US1253688A - Telephone-exchange. - Google Patents

Description

M. F- HILL.

TELEPHONE EXCHANGE.

APPLICATION FILED MAR-24.1908.

1,253,688. Patented Jan. 15, 1918.

5 SHEETS-SHEET I.

(ar/Jr/ M; F. HlLL.

TELEPHONE EXCHANGE.

APPLICATION FILED Mn. 24. 1908.

Patented Jan. 15, 1918.

6 SHEETS-SHEET 2- Wxjbwaaea: 3 4 Inward 07':

33$ 2,11% H r y wawaedx M. F. HILL.

TELEPHONE.EXCHANGE.

APPLICATION FILED MAR. 24. 190B.

Patented J an. 15, 1918.

6 SHEETSSHEET 4- M. F. HILL.

TELEPHONE EXCHANGE. APPLICATION FILED MAR. 24. I908.

1 ,253,688. Patented Jan. 15, 1918.

6 SHEETS-SHEET 5.

. F. HILL.

TELEPHONE EXCHANGE.

APPLICATION r'uznumu. 190s.

Patented Jan. 15, 1918.

6 SHEETS-SHEET 6- Ingauy" I III m UNITED STATES PATENT OFFICE.

MYBON FRANCIS HILL, 0] BOSTON, MASSACHUSETTS, ASSIGNOR 0F ONE-HALF T0 EDWARD E. CLEMENT, OF WASHINGTON, DISTRICT.- OF COLUMBIA.

TELEPHONE-EXCHANGE.

Specification of Letters latent.

Patented Jan. 15, 1918.

Application med March 24, 1908. Serial No. 423,051.

a citizen of the United States, residing in Boston, county of Suffolk, State'of Massa' chusetts, have invented certain new and use.

ful Improvements in Telephone-Exchanges, of which the following is a specification, reference bein had to the accompanying drawings, in w ich similar parts are designated by the same letters of reference.

My invention relates to telephone exchanges, and has for its object the reduction of the wiring and apparatus and the resultin simplification of the exchange.

y invention consists in the substitution of a few circuits controllable by a-. large number of subscribers for the individual circuits heretofore used in such a way that any person may control at all times one of the few common circuits. More particularly my invention consists in an exchange in which the subscribers are divided into groups preferably of about one hundred each, each group provided with a number of trunk lines, reaching from the central exchange to short individual circuits, which in turn are connected to the subscribers station.

For the busiest groups of subscribers fif teen or twenty trunk lines are required, while for suburban groups but a few trunk lines are required, perhaps not more than eight or ten.

For each group the trunk lines are d1- vided into two sets, one of receiving trunk lines and the other of transmitting trunk lines. The receiving trunk lines are connected to a single board of the multiple switch board central station. When any subscriber of a group takes his telephone oii' from its hook, his individual short circuit is auto; matically connected to one of the idle re-" ceiving trunk lines, and this connection opcrates an indicator at the board to which the receiving trunk line is connected, informing the operator that a subscriber desires a connection. The operator then finds out the number of the' desired subscriber, connects the receiving trunk line to a transmitting trunk line, belonging to the group of the desired subscriber, and automatically causes, by means of a commutator at her board, the

transmitting trunk line to be connected to that subscriber.

The transmitting trunk lines of each group are connected in multiple to all the boards of the exchange. Any transmitting trunk line of a group may be connected automatically to any subscriber of that group under the proper conditions.

In the drawings,

Figure 1, represents in diagram view the plan of the circuits of the exchange.

Fig. 2, shows the automatic switches which interconnect the subscribers circuits and the trunk lines of a group, and the circuits by which they are controlled.

F g. 3, shows in diagram view the connection of two transmitting trunk lines to two boards of an exchange, and the substitute for a multiple switch board test circuit.

Fig. 4, shows a. face view of a section of the board, to which the transmitting trunk lines of a group are connected.

Fig. 5, s ows in sectional view one form of an indicating spring jack.

F1 6, shows a vertical sectional view of a, (ll: erent form of an indicating spring we Fig. 7, shows a sectional view of a third modification.

t Fig. 8, shows a plan view of a transmitin which said switch is controlled.

Fig. 9, shows the commutator outfit of a central ofiice operator by means of which a transmitting trunk line is connected to a subscribers circuit.

Fig. 10, shows in side view part of the circuit controller.

Fig. 11, shows an edge view of the apparatus which controls the operation of a transmittin trunk line switch.

Fig. 12, s ows in side view a trunk line switch.

Fig. 13, shows a portion of the same in plan view.

' Fig. 14 shows an end view of part of the commutator apparatus. a

Fig. 15 shows a side view of part of the transmitting opcrators cord switch with the plug re- 100 terminal switch, and the circuits by Fig. 18 is a detail.

Fig. 19 is a diagram of the telephone switch hook in normal position.

Fig. 20 is a similar view of the hook 111 actuated position.

Fig. 21 is a die ram of the mechanical line relay in one 0 its actuated positions.

Fig. 22 is a similar view of the relay in another one of its actuated positions.

In Fig. 1, are shown two boards of a multiple switch board exchange to which are connected receiving and transmitting trunk lines. T8, T8, Ta are transmitting switches by means of which the transmitting trunk lines Tt, T15 and Tt', are connected to short individual circuits, A, A, A, B, B, &c. To each of these short individual circuits A, A, A, B, B, &c., are connected subscribers outfits like that shown in diagram view in A.

The two wires a and b, of the short metallic circuit are normally connected to bells a, contact a switch lever a normally connected, thereto, and back to the wire I).

When the telephone a, is switched for use,

- the circuit is transferred from the bells a,

to the subscribers telephone a, secondary coil a, contact a, and switch lever a, temporaril connected thereto.

The ocal circuit including the contact a", primary coil a", transmitter a", battery a", and contact a is closed at the same time.

The two wires are open to each other while the switch lever a, is in transit between the contacts a and a. When the telephone is removed from the hook the usual automatic spring device causes the heel contact a, of the switch lever to strike the insulated contact a, on the lever (1", thus grounding the wire I), through the switch lever a, heel contact a insulated contact a, condenser a", and ground at G.

The lever is then released and the projection a of insulating material prevents the contact a from touching the contact a". When the telephone is restored to its hook, the contact a insulated from but mounted upon the switch lever a comes'into contact with the lower surface of lever a", thus grounding the wire a, through the tension spring a. .When the hook is released-the insulated projection a", prevents a connection between the contacts a? and a". Thus when the rear end' of the switch-hook lever a moves downward, the metal at wa en gages the contact plate a" without strikin the metal at a; and when the rear end 0 the lever a moves upward, the contact plate a? engages the metal a" without striking the plate a.

The telephone a has a flexible cord support a, secured to a contact spring a, adapted while the telephone is suspended therefrom to make contact with the contact point 0", thus closing the circuit of the bells messes,

a, in a shunt around the telephone circuit a, a), while the tele hone is switched for use. The purpose of t is device will be seen later. The wires a; b, of the short individual metallic circuit, are connected by multiple branches 0 and d to each receiving switch R8 and transmitting switch, of the group to which the subscriber belongs. These connections are shown in Figs. 1 and 2. The form of switches in Fig. 2 is preferred. Those in Fig. l are simplified to better illustrate line circuits.

