7 again 6 times the before mentioned circuits are closed and
lever LV3 is pulled. This first drops the arm A M 14 from detent DT2,
and AM 15 rests on the end of the spring S P 5. At the same time the tail TL 2
raises escapement ES 26 times, each time allowing one tooth of the wheel E W 3
to pass, so that contact C is lowered six bars. The contact C is now in connection
with bar No. 316.
86. On the last return of S P 5 of the timer TR, the arm A M 15 escapes and
drops, thus bringing A M 6 and STP into the third position P 3. The latter
throws the bridges BRG and BRG2 over into the third position, which
join C 8 to C 10 and C 11 to CE thus joining L to C and earthing A's B R.
This state of the connection is shown in Fig. 38.
87. A then turns his magneto M so that his ringing current is in the same
direction as his switching current. This will pass through the circuit shown in
Fig. 39. It passes through A's magnet PM, partly through B's magnet P M, and
partly through B's SRM to earth. This current, being contrary in direction
to B's switching current, will cause B's_arinature A R M 2 to be thrown over
thus bringing B's bridges BRG and B RG2 into the second position cutting
B

page_text: out the SRM. The current through B's SR M closed B's local switching
circuit BLS C, and moved B's lever LV, therefore B's A M 6 will fall into
the second position P 2, release the B's bridge BRG 3, and from the position
of the armature A R M 2 close B's resetting circuit B R C.
88. This will reset B's instrument S, and would throw B's AR M 2 back into
its original position through the momentum of the bridge BRG3 when jerked
back by B's AM 6. All this has taken place in the fraction of a second of time;
and A, still ringing, will be passing current through B's magnet PM when the
resetting circuit is opened, and this keeps ARM2 thrown over and the
bridges BRG and BRG 2 in the second position while the current now passes
through L to point B and rings the bell B L as shown in Fig. 40.
89. A and B now speak through the circuit shown in Fig. 41.
90. To disconnect and reset, A reverses the motion of his magneto M, and
sending a resetting current through the circuit shown in Fig. 42, throws over
both A's AR M 2 and B's AR M 2. In A's case, it will join the cups C 12
and C 13 and close the resetting circuit A RC. In B's case, it will throw
back B's AR M 2 into the normal position and join C 9 to C 8, when part of
A's resetting current passing through B's SRM will move lever LV and
free A M 6 as shown in Fig. 43. B is shown as depressing his key 7 to
help A's resetting operation. B might have used his magneto M in the same way.
91. It now remains for B to reset his own instrument, which is done by sending
a resetting current. This is shown in Fig. 44 and finally both instruments resume
their normal state shewn in Fig. 35.
92. It will be noticed that when B was rung up by A, A's ringing current is in
the same direction as B's resetting current; and vice versa, A's resetting current is
in the same direction as B's switching and ringing current. If they leave their
instruments connected and A wanted to ring up B, A would ring in the usual
manner; while if B wanted to ring A up, he would send his resetting current
through, and if he wants to disconnect from A he will send his switching current
through, after which he will have to reset his own instrument as above described.
93. In the foregoing system, it will be noticed that C is not joined to L until
the switching operations are finished. C may be joined to L during switching, but
part of the switching current would be shunted through the bars it passed over and
derange the existing connection.
94. Each point connected by one linewire to the exchange. An electro magnet
with polarized armature permanently connected to the linewire, and a guard magnet
in either or both contact C or BR circuits.
The switching instrument S and connections being as shown in Fig. 36, a resetting
current passed through the switching circuit from A would generally move the
instrument S and throw AR M 2 over, which would reset the instrument (44).
But if from some cause the instrument S were not moved, AR M 2 would still
be thrown over and bring the bridges BRG and BRG2 into the second
position, disconnecting contact 9 from contact 8. There being no circuit
through B R, A cannot move his instrument until A R M 2 is replaced.
95. To prevent this occurring, I put an electro magnet M 4, Fig. 1, into the
bar circuit. Its armature governs a detent normally keeping the bridges BRG
and BR G2 in the first position, and will not raise it unless a current passes
to or from BR. Therefore A cannot move the bridges unless his instrument
is moved, or a circuit is formed through the bar. This will not interfere with the
bridges BRG and BRG 2 being brought into the third position, as the detent
would be automatically raised by the arm A M 6. Such a magnet I call a guard
magnet.
96. In a similar way, an electro magnet may be put in the contact C circuit, its
armature governing the contact of an earth shunt between this magnet and
contact 10. If a circuit can be completed through C, the earth shunt is broken
by the current passing through the magnet; but if no current passes through C,

page_text: a resetting current may be passed through the earth shunt, and close the local
resetting circuit. The resistance of the earth shunt will be altered to suit
circumstances.
These guard magnets may be applied to any of the systems of connections,
where no other safeguards are supplied against incomplete circuits and bad
contacts.
97. Each subpoint connected by one linewire to the exchange. A magnet with
polarized armature common to both the C and BR circuits, that is, it is put in
circuit with C or B R as required.
Fig. 45 shows an arrangement of the one linewire system shown in Fig. 1, in
which the magnet PM (31) is taken out of the switching circuit, and only
introduced into the C or BR circuits as required. Fig. 46, the permanent
connections. Fig. 47, the normal contacts when at rest. Fig. 48, the switching
circuit. When contact C has reached the required bar BK, the switching
instrument S automatically arranges the connections as shown in Fig. 49. PM is
now in the C circuit. The ringing circuit is shown in Fig. 50 and the speaking
circuit in Fig. 51. To disconnect and reset, a resetting current is passed through
the ringing circuit Fig. 50, P M reverses its armature and joins contacts 13 and 14
completing the local resetting circuit, after which the connections are replaced in
their normal state as shown in Fig. 47.
98. The ringing current from the bar will pass to earth through P M, Fig. 47.
P M will throw its armature over disconnecting 11 from E, 8 from 9 and
connecting 8 to 11; the current will then pass to A's bell as shown in Fig. 52.
Fig. 53 is a diagram of the cup connections for each position of the bridges here
shown. Five bridges are used, fixed on one bar similar to B R 2 (35). Cups 13
and 14 are the poles of the local resetting circuit.
By the introduction of another cup CC, the contact C may be connected
to PM after the switching is completed instead of being permanently joined as
shown.
99. In Fig. 54 is shown another method of accomplishing the same purpose as
that shown in Fig. 45. Fig. 55 shows the permanent connections. Fig. 56, the
Fig. 58 the
normal connections when at rest, Fig. 57 the switching circuit.
connections made by the switching instrument after switching. Fig. 59, the ringing
circuit. Fig. 60, the speaking circuit. Fig. 61, the ringing circuit when another
point B rings through A's bar. Fig. 62, the diagram of cups showing those
connected for three positions of the bridges there shown. C 14 and C 15 are the
local resetting circuit contacts.
100. Each point joined by one linewire to the exchange. Two magnets with
polarized armatures, one in the C circuit and the other in the BR circuit.
In Fig. 63 is shown a one linewire system with a magnet P M in both contacts C
and BK circuits namely CPM and BRP M. Fig. 64 shows the permanent
Fig. 66, the
connections. Fig. 65 shows the normal contacts when at rest.
switching circuit. After switching, the switching instrument makes the connections
shown in Fig. 67. CPM only controls the resetting circuit, that is joins the two
contacts 13 and 14. The ringing circuit is shown in Fig. 68, the current does not
alter the armature of CP M. The speaking circuit is shown in Fig. 69. To
disconnect and reset, the resetting current is passed through the ringing circuit
Fig. 68, throws over the armature CP M, and closes the resetting circuit, which
brings all the parts back into their original positions.
101. A ringing current from A's bar BR will pass first through BR PM to
Its armature being
earth. This magnet controls the contacts 8, 9, 11 and 12.
thrown over, will disconnect 11 and 12, and 8 and 9, and join 8 and 11. After this,
the current passes on to A and rings his bell as shown in Fig. 70.
102. Fig. 71 shows the cups. C 12, C11, C 8 and C 8 A. having bridges controlled
by BRP M. C8 A, C 10, and C9 having bridges controlled by the switching
instrument. C 13 and C 14 are controlled by CP M. These bridges have only
two positions to move between.

page_text: 103. In Fig. 72 is shown the bridges controlled by BRP M and the switching
instrument compounded on one axle, and have to take up three positions. First,
the normal one at rest; the second by the magnet BRPM; and the third by the
switching instrument. Magnet C P M as before controls contacts 13 and 14.
104. Each point connected by one linewire to the exchange. An electro magnet
with polarized armature and a shunt magnet with polarized armature, both used in
common in the C and BR circuits.
The use of a guard magnet with or without a shunt to earth was mentioned in
paragraphs 94, 95 and 96. An extended use of the same method inserting in the
earth shunt a magnet with polarized armature will now be described.
105. Fig. 73 shows the general connections of a one linewire system wherein the
series P M and the shunt S P M are used, connected to the C or BR circuits as
required. Fig. 74 shows the permanent connections. Fig. 75, the normal
connections when at rest. Fig. 76, the switching circuit. After switching, the
switching instrument S makes the connections shown in Fig. 77. In Fig. 78 is
shown the ringing circuit. When the ringing current reaches contact 10, two paths
are open to it, one through SPM which controls contacts 8 and 12, and 14 and 15
of the resetting circuit; and the other through P M which controls contacts 13
and E to the other point.
Should any part of the current pass through P M, it throws the armature of PM
over and disconnects 13 and E when all the current will pass on to B. The
speaking circuit is shown in Fig. 79.
To disconnect and reset, the resetting current is passed from A to B, throws
back the armature of PM, again closing contacts 13 and E. The current now
passing through SPM throws its armature over and closes contacts 14 and 15 of
the resetting circuit, which brings all their parts into their normal position.
106. When a ringing current from some other point enters A's bar it passes to
earth through S P M, throws its armature over and joins contacts 8 and 12, there-
upon another path is opened through P M to A. The portion of current passing
through PM will throw its armature over as before, and disconnect 13 and E, when
the whole current passes to A and rings his bell. This circuit is shown in Fig. 80.
B's resetting current reverses this motion.
107. Fig. 81 shows the contact cups. The connections between cups C 14
and C 15, C 8 and C8A and C 12 are controlled by the magnet SP M. Those
between C8A C9 and C 10, and C 11 and C 10 are controlled by the switching
instrument S, that between C 13 and CE by magnet PM.
108. Each point connected by one linewire to the exchange. An electro magnet
with polarized armature common to both C and B R circuits with separate shunt
electro magnet with polarized armature for each.
Fig. 82 shows how the last system may be used with a common series PM
with shunt magnet CS PM for the C circuit and shunt magnet BRSPM for the
bar BR circuit. Fig. 83 shows the permanent connections. Fig. 84, the normal
connections when at rest. Fig. 85, the switching circuit. Fig. 86 shows the
connections made by the switching instrument S after switching. Fig. 87, the
ringing circuit. Fig. 88, the speaking circuit.
109. Fig. 89 shows the ringing circuit when A is rung up from the bar BR.
P M controls contacts 13 and 14 with E, CSPM and BRSPM control
contacts 15 and 16 of the local resetting circuit, while in addition BRSPM
controls contacts 8, 9, and 12. The switching instrument controls contacts 8, 9,
10, and 11.
110. Each point connected by one linewire to the exchange. Separate electro
magnets with polarized armatures in each of the C and BR circuits, and one
shunt electro magnet with polarized armature common to both.
Fig. 90 shows the general connections when the system shown in Fig. 73 is used
with a common shunt magnet SP M, with separate series magnets CPM and
BRPM used in the C and B R circuits. Fig. 91 shows the permanent connections.
Fig. 92, the normal connections when at rest. Fig. 93, the switching circuit.

page_text: Fig. 94, the connections na:le by the switching instrument after switching. Fig. 95,-
the ringing circuit. Fig. 96, the speaking circuit.
111. Fig. 97, the ringing circuit when A is rung up from the bar. SPM controls.
contacts 14 and 15 of the local resetting circuit, and also the connections between 8.
and 9 and 12; the switching instrument S controls the contacts between 10 and 13,.
8 and 10 and 8 and 9, and CPM and B RPM the contacts 11 and E.
112. Each point connected by one linewire to the exchange. A separate electro.
magnet with polarized armature and separate shunt electro magnet with polarized
armature in each of the C and B R circuits.
Fig. 98 shows the general connections of the system shown in Fig. 73 when used
with a separate series and shunt magnets for both the C and B R circuits, namely
CPM the series and C S P M the shunt for the C circuit, and B R P M the series.
and BRSP M the shunt for the B R circuit.
Fig. 99 shows the permanent connections. Fig. 100 shows the norinal connections.
when at rest. Fig. 101, the switching circuit. Fig. 102 shows the connections.
made by the switching instrument after switching.
Fig. 13 shows the ringing circuit. Fig. 104, the speaking circuit. Fig. 105,
the ringing circuit when A is rung up from the bar.
113. C P M and BRPM control the contacts 11, 13 and E; the switching
instrument the contacts 8, 9, 10; CSP M, the contacts 14 and 15 of the local
resetting circuit; and BRS P M the contacts 14 and 15 and 8 and 12.
114. In Fig. 116 is shown the system shown in Fig. 1, with a complete metallic-
circuit through the linewires L and L 1, for which double bars B R and double
contacts C are used. Such a return may be used in all cases instead of the earth.
return. That shown in Fig. 116 is special to each point and necessitates double
bars and contacts, but if the return wire be a conductor or linewire insulated from.
the earth and running from the exchange in series through or branched to each
point in the most convenient manner single bars and contacts may still be used,.
the returns being made through this common return wire instead of the earth.
115. By means of the formula in paragraph 8, we may form two more circuits.
between the exchange and each point, in which two keys K 2 and K 3 may be
introduced, two magnets for any purpose required, for example two switching relay
magnets SRM 2 and S R M 3 both worked by the battery BY 4. SRM 2
and S R M 3 would be disconnected when speaking or ringing. K 2 and K 3 would
break the circuit through 7 when pressed.
116. Batteries at the exchange. The switching circuit has hitherto involved the
use of a battery at each point. It would be better at the exchange since one would
supply a large number of points. This can be applied to any system by the-
addition of an electro magnet to each switching instrument.
117. In Fig. 106 we have a general view of the system shown in Fig. 1 so fitted..
At the point is a key to close contacts 5 and 6. In the instrument S, an extra
contact 14 in connection with magnet M 5 and the earth. SR M is connected to a
battery BY and to earth.
Fig. 107 shows the permanent connections. Fig. 108 shows the normal con-
nections when at rest. To switch a current is sent from the magneto M through
the circuit shown in Fig. 109, that is, through the magnet M 5 and thence to earth.
This magnet disconnects from 14 and connects it to 9. All connection with
the earth is automatically broken at the point A and by pressing the key at 6
the switching circuit shown in Fig. 110 is formed and the contact C is placed on the
required bar as usual. After this the switching instrument makes the connections
shown in Fig. 111. Fig. 112 shows the ringing circuit. Fig. 113, the speaking
circuit. Disconnecting and resetting are performed in the usual manner and 8 is
again connected to 14 as shown in Fig. 108.
118. The ringing current from the bar passing through PM disconnects 8 from 14
and 9 as before described (45), leaving the only connection through 8 and 11. The
ringing circuit is shown in Fig. 114.
119. Branched battery wire. The next method of using a battery at the exchange

page_text: :
is to connect one pole to the switching relay magnets S R M of all the points, and
taking the other to every point in series or in multiple arc or branched like a tree.
This as an example is shown applied to the system described in Fig. 1 by Fig. 115.
This does not alter the method of using the switching instrument.
120. S R M with polarized armature. In the system shown in Fig. 1, the
magnet PM is always in circuit, in many others, the only magnet in the switching
circuit is the SRM. This, not having a polarized armature is affected in the same
way by both positive and negative currents, and the whole course of switching
operations would have to be gone through before the instrument can be reset.
To obviate this, I give SRM a polarized armature, so that it has two movements
similar to those of P M according to the currents passing. The switching current
passing through S R M would close the local switching circuit through one contact
of the polarized armature, and the resetting current close the local resetting circuit
through the other contact.
121. The same may be done by using an armature like that of P M in conjunction
with the armature of SR M, when the resetting current passes through the S R M it
will attract its armature ARM as usual and throw over the polarized armature
and close the local resetting circuit.
122. Each subpoint connected by one linewire to the exchange; a timer moving
a contact changer.
In Fig. 1, the motion of the magnet S M is transmitted to various parts of the
switching instrument of a timer working a book changer. There may be a magnet
similar to S M for each operation working a common timer, which by moving a
contact changer after each group of switching currents may bring the magnets SM
into the local switching circuit in order. The other arrangements of any system of
connections need not be altered.
123. Each subpoint connected by one linewire to the exchange. A magnet with
polarized armature vibrating between two contacts one for switching and the other
for moving a hook or other movable connection.
In Fig. 1 let BY be connected to a pole changer at 7 and the line L normally
connected to magnet PM and thence to earth. Let P M have a polarized
armature normally midway between two contacts. When a positive switching
current is passed through PM the movement of its armature closes the local
switching circuit. When a negative current passes, its armature is reversed and
closes a local circuit in which is a magnet that moves a hook on the armature of
the switching magnet S M. The connections of C and BR circuits being made
in the manner shown in the system, Fig. 1.
124. The hook changer may also be worked through a separate linewire.
125. Each point connected by two linewires to the exchange, one for switching
and the other for speaking.
In Fig. 117 is shown a system with two linewires SL and L connecting each
point with the exchange. One S L is used for switching and the other L for
speaking. Fig. 118 shows the permanent connections. Fig 119 shows the normal
connections when at rest. On pressing the key and connecting 5 and 6 the
switching circuit is completed as shown in Fig. 120. This being done the required
number of times, with the usual interval between the groups of currents, contact C
is in connection with the required bar BR. At the same time the bar BR is
disconnected from L. This state of the contacts is shown in Fig. 121. Then the
ordinary ringing and speaking will take place through L as shown in Figs. 122
and 123. To disconnect the key at 6 is again pressed and the switching
instrument S closes the resetting circuit by contacts 9 and 10.
126. In this case the switching instrument S is like that shown in Fig. 10
without the magnet P M or cups and magnet W M. It has an extra lever L V 6,
and the hook HK takes up four positions. When the resetting current is sent,
this lever LV 6 is pulled and closes the local resetting circuit and brings B W into
contact with B W 2, being held by a detent until the instrument is reset and restored
to the condition shown in Fig. 119.

page_text: 127. Two or more points on one linewire. Fig. 125.
A conductor L passes
through the points A B C and E X, in each through a magnet M. The earth may
form part of L between any points. Each station is fitted like A with a key K
and battery BY capable of properly working the magnets M of all the points.
Normally the circuit is completed through the magnets M and the keys K. On
pressing K, BY is brought into circuit and all the magnets M are excited.
128. Fig. 126. Each point ABC is fitted with M K and B Y like A. At EX the
line passes through M 2 a magnet whose armature is so adjusted that a current from
the battery BY at any point will cause contact 1 to leave contact 3 which it
normally touches and touch contact 2 thus bringing the battery BY 2 into circuit.
BY 2 is capable of working all the magnets M, M in circuit. If the currents
from BY 2 be switching currents the ringing and speaking currents must be such
that they will not affect the armature of M 2, that is alternating.
129. M 2 may have a polarized armature which will be attracted by the switching
currents, while the ringing currents being in the opposite direction will not affect
contacts 1 and 3.
130. It may be desired to use the B Y of each point for further switching without
having to change its poles. Therefore (Fig. 127) a magnet M is put preferably in
tbe BY 2 circuit; its armature carries a moving hook and is fitted with a timer.
L normally passes through contact 3 and magnet M 2. On pressing K a current
from BY passes through M 2 and makes contact between 1 and 2. M attracts its
armature and the timer keeps 1 in contact with 2 until the last current has passed.
After a short interval of time, the timer returns and makes contact 1 touch
contact 4 and also moves the hook. The armature of P M being polarized is not
affected by a current from BY, so the latter can be used for further switching.
A resetting current passing through P M in the opposite direction will throw its
armature over making 1 touch 4 when the current of B Y 2 passing through M and
all the other magnets M resets their hooks and switching instruments and causes 1 to
touch 3 as before.
131. Fig. 128. A conductor L passes through several points A B C and in each
through a magnet M. At any one point EX, L is connected by a battery BY 2
to another conductor in this case the earth. At the points are the keys K, K, by
which those points can be connected to the other conductor or the earth, thus
joining the poles of BY 2. When any K is depressed the circuit of BY 2 is
completed through the two portions of L on each side of the key K and BY 2.
The resistances of these sides will be equal if K be in one certain place and the
current in both parts of L will be supposed to be strong enough to work the
magnets M in each half.
The chances are that the resistances will differ the current in one side being
stronger than in the other and the more so as K nears BY 2. At A, B Y 2 would
be practically short circuited and none of the magnets be operated.
132. This may be corrected for any one point by putting resistances permanently
in the circuit. This will only make it worse for the other points. It will be
necessary to put a given resistance into circuit when any K is pressed and remove
it again as shown in Fig. 129. R is a resistance determined for each point,
normally short circuited by the contacts 17 and 18, which are opened on
depressing K.
133. Another method is to introduce more batteries at different points between
L and the earth, one at each point A B C and E X if necessary, so that the
least current that will pass through any magnet M shall be of sufficient strength to
operate it.
134. Another way of securing the same end is shown in Fig. 130. The same
letters apply to the same parts as in Fig. 128. M 2 is a magnet in the BY 2 circuit.
When attracted its armature causes 1 to leave 3 and touch 2 thus bringing into
circuit the battery BY 3. Normally 1 is in contact with 3. Each time the K at
any point is depressed the circuit of battery B Y 2 is completed and M 2 completes
the circuit of battery BY 3.

page_text: 135. It may be said that when any K is touched that most of the current
from BY 3 will pass through the path of least resistance. This will perhaps occur
when K is nearer the exchange than the others. It will be seen that before BY 2 is
cut out of circuit the armature of M 2 must rise, and to allow which the key K must
also be raised and break the BY 2 circuit. During the interval of the raising of
key K and the raising of the armature the current of B Y 3 will pass through the
whole circuit and properly actuate all the M's.
136. A flexible spring contact similar to that shown in Fig. 131 may be attached
to the armature of M 2 to keep 1 and 2 in contact for a little while after the
BY 2 circuit is broken. Fig. 131 shows the armature of M2 in two positions
when at rest and when attracted. A timer may be used with M 2 for the same
purpose.
137. One battery BY 3 may be used for both the batteries BY 2 and BY 3.
In Fig. 132, normally 1 touches 3 and 2 touches E. A key K being pressed the
.armature of M 2 breaks the above connections and causes 1 to touch 2.
138. To prevent an insufficient current passing through the circuit L,
BY 2 Fig. 130 may be made to balance BY 3.
139. Refer to Fig. 133. The two batteries BY 3, BY 3 may be employed, the
magnet M 2 bringing the contacts 1 and 1 into contact with 2 and 2. Normally
1 and 1 are in contact with 3 and 3. Like poles of BY 3, BY 3 may be connected
to 2 and 2.
140. In Fig. 134, BY 3 and BY 3 are both connected to earth through M 2,
normally 1 touches 3, a current through M 2 will make 1 touch 2. Unlike poles of
BY 3 and BY 3 may be connected to earth.
141. In Fig. 135, P M is a magnet with polarized armature, 16 and 17 are contacts
rand M a magnet similar to magnet M fitted with a timer and moving hook, Lis
normally in contact with 17 and 1 with 3. On pressing K at any point, BY 3 is
brought into circuit as usual. When the switching currents cease, the timer
asserts itself and brings the hook of M into the second position and L is connected
with 16.
P M is a magnet with polarized armature and is now in the L circuit. Its
armature is not affected by the currents passing in one direction but any in the
opposite direction will throw its armature over and make L touch 17. Any key K
being pressed will complete the circuit of BY 3 and reset M.
142. In Fig. 136 are shown the general connections of four points ABCD
connected by one linewire L to an exchange E X where one switching instrument S
is special to it. The switching instrument S, and those of any other points as F
and also the method of working them are supposed to be like the system shown
in Figs. 1 and 10. Any other system described may be used. The returns of all
the points connected with the exchange EX being made through a return wire
special to each or common to all as in this case represented by the wire CR W.
Points A B D are fitted with telephone apparatus T only as it is supposed that
they only want to speak to one another and to C. C is also fitted with a
battery BY and key 7 corresponding to B Y and key 7 of point F; in order to use
the switching instrument S.
143. L is broken at each point. One part passes through the telephone and
bells magneto &c. at T to contact 4 the other through the electro magnet M to
contact 5. The magnets M, M2, batteries BY 2, BY 3, keys K, contacts 1 2 3
are similar to those shown in Fig. 130, BY 2 BY 3 being in the exchange EX.
144. The armature of each M is provided with a movable hook and timer.
When the hook is in the first position each vibration of the armature propels a
toothed wheel by means of a pallet a distance of one tooth. On the same axle as
the toothed wheel is a disk carrying a stud on its edge, in a different position for
each point. At a certain stage in the revolution of any of these disks, the stud
will raise a detent; if the revolution is continued the detent is lowered again.
If, however the disk stops at that point, and the detent is raised, the timer in
moving the hook will raise another detent and allow L to come in contact with

page_text: contact 4 of that point.
contact with 5 and touch 4.
key K at any point must
and so on.
Both detents must be raised before L can break
To raise the first detent of EX one contact of the
be made, two to raise A's detent and three for B
145. Suppose A wants to speak to C. A taps his key K four times. This will
move C's detent, and after a short interval of time C's timer will raise C's second
detent and L will be in contact with 4. In pressing K, A has automatically
raised his own detent and his timer has put L in contact with A's contact 4. A can
now send his ringing current from his magneto which passes through C's bell and
rings him up. A and C now speak in the ordinary way.
146. The hooks at every point and the exchange bave now been moved into the
second position by their timers. To disconnect, either A or C presses K which
changes L from contact 4 to 5 bringing battery B into circuit and by attracting the
armature of each M with the hooks in the second position, resets each instrument
as before.
147. If A or C fail to press their K, either their telephone or call bells may be
in circuit, and from the high resistance the current may be unable to work the
magnets M, therefore between contact 4 and the telephone and battery at each
point, an electro magnet with polarized armature may be inserted through which
the current from BY 3 will pass and by throwing its armature over transfer L
from 4 to 5, when the magnets M will be excited and all the instruments reset.
148. Suppose wishes to speak to some point in connection with the
exchange EX. C presses key K once. After a second or two, L will be joined
to 5 at both C and EX. C must now be considered like any other point in
connection with E X. By tapping his key 7, he brings the movable contact C to
the bar he requires, and rings speaks and disconnects as usual. Then pressing
key K he resets the instruments at A B C D and E X.
149. Should F wish to speak to C, he finds the bar of C's circuit as usual. The
bar BR contact 11 is connected with contact 16 magnet 3 and CR W. F taps
his key 7, four times: This passes a current through the magnet M 3, whose
armature closes the key K four times, the instruments at C and EX change L
from 5 to 4, the switching instrument S connects 11 with 8, and F can ring Č up.
F might have earthed his common return wire CR W four times to switch on to C
after finding the bar of C's circuit.
150. F disconnects and resets in the usual manner. This also causes the
exchange instrument S to reset and automatically close K once to reset the
instruments on C's circuit and brings 11 again into contact with 16.
C can disconnect by pressing his key K.
151. If the return circuit of the battery BY 2 be insulated from the earth,
and carried to each point, the line between the exchange and D may be completed
by the earth and this system may be used with an exchange also using the earth
return for its points as shown in Fig. 1.
152. As before shown the system in Figure 136 may have the line I earthed if
the switching circuit through BY 2 be insulated from the earth. It may be
required to use one wire and yet not join the first and last points.
153. Fig. 137 shows a system of connections. Points A B C D and E are fitted
as those in Fig. 136, like A or C or both. After leaving points A and D, the line
is normally joined to the poles of two batteries BY 2 BY 2 with reversed poles,
that pole of each battery being joined as required. In the battery circuit at
each end is an electro magnet M 2 fitted with a hook changer and timer.
PM2, PM 2 are two electro magnets with polarized armatures. By pressing any
key K the switching circuit is closed, and the two batteries send currents through
the line L, moving the armatures of all the magnets M to the earth through the K
which is pressed. The timers of M 2 and M 2 should be as nearly synchronous as
possible, and to prevent either battery being earthed by any delay of the other
timer each timer should raise 1 from 2 for a short space of time before it connects
1 with 3. The magnets P M 2 are unaffected by any current which passes through L
C