The branches 0 and d, are connected to y the contacts cand d, on eachswitch. On

each switch are ring contacts 0 and d in 1u'xtaposition to the contacts 0 and d, and adapted to be connected thereto by the contacts 0 and d reslpectively, mounted upon the circuit closing ever of each switch- To the ring contacts a and d, are connected two wires 0, d of the metallic circuit of each trunk line.

The connection between a subscribers metallic circuit and a receiving trunk line Rt is effected as follows :When the subscriber removes his telephone from its hook thus switching it for use, a circuit is closed from the ground G, condenser a contacts a and a, switch lever a", line conductor 6, to the automatic sub-central switches, individual branch wire 6, coil 6, contacts e conductor e common to all the subscribers of the group, conductor e to the central exchange,

current generator D, and ground G.

Current from the battery B energizes the relay e, over the circuit including relay e, resistance e (about equal to that of the magnet e) contacts e, e, resistance 6", thus releasing the escapement e of the weight or motor e.

The motor e" propelsat a regularspeed the shaft f, upon which are mounted the receiving and transmitting switches R8, R8, T8, and Ta.

A reslstance e" graduates the amount of current supplied to the relay 6.

The alternating current on the circuit just traced, energizes the coil 6', as shown in Fig. 21, which produces a change in the circuits, so that the subscribers line will secure a connection to one of the receiving trunk switches but no other. As the coil 6 is energized, its core attracts the armature of lever e Since the upper end of lever e is in contact with the contact plate 6 mounted on the lever e it slides on the plate which acts as a cam lifting the lever e until the upper tion of the contact 6'' is withdrawn from contact with the back contact e". From this mechanical operation it will be seen how the -17, of the magnet operating the circuit closer h, wire 1?, brush contact 11, ring contact a, common to the sets of contacts of all the subscribers of the group, wire c, containing contacts 6 normally closed, there being a separate wire 6 and separate contacts 6", for each receiving switch, wire e", to battery B.

The same circuit might be traced through any other receiving switch belonging to this group in case its traveling arm and contact brushes reach the subscribers terminals first.

- The sets of contacts belonging to each subscriber are so arranged with relation to the normal position of the circuit closers h of the various switches, that no two circuit 'closers' will be in position to make contact with the subscribers line simultaneously.

To effect this the sets of contacts of a subscribers line, line a b for example, are arranged in the same vertical line, while the normal positions of the circuit closers h are arranged spirally, or at different points around the shaft f.

Presuming that the circuit closer h. and

switch arm 15., of the switch Rs, make connection with the contacts of line a 7), the coils a? of the magnet will attract the armature It, pivoted at h, operating the circult closer b. so that the contact 0 crosses the contact 0' and cflthe contact (i crosses the contacts 11 and d, and the contact a" makes connection with the individual switch board.

contact e, so that it falls back to its normal position except that it does not strike contact e" on account of the insulated back stop e" interposed by the lifted armature,

as shown in Fig. 22. When a is deenergized 7 by the retraction of lever e' the shaft f stops.

The contactse are opened before the con tacts e and o' of the circuit closer h cross connect the contacts a, 0 and cl, d

The contacts e and e when held open, as described revent a transmitting switch T8, or T82 ii-om making connection with this line.

Thusit will be seen, after any subscribers circuit a, b, has been connected to a receiving switch, R82 for example, no other receiving switch R8, or transmitting switch Ta, or T82, can be connected to it.

The circuit of the subscribers line a, b, when thus connected is continuous through the two limbs c. and d of the receiving trunk line Rt to the central station (see Fig. 1,) where these limbs are connected, through intermediate switch apparatus controlled by the operator, to the two contacts a and d of a connecting plug P.

If the subscribers line a, I), had been connected to any other trunkline of the group, Rt for example, it would have been connected to another plug, through another set of switching apparatus controlled by the same or another operator, who may be stationed at board No. 2, or elsewhere.

If a subscriber of another group had taken his telephone 01f his switch, subscriber No. 309 for example, connected to line B,

of magnet e,

he would have been connected to a receiving trunk line, Rt for example, and thus connected to a plug P controlled by an operator at board No. 3, as shown.

It will be noticed that the short individual metallic circuits'A, A, A and A" belonging to subscribers No. 201, No. 241, No. 242 and No. 243 may be connected through receiving trunk lines Rt. and Rt to switch plugs P under the control of an operator at board No. 2. These subscribers lines are but a few of the large number, one hundred for example, which may be connected through these switches R8 and Rs. There may be additional switches R8 and corresponding additional trunk lines Rt, to which the same subscribers lines may be connected.

In like manner the short individual metallic circuits belonging to subscribers No. 309, No. 310, No. 311, N0. 322, and N0. 313 lettered B, B, B and B and B may be connected through one or more receiving switches R8 to one or more receiving trunk lines Rt, and thence to plugs P at central. The subscribers lines referred to are but a few of the number that may be employed. Preferably however there are one hundred or less subscribers lines adapted to be connected to plugs P at board No. 3.

In like manner I divide all the subscribers of the exchange into groups of one hundred or less each, and so connect the subscribers" lines of each grou to switches and trunk lines that the lines 0 each roup may be connected to any section of t e central switch board preferably that individual to the grou All the subscribers having numbers un' er one hundred are connected to board 0, all subscribers numbered 100 and over and under 20) are connected to board No. 1, all subscribers numbered 200 and over andunder 300 are connected to board 2, and

so on. This relation between the number of the subscriber and the number of the board at central is not necessary but is more convenient. Except for convenience sake this arrangement is entirely unnecessary. And the system will work quite as well if the receiving trunk lines are distributed among the various boards so as to even up the work of the operators. Receivin trunk lines from several groupsof subscr bers might be connected to a single board under the supervision-of a single operator. When applied to an exchange system in which the multiple switch board feature is not used all the trunk lines would be supervised at a single board,

The groups of subscribers may if desired have any desired number of circuits as long as each group has a different designating character fromany other group.

The connection between a subscribers line A. and a receiving trunk line Rt has been described. A complete metallic circuit is established through the subscribers conductors a and b to the trunk line conductors c and d. This circuit is normally completed through the contact springs a, 11, contact springs impedance 00118 (1, leading to an alternating current generator CG which will be described later. There is a separate generator for each receiving trunk line. The current is of such a character that it will energize the coil 0", causing the annunciator c to attract its flap in such a way as to display its signal, informing the operator that a call has been sent in from some subscriber of the two'hundreds group over the trunk line Rt. Incidentally the pairs of contacts a and d" are closed but at present this has no function. These contacts are closed by the two armatures, one at each end of the coil e" being drawn up against the front contacts a" and d.