page_text: in one direction. The resetting current being in the opposite direction will throw
their armatures over and bring 1 into connection with 2, and by pressing any key K
all the instruments will be reset and M2 M2 will bring the armatures of the
magnets PM 2 back into their normal positions. Any point ABCD or E may
be an exchange fitted with automatic switching apparatus and used as shown on
Fig. 136.
154. This system of connections may be worked with one battery BY 2,
magnet M 2 and PM 2 at one end as shown, the other end of L being earthed.
The line normally passes through PM 2. A magneto current through PM 2
transfers L to the battery circuit which does the switching. The timer
of M 2 transfers the line L back to the P M 2 circuit for ringing and speaking.
The keys Kare here used to break the battery circuit instead of completing it when
pressed.
155. In Fig. 138 is shown a system for one line with balanced batteries at the
ends. In this system each point is fitted with the instrument shown in Fig. 139;
its magnet M corresponds with the magnets M in the Fig. 138. The line normally
passes through contacts 1, 2, 3, 5, magnet M, contacts 6 and 7 at each instrument.
K is a key with contacts so arranged that on pressing its handle to the right, the L
on the right of the point is earthed; and when pressed to the left, the line on the
left of the point is earthed. Suppose C wants to speak to A whose number is
one, he presses his key K to the left once. All the M's will be excited, and the
timers of A and C bring their respective contacts 3 and 4 into contact, and
joins A's contact 2 to earth and C's contact 6 to E. Both batteries are cut off
and ringing and speaking can go on as usual. To reset, either A or C by means of
pressing the key K to the right, release a detent, which keeps 3 in contact with 4
and makes 4 touch 5, and connects either 2 with 1 or 6 with 7 when currents from
both batteries will pass through all the magnets M, and reset the instruments.
156. Fig. 139 is a view of the instrument used with the last system. The two
way key K, polarized armature ARM 2 and the mercury or similar contacts are
special to this system all the rest, Figs. 125 to 137 using Morse keys or simple
one way keys and three metal contacts. The core of magnet M is divided at the
base. Between its ends oscillates a polarized armature ARM2 about the
ceutre CE 2. Its axle carries two arnis AM and A M 2, one of which will
always be resting upon one of the bridges BRG and BRG 2, turning with loose
collars upon the axle A L. The bridges tend to fall towards the cups C2 and C6.
Both bridges are kept turned towards cups C1 and C 7 so as to connect cups C2
and C1; and C6 and C7 by the detent DT turning on AL. When DT is
raised by the lever LV, both the bridges would turn and connect C2 and C 6
with CE, but one of them is kept down by one of the arms AM and AM 2
according to which side the polarized armature ARM 2 is inclined.
contacts 4 5 and 6 are connected by mercury contacts, they will be connected by
the bridge BRG 3. C3 is normally kept in contact with C5 by the detent DT.
When this is raised BRG 3 turns towards C4 and connects C3 with C 4. The
cups correspond with the respective contacts 1, 2, E, 6, 7, 3, 4 and 5.
When
157. The armature AR M of M is fitted with a movable hook H K, fitted with
guides rod and retracting spring as in Fig. 10. It is moved by means of a ladder
or rack R K, held in position by the detent DT 2 entering one of its slots.
DT2 turns upon the centre CE 2. The spring pallet PT is moved by the
timer T R and is attached to the lever LV 2 turning on the pin P N. The
lever LV 2 is moved by the rod RD pulled by the armature ARM and carries
the timer pallet PT 2. The lever LV 2 is moved by A R M against the opposition
of a spiral spring on PN which in turn moves the timer and hook HK. On
pin P N 2 move two levers one behind the other. LV 3 carries the pallet PT3
and hook HK 2. LV4 carries the hook HK 3 and arm A M 3 and arm AM 4
moving in connection with detent DT 4.
158. The axle A L 2 carries the toothed wheel T W and disk D. A L 2 also
carries a needle NL which indicates the position of the disk D, bearing figures as

page_text: shown. Riding loosely on the same axle is an arm A. M 5 carrying the lever LV 5,
normally one end falls into the notch N H in the disk D. A pin PN 3 is put in D
in such a position, that after TW has been turned a certain number of teeth, it
will reach the pallet_PT 4. TW is prevented from returning by the detent
pallet PT 5. Pallet PT4 is mounted on the spring S P. One end of SP strikes
and keeps the lever LV 6 in the position shown. One arm of LV 6 keeps the
spring pallet SP 3 out of the path of LV 2 and another arm moves against
detent DT.
159. The axle of the key K carries a vertical handle shown by a dotted line, a
spring SP 2 which touches either terminal T or T 2 according to which side K is
pushed and an arm A M6 which will strike against the spring SP 3 when K is
turned to the right. K carries two arms AM 7 AM 7 which with depress the
spring SP 4, whichever way K is turned. SP4 carries a plate PL. When
SP4 is depressed, its end depresses the lever LV 5 and withdraws its end out of
the N H. The arm A M5 keeps in position the lever L. V 7 turning upon a centre
carried by a spring SP 5 in the position shown, when the arm is under the
plate PL. The terminals T, T2 are respectively connected to the linewire to the
left and right of the point. The spring and lever LV are connected to the earth
through the arm A M 5.
160. In turning the key K to one side or the other, one of the arms A M 7
depresses the spring SP 4, this in turn depresses the lever LV 5, raising its end
out of the notch NH and depresses the lever LV 7, lowers the spring SP which
lowers the lever LV 6 and allows the spring S P 3 to approach lever L V 2. The
other arm of LV 6 is caught and held by the detent DT 3. The passage of the
currents to earth has excited all the magnets M in circuit. The armature A R. M
is attracted moves the hook HK and lever LV 3 and turns the toothed wheel T W
one tooth by pallet PT 3 against the force of a spiral spring on AL 2. After the
required number of currents have been sent an interval of about two seconds is
allowed to pass.
In this period the lever L. V 2 has raised the spring S P 3 and
detent DT. One of the bridges B R G and B R G 2 turns and earths the linewire
on the opposite side of the point to that of the point called and also BRG 3
connects C4 with C3 thus bringing the telephone into circuit. The return of
lever L V 2 has also moved the hook H K. To reset, K is turned to the right
when the arm A M 6 strikes the spring S P 3. The lever LV is dropped and the
contacts assume their normal state. A current passes to the earth of the other
instrument. This is sufficient to release the lever L V of this instrument, a current
now passes through the circuit attracting all the armatures AR M, and pulling
levers LV4. They are held by the detent DT4 until the timer returns and
releases it by raising the detent.
161. During switching, at the other points, the attraction of armature ARM
has turned the wheel T W round in the same manner. The lever LV 5 going with
the disk has taken the arm A M5 away from the lever LV 7 thus breaking the
earth contact and causing LV 7 to miss the plate PL. If an intermediate point
turns his key he affects nothing.
162. If number 3 (C) wishes to speak to number 5 (E) he turns his key K five
times to the right. AR M 2 of No. 3 will be attracted to the right and that
of No. 5 to the left, and the stud of No. 5's disk D will depress SP, which will
lower lever LV 6 and so bring SP3 into range of lever LV 2. LV 6 will
not be held by detent DT3 only on the point pressing key K, the studs of the
others not lowering the spring S P far enough. On the return of levers LV 2,
levers LV will be raised and the line will be earthed on the right of No. 5 and the
left of No. 3. Then they can ring and speak as usual. In the ringing and speaking
circuits any current can be passed through as long as it does not affect the
magnets M or the armatures A R M 2. This can however be held on either side
by a projection from detent D T.
163. Another way of preventing LV 5 being carried round by D at the calling
point, the lever LV 7 may be made to withdraw the pallet PT 3 from the

page_text: wheel T W 2. This will however prevent the needle N L showing the point
called.
164. The switching current may pass through a relay magnet in each instrument
instead of through M. The relay will work A R M 2 and close a local battery
circuit with M in it.
165. Two or more points connected to one switching instrument in the exchange.
Fig. 13. Two points A and C are connected to one switching instrument in the
exchange EX, the instruments being similar to those described in Fig. 10,
though any other form of instruments may be used. Their lines pass through the
magnets PM 2, P M 2 with polarized armatures. Normally they are earthed
through contacts 16 and 16. The passage of the switching current from either point
through its magnet PM 2 cuts off the earth connection of both and connects one
to the instrument S by joining its contact. 16 to 17.
166. Their bars are provided with magnets P M 3 PM 3 with polarized armatures
which are normally earthed by joining contacts 11 11 to earth. A current from
either bar belonging to either point will pass through its magnet M 3 and cut off
its own earth and that of the point to which it belongs and connects to the line of
the point between the magnet P M 2 and the point. A reverse or resetting
current will restore the connections. It will be seen that the other point is
able to use the switching instrument S although the one point is speaking through
its bar B R.
167. Sub-exchanges. An exchange worked according to this invention may be
used as a sub-exchange in connection with another which may be a central or
another sub-exchange, trunk wires being laid between the two exchanges, some
terminating in bars BR in each exchange, their other ends passing to switching
instruments in the other exchange. To communicate from a point on one exchange
to that on another, say from A on exchange X to G on exchange Y; A first finds
the bar of a trunk wire between these exchanges X and Y in his own exchange X,
and then still uses his key 7 to move the instrument S in exchange Y to which the
trunk wire is attached and so finds G's bar in exchange Y. The resetting current
automatically resets the instruments.
168. To make the most use of the trunk wires, a trunk wire would be joined to
the terminal of a switching instrument in each exchange, the current passing
from a point on one exchange through the bar of the trunk switching instrument iu
his own exchange will not move it but will move the trunk instrument in the other
exchange and thus he will be able to find the bar of the point required.
169. In Fig. 13 is shown a central exchange EX connected by one linewire to a
sub-exchange SE to which are connected two or more points B and D. As the
number of points to be accommodated by one wire would be limited, the fixed
contacts or bars can be arranged in a circular ring BRR the moving contact being
a radial arm sweeping round on the contacts. The trunk line L and all the points
are connected to special contacts ou BRR. A branch from each passes through a
magnet PM 4 with polarized armature thence to earth.
170. If any one point sends a switching current through its P M 4, the armature
of P M 4 transfers terminal 8 to 9 whence the current passes through the switching
relay magnet S R M to earth and closes the local switching circuit containing a
switching magnet S M with timer and movable hook. This magnet being excited
moves the contact arm of BRR to a fresh contact for each current sent.
171. If point D wants the trunk wire, he will send one switching current, this
will bring his line into connection with the trunk wire. He waits a second or two
and the timer of the sub-exchange will bring his contact 8 into connection with 10
whence a path is open to the central exchange. Here the switching currents from
the point pass through the trunk switching instrument and puts it in communication
with any other point on the exchange. The resetting current resets all the
instruments it passes through.
A point on the central exchange EX can in like manner find any point on the
sub-exchange.

page_text: To disconnect the other points on the sub-exchange the first stroke of the sub-
exchange switching magnet will disconnect the earth of all the magnets P M 4 so
that no one can listen or move the instrument.
172. Another way of disconnecting the earths of the magnets P M4 is shown in
Fig. 12.
The armature ARM of this particular A M 4 carries an arm A M
which will strike against the contact strip S T in circuit with a magnet which will
raise ST and let A M pass. ST when first raised disconnects all the earths of the
imagnets P M 4 and is held by a detent. The resetting current releases it and
reduces all the parts to the normal position.
173. A point on the sub-exchange can switch on to any other point on the same
sub-exchange in the same manner as D did for the trunk line, only sending in each
case the required number of switching currents.
174. Fittings at the subpoints. At each point a source of electricity for
switching ringing and resetting must be supplied and in some cases a means of
changing its polarity or direction. The generator may be in the exchange one or
both poles being connected with each point through the earth or special conductors;
or a special generator may be supplied to each point. Where a magneto is used,
one generator may be used for switching, and the magneto for ringing and
resetting. A magneto at the point may be used for all purposes, each revolution of
the driving wheel corresponding to the passing of one or more currents in the
switching circuit, and to distinctly mark each current, the current from the magneto
may be automatically suspended for a portion of each revolution by means of an
insulating segment on a commutator on the driving axle. Where it is required to
reverse the magneto current, its rotation may be reversed, or its connections to the
line may be altered by a key, or a driving handle on the same axle as the ordinary
one but in a different plane may be used (for instance on the other end) which shall
automatically make the required connections.
175. The number of switching currents sent to the exchange and indirectly the
number of the point in connection may be recorded as follows.
A. counting apparatus may be moved mechanically by the switching key, or
electro mechanically by each current. In either case, each motion will move by
means of a pallet a toothed wheel with numbers on the edge a distance of one
tooth. Separate keys may be used for hundreds tens and units closing by branch
wires the same switching circuit and moving separate counting wheels. These
branches may contain separate magnets in circuit for moving the wheels by the
currents. If one key or magnet only be used, the separate wheels for the
hundreds tens and units may be employed, a timer changing the connection of
the key or magnet from one wheel to another. The timer may be arranged to
indicate the moment of change by ringing a bell or moving an indicator. This
timer should be set to move more slowly than that at the exchange to ensure the
exchange timer having acted. The sending of the resetting current may be made
to reduce the counters to zero mechanically or electrically.
176. The switching current may be sent by passing a moving contact connected
with a battery over a series of contacts connected with the line. The contacts are
numbered to show the number of currents sent. Such a moving contact may move
in a straight line between guides, or may be a radial arm moving by a handle round
a centre, the contacts being arranged in its path. There may be several moving
contacts for sending the currents corresponding to the hundreds tens and units on
different guides centres or revolving round the same centre. Normally they do
not touch the fixed contacts, the pressure of moving them making the contact.
prevent the currents being sent too quickly the arms may be adjusted to move a
train of wheels with friction brake or fan or escapement regulated by pendulum or
balance wheel.
To
Similar arms not transmitting currents may be set at the required figures, and
the other arms transmitting the currents may be moved by some motive power until
stopped by the aforesaid arms.
177. It may be so arranged that the switching key be kept down, and the

page_text: switching instrument automatically break the circuit and current in the switching
line at every stroke of the armature of the local switching magnet S M Fig. 10.
The switching current in the line passes through a magnet at the point which will
ring a bell or move a needle or regulate the number of currents on a similar counter
as described above. When the bell or other signal indicates the required number of
hundreds, the key is raised and an interval of time allowed to pass when it is again
depressed. When the interrupted currents again indicate the required number of
tens, the key is again raised, and so on for the units, thus only raising the key three
times.
178. In the exchange, the switching currents sent from the point may pass
through the switching magnet without the intervention of a relay. In most cases
it will be best to pass them through the relay magnet as before described. If
relays are not used, the relay magnet S R M Fig. 10 will not be required.
179. The parts of the instruments used in this invention to receive currents and
transform them into motion of different directions according to the direction of the
currents such as magnet P M, Fig. 10 and other figures may have the varied forms
shown in Figs. 10, 12, 19, 139, and 141 to 159 inclusive. They depend on the
directive action of electric currents and electro magnets upon other currents or
magnets permanent induced or electric.
180. In Fig. 141, the currents passing through the coils CO move the
permanent magnets M about the centre CE. In Figs. 142 to 159 inclusive,
different forms of electro magnets EM are shown acting on the permanent
magnets M, N and S indicating their poles and CE the centres about which
they turn. A R M in Fig. 143 is a soft iron armature, in Fig. 144 it is a permanent
magnet.
181. An electro magnet may be fitted with a soft iron armature and polarized
armature both acting independently from one another.
182. An electro magnet may be fitted with more than one soft iron armature and
at the same time with more than one polarized armature.
183. The cores of the electro magnets and the polarized armatures may be of
soft iron polarized by the proximity or contact of permanent magnets or by electro
magnets. The polarity of the latter may be altered at will or taken away by
changing the direction of or stopping the current passing through them.
184. When an armature or other part of the apparatus such as the bridges is
intended to return to the original position it occupied, for instance a central one,
it may be brought back by adjustable weights or springs as shown in Figs. 160
and 162 and also by cams projections or studs opposed by weights or springs. The
same means may be used in similar cases when the parts have to be retained in the
last position they acquire for instance on one side or the other of the centre,
the use of weights and springs being shown in Figs. 161 and 163. A R M represents
an armature, W T an adjustable weight, SP an adjustable spring.
185. If the motion of a moving part such as an armature is to be rendered gradual
or prevented from oscillating, a weak spring or bristle may be fastened to it to
strike against a projection or rub on a surface or a part for instance an armature
or a projection from it may dip into mercury or other liquid as shown in Fig. 164.
CE is the centre about which ARM a polarized armature turns, A M a pro-
jecting arm dipping into the mercury M'Y, which may also be the means of
passing the electric current through the armature to any contact it may touch.
186. The mercury cups used, may be made as shown in Fig. 165. CP, the cup;
SC, a threaded stalk fitting into the ferrule FL fitted to the stand ST, the
connecting wires being clamped by the screw SC 2. The mercury MY may be
covered with a layer of oil or glycerine LY to diminish oxidation, and the whole
may be covered with a cover CV to prevent the entry of dust. Holes in the covers
admit the needles. The cups may be made of any material that will hold mercury;
earthenware, glass, wood, indiarubber, gutta percha, ebonite, vulcanite, vulcanized
fibre, carbon, graphite; any metal or alloy such as copper, brass, iron, steel, tin,
platinum, lead, pewter, or aluminium &c. Those which are amalgamated being

page_text: protected by paint or varnish, the contact with the mercury being made by some-
metal not attacked by the mercury such as iron platinum carbon or graphite.
187. The needles may be pointed as shown, and made of any metal, being tipped
with some metal not attacked by the mercury. The tips may be made of pencils
of carbon or graphite. The needles may be varnished except the tips by which
contact is made.
188. The contacts may be made in the common way between solid metals..
Fig. 166. The axle AL forming these connections may have projecting bars or
studs BR which may form part of the circuits, the contacts being made by causing
them to rub against the springs SP. The bars or studs may also press springs
together forming the circuits through the springs only.
189. The needles may be made to touch springs shaped as shown in Fig. 167.
Springs similar to these shown in Figs. 166 and 167 may be fitted to the bridges.
and touch similar springs, fixed needles or contacts. In all cases the surfaces of
contact may be graphite or carbon.
190. Fig. 168. By fitting a spring SP on the end of a bridge BRG, two
cups CP, CP2, or contacts may be joined during the passing by the current
through the magnet while its cessation will allow the spring to assert itself and
raise them from contact. The dotted spring and bridge shows the position assumed.
after the current ceases.
191. Automatic exchanges have been designed in which the switching currents
are passed through different circuits to move different magnets, such alteration of.
circuits being made by the agency of another current passed from the point to the
switching instrument through the same or another linewire. The change of circuit
is used because each magnet only effects one operation so that as many magnets.
have to be used as there are operations to effect.
192. In the first place, I diminish the number of magnets required by making
one do the work of several, the motion of its armature being transmitted to several
parts of the instrument by a movable connection moved as required by means of
currents passing through the same or another circuit (123). This requires a current
to be sent from the point to move the connection.
193. I do away with this current for moving the connection by causing the
magnet of the switching instrument to work a timer, whose operation is suspended
If the
while the switching current passes, but is released when the current ceases.
armature of the magnet is not attracted for a given time, the timer moves the
connection between the magnet and the mechanism it has to work; thus by the
aid of one magnet, also fitted with a polarized armature (120) all the operations.
of the instrument S may be effected.
194. The movable connection may be attached to any part of the switching
instrument whose motion is to cause the movement of or to be transmitted to some
other part of the switching instrumen or cause the transmission of some external
form of energy or motion to some part of the instrument.
195. In changing its position, it may move in any path as in a straight or
circular path. Those in Figs. 10 and 139, 170 and 171, 172, 173, 174, 175 and 178.
being in straight lines, and that in Fig 169 circular, where connection CN moves
round the centre CE on the armature AR M. In Fig. 170 it moves in a straight
line or path along a guide G attached to the armature AR M. In Fig. 171 it also.
moves in a straight path along the rod R D.
196. When in any one position the movement of the movable connection will
depend on the movement of the part of the instrument to which it is attached..
Thus in Figs. 10, 139, 169, 170, 172, 173, 174, 175 and 178 it will move as the
armature or fitting to which it is attached; in Fig. 171, if the rod R D move
axially, connection CN will move with it round the axis of RD.
197. The motion of the part to which a movable connection may be attached
may be derived from any convenient source given to it by any form or source of
energy such as electricity, magnets, springs, weights, clockwork, or by hand, or
mechanism driven by other motors.

page_text: The moving connection may fixed to a part of the instrument which does not
move in itself, the connection being moved so as to transmit energy to various
parts of a moving part of the instrument by which it is conveyed to other parts
as required.
198. The position of the moving connection may be altered or the connection
may move by force applied to it in any convenient manner, by means of magnets,
springs, weights, or clockwork transmitted to the connection by levers, cords,
pallets, springs, wheels, pulleys, and its movement may be regulated and limited by
detents and escapements.
199. The movable connection may take any convenient form such as hooks,
projections, arms, pallets, brushes, contacts, wheels, and racks, being made to suit
the requirements.
200. The parts to which the movable connection transmits notion or energy or
moves, will be placed in its path, being made to efficiently receive the motion or
energy transmitted. They may be levers, rods, projections, pallets, studs, springs,
contacts, wheels, or cords. The movable connection may transmit electricity
from the parts to which it is attached to other parts by means of contacts.
201. It follows that the movable connection may be attached to or detached
from the armature of a magnet. In Fig. 172 the moving connection the hook HK
is shown detached from the armature ARM and attached to the fitting FT
suspended by a spring SP. The motion of AR M is transmitted to FT by two
hooks H K 2 and HK 3. The moving hook H K is similar in all respects to that
shown in Fig. 10.
202. The following are some of the ways of moving the movable connection.
In Fig. 173 the hook H K is moved thus: A timer or some other mechanism
causes RD to strike against the lever LV and bring pallet PT down on the
toothed wheel T W; at the same time the hook H K is turned a little on its axis
by the rod RD 2 attached to the lever LV 2, to free it from the hooks of the
parts it moves. The local switching circuit is closed and causes the armature AR M
to be attracted by the magnet. When the wheel T W moves forward the pallet. P T
catches in one of its teeth and thus lowers the hook.
203. In Fig. 174, the hook HK 2 is attached to the armature ARM by the
pin PN about which it turns, and according to its position will catch in the
hook HK 3 or H K 4. When the rod RD is pushed against the hook lever L V
by the timer, it raises the hook H K 2 as shown in the figure and on the armature
being attracted will turn lever LV 2 which causes the pallet PT to move the
toothed wheel T W and lower hook HK. The rod RD is now withdrawn
and H K falls, engages with hook H K 4, and the movement of the armature will
move the fitting FT which carries H K.
204. In Fig. 175, the hook H K is attached to a ladder or rack LD shown in
detail in Fig. 177. It slides along the face of the fitting FT shown in detail in
Fig. 176, and to this it is secured by the two screws SC moving in the
slots SL, SL. The movement of HK is governed by the escapement ES
shown in detail in Fig. 177 turning on an axle in the bearings B G. When it is
required to lower the hook HK, a timer or some other part raises the
escapement ES and allows H K to fall one tooth or slot in the ladder.
205. In Fig. 178, the movable connection is the book HK attached to a
ladder LD similar to that shown in Fig. 177, and sliding on the face of the
fitting FT. LD is kept in position by the detent DT on the spring SP. To
lower the hook H K, the rod RD is moved by a timer so as to strike the
spring SP, and raise detent DT just sufficiently to let LD slip, when RD is
raised from SP by the plane PL striking against the adjustable screw SC,
and DT springs back and holds the ladder LD.
206. The timer. A timer is used to bring about some movement of or to
accomplish some change in the parts of the mechanism at the end of a given
interval of time from the moment of starting the timer. The interval of time is
measured by causing the timer to do some work such as moving a pendulum,

page_text: balance wheel, overcoming mechanical, liquid, fluid or gaseous friction, driving a
fanwheel in air or a liquid, expelling fluids liquids or gases such as air from some
reservoir.
207. The timer may be driven by energy stored up in springs, weights, from the
motion of one of the moving parts of the instrument, or from any external sources as
springs, weights, electro magnets, or other motors or by the recoil of the pring
supporting or withdrawing an armature from the poles of a magnet.
208. A timer may be employed to move any part of the mechanism as before
shown, to move contacts, movable connections, complete contacts, release detents,
to make contacts for the transmission of electricity, to release and put in motion
any part of the mechanism which derives its motion from any other source than
the timer.
209. In Fig. 178, is shown a pneumatic timer consisting of the bellows BLS.
The armature ARM of the switching magnet SM pushes the rod RD 2 and
When the armature springs
opens the bellows, a valve allowing the air to enter.
back, the valve is shut and the air allowed to escape through a small adjustable
hole, thus slowly closing BLS. In this case a spring attached to the moving
bellows board propels the rod RD and lowers the hook H K.
210. In Figs. 10 and 139 are timers which depend upon the motion of a
pendulum to regulate their period.
211. Fig. 179 shows a simple form in which the arm AM turns round the
pin PN against the spiral spring SP. The spring SP2 carries the pallet PT
driving the wheel F W, escapement ES and pendulum P.
212. In Fig. 180, A M is turned against the pressure of the spiral spring SP,
by pushing the rod RD passing through the guides G. On the rod is the
To nut N T is fastened a
nut NT, against which the spiral spring S P presses.
spring SP2, carrying the pallet. PT engaging in the escapement wheel EW,
working an escapement E S and a pendulum P.
213. In Fig. 181 is shown another form in which the rod RD is pushed or
pulled by some motion of the instrument against the spiral spring S P, and carries
with it two nuts NT and NT 2. To NT is fixed a spring SP 2 carrying the
pallet PT; to NT 2 is fixed the spring S P3 carrying a pallet PT 2 to work
the escapement wheel E W escapement ES and pendulum P.
214. The arms A M in Figs. 179 and 180 and pallet PT Fig. 181 accomplish
any required movement at the end of the timer's period.
213. The moving contacts. The contacts springs weights and guides have been
shown in Figs. 10, 11 and 28.
216. The moving contacts may take the form of metal springs or small wheels
attached to springs and may be made of any suitable metal or alloy and may be
tipped with platinum or any hard metal such as iridium, or a button or wheel of
hard carbon. For metallic circuits more than two contacts mounted on the same
or separate carriages would be used.
217. The contacts are fixed to carriages made of a combination of wood or
similar insulating material and metal. The carriages may be combined with the
weights causing them to descend. The weights may be quite separate from the
carriages and be connected to them by cords.
218. In all cases the carriages or weights which hold the contacts will move
along guides attached to the frame rails. They may be made of wood or metal
or a combination of wood and metal of the forms shown in Figs. 10 11 28
and 182 to 188 inclusive. When wood is used the dimensions of the wooden
parts must be increased the carriages and weights being altered as necessary.
In Figs. 182 to 188, CS indicates the contact springs, CW the contact
weights, SB the switchboard, BR the contact bars; G, G, the guides.
219. In Fig. 182, the contact weights descend in cells formed by wooden
5 bars W W secured to the frame rails and enclosed by boarding or a metal
plate PL as shown. In the latter case C S would be insulated from the weight.
220. The carriages and weights may touch the guides at one or two points only
D