When the operator sees the annunciator 0 display its signal she lifts the plug P from the base P upon which it is. normally supported causing the release of contact springs c and 11' so that they may come into contact with the contacts 0 and d" as shown at board No. 3. This connects the two trunk line conductors a and d to the operators telephone set P, constructed in the usual manner, supplied with a transmitter current from battery B. Thus a converc, d, annunciator a, andv connected through a transmitting switch T8 to the short outlying metallic circuit of subscriber No. 322. ThlS connection is established automatically as will now be described.

It will be noticed that when the plug has .been withdrawn from its, resting place the contact springs 0" and d'have left the contact springs c and d which in turn have separated from and released the contact springs 0 and (P so that the latter make connection with the normally disconnected contact points 0 and d electrically connected to the commutator contacts a and (1 Thus the two contacts 0 and d of the plugs P are connected through the contact springs 0 and d, contacts a and d, to

the commutator contacts a and d. In connecting'to a transmitting trunk line the operator has connected to'the group to which the called subscriber belongs. All that remains for the operator to do is to select the particular subscriber of the group to which the trunk line is to be connected. This .she accomplishes by means of the commutator C, keyboard C, and plug P. These elements make u her commutator outfit. Upon the cylin er 0 which is made of insulating material in the modification which is being described, are mounted contact strips g of variable lengths of conducting material.

These contact strips 9' are so arran' with relation to the contact springs c" t at but two strips are adapted to touch all the contact springs c", three stripsfadapted to touch nine contact springs, four strips adapted to touch eight contact sprin and so on, so that each contact spring 0" 1s adapted to be connected through the strips 9 to the contact spring 0 a different number of times.

The contacts d" bear the same relation to the strips g as do the contact springs c". For groups of one hundred subscribers there are ten contact springs 0 ten springs d", and eleven strips g normally disconnected therefrom. The contact springs 0 and d" are connected to insulated cross bars 0 and d as shown. The plug P grounded at G is adapted to be connected to a single cross so i v touc that each strip 9' touches a contact spring.

taneously cross connecting these springs.

' When the plu P has been placed uponthe nected to those two cross upon Figs through the alternating. current generator D, a supply wire e reaching to the sub-1 cross bars 2 o thesets of cross bars 0 and ,d", and the cylinder 0 rotated once as dec" and dWconrs are connected to the contacts a and d by the four longest strips successively as described, establishin the following circuits, which may be trace 1 and 2':from ground G scribed, the contact. springs a central to which line No. 322' is connected, thence through contacts e, condenser on to the relay e", wire e, including the set of normally closed contacts n, (the orderof the relays and contacts being immaterial), thence by trunk line conductor (1, to spring jack contact d, plug contact d, contact.

sprin d", contact point d, wire d", contact one of the contact springs d", the one connected thereto bythe cross bar 2, of the set designated d fitheiice by way of plug P connected thereto, to'ground at G. This circuit is made and broken fopr times by the strips g of the commutator. The re- .lay e is energized four times. Referring now more particularly toFig. 2, it willbe seen thatwhen the relay 0? 1s energized it accomplishes two functions, in connection with the selecting and controlling apparatus.

there shown, whichis located at the subcentral station to which the called line is connected. V

Not only does it actuate the ratchet movement m of the units switch but it actuates the circuit-controller C. When the armature of relay e is drawn down, its heel e forces the link 0 upward, which in turn tilts the rocker '6" against the oifset m. This offset is. rigidly connected to the ratchet wheel operated by the pawlm and resists the rocker a so that the rocker which is pivoted on the pawl m lifts the pawl upward. As seen in Fig. 10, it catches the next tooth of the ratchet wheel and when the relay e is deenergized, the controller C is advanced one step. lVith it travels the offset m, which travels downward, and no longer resists any oscillations of the rocker e and this operation is not repeated.

This local circuit is closed four times as tacts will shortly be described.

with a spring 7 stroke.

scribed. The functions of these sets of con- When the circuit is closed four times the relay e operates the ratchet mechanism m",

propellin 5 the contact arm m, ai-oundto contact 0. 2 on the units switch m.

a As has been'described after strip g hasleft a contact spring 01 it makes contact 0" grounding the 0 side of the circuit as follows From ground at G, current generatorD,

supply wire e, contacts e normally closed, condenser es, relay e, contacts n, closed as described, trunk line conductor. a, jack contact 0, plug contact a", contact spring a,

.Eeontact point 0, commutator contact 0,

strips '9, contact spring a" connected to bar circuit is also energized fourtimes.

The relay e therefore attracts its armature four times thus actuating the ratchet mechanismm and propelling the contact a a numbered 2, plug P andground G'. This arm at around to contact No. 2 of the tens i switch. v The fourth time-that the circuit is closed, the relays e and e attract their armatures together and thus by means of the heels 0" and links e force upward libth ends of the rocker e, forcing the 'awl m. upward'so as to catch the next toot of the ratchet n When the relays are deenergized the rocker and pawl are released, and operate the controller another step, bringing itto its third and last position. Thus it opens the contacts n and n and closes contacts n and n by altering the position of the respective contact plates n, n, n, n. It is to be noted that the pawl m acts on its backstroke and not on its forward stroke. Its back stroke in the diagrammatic illustration of Fig. 2 is the downward stroke, but this showing is for convenience of diagram only, since. in the practical apparatus shown in Figs. 10 and f 11 the back stroke of pawl m is an upward The closing of contacts n establishes a circuit from the grounded. direct current generator D over thesupply wire e a through the restoring magnet M to the trunk line conductor 0. When this line is connected to ground by a subscriber or by an operator, the magnet M attracts its armature m and by means of mechanical connections, m? for example, withdraws the detents m and m permitting all the switchg apparatus to be restored to its normal position.

When the armature m." is attracted the insulated wedge m opens the contacts e and c. This prevents relay 6' for example, from being operated while the circuit controller C is returning to its normal position. The magnet M being operated whenever the 0 side of the conversation circuit is directly grounded is operated when a switch board, operator closes contacts a, for example, or whenever a subscriber hangs his telephone receiver upon its switch thereby causing the contacts a and a to come into electrical connection, grounding the.

conductor a directly through spring a". When the armature 'm is attracted b the restoring relay M, it closes the set 0 contacts m, glrounding the c1rcu1t mcludm relay M t rough wire m and three branc circuits, one branch m" containing contacts n closed exce t when the controller C is in its norma position shown, a second branch m containing contacts m closed except when the ratchet m is in its normal position, and the third branch in conta1ning contacts m closed under s1m1lar conditions. The contacts m and m are closed when the cleft wheel attached to the ratchet carries the cleft beyond the contact sprin As long as anyone of the three branc circuits is closed while restoring, the relay M will keep all the detents m, m", and m, withdrawn from their appropriate ratchets, thus insuring a return of all the switches to their normal position.

Therefore whenever a subscriber hangs up his telephone the apparatus controlling a'transmitting switch is restored.

To return now to the manner in which this switch apparatus controls the operation of a transmitting trunk switch, T8.