page_text: and carriages.
221. The contact carriages or weights contain one two or more contacts as
required for single line or metallic circuits.
222. The connections with the springs may be made by either the guides or
cords.
Where the carriage or weight touch more than one guide as in Figs. 183
and 184 it must be insulated from one the connection being made through the
other.
223. Where double contacts are required, the guides must be made up and two
parts insulated from one another each part used as a conductor as shown in
Fig. 185 at C Fig. 186 at A and C or double guides may be used as in Fig. 187
at B, the insulation of the springs from one another, and from the weights being
arranged by the use of insulating materials.
224. The cords used for supporting the contact carriages and weights may be made
of any suitable material such as cotton, silk, flax, gut or leather, or metal wire
stranded or plain. When the cords are used for conductors, they may be stranded
and twisted into the cords. When a single conductor is required it may be of brass
or copper wire without insulation. If two conductors are used, they must be
insulated from one another. The cord may be used for one conductor and the
guides for the other.
225. The cords may be shaped as narrow tape and wound on the reels layer
upon layer.
226. The bars may be as shown in Figs. 10 and 190 for single circuits.
227. For double or more contacts, two or more bars on the same face or on
both faces of a switchboard may be used but the compound bar shown in
Fig. 190 is better each bar being toothed square as shown or like the tooth of
a saw triangular so that two of them may be fitted together in the width of one
fat bar. The bars of the compound bar being insulated from one another.
The bars may be made of flat carbon rods.
228. The motors for raising and lowering the contacts may be driven by
electricity gas compressed air steam or any convenient motive power. The same
agency may supply the electricity necessary for working the exchange from
dynamoes, this current may be used direct or charge accumulators whence the
working current is drawn.
For small exchanges the motors may be driven by batteries or power stored up in
springs and raised weights, these being rewound as required.
229. The escapement wheels similar to E W, E W2, E W 3, Fig. 10 may have
their teeth on the circumference as EW EW 2 in Fig. 178, on the bevel, on the
face, crown as EW 3 in Fig. 10 or internally.
230. Two escapement wheels E W and E W 2 may be mounted on an axle
similar to A L4 Fig. 10 as in Figs. 191 and 192. One E W for the units has ten
teeth and the other E W 2 is a disk with the exception of a notch which coincides
with one tooth of E W. The pallet PT is mounted on a spring attached to a
lever LV turning about the centre pin PN. When L V is momentarily raised,
PT slips to the right releases wheel E W2 and AL4 makes one complete
revolution. If LV is depressed, PT slips to the left, releases EW and allows'
it to turn one tooth, PT being brought back into E W before another tooth
can pass.
231. In Fig. 178 is shown another form of escapement similar to that described
above in that the detent must be released directly the tooth has passed it. The
spring pallet PT by which the armature moves the fitting FT must be disconnected
from the fitting directly the detent is raised enough. This is done by an adjustable
screw SC 2 striking a plane on the spring pallet and pushing the pallet away from
the fitting FT and releases the hook HK.
232. In the instrument shown in Fig. 10, the moving contacts are lowered by
their own weights, the rewinding being done by a separate motor; it may be

page_text: required to put the contacts at the bottom of the switchboard and pull them up to
the required bar by a winding motor. This may take the form of a magnet with a
pallet fitted to its armature turning a toothed wheel on the axle A L4 tooth by
tooth. It would have to vibrate very quickly to move the contact ten bars between
two contacts of the switching key therefore some means of mutiplying its motion
will be necessary.
233. In Fig. 194, the axle A L4 has a toothed wheel T W with ten teeth fixed
on it, and a smaller one T W 2 gearing into the larger wheel T W 3 with ten times
the number of teeth. In front of this is another toothed wheel T W 3 with ten
teeth. A pallet PT will move T W and PT2 move T W 4. The switching
magnet first moves PT 2 and turns the wheel T W 4 one tooth and so causes T W
to make one revolution, thus raising the contact 10 bars, and so on for each
current. The hook of the switching magnet is moved, and will pull pallet PT
and turn the wheel T W one tooth for each current, and raises the contact one bar
at a time. In this way the contact is raised to the bar required.
234. Where the latter arrangement is still too quick, in Fig. 193 is shown a bevel
toothed wheel B W fixed on the axle A L 4. This turns a bevel toothed wheel B W 2
on the axle A L with ten times as many teeth as B W, and carrying the spring
contact CT. On A L 2 are two other wheels T W with 100 teeth and T W 2 with
ten teeth. The pallet PT turns T W 2 one tooth at a time, and pallet PT2
turns T W one tooth at at time. SP forms one pole of a circuit in which a magnet
is placed for winding the moving contact up to the required bar, while T W forms
the other pole, thus this circuit will be closed except when CT rests on the
the insulator 1 N fixed to T W.
235. The wheels and parts being as shown in the figure, the switching magnet
will pull PT and move IN away from CT. This will set the winding motor in
motion and begin raising the contact. PT moves T W round one tenth of a
revolution, therefore B W 2 will have to make one tenth of a revolution before it
can overtake IN and stop the winding motor, that is, B W will have to make a
complete revolution and thus raise the moving contact ten bars. This occurs for
each tooth PT turns the wheel T W 2.
236. A timer changes the hook of the switching magnet to pallet PT 2, each
stroke of PT2 will turn the wheel T W one hundredth of a revolution corresponding
to raising the contact one bar. In this way, the switching currents may succeed
one another as fast as they can be sent and the winding motor will keep on raising
the contact until CT touches I N.
237. Where the contacts are moved by their weight or by power, care should be
taken to balance them if necessary by causing the pilot weight to counteract their
weight, so that no more power is required than is necessary to raise them as long as
they fall or return properly.
238. In order that the moving contacts may be as close together as possible on
the faces of the switchboards, 1 arrange the switching instruments in rows one above
the other over the switchboards, and so arrange them in these rows that the cords
from the reels shall just clear the cords and reels of those below them.
239. If the number of points on an exchange be greater than can be served by
the instrument the exchange may be extended in the following way.
240. Suppose the instrument in Fig. 10 were made to serve 1000 points, more
may be served by using more reels and switchboards, or lengthening the switch-
boards and putting more bars on the faces.
241. Another way. From Fig. 10, it will be seen that the magnets PM
and SRM as well as the cup contacts control the magnets S M and W M
electrically, and that the cup contacts are controlled by the magnet S M, timer TR,
and lever LV 5 mechanically.
242. Take away the magnets P M and SRM and the cup contacts from the
rest of the instrument, and mount them on an instrument called the central instru-
ment, and let there be several combinations of the magnets S M, W M, timer T R,
reels, cords, contacts, and switchboards as shown in Fig. 10, each combination

page_text: serving 1000 bars BR and call them sub-instruments. Let the circuit of the
magnets S M and W M of each sub-instrument be taken to the central instrument,
and means of electrically or mechanically controlling the cup contacts at the
central instrument from each sub-instrument be provided. In the central instru-
ment the circuits of the magnets S M and W M will be broken by a contact
changer which will bring the magnets of any sub-instrument into the local switching
circuit as desired.
243. Normally the local switching circuit passes through a magnet at the central
instrument working the contact changer and also a timer. Suppose the point to
whom the central instrument is allotted requires to speak to point 2369, he first
taps his switching key twice. This closes the local switching circuit twice and
the magnet in the central instrument brings the magnets S M and W M of the
second sub-instrument into the local switching and resetting circuits. The timer
of the central instrument will then cut the first magnet out of circuit, and the
point is connected as usual to the sub-instrument and finds the 2369th bar in the
usual manner.
244. The resetting current resets the sub-instrument and the central instrument
in the usual manner by completing the resetting circuit containing an extra
magnet in circuit with the W M of the second sub-instrument for replacing the
contact changer.
245. This system of telephone exchange may be used along with any system of
telephone exchange now in use.
246. Operators may be employed at the exchange to attend to the trunk wires
if required.
247. This system of telephone exchange may be used in connection with any
existing exchange for sub-exchanges as before described or they may be under the
control of the operators who may use the exchange wire to connect to any point
on the sub-exchange, while the points on the sub-exchange can call up the
exchange as required.
Dated this 8th day of June 1893.
COMPLETE SPECIFICATION.
Improvements in Automatic Electric Exchange.
I, ROBERT PIPPETTE, of 51, Upper Tulse Hill, S. W., 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 :-
A. My invention relates to automatic electric exchange by means of electrically
controlled mechanism.
B. The object of my invention is to enable a point, for instance A, to be
connected electrically with a point, for instance B, by mechanism electrically
controlled from the point A. In the same manner, the point B may be enabled
to be connected electrically with the point A by mechanism electrically controlled
from the point B.
C. Generally, the object of my invention is to enable any point of any given
number of points, for instance A, B, C, D, to be connected electrically to any point
of the same number by means of mechanism electrically controlled from each
point respectively. Thus A can be connected electrically to B, C, or D, by
mechanism electrically controlled from A; B can be connected electrically
to A, C or D by mechanism electrically controlled from B; C can be connected
electrically to A, B, or D by mechanism electrically controlled from C; and D
can be connected electrically to A, B or C by mechanism electrically controlled
from D.

page_text: D. My invention will enable any point of a given number of points, for instance
A, B, C, D, to be connected electrically with any point of the same number as
shown above, or with any point of a further number of points, for instance E, F, G,
each of which is simply connected electrically to my mechanism for the purpose
of such connection, by mechanism electrically controlled from each of the
points A, B, C, D.
E. My invention will also enable a point, for example A, to be connected
electrically with a point, for example B, by mechanism electrically controlled from
a point, for example C.
F. My invention will also enable any point of a given number of points, for
example A, B, C, D, to be connected electrically with any point of the same
number, or with any point of a further number of points, for instance E, F, G,
each of which is simply connected electrically to my mechanism for the purpose
of such connection, or to a point, for example H, by means of mechanism
electrically controlled from the point H.
In all cases, my invention also provides for the separation or disconnection of
the points connected.
G. By electrical exchange, I understand the method or operation of connecting
up existing conductors so as to form them into one or more continuous conductors
from any one point to any other.
H. However, such operations as telegraphy, telephony, and the transmission of
power &c. by electricity are performed by means of induction through the agency
of transformers and condensers or by relays and repeaters, where in no sense is
there a continuous metallic conductor between the given points, yet I understand
electrical exchange to mean the method or operation or process of arranging
various existing conductors in relation to one another so that the electrical
currents transmitted from any point shall cause electrical currents to be transmitted
to and received by any other point, whether such currents are the original currents,
or are induced from the original currents by transformers or condensers, or by
circuits electro mechanically operated by the original currents by relays or
repeaters.
1. To illustrate my meaning, ordinary electrical exchange implies the formation
of one or more continuous conductors from any one point to any other, such as
will be hereinafter described between the points A and B.
J. But for instance, in a telephone system, each point may be provided with a
small transformer at the exchange, the primary being connected to the linewire,
and the function of the switching instrument of any given point, say A, may be
to connect A's secondary coil to the linewire of any other given point, say B, or
to connect A's linewire to the secondary coil of B's transformer.
K. Again each point, and for instance A, may be provided with a small coil at
the exchange connected to the linewire of the point, and the function of A's
switching apparatus would be to bring A's coil into close proximity to a similar
coil of any other point, say B, so that they would speak to one another by
induction between the coils.
The same would apply to connection electrically by condensers or relays.
L. Referring to the drawings left with my Provisional Specification
Figure 1 shows the arrangement of any two points, A and B, connected to the
exchange E X.
Figures 2 to 8 inclusive, are contact diagrams of the system shown in Figure 1.
Figure 9 shows the arrangement of the contact cups of a switching instrument
used in the system shown in Figure 1.
Figure 10 is an elevation of a switching instrument, the one shown being adapted
in certain parts for use in the system shown in Figure 1.
Figure 11 is the elevation of a portion of the switch-board used with the
instrument shown in Figure 1', showing the moving contacts of three points.
Figure 12 is a detail of a portion of a sub-exchange and is described in
paragraph 172.

page_text: Figure 13 shows the arrangement of two or more points connected by one
linewire to a central exchange, the description of which commences at para-
graph 165, and also the arrangement of two or more points connected to a
sub-exchange which is in turn connected to a central exchange, the description
commencing with paragraph 167.
Figures 14 to 33 inclusive are details of the various parts of the switching
instrument shown in Figure 10.
Figure 34 shows a more detailed arrangement of the system shown in Figure 1.
Figures 35 to 44 inclusive are contact diagrams of the connections shown in
Figure 34.
Figure 45 shows a modification of the arrangements of any two points A and B
connected to an exchange EX.
Figures 46 to 52 inclusive are contact diagrams of the system shown in
Figure 45.
Figure 53 shows the arrangement of the contact cups of a switching instrument
used in the system shown in Figure 45.
Figure 54 shows a modification of the arrangements of any two points A and B
⚫ connected to the exchange E X.
Figures 55 to 61 inclusive are contact diagrams of the system shown in
Figure 54.
Figure 62 shows the arrangement of the contact cups of a switching instrument
used in the system shown in Figure 54.
Figure 63 shows a modification of the arrangement of any two points A and B
.connected to the exchange EX.
Figures 64 to 70 inclusive are contact diagrams of the system shown in
Figure 63.
Figures 71 and 72 show the arrangement of the contact cups of a switching
instrument used in the system shown in Figure 63.
Figure 73 shows a modification of the arrangements of any two points A and B
-connected to the exchange EX.
Figures 74 to 80 inclusive are contact diagrams of the system shown in
Figure 73.
Figure 81 shows the arrangement of the contact cups of a switching instrument
used in the system shown in Figure 73.
Figure 82 shows a modification of the arrangement of any two points A and B
-connected to the exchange EX.
Figures 83 to 89 inclusive are contact diagrams of the system shown in
Figure 82.
Figure 90 shows a modification of the arrangement of any two points A and B
connected to the exchange E X.
Figures 91 to 97 inclusive are contact diagrams of the system shown in
Figure 90.
Figure 98 shows a modification of the arrangement of any two points A and B
connected to the exchange E X.
Figures 99 to 105 inclusive are contact diagrams of the system shown in
Figure 98.
Figure 106 shows a modification of the arrangement of any two points A and B
connected to an exchange EX.
Figures 107 to 114 inclusive are contact diagrams of the system shown in
Figure 106.
Figure 115 shows the arrangement of any two points A and B connected to the
-exchange E X, the points using a battery at the exchange in common.
Figure 116 shows the system shown in Figure 1 with metallic circuits.
Figure 117 shows the arrangement of any two points A and B with separate
linewires for switching and speaking.
Figures 118 to 124 inclusive are contact diagrams of the system shown in
Figure 117.

page_text: Figures 125 to 135 inclusive show different systems and parts of systems using
one linewire for two or more points.
Figure 136 shows the arrangement of a system using one linewire for two or
more points in connection with an exchange.
Figures 137 and 138 each show the arrangement of systems using one Fnewire.
for two or more points with balanced batteries.
Figures 139 and 140 show an instrument used at any point on a system using
one linewire for more than one point, but adapted in parts for use with the system
shown in Figure 138.
Figures 141 to 159 inclusive show details of various apparatus influenced by
difference in the direction of electrical currents.
Figures 16 to 164 inclusive show methods of governing the movements of
armatures and similar moving parts.
Figures 165 to 168 inclusive show methods of making connections between:
contacts.
Figures 169 to 171 inclusive show methods of transmitting the mechanical motion.
of one moving part to another.
Figures 172 to 181 inclusive show methods of changing the positions of moving
connections and modifications of timers.
Figures 182 to 190 inclusive show details of modifications in the construction of
switchboards moving contacts and guides.
Figures 191 to 194 inclusive show details of modifications in the escapements and.
methods of changing the position of moving contacts.
M. Referring to the drawings left with my Complete Specification
Figures 195 and 196 show two views of a contact maker to facilitate switching.
Figure 197 shows an improved switching key.
Figures 198, 199, and 200 show the elevation and details of a modification of a
switching instrument, the one shown being adapted in certain parts for use with the
system shown in Figure 1.
Figure 201 shows a modification of a system for the connection of two or more.
points using two linewires.
Figure 202 shows an elevation of the switching instrument used at each point of
the system shown in Figure 201.
Figure 203 shows a detail of a part of the instrument used at the initial point or
exchange in the system shown in Figure 201.
Figures 204 and 205 show modifications of the system shown in Figure 201:
Figure 206 shows a modification of the systems shown in Figures 201, 204
and 205 using one linewire only.
Figure 207 shows a selector as used in this system of automatic electric-
exchange.
Figures 208 to 213 inclusive show various parts and details of a switching
instrument, certain parts of which are used in common by a certain number of
points.
Figure 214 shows the same system applied to larger exchanges.
Figure 215 shows the use of a distributor in this system of automatic electric.
exchange.
Figure 216 shows the use of a protecting circuit to secure privacy.
Figure 217 shows a modification in the construction of switchboards.
Figures 218 and 219 show modifications in the construction of moving contacts.
1. In Patent No. 16768, 1892, the adoption of moving connections and the use
of timers for effecting different operations in connection with automatic telephone
exchanges were described. In the present Specification I purpose describing their
application to electric exchange for any purpose, but especially with regard to
telephony. I shall describe a complete system of automatic electric telephone
exchange applicable to areas of any size.
2. To connect one point electrically with any one of several others, that is, by
conductors for the transmission of electric currents, it is usual to connect each point.

page_text: by two or more conductors to a point called an exchange, where an attendant is
stationed to connect the various conductors as persons using the points require.
3. My invention briefly consists of apparatus by which a person at any one point
may, without the intervention of an attendant or operator at the exchange, cause
the conductors of that point to be put into connection with the conductors of any
other point in connection with the exchange, so that electrical currents may be
transmitted from one to the other.
4. For this purpose each point is supplied with an apparatus for moving and
controlling by electricity a switching instrument in the exchange.
5. Each point is connected as usual to the exchange by two or more conductors.
6. One of these conductors may be replaced by the earth used in the common
manner as a return and it shall be considered as a conductor whatever its true
function may be. In the same manner wherever the earth is used in this
Specification, a conductor insulated from it may be substituted.
7. The other conductor or conductors is or are the ordinary metallic conductors
such as linewires insulated in any ordinary manner from one another, and from the
earth between the point and the exchange, so that by using the earth as a conductor,
the number of wires required may be limited to one used for both controlling the
switching instrument and transmitting the required electric currents after the
connection is made.
8. The number of circuits to be obtained from any number of conductors using
N (N-1)
any two at a time will be expressed by the formula
where N equals the
number of conductors, including the earth if used.
2
9. The electric currents used for controlling and working the switching
instruments in the exchange, and for the general purposes of this invention, may
be derived from any convenient and suitable source and may be generated by
friction, chemical action, heat, magnetism, and induction from other currents; or
by any form of dynamic machine whereby energy is changed into electricity.
10. As before stated (3), the object of connecting the conductors of any two
points is for the transmission of electricity from one to the other. These currents
of electricity may be used for any purpose required. However generated, they
may be of any tension, quantity, and character; continuous or intermittent in
either direction, undulating, varying in intensity and quantity, or both; alternating,
oscillating; or any combination, variation of combination and sequence of com-
bination, and variation of combination of these properties; except where they
would interfere with the working of the system. For the purpose of explaining
this invent on, it will be supposed that the currents will be used for the purposes of
and for telephonic communication, but they may be used for any system of tele-
graphic communication such as needle, Morse, A BC, sounder, type printing,
writing, automatic, bells, &c. or for the transmission of power, and for electric
lighting &c.
11. In the exchange, the wire or wires from each point pass to a switching
instrument special to and controlled by electricity from that point, by which a
person using that point can put his own wire or wires into connection with those of
any other point; and having finished his communication, cause his own to be
disconnected from them and reset the switching instrument; and also at will to
cause another point's wires which may be in connection with his own to be
disconnected.
12. I shall first describe one modification according to this invention to present a
general view of its parts. Subsequently the other modifications will be explained
and more easily understood.
13. Each point connected by one linewire to the exchange. A magnet P M
with polarized armature permanently connected to the linewire.
In Figure 1 is shown a diagram of the general connections at two points A
and B, and an exchange EX; the contacts denoted by the figures or numerals
being shown open.

page_text: 14. Figures 2 to 8 inclusive are contact diagrams of the circuits used in
working this modification for any one point and its switching instrument in the
exchange.
This graphic method of showing the circuits and their changes will be used
throughout. The dots or small rings represent the contacts and parts of the
mechanism denoted by the numbers and letters above them. The lines joining
these rings represent conductors connecting the several parts.
The same letters or numerals refer to like parts of both A and B or any other
point.
15. Refer to point A, and the parts in the exchange in connection with it,
Figure 1.
E represents the earth return, M, a magneto to supply a continuous current at
will in either direction according to the direction of rotation. Contact 2 is
normally in connection with contact 3, the rotation of M automatically places it in
contact with 1.
16. Instead of M and contact 1, M with a closed circuit may be placed between
the bell B L and contact 2. The circuit of the armature of M being opened on
rotation when the current will pass to line.
17. BL, a bell capable of being rung by a continuous current or intermittent
current in the same direction. The ringing current may pass through a magnet
whose armature closes a local battery circuit in which the bell is placed. Alter-
In this case a
nating currents may be used for ringing the ordinary magneto bell.
key will have to be provided at the point to put the ringing circuit in connection
with another collector on the magneto axle. T, represents in one letter, the
telephone, transmitter and battery, induction coils and contacts. 3 is normally in
contact with 2, the unhooking of the telephone will break this connection and make
it touch 4.
18. The above arrangement of the parts between contact 5 and the earth is not
essential to the invention and may consist of any telephone outfit, as long as some
adequate source of electricity is provided, whose direction can be changed at will,
and also a bell, buzzer, or other audible or visible signalling arrangement for
attracting attention, that can be actuated by the said current.
19. 7, a key contact normally kept by a spring in contact with 5, but may be
depressed and brought into contact with 6. Contacts 5. 6. and 7 really form the
three contacts of a Morse key, which may be used in their place.
BY, a battery of sufficient power to work the magnets of the switching
instrument S in the exchange. L, the linewire connecting A with E X.
20. In the exchange EX, L passes to the switching instrument S, special to A.
It contains P M, an electro magnet with polarized armature, making and breaking
certain contacts, 8 with 9, and 12 with 13. Contacts 12 and 13 not shown in
Figure 1 are the terminal contacts of the resetting circuit of the switching
instrument S. In this case, P M is permanently connected with L (13).
SR M, an electro magnet working a relay closing and opening the local switching
circuit LSC of S. For LSC see ALSC and B LSC Fig. 35.
C, a moving contact special to A. There may be more than one.
BR, the contact bar special to A.
21. Point B, and every other point in connection with the exchange, is supplied
with similar parts as above described for A.
The office of S is to provide a means under the control of a person at the point
to which it is allotted of putting the moving contact C of that point in connection
with the bar BK of any other point; through which connection, communication is
established between the two points, and of parting the connections and resetting S
when required.
22. Figure 2 shows the permanent connections of the parts before mentioned.
Figure 3 shows the contacts normally connected when point A is ready to receive
a call or to switch.
23. Switching, ringing, speaking, and resetting. Suppose point A wishes to
17

page_text: speak to point B whose number is for instance 316. By depressing key 7, A closes
the circuit shown in Figure 4, thus sending a current from BY to the exchange
called a switching current, first three times, then once, and six times allowing a
small interval of time to elapse between each group of currents. Then the
switching instrument S automatically makes the connections in the exchange shown
in Figure 5. A's contact C is now in connection with B's bar B R, and A's
bar BR is earthed.
24. Either B's bar is earthed from a similar cause, or B is ready to receive a
call, and his connections are as shown for A. in Figure 3. If the latter, then a
current from A's magueto M, called a ringing current, in the same direction as the
switching current will pass from point A to B's instrument S whence it may partly
pass through B's SRM to earth, and partly to B through PM. The current
through B's SRM may move B's S, but that through B's PM throws over its
armature, resets B's S if moved, and cuts SRM out of circuit with the earth
through contact 9. Then the whole of A's ringing current passes on to B ringing
his bell B L. This circuit is shown in Figure 6. Figure 7 shows the speaking
circuit.
25. When finished, A disconnects the wire and resets S, by sending a current
called the resetting current in the opposite direction to the switching or ringing
currents from the magneto M, through the circuit shown in Figure 6 to B. Because
this current is in the same direction as B's switching current, it throws the
armature of B's P M back into its original position, reestablishing contact 9. Part
of the resetting current passes as before (24) through SR M to earth and moves
B's instrument S. At the same time, the armature of A's P M has been thrown
over joining contacts 12 and 13 of the resetting circuit, thus resetting S for
another call or use, the armature of PM being automatically thrown back
into its original position. It only remains for B to reset his own instrument S.
This is done by sending his resetting current through his instrument. Both
instruments and lines are now in their normal condition, with contacts as shown in
Figure 3.
26. Had B's bar BR been earthed when A rang through, A would have received
no answer, and would reset his instrument as described (25).
27. If another point, say B, sends his ringing current through A's bar, the
same changes take place in A's instrument S as described for B's instrument S
when A rang B up (24). In this case the ringing circuit shown in Figure 8, is
established.
28. The switching instruments. In Figure 10. is shown the exchange switching
instrument S. It contains all the parts special to any one point mounted on a base
plate BA; so arranged, that the over-all thickness of the instrument shall be as
small as possible, say 1 inch.
29. LT, the terminal to which the line L is connected; ET, the earth terminal.
BRT, the terminal to which the bar B R is connected; CT, the moving contact C
terminal, BT-BT2, the two terminals of the battery BY2 working the local
switching circuit. RT and RT 2, two terminals of the resetting circuit.
30. SRM is the switching relay electro magnet. Its armature ARM is
supported by the spring SP, insulated from SR M. The distance of AR M from
the poles of SRM is regulated by the set screw SC. ARM carries a
contact KT, which strikes against the contact KT 2, and completes the local
switching circuit.
31. PM, an electro magnet, before shown in Figure 1 with polarized armature ;
the poles PL and PL2 are placed between the poles of the polarized
armature A R M 2 as shown in Figure 19.
32. The armature A R M 2 is made up of two permanent magnets M 2 and M 3
fixed on the axle AL by the screws SC2 SC3 entering the collar CL fixed on
the axle A L. Their opposite poles are opposed. PLN indicates the north pole,
and PLS the south pole of each magnet M 2 and M 3.
33. See Figures 10 and 14. AL is carried by support SPT and the

page_text: yoke YK of P M, and carries the arm AM and cross arm A M2. The cross
section of A L, Figure 15, will show that the arms are inclined to one another, so
that they may be nearer the bridges but not so much as to touch BRG 3 at the
same time.
34. AL also carries the arm A M 3 parallel to the centre line of AR M 2.
Upon A M 3 screws the adjustable weight W T, of such mass, that when it passes
the centre of A L to either side, it shall overbalance the turning moments of the
bridges BR G, BRG 2 and BRG 3 when opposed to it, and cause AR M 2 to
remain in the position in which it has been placed by P M. Thus when AR M 2
is turned towards the base plate BA, A M will turn the bridge BRG 3 in the
same direction; when inclined from BA, A M 2 will turn BRG and BRG 2 in a
like direction.
The normal position of AR M 2 is when it is turned or inclined towards BA,
as shown in Figure 14. A current passing through P M in the direction of the
switching current from B V, will keep A R M in its normal position; a current in
the reverse direction, such as a resetting current or ringing current from B will
throw A R M over to the other side.
35. Riding loosely on A L, are three collars CL2 CL3 CL4. Two CL2
and CL3 are connected by the insulating bar BR 2. Through the latter pass the
bridges BRG and BRG 2. Collar CL4 with a similar insulating bar holds
bridge BRG 3. AM4 and A M 5 are two arms fitted to BR 2 and CL4
respectively.
BRG is fitted with
36. BRG and B RG2 are shown in Figures 17 and 18.
the needles N 9, N 8, N 11, and N 10, of which N 8 is the longest, N 11 next in
length, and N 9, N10 the least; BRG2 is fitted with the needles N 11 E just
behind N 11, and NE; N11 E being the same length as N 8; NE like N 10.
37. BRG 3 is shown in Figure 16 and is fitted with the needles N 12, N 13; of
which N 12 is the longer.
38. All the needles are placed over cups indicated by the same number
namely C 9, C8, C 11, C 10, CE, C 12, C 13; N 11 and N 11 E dipping into the
satne cup C 11.
39. The details of the cups are shown in Figure 22. The cup, say C8, is made
of some insulating material, or a metal with which mercury will not amalgamate.
In the bottom, is fitted a ferrule F L, with an internal screw. This screws on the
screw SC4 passing through the insulating shelf S H, and is fitted with two
clamping nuts NT and NT 2. The height of the cup can be adjusted by the
ferrule F L.
40. The cups contain mercury to the required level. The needles N 8, N 11 E,
N 12 dip into their respective cups in all positions of the bridges. Through the
weight of their respective sides, the bridges BRG and BRG 2 tend to turn
towards cup C 8, and bridge BRG 3 towards cup C 13. With reference to the
bridges BRG and BRG 2, when in the lowest or first position turned towards
cup C 8, all the cups C 9, C8, C 11 are connected; when BRG and BRG 2 are
turned a little towards C 10 so as to come into the second position, C 8 and C 11
are joined; when BRG and B RG2 are in the highest or third position, cups C 8
and C 10 are joined and C 11 is connected to CE. This is due to the lengths of
the needles. The same may be effected when the bridges have needles of equal
lengths by raising and lowering the level of the mercury in the cups.
41. Figure 9 is a diagram showing how the cups are joined for each position of
the bridges, cups C 12. C 13. excepted. The firm line shows the cups joined in the
first position of the bridges; the lines with two and three dots between the dashes,
the cups joined in the second and third positions of the bridges respectively. The
centre dotted line shows the axle upon which the bridges turn.
42. Above the cups will be seen the arm A M 6. This can assume three positions
as shown in Figures 20 and 21, namely P1, P2, P3. A M6 carries a stirrup STP
limiting the movement of A M 4. When A M 6 is in the first position P1
bridge BRG 3 cannot be turned towards cup C 13 since the arm A M 5 is kept

page_text: back by A M 6. A M 4 can move within the limits of the stirrup S.TP. Normally
it will assume the position shown in Figure 21, owing to the bridges BR G
and BRG 2 taking up their first position by reason of their tendency to turn
towards cup C 8 (40).
43. If a current in the same direction as A's resetting current pass through PM
it will throw the armature AR M 2 over from its normal position and turn the
bridges BRG BRG 2 towards C 10 thus bringing them into the second position
that is with cups C 8 and C11 only joined (40).
44. If through any cause the switching instrument S is moved, A M 6 will be
brought into the second position P 2, and the bridge BRG 3 is free to fall on
the arm A M of the axle A L. If ARM 2 be now turned from its normal
position as above described (43) A M will allow BRG 3 to join cups C 12 and C 13,
closing the resetting .circuit, and AM 2 will turn BRG BRG 2 to take up
their second position as above. When the instrument S is reset, A M 6 will be
brought with a jerk into its first position P 1, and the bridge BRG 3 striking the
arm A M 2 would by its momentum carry AR M 2 back into its normal position,
BRG, BRG 2 at the same time falling back into their first position. This is
what occurs when S is reset after a conversation.
The
45. But suppose a ringing current to enter A's BR from some other point B,
as before shown (27), part will pass through PM and part through SR M.
part through P M would throw AR M 2 over and bring B R G and BRG2 into
the second position, cutting out SR M. The part through SR M may have
moved A's instrument S, when AM 6 will take up its second position P 2, and
allow BRG 3 to close the resetting circuit and reset S, and would finally jerk
back the armature AR M 2 into its normal position as shown (44). This has
taken up the fraction of a second of time. B naturally rings for two or three
seconds and the whole of the current passing through P M to A will keep A R M 2
still thrown over, so that although AM 6 is now brought back into the first
position P1, AR M 2 will keep BRG and BRG 2 in their second position.
46. Whenever the switching instrument S has brought A's moving contact Ca
into connection with required bar BR, it automatically moves A M 6 into the third
position P3, the stirrup brings BRG and BRG 2 into their third position (40),
thus joining cups C8 and C 10, the armature A R M 2 remaining in the normal
position.
47. When it is required to disconnect and reset S, A's resetting current being a
contrary in direction to the switching current will throw A R M 2 over and join
cups C 12 and C 13 closing the resetting circuit. The arm A M6 and the bridges
are brought back into the normal positions as described in paragraph 44.
48. A table to show at a glance the cups connected by each position of A R M 2
and A M 6. The lines joining the cups denote those connected.
Position of A. M 6.
P1
A R M 2 in its normal
position.
C12 C9—C8—C11
AR M 2 thrown over.
C 12 C9 C8-C11
4

page_text: The rod RD slides through two holes in F T, and is kept in the position shown by
a spiral spring SP 3, the lower end bearing on FT, and the upper end against the
nut NT3. RD carries the movable hook H K. To HK, one end of the
cord CD is fastened, the other passing round the grooved wheel W L. . On
the same axle is the toothed wheel T W held in position by the detent DT.
50. In connection with the moving hook HK, the timer TR may be now
described. When AR M3 is attracted, the fitting FT strikes against the end of
the rod RD 2. To the other end of RD2 is fastened a cord CD 2 passing round
the axle A L 2. Passing round A. L 2 in the opposite direction to C D 2, is another
cord CD3 fastened to the spring S P 4. Fixed on the axle AL 2 is an arm A M 7
carrying a pallet PT mounted on a spring. At the back of AM 7 is a stud or
projection ST, engaging with grooved collar CL5, fastened on the rod RD 3.
The pallet PT2 is mounted on spring SP 5 fastened to the end of RD 3.
SP5 has a step or bend near pallet PT2. The escapement wheel EW rides
loosely on AL 2. The escapement ES engages with the teeth of E W. The
adjustable pendulum P 4 regulates the time of the vibrations of E S.
51. On armature AR M3 being attracted by S M, the rod R D 2 is pushed back,
CD2 turns the axle A L 2 in opposition to the spring SP 4. At the same time
A M7 is turned. The stud ST at the back of A M7 moves RD 3 with it for a
short distance retracting the pallet PT 2. When the step in S P 5 strikes against
the fitting FT 2, it raises PT 2 out of the way of T W. AM 7 continuing to turn
leaves the collar C L 5, and comes to rest at some point, and at the same time the
pallet PT slips over the teeth of E W.
52. The current ceasing in SM, ARM3 springs back. SP4 gives up the
force stored in it, and now turns AL2 in the opposite direction. Pallet PT
engages with the teeth of E W and turns it and puts the escapement ES in motion.
This allows AL 2 to turn at a set rate. When A. M 7 reaches the collar C L 5 it
pushes it forward, and pallet PT2 will engage with a tooth of T W and turn it a
distance of one tooth.
53. If A R M 3 remains unattracted until detent DT slips over the next tooth,
the hook HK will be lowered.
If it is attracted before PT2 reaches TW, the hook HK will not be lowered.
Thus HK will not be lowered until a certain interval of time has elapsed since
ARM 3 was last attracted.
54. HK engages with three other hooks HK2 HK3 and HK5 on the
levers LV, LV 2, LV 3. A view of the levers LV LV 2 and LV 3 towards S M,
is shown in Fig. 23 and the opposite side in Figure 24.
55. Lever LV turns on pin P N, levers LV 2 LV 3 on pin P N 2.
56. Lever LV is again shown in Figure 26. Its parts are the hook H K 2, the
detent DT2, and the arm A M8 carrying a pallet PT 3 on a spring SP 6.
Lever LV 2 is again shown in Figure 25. Its parts are the hooks H K 3, HK 4
and tail TL.
Lever LV 3 is again shown in Figure 27.
detent DT 3, and tail T L 2.
Its parts are the hook HK 5, the
When at rest the three hooks HK 2, HK 3, H K 5 are in a straight line.
57. BR, BR are metal bars fixed to the body of the switchboard SB, and
insulated from one another. Each BR is special to some point, and is connected
to the BRT of that particular point's switching instrument.
58. For cleaning, S B is made movable and is fitted with a metal tongue T G at
top and bottom, fitting in a metal groove GR, screwed to the frame rails F R.
59. The switchboards S B are made in convenient lengths to serve a convenient
number of switching instruments, like bars of each group of switchboards being
connected in series or connected by branches from one wire.
60. There is any convenient number of bars BR on each board, and also on both
faces of a board. In this case, there are 100 bars on each face of each board, and
as many boards as may be required. Two are shown in Figure 10.
61. Parallel to the faces of bars and fixed by the ears R to FR, FR, are the

page_text: metal guides G, of the section and form shown in Figure 28. All those guides
on the faces of all the boards SB belonging to one switching instrument are
electrically connected in series or multiple branch to the terminal CT of that
instrument.
62. Along these guides G slide the moving contacts C. Each consists of the
weight W T2, secured by the clips CP to the guides G, as shown in Figure 28.
CS is the contact spring, screwed to WT 2, and presses lightly on the faces of the
bars BR. The upper part of W T2 is fitted with a ring RG, and adjustable
To R G is
coupling CP 2, containing an internal right and left handed screw.
fastened the cord CD 4, for raising and lowering the contact C. Figure 11 shows
the arrangement of the contacts of different points, side by side, on the faces of the
bars B R.
63. The cords CD are wound upon the reels RL. The reels RL have hollow
axles A L3 revolving in the bearings B G.
64. On one end of each axle AL 3 is shown a disk D.
views of D. A portion of the edge of D is cut away at P 5.
the spring S P 7. The most important part of SP7 is the
above the surface of D.
Figure 29 shows two
On the back of D is
projection PJ raised
65. A L4 is a long axle passing through the hollow axles AL 3, supported on
suitable bearings. Two of these bearings are shown at BG 2 aud BG 3. AL4 is
provided with the arms A M 9 revolving just in front of the disk D.
It is
66. Each reel R L tends to turn by reason of the contact weight WT 2.
detained by lever LV 4 forced by the spiral spring S P8 on the pin P N 3 into P 5
of the disk D, and presses the spring SP 7 and its projection PJ back to the face
of the disk.
If LV 4 be moved out of P 5, RL will be turned by the weight WT2 until
the PJ of the spring SP7 strikes the arm A M9 of the axle A L4, when the
further descent of contact. C will be governed by the movement of A L4.
67. A L5 is an axle supported on suitable bearings BG 4, BG 5, BG 6. The
escapement wheel E W 2 is fixed on one end of A L5 which carries a collar C L 6.
To CL6 one end of the spiral spring SP9 is fastened, the other end being
fastened to B G 4. AL5 can move in two directions; lengthways and axially,
both in opposition to the spring SP 9. On A L5 are the radial arms A M 10
arranged at equal angular distances from one another, so that for each position
of A L 5, only one of the arms A. M 10 will be opposite one of the levers LV 4.
68. E W 2 is turned one tooth at a time by the spring pallet PT3 of lever LV,
this against the spring S P 9, and is prevented from returning by the detent DT 4.
Having brought the required arm AM 10 opposite the required lever LV 4, the
lever LV 2 is pulled by HK. The hook HK 4 draws EW 2 and the axle AL 5
lengthways, and the latter is prevented from returning by the notch NH in
detent DT 4. The other end of LV 4 is drawn out of the P 5 in which it was.
PJ is pushed forward by the spring S P 7, and the reel R L is free to drop on the
arm A M 9, which now carries the whole of the weight of the contact c.
69. We now return to A L 4. It is fitted with a pilot reel PRL carrying the
pilot weight PW. In front of PRL is an escapement wheel E W 3, shown in
elevation in Figure 30. One of its teeth is replaced by a pin P N 4.
70. Riding loosely on AL4 between E W 3 and the bearing BG 2, is an
arm AM 11 carrying the escapement ES 2 shown in elevation and plan in
Figure 32. ES 2 has two pallets PT4 PT 5 and vibrates on the centre screw SC 5.
ST2 is a stud by which the arm A M 11 is held by the escapement ES 3.
A M 12 is an arm by which the tail T L 2 of lever LV 3 lifts ES 2 and allows one
tooth at a time to escape.
71. The bearing B G 2 carries the escapement ES 3, shown in elevation and plan
in Figure 31. It vibrates on the axle A L 6 between the bearings BG 7 and BG 8.
Its two pallets are PT6 and PT 7, and it has an arm A M 13 by which the tail TL
of the lever LV 2 raises it, and allows the stud ST2 to pass, when axle A L 4
and E W 3 will make a complete revolution carrying ES 2 with them.

page_text: 72. The axle A L 4 is square for the remainder of its length. On this part, the-
grooved collar C L 7 slides carrying the bevel toothed wheel B W. This is pushed
backwards and forwards by the forked end of the spring S P 10. SP 10 is attached
to the armature AR M4 of the winding magnet W M. AR M 4 is supported by
the spring SP 11.
73. To reset the switching instrument, B W is brought into contact with B W 2:
on the axle A L 7. BW 2 being turned, A L 4 raises the pilot weight P W and
the contact C used. The cord PCD of the pilot weight is provided with an:
adjustable stop STP 2. This is raised on the cord and strikes against the fork FK
of the resetting rod RD 4, and raises the lever L V 5 moving about the pin P N 5.
Various pins PN 6, P N 7 on LV 5 raise the detent DT releasing the hook HK
which returns to its first position, raises detent DT 4, and the arm A M 14 to
deteut DT 2. The latter operation opens the resetting circuit and replaces the
bridges. Thereupon the rod RD 4 drops until the stud ST2 of the arm AM 11
is held by the escapement ES 3. Refer to paragraph 70.
74. AL 7 runs by a given number of the switching instruments, carrying a bevel
toothed wheel B W 2 for each. A L 7 is turned by the winding motor W MR, set
in motion by the starting electro magnet S M 3 in series with W M and the battery
BY 3. S M 3 is only supposed to release or start the motor W MR, which is
worked by some other motive power such as steam, gas, electricity weights or
springs.
75. See Figure 33 A L 8 is an axle turning in the bearings B G 9, BG 10, and
has the arms A M 14, A M 15 and A M 16. A M 16 is connected by pins and a
connecting rod RD 5 to A M 17; A M 6 and A M 17 (see Figure 21) are fixed on
the short axle A L 9 so that A. M 6 is governed by the movement of A M 14.
76. There are three stages in the movement of A. L 8. In the first position A. M 14
rests on detent DT 2, then A M 6 and S T P are in the first position P 1, Figures 20,
and 21.
77. On lever L V being pulled by hook HK, A. M 14 drops on to the detent DT 3,
of lever L V 3 and A M 6 and STP come into their second position P 2.
78. When lever LV 3 is pulled by hook HK, A M 14 drops down and A. M 15.
rests on the spring S P5 of the timer as SP5 moves to the right A M 15 escapes
and drops allowing A M6 and S T P to reach their third position P 3. On resetting
the instrument S, the lever L V 5 raises A. M 14 again to detent DT2 (73).
79. Now I will describe the use of the instrument. In Figure 34 is shown a
diagram of the contacts and circuits for any two points A and B. The batteries BY 2.
and BY 3 and the magnet S M 3 being used in common by all the switching
instruments. The contacts are shown open.
80. Upon inspection of Figure 34 and contact diagram Figure 35, A and B's local
switching circuits ALSC and BLSC are seen to comprise KT, BT, BY 2,.
BT 2, S M, and K T 2, and that A and B's local resetting circuits ARC and BRC
comprise C 12, RT, SM 3, BY 3, RT 2, W M and C 13. With the exception.
of BY 2, BY 3 and S M 3, these parts denoted by the letters included by the
lines AS and BS belong to A and B's switching instruments respectively.
81. Figure 35 shows the permanent connections of the various parts from.
A's earth to B's earth. Figure 36 shows the normal connections when A and Bare-
set to receive a call or to switch.
82. As before (23) I will suppose that A wishes to speak to B whose number
is 316. Taking key 7 A presses it three times. Each time a current is sent
from BY through the switching circuit shown in Figure 37 and the magnets P M
and S R M are excited. The armature AR M 2 of P M remains in its normal
position and keeps the bridges BRG BRG 2 and BRG 3 in the first position,.
and the armature ARM of SR M completes the local switching circuit ALSC
by which magnet S M is excited, and armature ARM 3 attracted. Hook H K
pulls lever LV which first drops A M 14 on the detent DT 3, thus bringing A. M 6-
into the second position P 2, and turns the escapement wheel E W 2 three teeth by
pallet PT 3. This brings the third arm A M 10 opposite the end of the third

page_text: lever LV 4 of the third reel RL. At the same time the armature A RM 3 bas
moved the timer TR as described in paragraph 51.
83. After these three currents have passed, a small interval of time is allowed to
elapse when the pallet PT 2 of the timer T R will lower the hook HK from HK 2
to H K 3.
84. On pressing key 7 again once, the same circuits are completed and H K pulls
lever LV 2. This first draws axle A L 5 forward, and the third arm A M 10 raises
the third lever LV4 from the disk D of the third reel R L, and allows the
spring SP7 to push the projection PJ forward; R L being free, turns by the
weight W T2 and rests on the third arm A M 9 of axle A L4. At the same time
the tail T L of lever LV 2 raises the escapement ES 3, and allows the stud ST 2
to pass, thus letting E S 2, E W 3 and the axle AL 4 to make a complete revolution,
and the third contact C is lowered a distance equal to ten bars, but does yet not
reach the bars.
Every time key 7 is pressed C is lowered a distance equal to ten bars, and had it
been pressed three times C would have reached the twentieth bar.
As before hook H K is lowered down to hook H K 5 by T R.
85. On pressing key 7 again 6 times the before mentioned circuits are closed,
and lever LV 3 is pulled. This first drops the arm AM 14 from detent DT 2,
and AM 15 rests on the end of the spring $ P 5. At the same time, the tail T L 2
raises escapement ES 2 6 times, each time allowing one tooth of the wheel E W 3
to pass, so that contact C is lowered six bars. The contact C is now in connection
with bar No. 316.
86. On the last return of S P 5 of the timer T R, the arm A M 15 escapes and
drops, thus bringing A M 6 and STP into the third position P 3. The latter
throws the bridges BR G and BRG 2 over into the third position, which join C 8
to C 10 and C 11 to C E thus joining L to C and earthing A's B R. This state of
the connection is shown in Figure 38.
87. A then turns his magneto M so that his ringing current is in the same
direction as his switching current. This will pass through the circuit shown in
Figure 39. It passes through A's magnet P M, partly through B's magnet P M,
and partly through B's SRM to earth. This current, being contrary in direction
to B's switching current, will cause B's armature AR M 2 to be thrown over thus
bringing B's bridges BRG and BRG2 into the second position cutting out
the SR M. The current through B's SRM closed B's local switching
circuit BLS C, and moved B's lever LV, therefore B's A M 6 will fall into
the second position P 2, release the B's bridge B R G 3, and from the position of
the armature AR M 2 close B's resetting circuit BRC.
88. This will reset B's instrument S, and would throw B's AR M 2 back into
its original position through the momentum of the bridge BR G 3 when jerked
back by B's A M 6. All this has taken place in the fraction of a second of time;
and A, still ringing, will be passing current through B's magnet P M when the
resetting circuit is opened, and this keeps A R M 2 thrown over and the
bridges BRG and BRG 2 in the second position while the current now passes
through L to point B and rings the bell B L'as shown in Figure 40.
89. A and B now speak through the circuit shown in Figure 41.
90. To disconnect and reset, A reverses the motion of his magneto M, and sending
a resetting current through the circuit shown in Figure 42, throws over both
A's AR M 2 and B's AR M 2. In A's case, it will join the cups C 12 and C 13
and close the resetting circuit ARC. In B's case, it will throw back B's ARM 2
into the normal position and join C 9 to C 8, when part of A's resetting current
passing through B's SR M will move lever LV and free A M 6 as shown in
Figure 43. B is shown as depressing bis key 7 to help A's resetting operation.
B might have used his magneto M in the same way.
91. It now remains for B to reset his own instrument, which is done by sending
a resetting current. This is shown in Figure 44, and finally both instruments
resume their normal state shewn in Figure 55.

page_text: 92. It will be noticed that when B was rung up by A, A's ringing current is in
the same direction as B's resetting current; and vice versa, A's resetting current is
in the same direction as B's switching and ringing current. If they leave their
instruments connected and A wanted to ring up B, A would ring in the usual
manner; while if B wanted to ring A up, he would send his resetting current
through, and if he wants to disconnect froin A he will send his switching current
through, after which he will have to reset his own instrument as above described.
93. In the foregoing system, it will be noticed that C is not joined to L until
the switching operations are finished. C may be joined to L during switching, but
part of the switching current would be shunted through the bars it passed over and
derange the existing connection.
94. Each point connected by one linewire to the exchange. An electro magnet
with polarized armature permanently connected to the linewire, and a guard
magnet in either or both contact C or BR circuits.
The switching instrument S and connections being as shown in Figure 36, a
resetting current passed through the switching circuit from A would generally
move the instrument S and throw A R M 2 over, which would reset the instru-
ment (44). But if from some cause the instrument S were not moved, A R M 2
would still be thrown over and bring the bridges BRG and BRG2 into the
second position, disconnecting contact 9 from contact 8. There being no circuit
through B R, A cannot move his instrument until A R M 2 is replaced.
95. To prevent this occurring, I put an electro magnet M. 4, Figure 1, into the
bar circuit. Its armature governs a detent normally keeping the bridges B RG
and BRG 2 on the first position, and will not raise it unless a current passes to or
from B R. Therefore A cannot move the bridges unless his instrument is moved,
or a circuit is formed through the bar. This will not interfere with the
bridges BRG and BRG 2 being brought into the third position, as the detent
would be automatically raised by the arm A. M 6. Such a magnet I call a guard
magnet.
96. In a similar way, an electro magnet may be put in the contact C circuit, its
armature governing the contact of an earth shunt between this magnet and
contact 10. If a circuit can be completed through C, the earth shunt is broken
by the current passing through the magnet; but if no current passes through C, a
resetting current may be passed through the earth shunt, and close the local
resetting circuit. The resistance of the earth shunt will be altered to suit
circumstances.
These guard magnets may be applied to any of the systems of connections,
where no other safeguards are supplied against incomplete circuits and bad
contacts.
97. Each subpoint connected by one linewire to the exchange. A magnet with
polarized armature common to both the C and BK circuits, that is, it is put in
circuit with C or BR as required.
Figure 45 shows an arrangement of the one linewire system shown in Figure 1,
in which the magnet P M (31) is taken out of the switching circuit, and only
introduced into the C or BR circuits as required. Figure 46, the permanent
connections. Figure 47, the normal contacts when at rest. Figure 48, the
switching circuit. When contact C has reached the required bar BR, the
switching instrument S automatically arranges the connections as shown in
Figure 49. PM is now in the C circuit. The ringing circuit is shown in
Figure 50 and the speaking circuit in Figure 51. To disconnect and reset, a
resetting current is passed through the ringing circuit Figure 50, P M reverses its
armature and joins contacts 13 and 14 completing the local resetting circuit, after
which the connections are replaced in their normal state as shown in Figure 47.
98. The ringing current from the bar will pass to earth through P M, Figure 47.
PM will throw its armature over disconnecting 11 from E, 8 from 9 and
connecting 8 to 11; the current will then pass to A's bell as shown in Figure 52.
F

page_text: i
Figure 53 is a diagram of the cup connections for each position of the bridges here
shown. Five bridges are used, fixed on one bar similar to BR 2 (35). Cups 13
and 14 are the poles of the local resetting circuit.
By the introduction of another cup CC, the contact C may be connected to P M
after the switching is completed instead of being permanently joined as shown.
99. In Figure 54 is shown another method of accomplishing the same purpose as
that shown in Figure 45. Figure 55 shows the permanent connections. Figure 56,
the normal connections when at rest, Figure 57 the switching circuit. Figure 58
the connections made by the switching instrument after switching. Figure 59, the
ringing circuit. Figure 60, the speaking circuit. Figure 61, the ringing circuit
when another point B rings through A's bar. Figure 62, the diagram of cups
showing those connected for three positions of the bridges there shown. C 14
and C 1 are the local resetting circuit contacts.
100. Each point joined by one linewire to the exchange. Two magnets with
polarized armatures, one in the C circuit and the other in the BR circuit.
In Figure 63 is shown a one linewire system with a magnet P M in both contact C
and B R circuits namely CPM and BRP M. Figure 64 shows the permanent
connections. Figure 65 shows the normal contacts when at rest Figure 66, the
switching circuit. After switching, the switching instrument makes the connections
shown in Figure 67. CPM only controls the resetting circuit, that is joins the
two contacts 13 and 14. The ringing circuit is shown in Figure 68, the current
does not alter the armature of CPM. The speaking circuit is shown in Figure 69.
To disconnect and reset, the resetting current is passed through the ringing
circuit Figure 68, throws over the armature CPM, and closes the resetting
circuit, which brings all the parts back into their original positions.
101. A ringing current from A's bar BR will pass first through BRPM to
earth. This magnet controls the contacts 8, 9, 11 and 12. Its armature being
thrown over, will disconnect 11 and 12, and 8 and 9, and join 8 and 11.
After this,
the current passes on to A and rings his bell as shown in Figure 70.
102. Figure 71 shows the cups. C 12, C 11, C8 and C8 A having bridges
controlled by BRPM. C8A, C 10, and C 9 having bridges controlled by the
switching instrument. C 13 and C 14 are controlled by CP M. These bridges
have only two positions to move between.
103. In Figure 72 is shown the bridges controlled by BRPM and the switching
instrument compounded on one axle, and have to take up three positions. First,
the normal one at rest; the second by the magnet BRPM; and the third by the
switching instrument. Magnet C P M as before controls contacts 13 and 14.
104. Each point connected by one linewire to the exchange. An electro magnet
with polarized armature and a shunt magnet with polarized armature, both used in
common in the C and B R circuits.
The use of a guard magnet with or without a shunt to earth was mentioned in
paragraphs 94, 95 and 96. An extended use of the same method inserting in the
carth shunt a magnet with polarized armature will now be described.
105. Figure 73 shows the general connections of a one linewire system wherein
the series P M and the shunt SPM are used, connected to the C or BR circuits
as required. Figure 74 shows the permanent connections. Figure 75, the normal
connections when at rest. Figure 76, the switching circuit. After switching, the
switching instrument S makes the connections shown in Figure 77. In Figure 78
is shown the ringing circuit. When the ringing current reaches contact 10, two
paths are open to it, one through S P M which controls contacts 8 and 12, and 14
and 15 of the resetting circuit; and the other through PM which controls
contacts 13 and E to the other point.
Should any part of the current pass through P M, it throws the armature of PM
over and disconnects 13 and E when all the current will pass on to B. The speaking
circuit is shown in Figure 79.
To disconnect and reset, the resetting current is passed from A to B, throws