The first step forward of the controller C closed the set of contacts 10. as described. This closes the following circuit including .magnet e.'battery B, magnet e, resistance m, wire m", contacts n, wlre m", e, back to battery B. This magnet e at once releases the escapement e" causing the shaft or arbor f to rotate under the influence of the motor e, so that the transmitting switch Ts rotates with the shaft, and is ready to close an circuit under the control of the units an tens switches.

When the contacts n are closed as has been'described, and when the armsm and m" rest upon the contacts 2 oftheir respective switches representing subscriber No. 22,

the following circuit is established :arm m", contact 2, wirem", contact e, of the transmitting switch Ts, contact i,mounted upon but insulated from the switch arm h, wire 5, coils i, thence by wa of -wire i, to the contact 2'', contact e" o the switch, wire e, pair of contacts e a, open while the line a, b is connected to any of the switches, resistance e, battery B, wiping contact 6, the conducting shaft f, switch lever h, contact if, mounted upon and electrically connected thereto, ring contact a, conductor. m", contact 2 on the switch m, contact arm m of the switch, contacts n now closed by the circuit controller C by the contact plate back to' the contact arm m.

This circuit may be closed only when the wire switch arm h, of the transmitting switch Ts comes into electrical .connect1on with the set of contacts belonging to the line a b of the subscriber No. 22 called. For the purposes of illustrating the manner in which a transmitting switch establishes a connection between a trunk line and a subscribers line, the line a b is represented as belonging to subscriber No. 322 for example, and the group of switches T8 and T8 may be regarded temporaril as representing the automatic sub-centra of the 300 group. When therefore the above circuit is established the armature h of the switch Ta is attracted causing the contacts a and d to cross connect the contacts a and d with the ring contacts 0 and d respectively. A circuit is thus established between the subscribers line and the transmitting trunk line. Another transmitting switch Ta is controlled by another trunk ine Tt, the local circuits of which are not shown but which are the du licates of those connected to and. contro led b the trunk line Tt. It has been describe how an operator has caused a connection between a transmitting trunk line Tt and a called subscriber. It is necessary that the operator should know that this circuit has been established.

When the lifting of the plug caused the separation of the contacts 0 and from the contacts 0 and d, the coil 0 released the armature opening the contacts 0 and 11. Having operated her commutator as has already been described she tips her commutator P1606 P ivoted at P so that the insulated arms connect the contact springs 0 and d with the contact springs c and d and at the same time disconnecting the contact springs a and from the contacts a and d. At the same time the insulated base P disconnects the contact springs a and d from the contacts 0 and d establishing the following circuit from the supply current generator CG over the wires 0 and d", hlgh resistances or impedances and coils c" and d, contact springs and d, contact springs c and d now connected thereto, plug contacts 0 and d", jack contacts 0 and d, of the transmitting trunk line Tt, through the contacts of the transmitting switch T8 as described,

to the subscribers line connected thereto.

moves his telephone receiver from its hook,

switching the call device out of circuit.

When the contacts 0 and d are closed as described the receiving trunk line conductors e and d are connected through the v reason already stated in connection with the description of the magnets e, e, and the levers e' and 6". i The operator noticing that the called subscriber is busy informs the calling subscriber to this effect, and he may drop his receiver without hanging it upon its hook and wait for the called Sub scriber to finish his engagement. Dropping his receiver in this way leaves it hanging upon the cord (1 thus causing the spring contact a to come into contact with the contact a" closing the circuit of the call device a in a shunt around the telephone set. \Vhen the busy called subscribers business is over his line is automatically connected to the calling subscribers line without the intervention of the central operator, and both,

subscribers are called up automatically.

This automatic connection'depends upon the condition of the circuit of the called subscriber. As long as it is connected elsewhere the contacts e are. open. When this connection is dissolved the contacts a are closed the transmitting trunk. line switch Ta is operated, closing the circuit between the trunk line and the subscribers line, energizing the coil 0 of the operators outfit at central, causing this trunk line to be connected to the receiving trunk line, to which the callin subscriber is connected through the contacts 0 and d", causing a current from the supply generator CG to actuate the call device a, polarized bells for example, of the calling subscriber. At the same time the operator is informed of this connection by the attracted flap of the indicator 0.

The operator may at any time by closing the pairs of contacts 0 and d by means of normally open key contacts cut her telephone into the circuit, to determine by listening in,

the condition of the line, or to talk with either subscriber.

. 'The indicator 0 indicates busy as long as a circuit remains establishechbut as soon as a circuit is opened by the operator or either subscriber in disconnecting the circuits and grounding the b-limb, this indicator releases its flap, indicating the disconnection to the operator.

When a subscriber hangs up histelephone and the restoring relay M attracts the armature at which releases the ratchet mechanism of the three switches m, m" and C as described, the plate n opens the contacts 1: thereby releasing thearmature h of the transmitting switch Ts so that this switch disconnects the subscribers line a, b, from the transmitting trunk line Tt. The Weight of the armature It causes the catch h to become engaged with a detent h which causes the arm h to be carried around again, by the shaft f which is turning under the influence of the motor a. When the transmitting switch closed the circuit between the subscribers line a, b, and the trunk line T2), the contact 11" coming into contact with the contact a closed a parallel circuit from the wire 2', through the relay e to the battery B, opening the contacts e and e, and e.

The opening of contacts 6 prevents the subscriber from getting a different connection while connected with. The opening of contacts 6 and e" prevents another trunk line Tt rom being connected to the same subscriber, so that while two subscribers are connected together for conversation.

by an operator their circuit can not be interrupted or interfered with by another subscriber or any otheroperator or the same operator overanother trunk line. When the operator who has established the circuit closes the contact c or when either subscriber hangs up his telephone, the 0 side of the established circuit is grounded thereby restoring the .transmitt-mg switch apparatus,'as;deseribed by means of the relay M, and at the same time establishing a circuit from the grounded current generator D over the supply wire a, relay M, to the wire 0 of the receiving trunk line Rt which has been connected to the calling subscriber. The relay M attracts its armature e, which causes the insulating wedge a to open the normally closed contacts e, thereby cutting off the current from the coils i of the receivingswitch magnet, so that when the 0 side of the circuit is grounded as described the receiving switch as well as the transmitting switch is released, and by assuming its normal position disconnects the calling subscriber from the receiving trunk line Rt.

Summing up the operations already described they are briefly as follows :Referring to Fig. 1, subscriber No. 201 for example, desires connection with another subscriber No. 322 for example.

Subscriber No. 201 removes his telephone from its switch lever thus establishing aconnection over a receiving trunk line Rt for example, to the operator at board No.