page_text: back the armature of PM, again closing contacts 13 and E. The current now
passing through SPM throws its armature over and closes contacts 14 and 15
of the resetting circuit, which brings all their parts into their normal position.
106. When a ringing current from some other point enters A's bar it passes to
earth through SP M, throws its armature over and joins contacts 8 and 12, there-
upon another path is opened through P M to A. The portion of current passing
through P M will throw its armature over as before, and disconnect 13 and E, when
the whole current passes to A and rings his bell. This circuit is shown in Figure 80.
B's resetting current reverses this motion.
107. Figure 81 shows the contact cups. The connections between cups C 14
and C 15, C 8 and C 8 A and C 12 are controlled by the magnet SP M. Those
between C8 A C 9 and C 10, and C 11 and C 10 are controlled by the switching
instrument S, that between C 13 and CE by magnet P M.
108. Each point connected by one linewire to the exchange. An electro magnet
with polarized armature common to both C and B R circuits with separate shunt
electro magnet with polarized armature for each.
Figure 82 shows how the last system may be used with a common series P M
with shunt magnet C SPM for the C circuit and shunt magnet BRSPM for the
bar BR circuit. Figure 83 shows the permanent connections. Figure 84, the
normal connections when at rest. Figure 85, the switching circuit. Figure 86
shows the connections made by the switching instrument S after switching.
Figure 87, the ringing circuit. Figure 88, the speaking circuit.
109. Figure 89 shows the ringing circuit when A is rung up from the bar B R.
P M controls contacts 13 and 14 with E, CSPM and BRSPM control
contacts 15 and 16 of the local resetting circuit, while in addition BR SPM
controls contacts 8, 9, and 12. The switching instrument controls contacts 8, 9, 10,
and 11.
110. Each point connected by one linewire to the exchange. Separate electro
magnets with polarized armatures in each of the C and B R circuits, and one shunt
electro magnet with polarized armature common to both.
Figure 90 shows the general connections when the system shown in Figure 73 is
used with a common shunt magnet SP M, with separate series magnets CPM
and B R P M used in the C and B R circuits. Figure 91 shows the permanent
connections. Figure 92, the normal connections when at rest. Figure 93, the
switching circuit. Figure 94, the connections made by the switching instrument
after switching. Figure 95, the ringing circuit. Figure 96, the speaking circuit.
111. Figure 97, the ringing circuit when A is rung up from the bar.
SP M controls contacts 14 and 15 of the local resetting circuit, and also the
connections between 8 and 9 and 12; the switching instrument S controls the
contacts between 10 and 13, 8 and 10 and 8 and 9, and CPM and BRP M
the contacts 11 and E.
112. Each point connected by one linewire to the exchange. A separate electro
magnet with polarized armature and separate shunt electro magnet with polarized
armature in each of the C and B R circuits.
Figure 98 shows the general connections of the system shown in Figure 73 when
used with a separate series and shout magnets for both the C and BR circuits,
namely CPM the series and CSPM the shunt for the C circuit, and BRP M
the series and BRSPM the shunt for the BR circuit.
Figure 99 shows the permanent connections. Figure 100 shows the normal
connections when at rest. Figure 101, the switching circuit. Figure 102 shows
the connections made by the switching instrument after switching.
Figure 103 shows the ringing circuit. Figure 104, the speaking circuit.
Figure 15, the ringing circuit when A is rung up from the bar.
113. CPM and BRPM control the contacts 11, 13 and E; the switching
instrument the contacts 8, 9, 10; CS PM, the contacts 14 and 15 of the local
resetting circuit; and BRS P M the contacts 14 and 15 and 8 and 12.
114. Metallic circuits. In Figure 116 is shown the system shown in Figure 1,

page_text: with a complete metallic circuit through the linewires L and L 1, for which double
bars B R and double contacts C are used. Such a return may be used in all cases
instead of the earth return. That shown in Figure 116 is special to each point and
necessitates double bars and contacts, but if the return wire be a conductor or
linewire insulated from the earth and running from the exchange in series through
or branched to each point in the most convenient manner single bars and contacts
may still be used, the returns being made through this common return wire instead
of the earth.
115. By means of the formula in paragraph 8, we may form two more circuits
between the exchange and each point, in which two keys K2 and K3 may be
introduced, two magnets for any purpose required, for example two switching relay
magnets SRM 2 and SR M 3 both worked by the battery BY 4. SRM2
and S R M 3 would be disconnected when speaking or ringing. K 2 and K 3 would
break the circuit through 7 when pressed.
116. Batteries at the exchange. The switching circuit has hitherto involved the
use of a battery at each point. It would be better at the exchange since one would
supply a large number of points. This can be applied to any system by the
addition of an electro magnet to each switching instrument.
117. In Figure 106 we have a general view of the system shown in Figure 1 so
fitted. At the point is a key to close contacts 5 and 6. In the instrument S, an
extra contact 14, in connection with magnet M 5 and the earth. SR M is connected
to a battery B Y and to earth.
Figure 107 shows the permanent connections. Figure 108 shows the normal
connections when at rest. To switch a current is sent from the magneto M through
the circuit shown in Figure 109, that is, through the maguet M 5 and thence to
earth. This magnet disconnects 8 from 14 and connects it to 9. All connection
with the earth is automatically broken at the point A and by pressing the key at 6
the switching circuit shown in Figure. 110 is formed and the contact C is placed on
the required bar as usual. After this the switching instrument makes the
connections shown in Figure 111. Figure 112 shows the ringing circuit.
Figure 113, the speaking circuit. Disconnecting and resetting are performed in
the usual manner and 8 is again connected to 14 as shown in Figure 108.
118. The ringing current from the bar passing through P M disconnects 8
from 14 and 9 as before described (45), leaving the only connection through 8
and 11. The ringing circuit is shown in Figure 114.
119. Branched battery wire. The next method of using a battery at the
exchange is to connect one pole to the switching relay magnets S R M of all the
points, and taking the other to every point in series or in multiple arc or branched
like a tree. This as an example is shown applied to the system described
in Figure 1 by Figure 115. This does not alter the method of using the switching
instrument.
To
120. S R M with polarized armature. In the system shown in Figure 1, the
magnet PM is always in circuit, in many others, the only magnet in the switching
circuit is the SR M. This, not having a polarized armature is affected in the same
way by both positive and negative currents, and the whole course of switching
operations would have to be gone through before the instrument can be reset.
obviate this, I give SR M a polarized armature, so that it has two movements
similar to those of P M according to the currents passing. The switching current
passing through S R M would close the local switching circuit through one contact
of the polarized armature, and the resetting current close the local resetting circuit
through the other contact.
121. The same may be done by using an armature like that of P M in conjunction
with the armature of S R M, when the resetting current passes through the SR M
it will attract its armature AR M as usual and throw over the polarized armature
and close the local resetting circuit.
122. Each subpoint connected by one linewire to the exchange; a timer moving
a contact changer.

page_text: In Figure 1, the motion of the magnet S M is transmitted to various parts of the
switching instrument of a timer working a hook changer. There may be a magnet
similar to S M for each operation working a common timer, which by moving a
contact changer after each group of switching currents may bring the magnets S M
into the local switching circuit in order. The other arrangements of any system
of connections need not be altered.
123. Each subpoint connected by one linewire to the exchange. A magnet with
polarized armature vibrating between two contacts one for switching and the other
for moving a hook or other movable connection.
In Figure i, let BY be connected to a pole changer at 7 and the line L normally
connected to magnet P M and thence to earth. Let PM have a polarized
armature normally midway between two contacts. When a positive switching
current is passed through PM the movement of its armature closes the local
switching circuit. When a negative current passes, its armature is reversed and
closes a local circuit in which is a magnet that moves a hook on the armature of
the switching magnet S M. The connections of C and B R circuits being made in
the manner shown in the system, Figure 1.
124. The hook changer may also be worked through a separate linewire.
125. Each point connected by two linewires to the exchange, one for switching
and the other for speaking.
•
In Figure 117 is shown a system with two linewires SL and L connecting each
point with the exchange. One SL is used for switching and the other L for
speaking. Figure 118 shows the permanent connections. Figure 119 shows the
normal connections when at rest. On pressing the key and connecting 5 and 6 the
switching circuit is completed as shown in Figure 120. This being done
the required number of times, with the usual interval between the groups of
currents, contact C is in connection with the required bar B R. At the same time
the bar BR is disconnected from L. This state of the contacts is shown
in Figure 121. Then the ordinary ringing and speaking will take place
through L as shown in Figures 122 and 123. To disconnect the key at 6 is
again pressed and the switching instrument S closes the resetting circuit by
contacts 9 and 10.
126. In this case the switching instrument S is like that shown in Fig. 10
without the magnet PM or cups and magnet W M. It has an extra lever L V 6,
and the hook H K takes up four positions. When the resetting current is sent,
this lever LV 6 is pulled and closes the local resetting circuit and brings B W
into contact with BW 2, being held by a detent until the instrument is reset and
restored to the condition shown in Figure 119.
A conductor L passes
127. Two or more points on one linewire. Figure 125.
through the points A B C and EX, in each through a magnet M. The earth may
form part of L between any points. Each station is fitted like A with a key K
and battery BY capable of properly working the magnets M of all the points.
Normally the circuit is completed through the magnets M and the keys K. On
pressing K, BY is brought into circuit and all the magnets M are excited.
128. Figure 126. Each point A B C is fitted with M K and BY like A. At
EX the line passes through M a magnet whose armature is so adjusted that
a current from the battery BY at any point will cause contact 1 to leave
contact 3 which it normally touches and touch contact 2 thus bringing the
battery BY 2 into circuit. BY 2 is capable of working all the magnets M, M in
circuit. If the currents from BY 2 be switching currents the ringing and speaking
currents must be such that they will not affect the armature of M 2, that is
alternating.
129. M 2 may have a polarized armature which will be attracted by the switching
currents, while the ringing currents being in the opposite direction will not affect
contacts I and 3.
130. It may be desired to use the BY of each point for further switching
without having to change its poles. Therefore (Figure 127) a magnet M is put

page_text: preferably in the B Y 2 circuit; its armature carries a moving hook and is fitted
with a timer. L normally passes through contact 3 and magnet M 2. On
pressing K a current from BY passes through M 2 and makes contact between 1
and 2. M attracts its armature and the timer keeps 1 in contact with 2 until the
last current has passed. After a short interval of time, the timer returns and
makes contact 1 touch contact 4 and also moves the hook. The armature
of PM being polarized is not affected by a current from B Y, so the latter can be
used for further switching. A resetting current passing through PM in the
opposite direction will throw its armature over making 1 touch 4 when the current
of BY 2 passing through M and all the other magnets M resets their hooks and
switching instruments and causes 1 to touch 3 as before.
131. Figure 128. A conductor L passes through several points ABC and in
each through a magnet M. At any one point EX, L is connected by a
battery BY 2 to another conductor in this case the earth. At the points are the
keys K, K, by which those points can be connected to the other conductor or the
earth, thus joining the poles of BY 2. When any K is depressed the circuit
of BY 2 is completed through the two portions of L on each side of the key K
and BY 2. The resistances of these sides will be equal if K be in one certain
place and the current in both parts of L will be supposed to be strong enough to
work the magnets M in each half.
The chances are that the resistances will differ the current in one side being
stronger than in the other and the more so as K nears BY 2. At A, BY 2 would
be practically short circuited and none of the magnets be operated.
132. This may be corrected for any one point by putting resistances perinanently
in the circuit. This will only make it worse for the other points. It will be
necessary to put a given resistance into circuit when any K is pressed and remove
it again as shown in Figure 129. R is a resistance determined for each point,
normally short circuited by the contacts 17 and 18, which are opened on
depressing K.
133. Another method is to introduce more batteries at different points between L
and the earth, one at each point A B C and EX if necessary, so that the least
current that will pass through any magnet M shall be of sufficient strength to
operate it.
134. Another way of securing the same end is shown in Figure 130. The same
letters apply to the same parts as in Figure 128. M2 is a magnet in
the BY 2 circuit. When attracted its armature causes 1 to leave 3 and touch 2
thus bringing into circuit the battery BY 3. Normally 1 is in contact with 3.
Each time the K at any point is depressed the circuit of battery BY 2 is
completed and M 2 completes the circuit of battery BY 3.
135. It may be said that when any K is touched that most of the current
from BY 3 will pass through the path of least resistance. This will perhaps occur
when K is nearer the exchange than the others. It will be seen that before BY 2 is
cut out of circuit the armature of M 2 must rise, and to allow which the key K must
also be raised and break the BY 2 circuit. During the interval of the raising of
key K and the raising of the armature the current of BY 3 will pass through the
whole circuit and properly actuate all the M's.
136. A flexible spring contact similar to that shown in Figure 131 may be
attached to the armature of M 2 to keep 1 and 2 in contact for a little while after
the BY 2 circuit is broken. Figure 131 shows the armature of M2 in two
positions when at rest and when attracted. A timer may be used with M 2 for the
same purpose.
137. One battery BY 3 may be used for both the batteries BY 2 and BY 3.
In Figure 132, normally 1 touches 3 and 2 touches E. A key K being pressed the
armature of M 2 breaks the above connections and causes 1 to touch 2.
138. To prevent an insufficient current passing through the circuit L,
BY 2 Figure 130 may be made to balance BY 3.
139. Refer to Figure 133. The two batteries BY 3, BY 3 may be employed,

page_text: the magnet M 2 bringing the contacts 1 and 1 into contact with 2 and 2.
Normally 1 and 1 are in contact with 3 and 3. Like poles of BY 3, BY 3 may be
connected to 2 and 2.
140. In Figure 134, BY 3 and BY 3 are both connected to earth through M 2,
normally touches 3, a current through M 2 will make 1 touch 2. Unlike poles
of BY 3 and BY 3 may be connected to earth.
141. In Figure 135, P M is a magnet with polarized armature, 16 and 17 are
contacts and M a magnet similar to magnet M fitted with a timer and moving hook,
L is normally in contact with 17 and 1 with 3. On pressing K at any point,
BY 3 is brought into circuit as usual. When the switching currents cease, the
timer asserts itself and brings the hook of M into the second position and L is
connected with 16.
Its
P M 2 is a magnet with polarized armature and is now in the L circuit.
armature is not affected by the currents passing in one direction but any in the
opposite direction will throw its armature over and make L touch 17. Any key K
being pressed will complete the circuit of B Y 3 and reset M.
142. In Figure 136 are shown the general connections of four points A B C D
connected by one linewire L to an exchange EX where one switching instrument S
is special to it. The switching instrument S, and those of any other points as F
and also the method of working them are supposed to be like the system shown in
Figures 1 and 10. Any other system described may be used. The returns of all
the points connected with the exchange EX being made through a return wire
special to each or common to all as in this case represented by the wire CR W.
Points A B D are fitted with telephone apparatus T only as it is supposed that
they only want to speak to one another and to C. C is also fitted with a
battery BY and key 7 corresponding to BY and key 7 of point F; in order to
use the switching instrument S. There is, however, nothing to prevent all the
points A, B, and D being fitted as C.
143. L is broken at each point. One part passes through the telephone and bells
magneto &c. at T to contact 4 the other through the electro magnet M to contact 5.
The magnets M, M 2, batteries BY 2, BY 3, keys K, contacts 1 2 3 are similar to
those shown in Fig. 130, BY 2 BY 3 being in the exchange EX.
144. The armature of each M is provided with a movable hook and timer.
When the hook is in the first position each vibration of the armature propels a
toothed wheel by means of a pallet a distance of one tooth. On the same axle as
the toothed wheel is a disk carrying a stud on its edge, in a different position for
each point. At a certain stage in the revolution of any of these disks, the stud
will raise a detent; if the revolution is continued the detent is lowered again. If,.
however the disk stops at that point, and the detent is raised, the timer in moving
the book will raise another detent and allow L to come in contact with contact 4
of that point. Both detents must be raised before L can break contact with 5 and
touch 4. To raise the first detent of EX one contact of the key K at any point
must be made, two to raise A's detent and three for B and so on.
145. Suppose A wants to speak to C. A. taps his key K four times. This will
move C's detent, and after a short interval of time C's timer will raise C's second
detent and L will be in contact with 4. In pressing K, A has automatically
raised his own detent and his timer has put L in contact with A's contact 4. A can
now send his ringing current from his magneto which passes through C's bell and
rings him up. A and C now speak in the ordinary way.
146. The hooks at every point and the exchange have now been moved into the
second position by their timers. To disconnect, either A or C presses K which
changes L from contact 4 to 5 bringing battery B into circuit and by attracting
the armature of each M with the hooks in the second position, resets each
instrument as before.
147. If A or C fail to press their K, either their telephone or call bells may be
in circuit, and from the high resistance the current may be unable to work the
magnets M, therefore between contact 4 and the telephone and battery at each

page_text: point, an electro magnet with polarized armature may be inserted through which
the current from BY 3 will pass and by throwing its armature over transfer L
from 4 to 5, when the magnets M will be excited and all the instruments reset.
148. Suppose C wishes to speak to some point in connection with the
exchange EX. C presses key K once. After a second or two, L will be joined to 5
at both C and EX. C must now be considered like any other point in connection
with EX. By tapping his key 7, he brings the movable contact C to the bar he
requires, and rings speaks and disconnects as usual. Then pressing key K he resets
the instruments at A B C D and E X.
The
149. Should F wish to speak to C, he finds the bar of C's circuit as usual.
bar BR contact 11 is connected with contact 16 magnet 3 and CR W. F taps his
key 7, four times. This passes a current through the magnet M 3, whose armature
closes the key K four times, the instruments at C and E X change L from 5 to 4, the
switching instrument S connects 11 with 8, and F can ring C up. F might have
earthed his common return wire CR W four times to switch on to C after finding
the bar of C's circuit.
150. F disconnects and resets in the usual manner. This also causes the
exchange instrument S to reset and automatically close K once to reset the
instruments on C's circuit and brings 11 again into contact with 16.
C can disconnect by pressing his key K.
151. If the return circuit of the battery BY 2 be insulated from the earth, and
carried to each point, the line between the exchange and D may be completed by
the earth and this system may be used with an exchange also using the earth return
for its points as shown in Figure 1.
152. As before shown the system in Figure 136 may have the line L earthed if
the switching circuit through B Y 2 be insulated from the earth. It may be required
to use one wire and yet not join the first and last points.
153. Figure 137 shows a system of connections. Points A B C D and E are
fitted as those in Figure 136, like A or C or both. After leaving points A and D, the
line is normally joined to the poles of two batteries BY 2 BY 2 with reversed poles,
that pole of each battery being joined as required. In the battery circuit at each
end is an electro magnet M 2 fitted with a hook changer and timer. P M 2, P M 2 are
two electro magnets with polarized armatures. By pressing any key K the switching
circuit is closed, and the two batteries send currents through the line L, moving
the armatures of all the magnets M to the earth through the K which is pressed.
The timers of M 2 and M 2 should be as nearly synchronous as possible, and to
prevent either battery being earthed by any delay of the other timer each timer
should raise from 2 for a short space of time before it connects 1 with 3.
magnets P M 2 are unaffected by any current which passes through L in one
direction. The resetting current being in the opposite direction will throw their
armatures over and bring 1 into connection with 2, and by pressing any key K all
the instruments will be reset and M 2 M 2 will bring the armatures of the
magnets PM 2 back into their normal positions. Any point A B C D or E may
be an exchange fitted with automatic switching apparatus and used as shown in
Figure 136.
The
154. This system of connections may be worked with one battery BY 2,
magnet M 2 and P M 2 at one end as shown, the other end of L being earthed.
The line normally passes through PM 2. A magneto current through PM 2
transfers L to the battery circuit which does the switching. The timer of M2
transfers the line L back to the PM 2 circuit for ringing and speaking. The
keys K are here used to break the battery circuit instead of completing it when
pressed.
155. In Figure 138 is shown a system for one line with balanced batteries at the
ends. In this system each point is fitted with the instrument shown in Figure 139;
its magnet M corresponds with the magnets M in the Figure 138. The Hine
normally passes through contacts 1, 2, 3, 5, magnet M, contacts 6 and 7 at each
instrument. K is a key with contacts so arranged that on pressing its handle to

page_text: the right, the L on the right of the point is earthed; and when pressed to the left,
the line on the left of the point is earthed. Suppose C wants to speak to A whose
number is he
one,
All the M's will be excited,
bis key K to the left once.
presses
and the timers of A and C bring their respective contacts 3 and 4 into contact, and
joins A's contact 2 to earth and C's contact 6 to E. Both batteries are cut off and
ringing and speaking can go on as usual. To reset, either A or C by means of
pressing the key K to the right, release a detent, which keeps 3 in contact with 4
and makes 4 touch 5, and connects either 2 with 1 or 6 with 7 when currents from
both batteries will pass through all the magnets M, and reset the instruments.
156. Figure 139 is a view of the instrument used with the last system. The
two way key K. polarized armature A R M 2 and the mercury or similar contacts
are special to this system all the rest, Figures 125 to 137 using Morse keys or
simple one way keys and three metal contacts. The core of magnet M is divided
at the base. Between its ends oscillates a polarized armature AR M 2 about the
centre CE 2. Its axle carries two arms A M and A M 2, one of which will always
be resting upon one of the bridges BRG and B RG 2, turning with loose collars
upon the axle A L.
The bridges tend to fall towards the cups C 2 and C 6. Both
bridges are kept turned towards cups C1 and C 7 so as to connect cups C 2 and C 1;
and C 6 and C7 by the detent DT turning on A. L. When DT is raised by the .
lever LV, both the bridges would turn and connect C2 and C 6 with CE, but one
of them is kept down by one of the arms A M and A M 2 according to which side
the polarized armature A R M 2 is inclined. When contacts 4 5 and 6 are
connected by mercury contacts, they will be connected by the bridge BRG 3.
C3 is normally kept in contact with C 5 by the detent D T. When this is raised
BRG 3 turns towards C 4 and connects C3 with C 4. The cups correspond with
the respective contacts 1, 2, E, 6, 7, 3, 4 and 5.
157. The armature AR M of M is fitted with a movable hook H K, fitted with
guides rod and retracting spring as in Fig. 10. It is moved by means of a ladder
or rack RK, held in position by the detent DT2 entering one of its slots.
DT2 turns upon the centre CE 2. The spring pallet PT is moved by the
timer TR and is attached to the lever LV 2 turning on the pin PN. The
lever LV 2 is moved by the rod RD pulled by the armature A R M and carries
the timer pallet PT 2. The lever L V 2 is moved by A R M against the opposition
of a spiral spring on PN which in turn moves the timer and hook H K. On
pin PN2 move two levers one behind the other. LV 3 carries the pallet PT3
and hook HK 2. LV4 carries the hook H K 3 and arm A M 3 and arm AM 4
moving in connection with detent DT 4.
158. The axle A L2 carries the toothed wheel T W and disk D. AL 2 also
carries a needle N L which indicates the position of the disk D, bearing figures as
shown. Riding loosely on the same axle is an arm A M5 carrying the lever LV 5,
normally one end falls into the notch N H in the disk D. A pin P N 3 is put
in D in such a position, that after T W has been turned a certain number of teeth,
it will reach the pallet PT 4. TW is prevented from returning by the detent
pallet PT5. Pallet PT4 is mounted on the spring S P. One end of S P strikes
and keeps the lever LV 6 in the position shown. One arm of LV keeps the
spring pallet SP3 out of the path of LV 2 and another arm moves against
detent D T.
159. The axle of the key K carries a vertical handle shown by a dotted line, a
spring SP 2 which touches either terminal T or T 2 according to which side K is
pushed and an arm AM6 which will strike against the spring S P 3 when K
is turned to the right. K carries two arms AM 7 AM 7 which will depress the
When S P 4
spring SP4, whichever way K is turned. SP 4 carries a plate PL.
is depressed, its end depresses the lever L V 5 and withdraws its end out of the N H.
The arm A M5 keeps in position the lever L V 7 turning upon a centre carried by
a spring SP5 in the position shown, when the arm is under the plate PL. The
terminals T, T2 are respectively connected to the linewire to the left and right of
G