\ trunk lines the trunk line plug to a transmitting trunk line Te for example, at a trunk'switch section numbered 3, and by operating herv commutator outfit causes that trunk linev to be connected to the desired subscriber. She does not select a transmitting trunk line in use at another board on account of a multiple switch board busy test which will be described later. The operator then turns her cord switch lever P and was her attention to other calls. The in icator c" at once indicates whether the desired connection has been established and if. it has been, the called subscribers bells are automatically rung. If the called subscriber is busy, the calling subscriber may wait with his telephone at his ear, for the desired con.- nection, or he, may drop his telephone and return to his work, in which case, when the called subscriber is through the connection between the called and the calling subscriber is automatically established and the bells of both run When either subscriber hangs up his te ephone, he disconnects the entire circuit and the indicator 0 at central releases its flap, informing the operator of the disconnection. If both subscribers should by accident fail to operate the restoring apparatus of the sub-central switches, the

operator may, as soon as she ascertains this fact by listening in, restore the apparatus by closing the contacts a.

Fig. 3 shows a test system which. may be used with my invention, although it is obvious that an suitable test system may be used in its p ace. Two boards are shown, board 2 and board 3. At each board is a spring jack J for each of two transmitting Tt and Tt". Each jack contains the contacts a and d" already described, and a third contact 7'. The test contact j of all the jacks connected to a transmitting trunk line are connected together by a test wire j. Each contact 7' is connected to a test battery J through individual coils or lamps j, and the other pole of the test battery is connected. to a third contact J 2 on the plug P of each receiving trunk line. The plu also has contacts a and d already descri ed. The contacts in Fig. 3, are somewhat difierently arranged from the contacts in Fi 1. This arrangement lies within the skill of the electrical en ineer. When a plug is inserted in a jac as shown, a circuit 1s established from the batte J over wire to the contact of the jac connected to, y way of wire 9 to the contact 7' of all the other jacks of the line, thence in series from the contact j of each jack through the coils or lamps 7" of each ack, to the test batter? J.

In Fig. 5,-is shown one arm of the jack J. This jack has a test contactfl, the two circuit as described, the core aasaaee sulated. support oi an incandescent lamp j, but insulated therefrom. This lamp ,1 is a small lamp of the Edison or any other type, and'is mounted to the rear of the switch hole and 'ust beyond the reach of the plug P. Eac lamp is preferably provided with a. reflector j adapted to reflect the light strongly out of the switch. hole of its jack, and out of no other switch hole. The reflector may be mercury on the glass itself, and a pro ecting tube provided to exclude the light from other jacks.

In Fi 6 is another form of jack. In this figure t e lamp 7'" is inclosed in a long reor non-refl cylinder j adapted to exc ude the light from other Jack. holes. The jack contacts 0 and d and. j m be mounted in any suitable we In Fig. l, is a third form of jack. In t is jack is a coil j having an a rture j to permit the passage of ighti rom one or more lamps j" with reflectors 7'. The lamps and reflectors, one or both, may be individual to each 1ack, or common to two or more jacks, and

mally the jacks lighted. When however, the C011 7" is energized b 1 a closed test attracts the magnetic finger j, attracting the flap .j, shutting off the light from the jack hole renderin it dark, which in this form oi jack, indicates the line to be busy.

I prefer however the. forms shown in Figs. 5 and 6. Although I show this jack for a busy test, that is, to show that a. subscriber is to begin conversation, that a. conversation is in rogress, or that it is over, it is obvious that 1t me be used for other purposes, that is, for cal ing, for clearing out, for line signal work, and various similar pures. I In Fig. 4 are shown avnumber of jacks, three of which. indicate busy. This is a section of one of the switch. boards to which all the transmigtzg trunk lines of group No. 2, are conn By inserting a plug in any one of these jacks, the operator controls a connection between a. transmitting trunk line and any subscriber of the 200 group.

The switch board is divided into sections similar to this. To each section are conis accomplished. This switch shows in plan view the sets of contacts of a hundred subline contacted and (Z mounted upontheinshould be constantly burning, so that norscribers. Upon the switch are ring contacts c and 01 common to all the subscribers of the group andconnected to the trunk line c, d, e", e and e. The ring escapes conductors a and (1*, as shown in Figs. 2 and 12. The line wires a b of each subscriber are connected to a difi'erent pair of contacts 0' and d. a

The contactsc and e are connected to the wires e" and e and e respeotivel there being a different set of those wires or each subscriber as shown. There are 10 contacts e", one of these contacts being common to 10 subscribers. Each contact c" is connected to a contact upon switch m. The contact e numbered 0 isconnected to the contact marked 0 upon the switch m. The contact a" numbered 1., is connected to the contact m" numbered 1, &c. The contacts e are connected to the contacts of the switch m Contacts 2 numbered 0 are connected to contacts 0 of the switch. Contacts numbored 1 are connected to contact No. 1 of the switch, &c. The set of contacts belonging to each subscriber comprise individual contacts and d are common to all the subscribers connected to the switch. Each contact a is common to a different. set of 10 subscribers.

Contact 0 for example, is common to subscribers 0 to v9 of the group. Contact 3, for example, is common to subscribers 30 to 39 of the group, 620., so that the switch m selects the unit of a subscribers number and the switch m selects the tens thereof. For each subscriber there are separate contacts 8" and resistance a.

The functions of the circuits and apparatus have alread been shown in connection with Figs. 1 an 2.

Fig. 9 shows the operators commutator outfit already described or illustrated in diagramin Fig. 1. Upon a plate of insulating material C are mounted cross strips of conducting'material d". Through each strip d" roject push buttons C, so mounted as to ide u and down throu h the stri and through e support 0". T e strips are separated from each other'by insulating material C. Each push button C has around its neck a spring C", one end of which is soldered to the push button and the other end soldered to the strip upon which the push button is mounted. This soldering is not necessary but is preferred on account of the good electrical connection which results therefrom.

their normal position, holding the push but-' ton in its operative position. When another push button is depressed and the bars are.

again separated this push button 0 is released and the other one held in its place. If the same push button is again depressed contacts a The lower end of each usb 7 button is rovided with a point and he ow it will spring back as far as the notch C and there be held a second time. 'The bars a" are at each end mounted u on but in-' with a support G which is mounted by means of toggle-joints (1" upon the insulating plate O. A cord C" attached to the tog- .gle oints .0, running over the pulley C",

and connected through a s ring 0" to a weight C holds these gri irons in their.

normal the togg e-joints, to keep them in a norma osition with thepost c? touchin position. c

Pivoted upon the bar C is a lever 0", one end of which is pivoted to the movable bar C and the other endof which carries an insulated stop C Against. this stop normally rests a stud or roller C, secured to the commutator wheel C, holding the commutator in its normal position; When a ush button 0 is depressed it moves the ars C mounted upon the cross bars G which in turn causes the lever C to remove the stop G from beneath the roller 0'', re-

leasing the commutator wheel 0. A ke C" V i with studs C causes the friction clu C" to turn on its axis 0 and b means of the spring connection C? causes e commutator wheel C to turn in the direction of the arrow.

"As the bar C returnsat once to its normal position when a push button has completed its downward movement, the catch C" is restored to its first position so that when the commutator C has completed a rotation the stud or roller C will prevent it from turning any farther. The shaft C" may housed in common for several or all commutators; and is regulated'to prevent a too rapid motion of the commutator. The commutator wheel G is mounted loosely upon the shaft C but prevented from lon 'tudinal movement. The shaft C" is rigi y connected to the key C".