page_text: the point.
The spring and lever L V are connected to the earth through the
arm A M 5.
160. In turning the key K to one side or the other, one of the arms AM 7
depresses the spring SP 4, this in turn depresses the lever L V 5, raising its end
out of the notch NH and depresses the lever L V 7, lowers the spring SP which
lowers the lever LV 6 and allows the spring S P 3 to approach lever L V 2. The
other arm of LV 6 is caught and held by the detent DT 3. The passage of the
currents to earth has excited all the magnets M in circuit. The armature ARM
is attracted moves the hook H K and lever L V 3 and turns the toothed wheel T W
one tooth by pallet PT 3 against the force of a spiral spring on AL 2. After
the required number of currents have been sent an interval of about two seconds
is allowed to pass.
In this period the lever LV 2 has raised the spring SP 3 and
detent D T. One of the bridges BRG and BRG 2 turns and earths the linewire
on the opposite side of the point to that of the point called and also BRG3
connects C4 with C3 thus bringing the telephone into circuit. The return of
lever LV 2 has also moved the hook H K. To reset, K is turned to the right
when the arm A M 6 strikes the spring S P 3. The lever LV is dropped and the
contacts assume their normal state. A current passes to the earth of the other
instrument. This is sufficient to release the lever L V of this instrument, a current
now passes through the circuit attracting all the armatures A R M, and pulling
levers LV4. They are held by the detent DT4 until the timer returns and
releases it by raising the detent.
161. During switching, at the other points, the attraction of armature AR M
has turned the wheel TW round in the same manner. The lever LV 5 going
with the disk has taken the arm A M5 away from the lever LV 7 thus breaking
the earth contact and causing LV 7 to miss the plate PL. If an intermediate
point turns his key he affects nothing.
162. If number 3 (C) wishes to speak to number 5 (E) he turns his key K five
times to the right. A RM 2 of No. 3 will be attracted to the right and that of
No. 5 to the left, and the stud of No. 5's disk D will depress SP, which will lower
lever L V6 and so bring S P 3 into range of lever LV 2. LV 6 will not be held
by detent D T 3 only in the point pressing key K, the studs of the others not
lowering the spring SP far enough. On the return of levers L V 2, levers LV
will be raised and the line will be earthed on the right of No. 5 and the left of
No. 3. Then they can ring and speak as usual. In the ringing and speaking
circuits any current can be passed through as long as it does not affect the
magnets M or the armatures AR M 2. This can however be held on either side
by a projection from detent D T.
163. Another way of preventing LV 5 being carried round by D at the calling
point, the lever LV 7 may be made to withdraw the pallet PT3 from the
wheel T W 2. This will however prevent the needle NL showing the point
called.
164. The switching current may pass through a relay magnet in each instrument,
instead of through M. The relay will work AR M 2 and close a local battery
circuit with M in it.
165. Two or more points connected to one switching instrument in the exchange.
Figure 13. Two points A and C are connected to one switching instrument in the
exchange EX, the instruments being similar to those described in Figure 10,
though any other form of instruments may be used. Their lines pass through the
magnets PM 2, PM 2 with polarized armatures. Normally they are earthed
through contacts 16 and 16. The passage of the switching current from either
point through its magnet P M 2 cuts off the earth connection of both and connects
one to the instrument S by joining its contact 16 to 17.
166. Their bars are provided with magnets PM 3 PM 3 with polarized
armatures which are normally earthed by joining contacts 11 11 to earth. A
current from either bar belonging to either point will pass through its magnet M 3

page_text: and cut off its own earth and that of the point to which it belongs and connects to
the line of the point between the magnet P M 2 and the point. A reverse or
resetting current will restore the connections. It will be seen that the other point
is able to use the switching instrument S although the one point is speaking
through its bar B R.
167. Sub-exchanges. An exchange worked according to this invention may be
used as a sub-exchange in connection with another which may be a central or
another sub-exchange, trunk wires being laid between the two exchanges, some
terminating in bars B R in each exchange, their other ends passing to switching
instruments in the other exchange. To communicate from a point on one exchange
to that on another, say from Å on exchange X to G on exchange Y, A first
finds the bar of a trunk wire between these exchanges X and Y in his own
exchange X, and then still uses his key 7 to move the instrument S in exchange Y
to which the trunk wire is attached and so finds G's bar in exchange Y. The
resetting current automatically resets the instruments.
168. To make the most use of the trunk wires, a trunk wire would be joined to
the L terminal of a switching instrument in each exchange, the current passing
from a point on one exchange through the bar of the trunk switching instrument
in his own exchange will not move it but will move the trunk instrument in the
other exchange and thus he will be able to find the bar of the point required.
As
169. In Figure 13 is shown a central exchange EX connected by one linewire
to a sub-exchange SE to which are connected two or more points B and D.
the number of points to be accomodated by one wire would be limited, the fixed
contacts or bars can be arranged in a circular ring BRR the moving contact being
a radial arm sweeping round on the contacts. The trunk line L and all the points
are connected to special contacts on B RR. A branch from each passes through
a magnet P M 4 with polarized armature thence to earth.
170. If any one point sends a switching current through its P M 4, the armature
of P M 4 transfers terminal 8 to 9 whence the current passes through the switching
relay magnet S R M to earth and closes the local switching circuit containing a
switching magnet S M with timer and movable hook. This magnet being excited
moves the contact arm of BRR to a fresh contact for each current sent.
171. If point D wants the trunk wire, he will send one switching current, this
will bring his line into connection with the trunk wire. He waits a second or two
and the timer of the sub-exchange will bring his contact 8 into connection with 10
whence a path is open to the central exchange. Here the switching currents from
the point pass through the trunk switching instrument and puts it in communication
with any other point on the exchange. The resetting current resets all the
instruments it passes through.
A point on the central exchange EX can in like manner find any point on the
sub-exchange.
To disconnect the other points on the sub-exchange the first stroke of the sub-
exchange switching magnet will disconnect the earth of all the magnets P M 4 so
that no one can listen or move the instrument.
172. Another way of disconnecting the earths of the magnets PM 4 is shown
in Figure 12. The armature ARM of this particular A. M 4 carries an arm A M
which will strike against the contact strip S T and complete the circuit of a magnet
which will raise ST and let A M pass. ST when first raised disconnects all the
earths of the magnets PM4 and is held by a detent. The resetting current
releases it and reduces all the parts to the normal position.
173. A point on the sub-exchange can switch on to any other point on the same
sub-exchange in the same manner as D did for the trunk line, only sending in each
case the required number of switching currents.
174. Fittings at the sub-points. At each point a source of electricity for switching
ringing and resetting must be supplied and in some cases a means of changing its
polarity or direction. The generator may be in the exchange one or both poles
being connected with each point through the earth or special branched conductors;

page_text: or a special generator may be supplied to each point. Where a magneto is used,
one generator for instance a battery may be used for switching and the magneto
for ringing and resetting as shown and described in connection with Figure Ĭ and
others.
A magneto at the point may be used for all purposes, each revolution of the
driving wheel corresponding to the passing of one or more currents in the
switching circuit, and to distinctly mark each current, the current from the magneto
may be automatically suspended for a portion of each revolution by means of an
insulating segment on a commutator on the driving axle. When it is required
to reverse the magneto current, its rotation may be reversed, or its connections
to the line may be altered by a key, or a driving handle on the same axle as
the ordinary one but in a different plane may be used (for instance on the other
end) which shall automatically make the required connections.
175. The number of switching currents sent to the exchange and indirectly the
number of the point in connection may be recorded as follows.
A counting apparatus may be moved mechanically by the switching key, or
electro mechanically by each current. In either case, each motion will move by
means of a pallet a toothed wheel with numbers on the edge a distance of one
tooth. Separate keys may be used for hundreds tens and units closing by branch
wires the same switching circuit and moving separate counting wheels. These
branches may contain separate magnets in circuit for moving the wheels by the
currents. If one key or magnet only be used, the separate wheels for the hundreds
tens and units may be employed, a timer changing the connection of the key or
magnet from one wheel to another. The timer may be arranged to indicate the
moment of change by ringing a bell or moving an indicator. This timer should
be set to move more slowly than that at the exchange to ensure the exchange timer
having acted. The sending of the resetting current may be made to reduce the
counters to zero mechanically or electrically.
176. The switching current may be sent by passing a moving contact connected
with a battery over a series of contacts connected with the line. The contacts are
numbered to show the number of currents sent. Such a moving contact may move
in a straight line between guides, or may be a radial arm moving by a handle round
a centre, the contacts being arranged in its path. There may be several moving
contacts for sending the currents corresponding to the hundreds tens and units on
different guides centres or revolving round the same centre. Normally they do not
touch the fixed contacts, the pressure of moving them making the contact.
prevent the currents being sent too quickly the arms may be adjusted to move a
train of wheels with friction brake or fan or escapement regulated by pendulum or
balance wheel.
To
Similar arms not transmitting currents may be set at the required figures, and
the other arms transmitting the currents may be moved by some motive power until
stopped by the aforesaid arms.
177. It may be so arranged that the switching key be kept down, and the
switching instrument automatically break the circuit and current in the switching
line at every stroke of the armature of the local switching magnet S M Figure 10.
The switching current in the line passes through a magnet at the point which
will ring a bell or move a needle or register the number of currents on a similar
counter as described above. When the bell or other signal indicates the required
number of hundreds, the key is raised and an interval of time allowed to pass
when it is again depressed. When the interrupted currents again indicate the
required number of tens, the key is again raised, and so on for the units, thus
only raising the key three times. For the purpose of breaking the circuit in
the switching line, a small switch is moved by the timer at the end of its
outward travel and closes it again on its return after an arranged interval of, say,
one quarter of a second.
178. In the exchange, the switching currents sent from the point may pass
through the switching magnet without the intervention of a relay. In most cases

page_text: it will be best to pass them through the relay magnet as before described. If
relays are not used, the relay magnet S R M Fig. 10 will not be required.
179. The parts of the instruments used in this invention to receive currents and
transform them into motion of different directions according to the direction of
the currents such as magnet P M, Figure 10 and other figures may have the varied
forms shown in Figures 10, 12, 19, 139, and 141 to 159 inclusive. They depend
on the directive action of electric currents and electro magnets upon other currents
or magnets permanent induced or electric.
180. In Figure 141, the currents passing through the coils CO move the
permanent magnets M about the centre CE. In Figures 142 to 159 inclusive,
different forms of electro magnets EM are shown acting on the permanent
magnets M, N and S indicating their poles and CE the centres about which they
turn. ARM in Figure 143 is a soft iron armature, in Figure 144 it is a permanent
magnet.
181. An electro maguet may be fitted with a soft iron armature and polarized
armature both acting independently. from one another.
182. An electro magnet may be fitted with more than one soft iron armature and
at the same time with more than one polarized armature.
183. The cores of the electro magnets and the polarized armatures may be of
soft iron polarized by the proximity or contact of permanent magnets or by electro
magnets. The polarity of the latter may be altered at will or taken away by
changing the direction of or stopping the current passing through them.
184. When an armature or other part of the apparatus such as the bridges
is intended to return to the original position it occupied, for instance a central
one, it may be brought back by adjustable weights or springs as shown in
Figures 160 and 162 and also by cams projections or studs opposed by weights
or springs. The same means may be used in similar cases when the parts have
to be retained in the last position they acquire for instance on one side or the
other of the centre, the use of weights and springs being shown in Figures 161
and .163. AR M represents an armature, WT an adjustable weight, SP an
adjustable spring.
185. If the motion of a moving part such as an armature is to be rendered
gradual or prevented from oscillating, a weak spring or bristle may be fastened to
it to strike against a projection or rub on a surface or a part for instance an
armature or a projection from it may dip into mercury or other liquid as shown in
Figure 164. CE is the centre about which A R M a polarized armature turns,
A M a projecting arm dipping into the mercury MY, which may also be the
means of passing the electric current through the armature to any contact it may
touch.
186. The mercury cups used, may be made as shown in Fig. 165. CP, the cup;
SC, a threaded stalk fitting into the ferrule FL fitted to the stand ST, the
connecting wires being clamped by the screw SC 2. The mercury MY may be
covered with a layer of oil or glycerine L Y to diminish oxidation, and the whole
may be covered with a cover CV to prevent the entry of dust. Holes in the
covers admit the needles. The cups may be made of any material that will hold
mercury; earthenware, glass, wood, indiarubber, gutta percha, ebonite, vulcanite,
vulcanized fibre, carbon, graphite; any metal or alloy such as copper, brass, iron,
steel, tin, platinum, lead, pewter, or aluminium &c. Those liable to amalgamation
being protected by paint or varnish, the contact with the mercury being made
by some metal not attacked by the mercury such as iron platinum carbon or
graphite.
187. The needles may be pointed as shown, and made of any metal, being tipped
with some metal not attacked by the mercury. The tips may be made of pencils
of carbon or graphite. The needles may be varnished except the tips by which
contact is made.
188. The contacts may be made in the common way between solid metals.

page_text: Figure 166.
The axle AL forming these connections may have projecting bars
or studs BR which may form part of the circuits, the contacts being made by
causing them to rub against the springs S P. The bars or studs may also press
springs together forming the circuits through the springs only.
189. The needles may be made to touch springs shaped as shown in Figure 167.
Springs similar to these shown in Figures 166 and 167 may be fitted to the bridges
and touch similar springs, fixed needles or contacts. In all cases the surfaces of
contact may be graphite or carbon.
190. Figure 168. By fitting a spring SP on the end of a bridge BRG, two
cups CP. CP 2, or contacts may be joined during the passing by the current
through the magnet while its cessation will allow the spring to assert itself and
raise them from contact. The dotted spring and bridge shows the position assumed
after the current ceases.
191. Automatic exchanges have been designed in which the switching currents
are passed through different circuits to move different magnets, such alteration of
circuits being made by the agency of another current passed from the point to
the switching instrument through the same or another linewire. The change of
circuit is used because each magnet only effects one operation so that as many
magnets have to be used as there are operations to effect.
192. In the first place, I diminish the number of magnets required by making
one do the work of several, the motion of its armature being transmitted to several
parts of the instrument by a movable connection moved as required by means of
currents passing through the same or another circuit (123). This requires a current
to be sent from the point to move the connection.
193. I do away with this current for moving the connection by causing the
magnet of the switching instrument to work a timer, whose operation is suspended
while the switching current passes, but is released when the current ceases.
If the
armature of the magnet is not attracted for a given time, the timer moves the
connection between the magnet and the mechanism it has to work; thus by
the aid of one magnet, also fitted with a polarized armature (120) all the operations
of the instrument S may be effected.
194. The movable connection may be attached to any part of the switching
instrument whose motion is to cause the movement of or to be transmitted to some
other part of the switching instrument or cause the transmission of some external
form of energy or motion to some part of the instrument.
195. In changing its position, it may move in any path as in a straight or circular
path. Those in Figures 10 and 139, 170 and 171, 172, 173, 174, 175 and 178 being
in straight lines, and that in Figure 169 circular, where connection CN moves
round the centre CE on the armature AR M. In Figure 170 it moves in a
straight line or path along a guide G attached to the armature A R M.
Figure 171 it also moves in a straight path along the rod R D.
In
196. When in any one position the movement of the movable connection will
depend on the movement of the part of the instrument to which it is attached. Thus
in Figures 10, 139, 169, 170, 172, 173, 174, 175 and 178 it will move as the
armature or fitting to which it is attached; in Figure 171, if the rod RD move
axially, connection CN will move with it round the axis of Ŕ D.
197. The motion of the part to which a movable connection may be attached
may be derived from any convenient source given to it by any form or source
of energy such as electricity, magnets, springs, weights, clockwork, or by hand,
or mechanism driven by other motors.
The moving connection may fixed to a part of the instrument which does not
move in itself, the connection being moved so as to transmit energy to various parts
of a moving part of the instrument by which it is conveyed to other parts as
required.
198. The position of the moving connection may be altered or the connection
may move by force applied to it in any convenient manner, by means of magnets,

page_text: springs, weights, or clockwork transmitted to the connection by levers, cords.
pallets, springs, wheels, pulleys, and its movement may be regulated and limited
by detents and escapements.
199. The movable connection may take any convenient form such as hooks,
projections, arms, pallets, brushes, contacts, wheels, and racks, being made to suit
the requirements.
200. The parts to which the movable connection transmits motion or energy or
moves, will be placed in its path, being made to efficiently receive the motion or
energy transmitted. They may be levers, rods, projections, pallets, studs, spring,
contacts, wheels, or cords. The movable connection may transmit electricity fro..
the parts to which it is attached to other parts by means of contacts.
201. It follows that the movable connection may be attached to or detache.l
from the armature of a magnet. In Figure 172 the moving connection the
hook HK is shown detached from the armature ARM and attached to the
fitting FT suspended by a spring SP. The motion of A R M is transmitue.l
to FT by two hooks HK 2 and H K 3. The moving hook H K is similar in all
respects to that shown in Figure 10.
202. The following are some of the ways of moving the movable connection.
In Figure 173 the hook H K is moved thús. A timer or some other mechanism.
causes RD to strike against the lever L V and bring pallet PT down on the
toothed wheel T W; at the same time the hook H K is turned a little on its axis.
by the rod RD2 attached to the lever LV2, to free it from the hooks of the parts it
moves. The local switching circuit is closed and causes the armature AR M to be
attracted by the magnet. When the wheel T W moves forward the pallet PT
catches in one of its teeth and thus lowers the hook.
203. In Figure 174, the hook H K 2 is attached to the armature A R M by the
pin PN about which it turns, and according to its position will catch in th
hook HK 3 or H K 4. When the rod RD is pushed against the hook lever L V
by the timer, it raises the hook HK 2 as shown in the figure and on the
armature being attracted will turn lever LV 2 which causes the pallet PT to move
the toothed wheel T W and lower hook H K. The rod RD is now withdrawa
and H K falls, engages with hook H K 4, and the movement of the armature will
move the fitting FT which carries H K.
204. In Figure 175, the hook HK is attached to a ladder or rack L D shown in
detail in Figure 177. It slides along the face of the fitting F T shown in detail in
Figure 176, and to this it is secured by the two screws SC moving in the
slots SL, SL. The movement of H K is governed by the escapement ES shown.
in detail in Figure 177 turning on an axle in the bearings B G. When it is
required to lower the hook HK, a timer or some other part raises the
escapement ES and allows HK to fall one tooth or slot in the ladder.
205. In Figure 178, the movable connection is the hook HK attached to a
ladder LD similar to that shown in Figure 177, and sliding on the face of the
fitting FT.
ID is kept in position by the detent DT on the spring SP. To
lower the hook H K, the rod RD is moved by a timer so as to strike the
spring SP, and raise detent DT just sufficiently to let L D slip, when R D is raised
from SP by the plane PL striking against the adjustable screw S C, and DT
springs back and holds the ladder LD.
206. The timer. A timer is used to bring about some movement of or to
accomplish some change in the parts of the mechanism at the end of a given interval
of time from the moment of starting the timer. The interval of time is measured
by causing the timer to do some work such as moving a pendulumi, balance wheel,
overcoming mechanical, liquid, fluid or gaseous friction, driving a fanwheel in air
or a liquid, expelling fluids liquids or gases such as air from soine reservoir.
207. The timer may be driven by energy stored up in springs, weights, from the
motion of one of the moving parts of the instrument, or from any external source
as springs, weights, electro magnets, or other motors or by the recoil of the spring
supporting or withdrawing an armature from the poles of a magnet.

page_text: 208. A timer may be employed to move any part of the mechanism as before-
shown, to move contacts, movable connections, complete contacts, release detents,
to make contacts for the transmission of electricity, to release and put in motion
any part of the mechanism which derives its motion from any other source than the
timer.
209. In Figure 178, is shown a pneumatic timer consisting of the bellows BLS.
The armature ARM of the switching magnet S M pushes the rod RD 2 and opens
the bellows, a valve allowing the air to enter. When the armature springs back,
the valve is shut and the air allowed to escape through a small adjustable hole, thus
slowly closing BLS. In this case a spring attached to the moving bellows board
propels the rod RD and lowers the hook HK.
210. In Figures 10 and 139 are timers which depend upon the motion of a
pendulum to regulate their period.
211. Figure 179 shows a simple form in which the arm A M turns round the
pin P N against the spiral spring S P. The spring S P 2 carries the pallet PT
driving the wheel W, escapement ES and pendulum P.
212. In Figure 180, A M is turned against the pressure of the spiral spring SP,
by pushing the rod RD passing through the guides G. On the roil is the nut NT,
against which the spiral spring SP presses. To nut N T is fastened a spring S P 2,
carrying the pallet PT engaging in the escapement wheel E W, working an escape-
ment ES and a pendulum P.
213. In Figure 181 is shown another form in which the rod RD is pushed or
pulled by some motion of the instrument against the spiral spring SP, and carries
with it two nuts NT and NT2. To NT is fixed a spring SP 2 carrying the
pallet PT to NT 2 is fixed the spring S P 3 carrying a pallet PT 2 to work the
escapement wheel E W escapement ES and pendulum P.
214. The arms AM in Figures 179 and 180 and pallet PT Figure 181
accomplish any required movement at the end of the timer's period.
215. The moving contacts. The contact springs weights and guides have been
shown in Figures 10, 11 and 28.
216. The moving contacts may take the form of metal springs or small wheels
attached to springs and may be made of any suitable metal or alloy and may be
tipped with platinum or any hard metal such as iridium, or a button or wheel of
hard carbon. For metallic circuits more than two contacts mounted on the same or
separate carriages would be used.
217. The contacts are fixed to carriages made of a combination of wood or
similar insulating material and metal. The carriages may be combined with the
weights causing them to descend. The weights may be quite separate from the
carriages and be connected to them by cords.
218. In all cases the carriages or weights which hold the contacts will move along
guides attached to the frame rails. They may be made of wood or metal or a
combination of wood and metal of the forms shown in Figures 10 11 28 and 182 to
188 inclusive. When wood is used the dimensions of the wooden parts must be
increased the carriages and weights being altered as necessary.
In Figures 182 to 188, CS indicates the contact springs, CW the contact
weights, S B the switchboard, B R the contact bars; G, G, the guides.
219. In Figure 182, the contact weights descend in cells formed by wooden
bars W W secured to the frame rails and enclosed by boarding or a metal plate PL
as shown. In the latter case CS would be insulated from the weight.
220. The carriages and weights may touch the guides at one or two points only
so as to reduce friction, and may also run on rollers or wheels attached to the weights
and carriages.
221. The contact carriages or weights contain one two or more contacts as
required for single line or metallic circuits.
222. The connections with the springs may be made by either the guides or
cords.
Where the carriage or weight touch more than one guide as in Figures 183

page_text: and 184 it must be insulated from one the connection being made through the
other.
223. Where double contacts are required, the guides must be made up into two
parts insulated from one another each part used as a conductor as shown in
Figure 185 at C Figure 186 at A and C or double guides may be used
as in Figure 187 at B, the insulation of the springs from one another, and from the
weights being arranged by the use of insulating materials.
224. The cords used for supporting the contact carriages and weights may be made
of any suitable material such as cotton, silk, flax, gut or leather, or metal wire
stranded or plain. When the cords are used for conductors, they may be stranded
and twisted into the cords. When a single conductor is required it may be of brass
or copper wire without insulation. If two conductors are used, they must be
insulated from one another. The cord may be used for one conductor and the
guides for the other.
225. The cords may be shaped as narrow tape and wound on the reels layer upon
layer.
226. The bars may be as shown in Figures 10 and 190 for single circuits.
227. For double or more contacts, two or more bars on the same face or on both
faces of a switchboard may be used but the compound bar shown in Figure 190 is
better each bar being toothed square as shown or like the tooth of a saw triangular
so that two of them may be fitted together in the width of one flat bar. The bars
of the compound bar being insulated from one another.
The bars may be made of flat carbon rods.
228. The motors for raising and lowering the contacts may be driven by
electricity gas compressed air steam or any convenient motive power. The same
agency may supply the electricity necessary for working the exchange from
dynamoes, this current may be used direct or charge accumulators whence the
working current is drawn.
For small exchanges the motors may be driven by batteries or power stored up
in springs and raised weights, these being rewound as required.
229. The escapement wheels similar to E W, E W 2, EW 3, Figure 10 may have
their teeth on the circumference as E WE W 2 in Figure 178, on the bevel, on
the face, crown as E W 3 in Figure 10 or internally.
230. Two escapement wheels EW and EW 2 may be mounted on an axle similar
to AL 4 Figure 10 as in Figures 191 and 192. One E W for the units has ten
teeth and the other E W 2 is a disk with the exception of a notch which coincides
with one tooth of E W. The pallet P T is mounted on a spring attached to a
lever LV turning about the centre pin PN. When LV is momentarily raised,
PT slips to the right releases wheel E W 2 and A L 4 makes one complete
revolution. If LV is depressed, P T slips to the left, releases EW and allows
it to turn one tooth, PT being brought back into. E W before another tooth
can pass.
231. In Figure 178 is shown another form of escapement similar to that described
above in that the detent must be released directly the tooth has passed it. The
spring pallet PT by which the armature moves the fitting FT must be disconnected
from the fitting directly the detent is raised enough. This is done by an adjustable
screw SC 2 striking a plane on the spring pallet and pushing the pallet away from
the fitting FT and releases the hook H K.
232. In the instrument shown in Figure 10, the moving contacts are lowered by
their own weights, the rewinding being done by a separate motor; it may be
required to put the contacts at the bottom of the switchboard and pull them up to
the required bar by a winding motor. This may take the form of a magnet with
a pallet fitted to its armature turning a toothed wheel on the axle A L 4 tooth by
tooth. It would have to vibrate very quickly to move the contact ten bars between
two contacts of the switching key therefore some means of multiplying its motion
will be necessary.
233. In Figure 194, the axle A L4 has a toothed wheel T W with ten teeth

page_text: fixed on it, and a smaller one T W 2 gearing into the larger wheel T W 3 with ten
times the number of teeth. In front of this is another toothed wheel T W 3 with
The switching
ten teeth. A pallet PT will move T W and PT2 move T W 4.
magnet first moves PT2 and turns the wheel T W 4 one tooth and so causes T W
to make one revolution, thus raising H contact 10 bars, and so on for each current.
The hook of the switching magnet is moved, and will pull pallet PT and turn the
wheel T W one tooth for each current, and raises the contact one bar at a time.
In this way the contact is raised to the bar required.
234. Where the latter arrangement is still too quick, in Figure 193 is shown a
bevel toothed wheel B W fixed on the axle A L 4. This turns a bevel toothed
wheel B W 2 on the axle A L with ten times as many teeth as BW, and carrying
the spring contact CT. On A L 2 are two other wheels T W with 100 teeth
and TW 2 with ten teeth. The pallet PT turns T W 2 one tooth at a time, and
pallet PT2 turns T W one tooth at a time. SP forms one pole of a circuit in
which a magnet is placed for winding the moving contact up to the required bar,
while T W forms the other pole, thus this circuit will be closed except when CT
rests on the insulator IN fixed to T W.
235. The wheels and parts being as shown in the figure, the switching magnet
will pull PT and move 1 N away from CT. This will set the winding motor in
motion and begin raising the contact. PT moves TW round one tenth of a
revolution, therefore B W 2 will have to make one tenth of a revolution before it
can overtake I N and stop the winding motor, that is, B W will have to make a
complete revolution and thus raise the moving contact ten bars. This occurs for
each tooth PT turns the wheel T W 2.
236. A timer changes the hook of the switching magnet to pallet PT 2, each
stroke of PT 2 will turn the wheel T W one hundredth of a revolution corre-
sponding to raising the contact one bar. In this way, the switching currents may
succeed one another as fast as they can be sent and the winding motor will keep
on raising the contact until CT touches I N.
237. Where the contacts are moved by their weight or by power, care should
be taken to balance them if necessary by causing the pilot weight to counteract
their weight, so that no more power is required than is necessary to raise them as
long as they fall or return properly.
238. In order that the moving contacts may be as close together as possible on
the faces of the switchboards, arrange the switching instruments in rows one
above the other over the switchboards, and so arrange them in these rows that
the cords from the reels shall just clear the cords and reels of those below them.
239. If the number of points on an exchange be greater than can be served by
the instrument the exchange may be extended in the following way.
240. Suppose the instrument in Figure 10 were made to serve 1000 points, more
may be served by using more reels and switchboards, or lengthening the switch-
boards and putting more bars on the faces.
241. Another way. From Figure 10, it will be seen that the magnets PM
and S R M as well as the cup contacts control the magnets S M and W M
electrically, and that the cup contacts are controlled by the magnet S M, timer T R,
and lever L V 5 mechanically.
242. Take away the magnets P M and SR M and the cup contacts from the
rest of the instrument, and mount them on an instrument called the central
instrument, and let there he several combinations of the magnets S M. W M,
timer T R, reels, cords, contacts, and switchboards as shown in Fig. 10, each
Let the circuit
combination serving 1000 bars BR and call them sub-instruments.
of the magnets SM and WM of each sub-instrument be taken to the central
instrument, and means of electrically or mechanically controlling the cup contacts
at the central instrument from each sub instrument be provided. In the central
instrument the circuits of the magnets S M and W M will be broken by a contact
changer which will bring the magnets of any sub instrument into the local switching
circuit as desired.

page_text: 243. Normally the local switching circuit passes through a magnet at the central
instrument working the contact changer and also a timer. Suppose the point to
whom the central instrument is allotted requires to speak to point 2369, he first
taps his switching key twice. This closes the local switching circuit twice and
the magnet in the central instrument brings the magnets S M and W M of the
second sub instrument into the local switching and resetting circuits. The timer of
the central instrument will then cut the first magnet out of circuit, and the point
is connected as usual to the sub-instrument and finds the 2369th bar in the usual
manner.
244. The resetting current resets the sub-instrument and the central instrument
in the usual manner by completing the resetting circuit containing an extra magnet
in circuit with the W M of the second sub-instrument for replacing the contact
changer.
245. This system of telephone exchange may be used along with any system of
telephone exchange now in use.
246. Operators may be employed at the exchange to attend to the trunk wires
if required.
247. This system of telephone exchange may be used in connection with any
existing exchange for sub-exchanges as before described or they may be under
the control of the operators who may use the exchange wire to connect to any
point on the sub-exchange, while the points on the sub-exchange can call up the
exchange as required.
248. Refer also to paragraph 174. In Figure 1 and in other figures, a
battery BY is used for switching. If the relay magnets at the exchange are set
finely enough, the telephone transmitter battery may be used for switching, and
also for ringing, and with a pole changer, for resetting. Thus in some cases, the
magnets may be dispensed with and the battery BY used for all purposes.
249. Referring to paragraph 176, a simple form of switch for transmitting the
switching currents is shown in Figures 195 and 196. The knob N rotates about
the axle A L and carries a contact spring C7 which normally touches contact
screw C5 and is connected to the linewire through the spiral spring S or through
the axle A L. 1, 2, 3, 4, 5, 6, 7, 8, 9 are contact studs all connected to one another
and to the battery BY and thence to earth E. The knob N and with it the
spring C7 are pushed away from the plane of the contact studs PE by the
pressure of the spiral spring S on the knob N. The spring S also tends to keep
contacts C 7 and C 5 together. C5 and C 7, the contact studs and battery BY
correspond to the contacts 5, 7, 6 and battery B Y of Figure, 1 respectively. In
N is pushed towards the plane of the contact studs and rotated to the right
and by a regular and uniform motion makes contact with each contact stud in
succession until the required stud is reached, when N is released it flies up and
back to the contact C 5. The same operation is repeated until the switching is
ISC,
concluded.
A
250. Referring to paragraph 177, we may also arrange a train of clockwork at
each point driven by a spring or weight wound up as required, a fanwheel may be
used to give a regular motion to the clockwork. A contact spring is so situated
near one of the wheels that it makes contact with each tooth as it passes.
switching key is so arranged that it normally stops the motion of the wheels, but
when depressed it first separates contacts 5 and 7, Figure 1, and liberates the train
and contact is made and broken as described. If the battery B Y, Figure 1, be
connected to the axle of the toothed wheel and the line L to the spring contact,
switching currents will be transmitted to the line as often as contact is made.
These contacts may be rendered audible by making the teeth of the same wheel
raise and release a small hammer after the passage of each tooth and thus sounding
a bell.
When the switching key is raised it stops the train of wheels in such a
position that no current passes between the battery and liue and at the same time
contact between 5 and 7 is restored.
251. In paragraph 92, it is stated that when A switches on to B and they

page_text: arrange to leave their instruments connected, if B wishes to ring A up, he must
send his resetting current through. This may be overlooked. I therefore arrange
that switching be performed by the battery BY and that the magnets be made to
give alternating currents which may be used for ringing through from one to the
other in either direction. The alternations in the current being so rapid that the
polarized armatures of the magnets in circuit will only quiver and not be displaced.
252. Refer to paragraph 174. The use of a magneto for switching ringing and
resetting requires a key for changing the direction of the currents, if not done by
changing the direction of rotation; and where also the ringing current alternates
the key shown in Figure 197 may be used. The handle H moves the axle A L
carrying the bar BR. On BR are fixed two metal strips ST and S T 2 insulated
from BR and from one another. ST and ST 2 carry two contact springs S P
and SP 2 which normally touch the pair of contact studs B. The springs SP 3
and SP 4 are connected to the line L and the earth E and touch the
strips ST and ST 2 respectively and form part of the ringing circuit, that is,
the magneto is included in the circuit between them. They also tend to keep the
bar BR in the central position shown. The contact studs B form part of the
alternating ringing circuit, so that if the magneto be rotated alternating currents
will be sent to the line.
253. If required for switching, the magneto is provided with a commutator to
rectify the alternating currents. One collector of this commutator is connected to
the lower stud of the contact studs marked A and to the upper one of those
marked A 2, and the other collector is connected to the remaining studs of the
Then on turning the handle H to the right, the springs SP and SP 2
touch the studs marked A and the switching currents are passed to the line. To
reverse the currents for resetting &c., H is turned to the left and currents in the
reverse direction are sent. H may be a pendent handle.
same.
254. With reference to the switching instrument shown in Figure 10, it is stated
in paragraph 24 that the ringing current from A's magneto M will pass to B's
instrument S where it will partly pass through B's magnet S R M to earth and
perhaps move B's instrument. This is undesirable, and we may prevent this effect
by making the mass of the armature of the magnet P M small, and that of the
magnet S R M relatively great, so that the armature of P M being moved first will
alter the contacts before the armature of SR M can have moved sufficiently to
have closed the local switching circuit.
255. In Figure 198 is shown a switching instrument similar to the improved
switching instrument shown in Figure 2 of the drawings left with the Complete
Specification of Patent No. 16768, 1892, coupled with the modification shown in
Figure 11 of the same Specification. It is now more simple, and for the purpose
of description arranged to work with the system shown in Figure of this
Specification, bearing in mind that the magnet P M also performs the functions of
the magnet S R M therein shown.
256. In Figure 198, P M is the electro magnet above mentioned. Between its
poles hang the polarized armatures PA and PA 2 which oscillate quite indepen-
dently of one another on the axle A L. PA normally hangs centrally between
the contact screws CS and C S 2. When deflected towards and touching C S, it
closes the local switching circuit including the magnet S M; and when deflected
towards and touching CS2 it closes the local resetting circuit including the
magnet W M.
PA2 carries the bridge BRG connecting the contact cups C
and C 2, and on account of the weight W T, PA 2 remains on the side to which it
was last deflected. In the position shown, it joins the cups and completes the
circuit between contact spring S 9 and the earth.
257. The contact springs S8, S9, S 10, S 11 correspond to contacts 8, 9, 10, 11,
in Figure 1. Contact springs S and S2 form part of the local switching circuit
which is broken as will be presently shown. Normally S8 touches S9 and S 11
and S touches S 2.
258. The switching magnet S7, its armature, the moving connection C N, are

page_text: similar to and similarly operated to those described in Patent No. 16768, 1892,
with this exception, the period of the timer will be increased to about four seconds,
the timer spring S P has an extra pallet P and a prolongation X. It is intended
that if no switching currents are received by the instrument for a period of two
seconds, the connection CN will be lowered in the usual manner, and if no
switching currents pass for a further period of two seconds the pallet P will
catch the end of the contact spring $8 drawing it to the left, when S8 will
leave S9 and S 11 and touch S 10, and allowing S 11 to touch S9 and separating S
and S 2.
259. The cord CD which lowers the connection CN supports the spring S P 2
for a purpose to be presently described. The connection CN when moved by the
armature of SM will operate either the bent lever LV or the bent lever LV 2,
both carried by one pin P N. When LV is operated it causes the rod RD to
nake a movement round its axis carrying the arms A M with it. When LV 2
is operated, it causes the rod RD 2 to make a movement round its axis carrying
the arms A M 2, of which only the ends are seen, with it. RD 2 can assume two
positions, that shown and that when drawn a little to the right by the spring S P 3
after RD2 is released by the detent DT on the spring SP2 when the latter is
lowered by the cord CD.
260. The moving contact CS is similar to that shown in Figure 11 of the
before mentioned Specification No. 16768, 1892, but the fork F K which holds it
in position as shown in Figure 198 has one side formed in two parts, the slit in
between allowing the suspending cord to freely pass, as shown in the section of
the moving contact in Figure 199.
261. The fork FK with the contact CS are carried by the carriage CE,
which is supported by the hooks H K upon the polished rails RL. The carriage CE
being attached to the weight WT 2 by the cord CD 2 tends to slip along the
rails to the right but is prevented from moving by the pallet P T 3 being detained
by one of the arms A M on the rod RD.
262. P2 and P3 are pallets carried by the spring SP4 attached to the
carriage CE and situated in the manner shown on plan in Figure 200.
Carriage CE carries the drum D rotating on the axle A L 2, and upon D the
cord supporting the contact weight is wound. D has two divisions, one for the
contact weight cord, and the smaller one for the cord C D 3, which is also attached
to a drum secured to the toothed wheel W L 2.
263. An escapement wheel E W with 10 teeth is fixed to the drum D, this is
prevented from rotating by the escapement ES, which vibrates on a pin on the
disk D K. The disk DK has a pin projecting radially from it, which is held by
the escapement ES 2 which vibrates on a pin fixed to part of the carriage C E.
The escapements are shown on plan in Figure 200 and it will be seen that the
tail of ES is turned towards the rod RD2 so that the arm A M 2 if moved to
the right would be in a position to operate E S. In the positiou shown, A M 2
would operate escapement ES 2.
264. The toothed wheel W L2 is supported by the spring SP 5, a prolongation
of which is carried up towards the armature of the magnet W M, and carries a
detent DT2 which will catch on the pin PN 2 when S P 5 is depressed by the
armature of W M. RD3 is a rod, which, when propelled to the left will touch
detent DT2 and release it from pin P N 2 and allow SP 5 to rise carrying W L 2
with it.
265. LV 3 is a bent lever, which, when operated to the left about its centre
pulls down the cord CD4 and with it the detent lever L V 4. LV 5 is a lever
operated by the lever LV 4, with a forked projection F K2 at one end.
FK 2 embraces armature PA only for a purpose to be presently described.
LV 6 is a bent lever operated by the descent and ascent of the contact CS.
If CS descends lever LV 6 falls and allows the hook H K to fall on to one
of the pins P N 3.
266. In using this instrument, the first switching current passing through

page_text: magnet PM will attract the polarized armature PA to the right causing it to
touch the contact screw CS, thus closing the local switching circuit. This will
operate the magnet S M, its armature, the moving connection C N and the timer.
The moving connection will operate the lever LV and cause the rod RD to
slightly rotate about its axis, in which case the first arm A M will escape from the
pallet P 3. Thereupon the carriage C E will move to the right until the pallet P 2
strikes the first arm A M and thus be detained. After the switching current
-ceases in the magnet PM, the local switching circuit will be opened and the
rod RD will assume its first position allowing the first arm A M to escape from
the pallet P 2. when as before the carriage CE will move to the right until the
pallet P 3 strikes against the second arm A. M of the rod R D. The carriage CE
is now in such a position, that, if the contact CS be dropped it will enter the first
guide G of the first switchboard S B. In the same way, two switching currents
will bring CE into position to allow the contact CS to enter the second guide of
the first switchboard and so on.
267. If an interval of more than two seconds but less than four seconds be
allowed to pass, the timer will lower the connection CN so that it may operate
the second lever L V 2. If now a further switching current be sent from the
One
point, it will operate the rod RD2 in the same manner as the rod R D.
of the arms AM 2 on RD2, for instance the first, will now be opposite the
escapement ES 2 on the carriage CE, and every time RD 2 is operated AM 2
strikes the tail of the escapement ES2 and releases the disk DK, and the
drum D by the descent of the contact weight CS will make one revolution and
drop the moving contact a distance of ten bars, and this will occur for each
switching current sent. On the descent of CS, the hook H K falls upon the first
pin P N 3.
268. If an interval of more than two seconds and less than four seconds be now
allowed to elapse after the cessation of the last switching current, the timer as
before will lower the cord CD and with it the spring S P 2, but not C N for the
latter is held by a pin on the lever L V 2 in its second position. The spring SP2
carries with it the detent DT and allows the rod RD2 to move a little distance
to the right due to the pull of the spring S P 3. The next switching current will
now operate the rod RD 2 as before but the first arm A M 2 will operate the
escapement ES on the carriage C E, and every time it is operated it will allow
the escapement wheel E W to advance one tooth and the contact weight CS will
.be lowered a distance of one bar and so on until the required bar is reached. The
movement of the contact weight will cause the cord CD3 to wind off the drum
of the wheel W L 2 on to the drum D on the contact carriage.
269. If now an interval of four seconds be allowed to pass since the last switching
current, the timer will cause the pallet P to draw the spring C 8 and make the
alterations in the connections as above stated, so that the connections will be those
shown in the contact diagram Figure 6, when point A can ring through to point B
and speak.
270. To reset, a current is sent through the line and through magnet P M in
the contrary direction to the switching currents, the polarized armature PA will
be attracted to the left and strike contact screw CS2 thus closing the local
resetting circuit and operating magnet W M whose armature will depress
spring SP 5, and the toothed wheel W L 2 will engage with the rotating rewinding
wheel W L 3, while detent DT 2 will catch on the pin P N 2 and close the resetting
circuit.
271. The cord CD3 will be wound back on the drum of wheel W L2 causing
the ascent of the contact CS until it strikes and operates lever LV 6 which will
release hook H K from the pin it touched and the carriage CE will now be drawn
back to the left striking in turn the lever LV 3 and the rod RD 2, carrying the
latter back into its first position where it will be retained by the detent DT. The
operation of the lever LV 3 will pull down cord C D 4 and thus operate the detent
lever LV 4 releasing and drawing up the connection CN. A projection

page_text: from LV 4 will raise spring S P and release spring S 8 which returns to its first
position and makes the normal contacts as shown in contact diagram Figure 3.
272. The operation of the rod RD 3 is to release the detent DT 2, thus opening
the resetting circuit and allowing the spring S P 5 to raise the wheel W L 2 out of
engagement with the wheel W L 3 whereupon the carriage CE slides to the right
until it is stopped by the first arm A. M on the rod R D. The effect of this is to
allow the return to the position shown with a sudden movement of the spring SP,
which suddenly descends and the projection X by the elasticity of the spring SP
gives a rapid tap on the bridge BR G, which has been thrown over to the right by
the resetting current and thus brings it into the position shown, when the instrument
is again ready to switch.
273. The office of the lever LV 5 is the following. If a ringing current be
received by this instrument through the bar, it will, in passing through the
magnet P M, attract the armatures PA and PA 2 to the left, and by means of
the bridge BRG cut off the connection with the earth and also close the
resetting circuit. The magnet W M will be operated, and the carriage CE will
be drawn to the left and by stricking the lever L V3 will operate lever LV4
and through it lever LV 5. The fork at the end of L V 5 will be forced downwards.
and push the armature PA from the contact screw CS2. The pressure of PA
on the side of the fork will prevent lever L V 5 rising so that while the ringing
currents are passing the resetting circuit will not be again operated. When the
ringing current ceases, the armature PA resumes its central position and the-
lever LV 5 rises into the position shown.
274. In all cases where the switching instrument timer has two periods, namely
a short one after which a change in the position of the connection CN takes place,.
and a longer one after which the contacts are rearranged as described above, we
may utilise every stage in the switching operations for bringing the moving contact
into connection with some other point. For instance, when the moving contact is.
wound up into the carriage it may make contact with a spring contact fixed to the
carriage which will sweep across contact bars placed horizontally in its path from
left to right and these may also be connected to different points so that all
available numbers in order may be used as the numbers of points except those with
ciphers.
275. The timer of the switching instrument may be arranged to have three periods,
at the end of the first the movable connection is shifted; at the end of the second the
movable connection is moved out of gear with the lever it would actuate and the
switching magnet is again operated, a current being sent to the linewire to
announce the change at the point by some suitable signal. After the switching
magnet is operated the first two periods of the timer are repeated a second and a
third time with the same result if no switching currents pass, but at the last.
repetition the timer would be allowed to enter upon the third period and rearrange
the contacts so that communication between the points may take place. The
operation of the switching key after any of these changes is announced at the
point will send the particular number of switching currents belonging to that.
group, so that numbers with ciphers may in this case be used as the numbers of
points.
276. Referring to Figures 126 to 140 inclusive, wherein are shown various.
systems of connecting several points by one or two linewires, the. switching
instruments are connected and operated in series. This would require a large
augmentation of battery power, therefore I prefer sometimes to adopt the following
modifications wherein the switching instruments at each point are placed in the
switching circuit in regular order, so that the maximum battery power to be
employed need only be sufficient to work the farthest switching instrument from
some predetermined point where the battery may be stationed.
277. Referring to Figure 201, three points are shown, namely A. (which may be
an exchange), B, and a terminal point, say G, all connected by two linewires L
and L 2, the latter broken at each point. The apparatus at each point consists of

page_text: a key K by which a current from the battery BY may be sent to line L, a battery BY
with one pole connected to earth E, the ordinary telephone apparatus, magneto &c. T,
the contacts 1 and 2 which when connected join the telephone instruments to L,
the electro magnet R M with its circuit connected to earth and to contact 6, and the
magnet PM with a polarized armature, in circuit with line L and contact 4.
278. In Figure 202 is shown the construction of the switching instrument at
each station. P M and R M are the electro magnets above named. The polarized
armature of P M is hung in the sling SL forming part of the lever LV turning
about the centre CE 2, the other end of the lever LV forms the armature AR M
of the magnet R M. ARM is kept away from the poles of RM by the
spring SP.
When A RM is attracted by the magnet R M the projection from it
touches contact screw S. S is connected to contact 5, and a circuit may be formed
from it through armature A. R M, a few coils of the magnet RM and thence to
the contact 7 for a purpose to be presently explained.
279. The contacts 1, 2, 4, 5, 6, 7 are again represented by the contact cups
numbered 1, 2, 4, 5, 6, and 7. The bridge BRG tends to fall by reason of the
weight of the one side towards the cup 4 and assume the position shown resting
on the stop ST. The bridge BRG 2 tends also to turn towards the cup 2
and assume the position shown resting on the stop S T 2. The armature PA
is provided with a spring SP 2 carrying at its two ends the pallets PT and PT 2.
Normally the bridge BR G connects cups or contacts 4 and 5 and bridge BRG 2
does not connect cups 1 and 2. If the armature PA be attracted to the left by
the magnet P M, the pallet PT will slip over the arm of the bridge BRG and
while the current is passing remain there, but when the current ceases PA will
return to its central position and draw bridge BRG with it and connect cups or
contacts 5 6 and 7 and disconnecting cup 4. It is important to note that this effect
takes place after the current ceases in the magnet PM, and may be called
'postponed action." In the same manner, if PA be attracted to the right PT 2
will slip over the arm of the bridge BRG 2 and when the current ceases will draw
the bridge BRG 2 over and join cups 1 and 2. The cord C connecting the two
bridges will in the latter case cause the bridge BRG to be turned over at the
same time and connect cups 5 6 and 7.
280. At the initial point A is another electro magnet M whose armature is fitted
with a spring and pallet similar to those of armature P A. Normally contact 9 is
connected to contact 10 but when a current passes through M, it attracts its
armature, and after the current ceases, the recoil of the armature connects
contacts 8 and 9.
Its circuit includes
281. P M 2 is an electro magnet with polarized armature.
contact 13 normally connected to contact 11, and the earth E. When the armature
of P M 2 is deflected one way it closes the circuit including the battery BY 2
and the magnet T M which operates a timer. On the stoppage of the current
in PM, the timer begins its period and for a short time closes contacts 11 and 12,
and performs other operations to be presently described.
M2 is an electro magnet similar to R M, Figure 202.
Its function is to reset
the system by closing the contacts 16 and 17 and also to reset the armature of
magnet M. It also possesses a contact screw similar to S, Figure 2C2, with which
its armature can make contact when attracted, the circuit through the armature
including a portion of the coils of the magnet.
282. Contacts 11 and 13, 9 and 10 being joined at A. and also contacts 4 and 5
at each station, we will suppose that point G wishes to speak to point B.
G depresses his key K twice because B is the second point on the system, this
causes the following movements to occur. K being depressed closes the circuit
through battery BY and magnet PM 2 sending a current in one direction. This
causes the armature of PM 2 to be deflected and close the circuit of magnet T M
and operate the timer. On raising the key K, the before mentioned circuit of
In so doing it
battery BY is opened, and the timer itself begins to return.
connects contacts 11 and 12 and closes the circuit through the magnet M for a

page_text: short time. When key K is again depressed it again operates the timer as before
and the circuit through M is opened, whereupon the armature of M is allowed to
recoil and its postponed action will take place and connect contact 9 to contact 8.
When the key K is again raised, the timer as before connects contacts 11 and 12
for a short time and closes the circuit through P M at point A, and as the timer
will not again be interrupted in its return by the closing of key K, it effects the
following operations.
It opens the circuit through A's PM whose armature has been deflected to the
left and allows it to return to its central position bringing with it the bridge BRG
and connecting the contacts 5, 6, and 7 and disconnecting contact 4. Then the
timer will reverse the poles of battery BY 2 and send a current in the opposite
direction through the magnet PM at point B. This will deflect its armature PA
to the right and the timer in its motion breaking the circuit, the armature PA in
returning to its central position will bring the bridge BRG 2 with it and close
contacts 1 and 2 and join contacts 5 6 7. On inspection it will be seen that the
instruments at B are now in circuit with the liue L and when G rings or speaks
his own instruments will be put into circuit with the line L, so that G can call up B
and converse with him. The timer continuing its course will separate contacts 11
and 13 because it would not be well to have any connection to earth through PM 2.
After a lapse of ten seconds, the timer again connects 13 and 11, and if no current
in the reverse direction to the switching current passes through P M 2 from line L,
the timer joins contacts 14 and 15 and is again operated, disconnecting contacts 14
and 15, and 11 and 13; so that at intervals of say 10 seconds contact 11 is tem-
porarily connected to 13 and if no current in the reverse direction to the
switching current is received through PM 2, the magnet T M is operated as
before.
In
283. But if either point wishes to reset the system, a current in the reverse
direction to the switching currents is passed through the linewire for a little time,
and when the timer again closes contacts 11 and 13, the armature of P M 2 is
deflected in the opposite direction and closes the circuit through contacts 16 and 17
operating magnet M 2 and all the magnets R M that are connected to earth.
each case the bridges will return to their normal position and make the normal
connections of the cups but until all the magnets R M in connection with the earth
are operated or as long as there is a connection to earth through one of them all
the rest will still hold their armatures on account of the armatures in each case
touching the contact screw S and connecting contacts 7 and 5 through the coils of
the magnets as before shown. When the last earth is cut off this current ceases,
the armatures of all the operated magnets R M rise and the instruments will be in
their normal condition. Magnet M2 also resets magnet M so that contact 9 is
again connected to contact 10.
284. Having explained the operation of the system I think it well to show the
operation of the timer since in a similar way it will be again used in other systems.
I need not show the timer itself as it is a device similar to any shown before.
Energy is stored up in a spring or other suitable reservoir from the magnet T M
and given out slowly, working a pendulum or other regulating appliance. The
period of the timer should be about 15 seconds, and the arm A M, Figure 203 is
so connected to it that on first closing the circuit of the inagnet T M, A M is
rotated about the centre A L to the position A. After the timer circuit is opened
A M will begin to move with the timer back towards its present position, taking
an interval of about fifteen seconds to accomplish it.
285. If the key K at any point be depressed, the timer will be operated as
before shown, and A. M will be turned round to the position A and held there
while K is held down. On raising K, the timer begins to allow AM to return
back, and spring pallet PT will in about half a second connect contact spring 12
to contact screw 11, sending a current from B Y2 through the line L. If before P T
reaches the lever L V, the key K is again depressed, the timer being operated,
the arm A M will again be brought back to the point A, and on its return
I

page_text: contact 12 will again be joined to contact 11, but if no further current is received,
A M passes on to lever L V.
286. Lever LV carries two contacts, one N is connected to the one pole of
battery BY 2, and contact P is connected to the other pole. Normally as shown,
one pole is in circuit one with contact 9 and the other pole with contact 12 through
the springs shown.
The arm A M will in its passage raise the lever LV and connect the one pole
of BY 2 to contact 11 and the opposite pole to contact 9 thus sending a reverse
current to line L, this will operate the bridge BR G 2 of the point required.
287. The further progress of the arm A M wil! move lever LV 2 about its
centre and by the cord throw over the bridge B RG from its present position
and disconnect contacts 11 and 13, thus cutting off magnet P M 2 from the line L.
The further progress of A M will take about ten seconds before it reaches a
projection from the bridge B RG and sends it back into the position shown again
connecting the cups and contacts 11 and 13. Passing on, A M will strike a
projection from the bridge B RG 2 and throw it over from the position shown and
connect the cups and contacts 14 and 15 thus operating the timer, when the
arm A M will be turned round towards the point A. until it strikes the lever L V 2,
which will by the cord C 2 pull back the bridge B RG 2 into its present position and
break the circuit of the magnet T M, and A M will under the influence of the timer
again return and repeat the operations above mentioned starting with the lever LV 2.
288. If when the contacts 11 and 13 are joined, a current in the reverse direction
to the switching currents or a resetting current be passed through the magnet PM2
from any point, the armature of P M2 is operated and the circuit of M 2 is closed.
This will send a current through the earth to each of the magnets R M but its own
armature will reset magnet M and also slightly draw aside the projection from the
bridge BRG 2 so that the arm A M will miss it and return to the position shown.
289. In Figure 204 is shown a modification of the above system. Each point
is supplied with a magnet M, directly or indirectly operating a timer, of which the
period shall be for instance ten seconds. Generally contacts 5 and 6 are joined at
each point. Each magnet M has also a polarized armature by which a current in
the reverse direction to the switching currents passing through M will connect
contacts 1 and 2. M3 is a magnet similar to magnet M in Figure 201, and
normally contact 9 is joined to contact 10. It will be noticed that no switching
battery is required at any point. Generally the line L is connected by the
contact 11 to contact 13, the electro magnet M 2 and battery BY to the earth.
The armature of magnet M 2 will when attracted close the contacts 11 and 12.
290. T M is a magnet operating a timer of the description above specified. If
point G wishes to speak to point B, G touches his key K twice because B is the
second point.
At the first contact M2 is operated and closes circuit of BY 2
through the magnets T M and M 3 operating the timer of T M. On raising the K
between the two contacts, magnet M 3 as before shown by postponed action joins
contact 9 and contact 8 while disconnecting contact 10, and M 2 opens the circuit
of battery BY 2. The second depression of K will close the circuit through M2 as
before and the circuit of BY 2 is closed through the magnet T M and the magnet M
of point A and operate its timer.
291. When the key K is again raised, the timer of A will return and for a period
of say ten seconds separate contacts 5 and 6, and connect contacts 5 and 7 and at
the end of the period will reinstate them The timer of T M will now proceed
as before described for Figure 201 to send a current in the reverse direction to the
switching current through the magnet M of the point B thereby connecting contacts 1
and 2, and bringing B's instruments into circuit when G and B can ring and speak.
292. The timer of T M will as before shown disconnect contacts 11 and 13 and
connect them again at intervals of about 10 seconds, when, if any current passes
through M 2 from the battery BY to some earth connection through the speaking
instruments of any point, the magnet T M will be operated.
293. To reset, a current in the reverse direction to the switching current is sent