Upon'the body of the commutator C are mounted theposts or rods g adapted to cross connect the strips 0 and d with the contact springs 0 and d" respectively. The last rod 9" to pass under the springs is so wide as to electrically connect all of the springs simultaneously to the strips 0 and d. cuts so that one rod effects or strikes only spring contacts a", and the other rod strikes contacts d". The rods g are so related to the sprin that all the springs 0" and d" strike an make contact with their respective strips atthe same time The rods g are double, and have The rods 9-, g" correspond to the-strips 93 9" in Fig, 1. The construction of these v strips and springs and cooperating parts is mally rest upon rod C covered preferably with ordinary soft rubber tubing. This rod .is mounted at each end upon a pivoted arm C pivoted at C to the insulated support C". A screw G working. in a threaded hole in the arm C and against the fixed plate C" adjusts the position of the rollers withrelation to the commutator rods.

The strips 0 and d are mounted upon an insulated support C which is connected at either end to a supporting spring C,

which in turn is'mounted upon the base C.

Through each spring C" passes the shank of a screw C having its threaded end working in a threaded hole in a rigid support C strips to the contact springs may be from time to time adjusted to allow for wear, and so forth. The function of these parts has already been described. The purpose of this figure issimply to show the preferred mechanical construction of the commutator outfit. 1

Upon a'push button (3 is mounted a in C 9 playing in a slot C. There may e a separate slot C? for each push button.

A portion of the keyboard is shown. The other parts are omitted as they-aremere duplication. v

There are intended to be 10 rows each containing 10 buttons, adapted to make 100 different combinations, as illustrated in diagram in Fig. 1, and wired as shown in that figure. Instead of a separate button for each number there may be one button only adapted to be inserted in any one of 100 holes. This button would be substantially then a plug. Such a plug should have a handle. The hollow in the lower end is necessary.

In Figs. 10 and 11 are shown some of the details of the construction of the transmitting switch ap aratus, that is, the apparatus that controls tl ie operation of a transmitting trunk terminal switch. In connection with Fig. 2 this apparatus has been described with relation to its electrical features, and now it is the purpose to set forth some of the preferred mechanical details. Some of the details, such as back stops and so forth .are omitted because of the danger of rendering the drawings unintelligible from comlexity. i

Upon an arbor or shaft n which is mounted loosely or rigidly in end supports m" are loosely mounted ratchet Wheels m",

In this manner the proximity of the main in the ratchet wheel and by a mechanin, m". These wheels are in electrical connection with the arbor, and are provided. with suitable devices to prevent longitudinal motion thereon. Thejratchet wheel n forthe cii'cuit controller C is shown in side view in Fig. 10.

Upon its faces are projections n, n, n" onone side, n, n on the other side, adapted to act on rollers n mounted on contact springs n, which are adapted to open and close the, pairs of contacts n, n, n, n", n, n, as shown in 2.

Itis operate by a pawl m in the direc tion of the arrow in its forward movement.

1 The pawl m is pivoted upon a lever rt -which in turn is pivoted upon a suitable rigid support 1'. The pawl m is provided with a roller 'r" which engages with the tooth next below its normal position (shown; and forces the tooth upward under the in uence of the weight 1'. The fixed roller r acting on the arm 1' of the pawl so guides the pawl that it may slide into position to engage a ratchet tooth, and when the tooth moves the wheel forward, is guided out of engagement with the tooth at the moment, that the detent 1' engages the next tooth for detention. The roller 1' also prevents further useless upward movement of the pawl.

This roller 7 may permit the pawl to recal connection with the detent withdraw the pawl from the ratchet wheel while restoring, as indicated in Fig. 17 The weight 1' attached to the arm 1' of the pawl tends to draw the pawl into engagement with the ratchet teeth, yet is strongly counteracted normally (or when the lever r is not subjected to an outside or magnetic force) by the weight hung upon the lever 1 The detent r is mounted upon a suitable pivoting support m, and upon its heel m I is provided with the insulating wedge m adapted to'open contacts 0 and e, but this opening does not happen until the detent has been withdrawn to its extreme position by the magnet M. This-is due to the flexibility of the springs resting against the wedge m.

Upon the detent r is mounted a slot 'm in which plays a rod 1' which in turn is carriedby the armature 'm. so that when the armature is drawn up by. the magnet M it withdraws the detent r from the ratchet wheel, permitting the latter to return to its normal position. The slot m is sufiiciently turned to its normal position. The wheel is g to permit the'detent to play over the provided wit a pulley m upon which a restoring weight wis hung by meansof a spring '1" and cord 1.

Upon the pawl m", see Fig. 11, is pivoted a cross bar e, having loose engagements r" with the ends of the armatures r", pivoted at r, and acting under the influence of magnets e' and e". The armatures T" have pawl movements m, m, like that shown and described in Fi 10 for the controller C.

These paw movements actuate the ratchet wheels m, upon each of which is mounted an arm m and m" ada to sweep over and make contact with studs 0' shown in Fig. 2. In Fig. 11, only stud m" is shown for convenience, on each switch m and m". These ratchet wheels also have pulleys m" with their cord springs and weights, r,

r, and r. They are also provided with detents m and m" and slots m in which works the rod r which withdraws the detents from their engagement with the .ratchets. Upon the hub of the ratchet wheel n" is a bar 112. normally resting against the upper side of the pivoted cross bar or link 6. When this switching apparatus is operated, first the magnet e is operated once, then the two. magnets are operated alternately a determined number of times, to correspond with the units and tens of the num ber signaled, and then the two magnets are operated simultaneously by the double rod 9 shown in Fi .9. When magnet e is operated the first time it draws down the pawl m so that it engages with the proper tooth, and at the same time tips the link e so that the other end of the link, the right end in the figure, strikes against the bar 111-, and

' the further movement of the link forces the pawl 1n downward so that it engages with the next tooth for operating purposes. When the current leaves the magnet e' the pawls lift upward again under the influence of their weights r, and advance the two ratchet wheels one tooth, where they are held by the detents. The succeeding alternating impulses over these magnets and the corresponding sides of the metallic circuit advance the two wheels m" and their switch arms m to their appropriate positions, but do not affect the pawl m on. account of the lost motion of the link connections '1'", and on account of the difierent position for the stop bar m due to the advance of the ratchet wheel n to which it is rigidly connected. Finally however the impulses wind up with simultaneous ones, one in each magnet and together they again draw the pawl m down suflicientlyto engage with the next tooth of the ratchet wheel n, thus advancing it another step into its third and final position. The condition of the contacts n, n, n n, n and n in these three positions have already been descri ed in c nnection with Fig. 2,

armature h.

"rigidly connected to the sleeve h.

and it is not necessary to repeat here. It is enough to say that the projections upon the two aces of the wheel n should be so placed and gaged as to accurately perform their proper functions.