page_text: from the magnets from either station to the other. In both cases by any ordinary
means it may act on the polarized armatures of the magnets M in circuit so as to
throw it into its normal position breaking the connections between contacts 1 and 2
at each station. There is now no connection between the line L and the earth,
therefore when the timer of T M again connects 11 and 13, the circuit of TM will
not be operated and the system will be brought into a state of rest.
294. In Figure 205, the only difference between the system there shown and that
shown in Figure 204 is that each point is fitted with a magnet M operating a timer of
which the period shall be say ten seconds and so arranged that if one current only
pass through the magnet M its timer shall after a lapse of about half a second
cause contact 5 to be joined to contact 6 instead of contact 4, and if no further
current pass, after a further interval of about two seconds join contacts 1 and 2, and
throw the speaking instruments into connection with the line L.
295. But if another current pass through M, that is, two in succession, the timer
will after about half a second after the cessation of the second current cause contacts
5 and 4 to be separated and contacts 6 and 7 to be joined so that the magnet M of
that point is cut off for a period of about ten seconds, and so on for each point in
succession. During this period of ten seconds the switching will be completed,
after which the timers will return the contacts at each point to their normal
position, as at the beginning.
296. Thus, if point G wishes to speak to point B, the second point, G as before
taps his key K twice. Two currents are therefore sent from the battery BY2
through the circuit. The first will pass through the magnet M of point A and
cause its timer to be operated. On raising the key K at point G before sending
the second current, the timer of A will in the interval connect contact 5 to
contact 6. The next current from the battery BY 2 will pass through the
magnet M of point A on its way to magnet M of point B, operating both their
timers. If now no further current is sent through the line from battery BY 2, the
tiner of station A will connect contacts 6 and 7 and the timer of point B will
connect contacts 1 and 2 and 5 and 6. At the expiration of the ten seconds before
mentioned the timers rearrange the contacts as they normally appear but contacts 1
and 2 remain joined so that G can ring up and speak to B. The timer of
magnet T M will in the same manner as that in Figure 203 disconnect the contacts 11
& 13 and again connect them until there exists no further connection between
the line L and the earth when the system returns to a state of rest.
297. In Figure 206, we have only one line shown for both switching and speaking.
Normally the line L is completed as shown in the figure, and connected to two
balanced batteries at the terminal points. On earthing the line L at any point
through the key K a current will pass through all the magnets M at each point and
also through the magnets M2 and M 3 at the terminal points. At one of the
terminal points say A, the magnet M 3 actuates a timer as usual and also a toothed
wheel which is moved by a pallet one tooth forward for each current sent through
the inagnet M 3.
298. The process of switching is thus conducted. If point G wishes to speak to
point B, the second point, G taps his key K twice, this causes the magnets Mat
each point and the magnets M 2 and M 3 to be operated twice, also operating the
pallet and toothed wheel at the point A twice. All the above named magnets
actuate timers which do not come into operation in the intervals between the
switching currents. Their periods may be about ten seconds. After the last
switching current has been sent from the point G and a period of about two seconds,
the timers of the magnets M at each point break the linewire at each point and turn
it into one of the systems before mentioned and shown in Figures 201, 204, and 205,
so that it really operates for the time being like one of them with respect to the
switching line.
299. The timer of magnet M 2 disconnects contacts 14 and 15, and the timer of
M3 will at the expiration of about the third second by means of a contact arm
attached to the toothed wheel before, mentioned (forming a repeater) send two

page_text: switching currents into the line and afterwards actuate the system according to the
particular method required. In the end the speaking instruments of point B are
connected to the line and the timers at each point rearrange the linewire as shown
in the figure and ringing and speaking may be carried on as usual.
300. The timers of the magnets M 2 and M 3 connect contacts 14 and 15, and 11
and 13 at intervals until either point disconnects the telephone instruments as before
described from the line when the timers will come to rest and the system. will
resume its normal state.
301. Referring to Figures 201, 204, 205, 206, the resetting currents may be
transmitted to the initial point by one separate linewire, in connection with
which, the contact 13 will be placed after switching until the resetting current is
passed, thus doing away with the necessity for making temporary contact between
contacts 13 and 11 as before explained. Circumstances will show whether the
extra linewire would pay. In a similar manner, the returns of the magnets RM,
Figure 201 may be a separate linewire also used for the purpose of resetting.
302. Referring to paragraph 139, methods of meeting the requirements of large
number of points are discussed. I now show how the method described in
paragraphs 241 to 244 inclusive may be operated.
The
Referring to Figure 207, if the exchange is required to serve 2000 points, to each
point allot two such instruments I and II with their switchboards for 1000
points as are shown for instance in Figure 198, but each without the magnets PM,
contact cups or springs. I also appropriate to each point a switching instrument
called a selector similar in form and action to that shown in Figure 198.
parts of the selector are included within the dotted line in Figure 207. The
switching magnet S M of the selector only moves a timer and the contact arm A
carrying two insulated contact springs, one of which will make contact with the
outer row of contact studs, and the other with the inner row.
303. The circuits of the switching magnets S M and the winding magnets W M of
cach instrument I and II are connected to common batteries (for convenience) BY
and BY 2 on one side and also by a separate wire from each to the selector C,
where they terminate in the rows of contact studs. The wires from the
magnets SM terminate in the inner row of contact studs and those from the
magnets W M terminate in the outer row of studs, so that the wires from
the magnets S M and W M of the first instrument 1 will terminate in the first pair
of contact studs and so on.
The inner contact on the arm A is connected with contact 16, the out contact
which makes contact with the W M circuit studs of either instrument being
connected to the contact screw SC 2. The contact screw SC is connected to the
switching magnet S M and thence to contact 15. Both the batteries B Y and B Y 2
are connected to the axle of the polarized armature PA operated by the
magnet P M.
304. The magnet S M operates the selector contact arm by means of a pallet
and spring P which engages with the toothed rachet wheel RW and turns the
arm A round so that the springs thereon will make contact with the first pair of
contact studs belonging to the switching instrument I for one operation of the
magnet S M, and with the second pair of contact studs when the magnet S M is
operated twice, and so on for the next if there are more than two pairs of contact
studs. The wheel R W tends to return by the pull of a spring but is held in
position by a detent. The magnet S M also operates a timer which will in turn
operate the cups and contact springs of this point mounted on the selector.
305. If for instance the point A, to whom the instrument is allotted wishes to
speak to point No. 2326, he first sends two switching currents through his line as
usual. These passing through magnet P M to earth, it deflects the armature PA
which touches contact screw SC thus closing the local switching circuit
through S M contacts 15 and 17 and battery BY, operating the timer of SM and
the wheel R W, and the latter brings the two contacts of the arm A into contact
with the two studs of the second instrument I I. In the interval which now

page_text: elapses, the timer of S M changes contact 15 to contact 16.
The next group of
currents will operate the magnets S M on the selector and the instrument II and
the timers of both. That of the selector will make no further change in the
interval of time between the groups of switching currents. That of the instru-
ment II will change the position of the moving connection and so on for the third
and fourth groups of currents, the timers of both the selector and "instrument I I
being operated by each.
306. After the fourth group of currents ceases, the timer of the selector after a
period longer than that between the previous groups of currents will change the
spring contacts of the selector as before specified including the disconnection of the
magnet PM from the earth and connecting the linewire to the moving contact of
instrument II, then conversation may take place as usual.
To reset, a resetting current is sent through the magnet P M of the selector,
which causes the circuit through the magnets WM of the selector and
instrument II and battery BY 2 to be operated when both instruments will be
reset.
307. The use of one instrument or parts of one switching instrument by two or
more points is possible in several ways.
Two or more points may be connected to one switching instrument in the
exchange as shown in Figure 13 and described in paragraphs 165 and 166.
Two or more points may be connected to a sub-exchange and thence to a central
exchange as shown in Figure 13 and described in paragraphs 167 &c.
Two or more points may be connected by one or two linewires to the exchange
as shown in many ways, in Figures 136 and 201 for instance.
In many of these cases, one point may monopolise the instrument or line and the
others have to wait.
I therefore sometimes prefer to arrange :-
Firstly, that the time during which a point makes use of an instrument shall be
shortened as far as possible.
Secondly, that a point shall be enabled to use the first disengaged instrument at
his disposal.
308. In the first instance we shorten the time during which a point is using a
switching instrument as follows:—
Referring to Figure 208, the axle A L is turned round by a switching magnet
which also operates a timer. On referring to Figure 209 we shall see how this is
specially done. In the course of switching, the switching magnet first pulls the
pallet PT, and each time turns the toothed wheel W L one tooth and with it the
axle A L. This is against the pull of a spring or weight which tends to draw W L
back. W L has say 12 teeth, and is prevented from returning to its normal
position by the detent D fixed on the quadrant Q. After W L is turned the
required number of teeth, the timer of the switching magnet transfers the moving
connection of its armature to the pallet PT 2.
309. Qhas teeth cut in its edge so arranged that ten teeth shall occupy an
angular distance equal to that occupied by one tooth on the wheel W L. Qalso
loosely turns round the axle A L as a bearing but is otherwise independent.
On pallet PT2 being pulled by the switching magnet. it turns the quadrant
round one tooth at a time against the tension of a spring similar to that of
wheel W L but Q is prevented from returning by the detent D 2. This movement
of the quadrant Q is also transmitted to the axle AL by the detent D.
310. The axle A L is provided with several arms or projections A M shown in
Figure 208, one of which is appropriated to each contact arm CA. The contact
arms CA are turned down at their outer ends so that contact is made with radial
contact bars fixed on the plane PE. The contact arins are insulated from one
another and from the axle A L.
Figure 210 will explain how each arm CA is operated by the axle A L. Each
arm is attached to the toothed wheel T W provided with teeth each occupying the
same angular distance as those on quadrant Q. The arm AM of the axle A L

page_text: appropriated to this contact arm CA will normally revolve in a plane above any
of the mechanism shown. SP is a spring so secured to the wheel T W that its
end may be raised by the bent lever LV attached to the post P. If the lever L V
raises the spring S P and axle A L turns, the arm A. M turns with it and will slip
under the end of SP against a stop on it and carry the wheel T W and the contact
arm CA along with it so that CA will partake of the same motion as the
axle A L.
311. AL will move CA against the tension of a spring or weight attached to
the cord CD3 which transmits its tension to the drum D on the underside of the
wheel T W. TW is prevented from running back by the detent D 3.
312. The special apparatus allotted to each point consists of one of the contact
arms CA with the different attachments shown in Figure 210, and the apparatus
shown on plan and elevation in Figures 211 and 212.
P M is an electro magnet with polarized armature PA, contact screws CS
and CS 2 of similar functions to those shown in Figure 198. The bridge B RG
turns loosely on the same axle as the armature PA and is so arranged that in the
position shown it connects the linewire of the point to earth through the cups L
and E, while if it is turned over either by the timer of the above mentioned
.switching magnet as will be shown, or by a reverse current in the magnet P M it
will connect the linewire to the contact arm CA through the cups L and C and
disconnect cup E.
313. M is an electro magnet in circuit with the switching magnet, a battery and
the contact CS, the other pole of the battery being connected to the armature PA.
The armature ARM of the magnet M when attracted, draws the spring
lever LV 2 with it, and when it reaches the poles of the magnet is held by the
detent D4. The effect of LV 2 being moved in this way horizontally is to bring
its end over the arm A M 3 fixed on the axle A L 2 which passes by the apparatus
appropriated for each point in the manner shown for this point.
The arm A M 8 fixed to the armature AR M is connected by the cord CD to
the lever LV fixed on the post P, Figure 210.
314. M 2 is an electro magnet similar to M and in circuit with the same battery
as magnet M and the contact CS 2, the other pole of the battery being connected
to the armature PA as before. When PA makes contact with CS2 the
armature AR M2 is attracted by M2 and operates axle AL 3, and the
hook HK loosely suspended to the arm A M 4 on the same axle Figure 213,
which tips the bridge BRG back into its normal position shown if thrown over.
The movement of AL 3 also operates the shield SH attached to a collar that
rides loosely on the axle AL2 as shown in Figure 213. When shield SH is
turned by the arm A M 4, it forces the polarized armature PA away from
contact CS2 and as long as PA is deflected to that side, S H will thus operate,
and leave PA when PA returns to its central position.
The armature ARM 2 is also connected by a cord CD2 attached to the
arm A M 9 fixed to the armature to the detent D3, so that when armature ARM 2
is attracted it pulls the detent away from the wheel T W so that the contact
arm CA may return to its normal position shown.
315. The wire between cup E and the earth is branched to a contact spring CE
and to another contact spring resting with a number of similar contact springs
belonging to the other points connected to this instrument, all resting on a metal
-bar connected to the earth.
It will be seen that when CA leaves the spring CE the latter comes into
contact with the earth contact screw S E and connects the cup E to earth.
If the switching magnet be operated it will first by an arm A M on the axle A L
take away the earth bar from the springs of all the points attached to this
instrument, and at the same time moving the arm of the point using the
switching instrument will leave this only connected to the earth through its
contact spring C E.
316. Suppose point A wishes to speak to a point No. 76.
He first taps his

page_text: At
switching key 7 times sending 7 currents through the magnet P M appropriated to.
him. This causes armature PA to strike the contact CS seven times and closes.
the circuit of the switching magnet and the magnet M. The switching magnet
operates the wheel W L through the pallet PT thus rotating the axle AL and
disconnecting the earths of all the other points connected to this instrument.
the same time the magnet M has attracted its armature ARM which is caught
by the detent D4, and lever LV 2 is brought within range of the arm A M 3..
The armature ARM also pulled the cord CD operating the lever LV and
raising the spring SP that it may be caught by the arm A M as it passes. The
seven operations of the pallet PT will rotate the axle A L seven teeth of
the wheel W L thus bringing the contact arm CA to the seventieth radial.
contact bar.
317. Allowing a small interval of time to elapse after the seventh current, the
timer will change the connection of the switching magnet to the pallet PT 2.
Then A sends six further switching currents through his line operating the same
circuits as before, so that the axle A I: and contact arm CA is advanced six.
contact bars by the pallet PT 2, so that the contact arm rests on the seventy sixth
bar. After a little time the timer will cause axle AL 2 to be rotated and by its
arm A. M 3 to raise the lever LV 2, throwing over the bridge BRG and joining
the linewire to the contact arm CA as before shown, and bringing the
projection PJ into such proximity to the armature PA, that the ringing currents.
which pass through the magnet P M shall not cause PA to touch the contact CS.
although deflected towards it.
318. The timer also raises both detents D and D2 thus resetting the switching
part of the instrument and connecting the earths of the remaining points'
lines so that any one of them may use the switching instrument in the same.
manner as A.
As before
A reverse current through PM, whether resetting or ringing from another
point will cause the armature PA to touch contact CS2 closing the circuit.
through the magnet M2 which attracts its armature and draws the detent D3.
from the wheel T W by the cord CD2 and operates the axle AL 3.
shown, AL 3 in rotating will raise hook HK tipping back the bridge BRG
into its normal position, cause the shield SH to force PA away from the
contact CS2 and raise detent D4 thus releasing the armature of magnet M which.
allows the lever LV 2 to resume its normal position.
It may also be arranged that the circuit through magnet M 2 shall be closed by.
the movement of detent D3 until contact arm CA. reaches its normal position.
319. Where the exchange is of a larger nature than that lastly shown, referring
to Figure 214, I arrange a moving contact and carriage CE similar to that shown
in Figure 198 and on it place a spring SP similar to that shown in Figure 210,.
which when the carriage CE is in its normal position as shown can be operated
by lever L V similar to that shown in Figure 210. The switching instrument is
similar in every respect to that shown in Figure 198, without the contact springs.
or cups or magnet P M. In place of the moving contact, the carriage carries a
bar BR which can be traversed from left to right with the carriage. On the
bar BR are fixed a number of hooks H K and an axle AL 7 carrying a number
of arms A M 10.
320. Each point is supplied with the magnets M, PM, and M 2 and fittings as.
shown in Figures 211 and 212.
The first group of currents sent from a point, say A, to the switching.
instrument will first close the circuit through the point's magnet M and the
magnet of the switching instrument as before shown. The armature of M will
raise lever LV by the cord CD, and with it the spring SP and bring the-
lever LV 2 within range of the arm A M 3 of the axle A L 2 as before shown.
The switching magnet causes the carriage carrying the bar BR to move to the
right, the hook HK picks up the spring SP and through it causes the carriage CE.
to find the proper switchboard required.

page_text: 321. In the interval between the first and second groups of switching currents,
the timer of the switching instrument will now cause the connection of the
switching magnet to change to the rod RD 2, Figure 198, which will operate the
axle AL 7 and through the arm A M operate the escapement ES2 of the moving
contact drum on the carriage C E. In the interval between the second and third
groups of currents, the timer will cause the axle A L 7 to be traversed instead of
the rod RD 2 of the switching instrument, so that the rod or axle AL 7 when
operated by the rod RD2 of the switching instrument moved by the third
group of switching currents, will now operate the escapement ES of the moving
contact drum on the carriage C E, in this manner the required bar is found on any
particular switchboard.
322. The timer will then after the lapse of four seconds, operate the axle AL 2,
and by its arm A M 3 the lever LV 2, and also close the circuit of the magnet W M
of the switching instrument so that it will be reset and leave the contact carriage CE
of the particular point where it was placed.
A resetting current as before shown will close the circuit of magnet M 2, and in
this case it will bring the wheel W L 2 into contact with W L3 and start the
rewinding motor. So that the moving contact of this point will be wound up into
the carriage CE and the latter drawn back to its normal position.
323. The next method is to provide a certain number of points with a smaller
number of switching instruments which may be each similar to that shown in
Figure 198 say 10 instruments to 100 points, and we arrange that any point can be
jointed to the first disengaged instrument.
The linewire of each point will be taken to a distributer appropriated to it. The
distributer is a small switching instrument as shown in Figure 215. The linewire
from the point in question there passes through the armature of magnet M 2 and
through contact spring 3, the magnet M to the earth.
324. The first switching current from the point passes through the magnet M,
operates its armature and releases the radial arın A M which is propelled by a
weight or spring round the axle A L. A M carries two insulated contact springs
which travel on two rows of contact studs. The outer contact spring of the
arm A M is connected to the spring SP which tends to keep the armature of
magnet M2 away from its poles, thence the circuit normally passes through
contact 1, magnet M 2 to battery BY which is also connected to contact 5 of each
switching instrument including instruments I and IV. The contact 4 of each
instrument is connected by a separate conductor to a contact stud appropriated to
it on the distributer. Normally contacts 4 and 5 are connected when the switching
instrument to which they belong is at rest or disengaged, but if in use they are
separated.
32. As stated above the first switching current from the point sent to its
distributer through its linewire L will pass to earth and operate the magnet M.
This will release the arm A M. We will suppose that instrument IV is the first
one disengaged and that instruments I, II and III are being used. The arm A M
will pass over the contact studs of instruments 1, II and III and no change will
take place. Directly the outer contact spring on the arm A M touches the outer
stud of instrument IV, the circuit of magnet M2 and the battery BY will be
completed because contacts 4 and 5 are in this case joined. The magnet M 2 will
attract its armature and the arm A M 2 will lock the arm A M in this position by
a detent catching in the teeth of the wheel W L to which A M is fixed.
326. Contact 3 will be disconnected and the circuit of the linewire L will be
continued through A M2 and wheel WL to the inner contact spring on the
arm A M and thence to instrument IV. There the first switching current will have
moved the instrument and disconnected contacts 4 and 5 before the armature of M 2
makes contact with contact 2. Thus the point will switch as usual, for the above
operation has taken so little time that it will not interfere with the first group of
switching currents.
The resetting current will reset instrument IV and again connect contacts 4

page_text: and 5. This will close the circuit through magnet M3 and battery BY. The
armature of M 3 being attracted, the armature of M 2 will be released from the
detent D, and the distributer arm A M will be returned to its normal position.
327. The magnet M 3 may be used only to reset the arm A M which releases the
detent D when A. M reaches its normal position.
By means of a third row of contact studs a separate contact on the arm A M and
separate conductor to each switching instrument, the magnet M 3 may be inserted
in the resetting circuit of the instrument used and operated with it instead of by
the contacts 4 and 5.
The arrangements for returning the arm A M are the same as those for resetting
the switching instrument shown in Figure 198.
328. We have shown that one point can cause another points line to be switched
off his bar when required, now by referring to Figure 216, I show, how that when
two points are speaking, the intrusion of a third point may be prevented.
I use a supplementary testing bar represented by the dotted line BR 2 and I
arrange that the contact holders shall also have another contact which shall touch
the supplementary bars only and be connected by another conductor CD shown by
the dotted lines to the switching instruments. I also arrange that when the
switching operations of any point are over, the timer of the switching instrument
before it connects the moving contact to the linewire shall bring the particular
testing bar it touches into contact with each pole of a battery in turn. The first
contact would include the magnet M which may be the rewinding magnet of the
switching instrument or so arranged that if a current pass through magnet M it
shall determine the resetting of the particular instrument to which it belongs. The
second contact will be permanent until the switching instrument is reset.
329. In the figure, B has switched on to A and at the time of switching no
other point was speaking to A, therefore when B's testing contact touched A's
testing bar and the contact was put in touch with the poles of the battery BY in
turn, no current passed through magnet M and now the testing contact of B's
instrument is supposed to be connected to the other pole of battery BY.
Suppose C wishes to switch on to A, C's testing contact comes into connection
with A's testing bar B R, then C's timer proceeds to put C's testing contact in"
touch with the first pole of battery B Y, that is through the magnet M. Instantly
a current passes through the magnet M viá B's testing contact and A's testing bar
and C's testing contact causing C's instrument to be reset. This occurs every time
C or any other point tries to switch on to A's bar until B has switched off.
It may be arranged that instead of resetting C's instrument, C's magnet M may
simply withold C's linewire coming into connection with his speaking contact
until B is switched off, when the circuit being broken through M, the necessary
contact takes place and C can ring A up.
330. Figure 217 shows an improved switchboard making use of both sides of the
bars BR. The bars BR are held between the posts P, P, placed at intervals.
The bars are separated from one another by slips of insulating material I which
may be continuous or only the width of the posts P, P. For the slips I, one of the
posts P may be cut into recesses or teeth between which the bars may be held and
clamped in place by the opposite post P. The latter arrangement will facilitate
the extraction and insertion of the bars from the end of the switchboard if
required.
331. Figure 218 shows a modified contact holder. M is a permanent magnet
mounted on 4 wheels, two of which W L and W L are shown. One pair of the
wheels W L makes the required contact with the bars they touch. The requisite
pressure is obtained by the attraction of the magnet M for the bars which would in
this case be made of iron galvanized on the contact faces.
332. If the bars in Figure 218 be of brass, and the wheels WL be so placed
that the magnet M is a little farther away from the bars, a vertical strip of iron
may be placed between the inside edges of the wheels so as to just clear them and
flat against and insulated from the bars. This will form a guide for the contact
K
;

page_text: carriage, and the requisite pressure is obtained by the attraction of the magnet M
for the strip of iron.
333. Figure 219 shows another form of contact holder in which M is an electro-
magnet. The contact spring S has an armature A R M fixed at its end. The
object is that while the contact holder is moving a current shall be sent through
the magnet M and attract its armature thus keeping C away from the bars, when
it arrives opposite the required bar the current is stopped and the spring brings C
into contact with the bar.
334. It will be seen that the mechanism before described may be controlled from
one or more points, so that one point can be put into connection electrically with
any other from a third point by taking an extra switching line to that point where
a battery and key may be used for operating the switching line, or in this case
the switching line may be similar to that shown in Figure 117 with a battery at
the exchange.
335. It would also be feasible for an operator from a given place firstly to control
the switching mechanism of several points, so that while they could themselves
switch on to any point they desired, the operator could switch any one of them on.
to any other point in the following manner :-
In paragraph 24, it was shown that A would in ringing through to B perhaps
Inove the latter's switching instrument. The operator in the case in point could
first switch on to the contact bar of the point whose instrument is to be operated,.
and by means of a reverse current which would not affect his own instrument would
move the instrument of the point as required. The resetting of the operator's
instrument might be effected by the timer, or by a separate circuit.
336. In another way, the operator might be able to switch on to the local
switching circuit of the point whose instrument is to be moved and operate that.
Having now particularly described and ascertained the nature of my said inven-
tion and in what manner the same is to be performed, I declare that what
I claim is
1. An electrical exchange system arranged substantially as described with
reference to Figure 1, or to Figure 13, or to Figure 34, or to Figure 45, or to
Figure 54, or to Figure 63, or to Figure 73, or to Figure 82, or to Figure 90, or
to Figure 98, or to Figure 106, or to Figure 115, or to Figure 116, or to Figure 117,
or to Figure 136, or to Figure 207 or to Figure 215 with the modifications
described and operating as specified.
2. An electrical exchange system arranged substantially as described with
reference to Figures 125 to 140 inclusive and to Figures 201 to 206 inclusive
with the modifications described and operating as specified.
3. The electrical exchange switching apparatus constructed substantially as
described with reference to Figures 10, 11, and Figures 14 to 34 inclusive with the
modifications described and operating as specified.
4. The electrical sub-exchange switching apparatus constructed substantially as
described with reference to Figures 13 and 12 with the modifications described
and operating as specified.
5. The electrical exchange switching apparatus constructed substantially as
described with reference to Figures 139 and 140 with the modifications described
and operating as specified.
6. The electrical exchange switching apparatus constructed substantially as
described with reference to Figures 198, 199 and 200 with the modifications
described and operating as specified.
7. The electrical exchange switching apparatus constructed substantially as
described with reference to Figures 202 and 203 with the modifications described
and operating as specified.
8. The electrical exchange switching apparatus constructed substantially as
described with reference to Figure 207 with the modifications described and
operating as specified.

page_text: 9. The electrical exchange switching apparatus constructed substantially as
described with reference to Figures 208 to 214 inclusive with the modifications
described and operating as specified.
10. The electrical exchange switching apparatus constructed substantially as
described with reference to Figure 215 with the modifications described and
operating as specified.
11. In an electrical exchange system, the method of using test circuits, bars,.
contacts &c. substantially as shown with reference to Figure 216.
12. The test circuits constructed substantially as described with reference to.
Figure 216 with the modifications described and operating as shown.
13. The timers constructed substantially as described with reference to
Figures 10, 139, 178 to 181 inclusive with the modifications described and operating
as specified.
14. The moving connections constructed substantially as described with reference.
to Figures 10, 139, and Figures 172 to 178 inclusive with the modifications
described and operating as specified.
15. The moving contacts constructed substantially as described with reference
to Figures 10, Figures 182 to 188 inclusive, 218 and 219, with the modifications.
described and operating as specified.
Dated this 7th day of March 189A
ROBERT PIPPETTE.

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