' Upon insulating supports a are mounted spring contacts m" an m normally out of engagement with the flanges of the respective pulleys 'm. on account of cuts or depressions at m' and m respectively, but when the wheels are not in their normal position these s rings are in contact with the flanges. This clbses the circuit to ground from the springs to the grounded supports m" for the purpose of retainin the armature m in its active position until the wheels are all restored, as fully described in connection with insulating sup rts n" are mounted the studs with which t e contact springs n come into contact when operated by the circuit controlling ratchet n, to close the contacts of the controller.

Fig. 12 shows inside view a modified and preferred form of a transmitting trunk ine switch already described in connection with Fig. 2- and Fig. 8. Upon a shaft f adapted to be rotated under the influence of some kind of motor is rigidly connected a collar k. This collar su ports on the shaft the loosely mounted co lar" h. Upon the shaft f is also mounted rigidl a second sleeve h and also the yoke h o the coils a" as also shown in Fig. 18. Each armature yoke h on the shaft is rigidly con nected thereto, and acts as armature for the magnet coils suspended below it. Each coil has a pole It so shaped as to attract a ring The poles h bear against a shoulder h" rigidly connected to the loosely mounted sleeve h. The ring armature It has an aperture sufliciently large to permit it to work up and down over the sleeve hf. When this ring armature is in its upper position shown, it impinges against the shoulder h" and is thereby prevented from coming into contact with, the poles h of the magnet, which at the time may be rotating under the influence of the shaft and motor. The armature h is pivoted ath upon an upright support it which is mounted upon the switch arm h. This switch arts is onnected to the armature h is a catch h normally engaged with a catch it rigidly connected to the collar h. When the armature h isnot attracted the catch h drives the switch arm h and all parts mounted thereon in the direction in which it rotates. When the catch it leaves the catch it the switch arm It stops its rota-tion, while the shaft f, the collar h, the sleeve h and the coils 1'. continue to rota e s" long as they are influenced by the motor. Upon the switch arm h are mounted the contact springs'i', i, and i; The contact. spring 2' 1s electrically connected with the switch arm, but the others are insulated therefrom except for the electrical connections. These springs play over the contacts 0, e and e, whose functions have already been described. Mounted upon but insulated from the arma ture h are two hollow rods h, one of which carries a bridging contact (1, the other of which carries a similar contact 0. These bridging contacts are pivotally mounted u on the bars h. The upper end of each 0? these contacts normally rests against stop h under the influence of sprin h.

One end of each spring h is. astenedto the bar around which it is coiled, and the other end of the spring is connected to the upper end of the contact mounted upon the bar. One bar It has an extension h which is guided by a properly formed guide piece mounted u h, which is mounted upon but electrically insulated from the switch board h". Mounted upon but electrically insulated from the bars h is a. spring contact i ada t'- ed to make connections with any one o a number of contacts 0" around the switch board. 7

Upon the sup ort h are mounted two contact springs adapted to make sliding contact with round annular ring h" n coils i of the m ct. h

rings h" orm the terminals 0 the magnet coils. One contact spring h is connected by means of wires 1' to the contact springs z" and i. The other contact spring h? is con nected by means of wire i to contact sprin i. A receiving trunk line switch is identical in construction with the transmitting switch shown in Fig. 12, except for the extra contact 0, spring 11, the construction of contacts a", and the electrical connections. This difierence is well shown'and described in connection with Fig. 2. I

The circuit closing apparatus in Fig. 12 is shown in itsactive position. Normally the weight of the armature h causes the catch h to engage with the catch h and the contacts a d, and i to be out of con-- nection with their respective switch board contacts.

Fig. 13 shows a top perspective view of the apparatus shown in Fi 12, or atleast a part of this apparatus. e mts of contacts of the various subscribers are shown, and the serrated edge h which guides the endh so that the circuit closers c and d.

make pro r connections with contacts .0 and d. springs i, z" and i make connections with successive sets of contacts. The moment the s leave one set of contacts they make e ectrical connections with the next set of contacts, so that the circuit closer h is ese.

t is also shown how the contact place. i A

' Upon the circuit closing bars 1:. is shown the contact spring 17 mounted upon insulating material. This spring 17 is so adjusted that it will slide easi y into place.

When the coils z" of this switch are energized over the circuit which has already been described, the armature h is attracted by the poles 10. causing the end h to strike the serrated guide It and steer the contacts 0' and (1 into such a position that they will make proper connections. In Fig. 12 it is shown how the two ends of the pivoted contacts c and d bear against their appropriate contact surfaces. 'means of this construction these contact pieces have a frictional action in attaining their position and an equal amount of ressure is bro ht to bear upon each of t e four pairs'o contacts:

as v

Normalsliyathese circuit controllers rotatewith the it f. They may travel over the switch board at the rate of at least one rotation in three seconds. This s has been found successful with solid core slow-acting ma ets, but with quicker acting magnets a higner speed may be attained. Y

15, is shown a side view of the o rator s cord switch, the front view bein own in Fig. 1. The lever P is pivo at P, and-is provided with a base P, upon which the plu normally rests. Aspr'ing P having ben s P workin on the edge of the basetends to hold the ise in its upper or lower position against the stops P The operator may tip the lever P into its upper or lowerposition, thereby altering the circuit connections as described in connection with Fig. 1. Y

The generator D which supplies the current for restoring the stem 8 cold supply a direct current prefera ly so toned down by electro-magnetic resistances and shunted by condensers as to be inaudible in the receivers by induction. It should be so toned as to 'well known to electrical engineers, by 1mpedances and condensers, and the subscribers bells a so constructed as to respond thereto. The current may be direct, and the bells of the circuit breaking variety; or the current may be alternating of a periodicity below 16 pulsations a second, and with the intermissions between the pulsations less than one hundredth of a second in length.

I This nature of current I prefer. When de- Ill be inaudible in the receivers in the manner veloped from a dynamo, and its irreglarities properly toned down, it acts satisfactorily both as calling and signaling current. The operation 0 the exchange with a current supply of this character is as follows:

'A subscriber desirin a connection takes down his receiver,

us permitting his nuance switch to ground the 6 side of his metallic circuit, and operating the first receiving switch whose contact springs pass over this subscribers set of. contacts As these switches are spirally arranged with respect to the various sets of contacts of this subscriber, as shown in dis ram in Fig. 1, but

one receiving switch wil o erate.

circuit conductors o the subscriber, and the metallic conductors of the receiving trunk line, between which is bridged the current generator CG, including a call annunciator a". The current from the generator operates this call annunciator over the circuit described, calling the attention of the operator to this receiving trunk line.

The operation of the receiving switch'has prevented the possibility of the calling subscribers line bein connected with any other trunk line, and t e telephone switch of the subscriber has closed the tele hone circuit.

The operator, seeing the ca annunciator display a signal, takes up the plug of the trunk line associated therewith and thus cuts her tele hone set into circuit, to find out the num ber of the called subscriber.

Having learned the number she inserts the plug into the jack at her .board of a transmitting trunk line running to the group to which the called subscriber belongs, and deresses a button C of her commutator outt shown in Fig. 9, causing the metallic conductors of the transmitting trunk line to make connection by means of the switch a 'paratus shown in Figs. 2 and 11 with tl ie metallic conductors of the called subscribers circuit. This connection will take place onlywhen the called subscriber is free. When the operator has thus inserted the plug in a jack andpresses her commutatorbutton,she tilts the switch 2 into the third os'ition already described, and leaves the lines to take care of themselves.

If the called subscriber is free the transmittin trunk line will immediately connect itself t ereto. ,The tilting of the operators 7 switch P has cut-the current from thereceivingtrunk line circuit just described and introduces it and the annunciator G into the circuit of the transmitting trunk. line as described, so that when the. metallic circuit'of the trunk line is connected to the called subscribers line, this generator is in a complete metallic circuit, and the anmmci ator a is again energized indicating to' the operator that the called subscriber has re-.' sponded. With the'relay d it closes the metallic ,COl'ldllCtOIS of the transmitting trunk line to the'metallic conductors of the annunciator also closes the circuit of subscriber, thus completing a metallic cirquit for conversation.

' When the current traverses the circuit of the called subscriber it operates his call bells as lon as his telephone is not switched for use. en he answers the call this current is inaudible in his telephone.

The closing of contacts a" and cl by tge t e generator CG to the circuit of the calling subscriber'again, and if he has dropped his telephone and returned to work leaving the contacts a" and a" closed to each other, rings his call bell a informing him that -his order has been fulfilled and that he has been connected to the called subscriber."

The circuit may be supervised by the op erator who has established these connections by looping or bridging her teleghone set into the circuit as already describe The pulsations of the alternating current ()Gr are preferably so slow as not to cause annoyance the called subscriber. Five or six pulsations to the second is quite suilicient for the purpose of calling and signaling. Whenconversation is over, and the subscribers have no further use for the metallic circuit which has been described the subscribers ha their telephones upon their switches thereby groundin the aw-0 side of their metallic circuit. his ground connection may be efi'ected by either subscriber or by both. That is, when the a side of the circuit is grounded by the firstsubscriber .who hangs n his telephone, or by both when they bot hang up their telephones together, the relays M and M? are operated as as been described with relation to Fig. 2, and the switches at the sub-central 'or, in other words, the transmittin and receiving trunk line switches, are re eased, and the connection between the subscribers metallic I circuits and the trunk line metallic circuits is opened by the disconnected contacts 0 and d thereby opening the circuitof the generator'current from CG, and releasing the'flap of the annunciator' 0, indicating to the operator "at the central station that the trunk lines are no longer in'use. She then withdraws the receiving 'trunk' line 'ug from the jack of the transmitting trunk ejack, and returns the plugto its normal resting place on the insulated support- P,'at the same timeipressing this-support back to its normal position shown in connection with the receiving trunk line Rt.

The relay M opens the contacts e of the receiving trunk line switch. y

The restoring circuit operates magnet M which, as will be seen in Fig. 11, releases the apparatus controlling the transmitting -switch. The contacts n are opened by the receiving trunk line connected to the calling whereby that switch resumes its normal position, and if the shaft f is rotating, it continues to rotate with it.

The speed with which a connection is established by my system depends upon the speed of rotation of the transmitting and receiving switches, and the speed with which the apparatus controlling transmitting switches is operated by the operators commutator outfits.

As the first one of the spirally arranged rewiving trunk closes a subscrib ers circuit to centr this circuit is closed almost instantaneo y. When the exchange is at its busiest time, this connection cannotbe delayed more than two seconds at the outside, so that when a subscriber takes down h' telephone from its switch, the connection central is established, and the call annunciator operated before the receiver reaches his ear. The operators telephone is cut in by her taking up the trunk line plug, and this is done in the usual manner, except that it is done more quickly than when the o rator has to insert a plug into the jack o a calling subscriber. This operation is saved by my system. After inserting the plug into the jack of the proper transmitting .trimk line, and at a glance she can see what trunk line is not busy, she presses down one s of her commutator buttons 0 and after one or two-' seconds tilts the handle of her switch P. This is plent of time for the apparatus to be 0 erated or controlling the transmitting t switch, for one second I find is the outside limit for the maximumnumber of impulses to be sent over each side of the metallic circuit, so that the time which has been consumed between the moment when the subscriber took down his receiver to the moment when the operator has finished her part in establishing the desired connection is at the outside not more than four seconds, and is generally not more than two or three seconds. The operators share of this time is still less.

If the called subscriber is free the connection to his line will be almost instantaneous, never more than two seconds late, and

1 this connection is indicated to the operator.

If, during the busy hours of the exch the operator has other connections to esta lish she can at once. turn her attention to them. If the called subscriber is busy, the indicator will not operate, and she will know that the connection has not been established. She can then loop or bridge her telephone into the circuit and tell the calling subscriber that he may. dro his telephone, and that he will be called w en the called subscriber is free. The calling is automatically efiected without further attention of the operator when the called subscriber is free. If the indicator tells'her tliat the connection has not been established after some time, and the trunk line is needed, the operator may close ers hav' 'additions required by my a pair of extra contacts 0" and withdraw the plu 'from the jack, leaving the trunk lines an trunk switches in their normal position.

It will be seen that my invention saves a great deal of time on the part of the central operator.

For an exchange of ten thousand subscriba single station, each board of e systems now in use requires a jack for each subscriber and aboutone hundred annunciators. A dozen or fifteen clearing-out annunciators are also used.

n my exchange, the are reduced from 10,000 in number to 1200 or 1500, the callin annunciators are entirely omitted, and a ut 12 or 15 annunciators used for both calling and clearing-out.

, In systems now .in use,-24 to '30 plugs are required for each operator. In my system {)lge plugs are reduced to one half the num- In systems now in use, the metallic circuits of the above exchange would be 10,000 in number, and each one would reach from the subscribers station to the central oflice. In my system these circuits are reduced to about 1000 to 2500 in numberfor the greater part of the distance.

To obtain these advantages requires that each operator shall have a commutator out fit like that shown in Fig. 9 and that from 10 to 25 trunk line switches be located at some outlying points in proximity to grou s of subscribers. That is, each group of su 'scribers shall have'a few switches in some place in their locality. These are the only i system.

It is obvious that single circuit lines ma be or anized into an exchange of this kin and t at by slight alterations two or more subscribers may use the same individual circuit. For the latter arrangement suitable automatic calls should be provided under the control of the o rator.

In the following'claims I shall make use of the term side switch by which it is to' be understood that a commutator or equivalent device for controlling and directing the" application of current to one or the other actuati elements of the main switch, as for examp e the commutator used in combination with the units and tens elements hereinbefore described.

For convenience I may also make use of the expressions double element selection and two-element selection. By this I mean that the selection of a unit in a given group is made by double selection of the group and the unit in the up. While my switch hereinbefore descri d is specifically a single motion switch, it is conceivable that the same general method of functioning mightapplied to what is known in the art

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