US1750934A - Telephone system - Google Patents

Description

March 18, 1930. c. E. LoMAx TELEPHONE SYSTEM Original Filed Dec. 6. 1922 5 Sheets-Sheet l March 18, 1930. c. E. LOMAX TELEPHONE SYSTEM Original Filed Dec. 6. 1922 3 Sheets-Sheet 2 Innen :JP

Elar'ence .E Lmmax March 18, 1930.

Original Filed Deo. 6. 1922 C. E. LOMAX TELEPHONE SYSTEM 70 orf/f5 co/mfcraffs IZZ/ |262 3 Sheets-Sheet 5 Clarence EL Umax atented 18, 193@ TES CLARENCE E. LOMAX, OF OAK PARK, ILLINOIS, ASSIGNOR, BY MESNE ASSIGNMENTS,

TO AUTOMATIC ELECTRIC INC., F CHICAGO, ILLINOIS, .EL CORPORATION OF DELA- WARE TELEPHONE SYSTEM Original application led December 6,

rlhe present invention relates to telephone systems in general, but more particularly to automatic telephone systems; and the main object is the provision of a new and improved common signalling equipment. Such an arrangement is not only cheaply manul factured, but it is reliable and lowers the maximum demand for ringing current in order to allow a source of ringing current of smaller capacity to be used than would ordinarily, as will be explained further hereinafter.

Other objects and features of this invention relating to the circuit arrangements, which are claimed in my application Serial No.

605,149,f1led December 6 1922, which application has matured into of which this application is a division, together with the main object will be er.- 23 plained fully later and will be apparent from that explanation and reference to the accompanying drawings which comprise Figs. 1-3, inclusive, and which show by means of the usual circuit diagrams a sucient amount of the apparatus used in a system embodying the. features' of the invention to enable the invention to be understood and its utility appreciated.

Figure 1 of the drawings shows a calling subscribers substation and line which terminates at the exchange in the banks of line finder switches and has associated with it the line circuit LC. Also, one of the finders is shown and the common finder allotter which allots the idle finders for use.

Figure 2 shows a connector permanently associated with the finder F, Fig. 1, and having access to the line of substation A and also the other lines of the private automatic exchange.

Figure 3 shows the common signalling equipment which constitutes the principal feature of this invention and which is used to supply ringing current, busy signalling current, and also dial tone to tell the calling subscriber' when to begin to dial the number.

The automatic substations A and A are similar to each other, and each has the usual talking, signalling, and switch controlling instrumentalities. The line circuits LC and latent No. 1,665,708,

1922, Serial No. 605,149. Divided and this application led ctober 20, 1927. Serial No. 227,436.

LC', in which the lines of these substations terminate, are similar to each other, and each has the usual line and cut-off relays which, however, have novel circuit arrangements as will be pointed out hereinafter.

Each of the finders, such as the finder F, Fig. 1, and the operating mechanisms 0 and O of the finder allotter FA is of the wellknown rotary type of switch, of which the wipers move in a forward direction only and have no normal position.

The connector C, Fig. 2, is of the wellknown vertical and rotary type, and accordingly, its bank contacts are arranged in horizontal rows or levels according to the usual and well-known practice.

In order to facilitate the ldetailed description of the operation of the apparatus shown; it will be assumed that the subscriber at substation A desires to converse with the subscriber at substation A.

`When the receive is removed at substation A, line relay 14 of the linecircuit LC energizes over the line conductors 11 and 12 by means of its upper winding, which is connected to conductor 12 through armature 15 of cut-O' Arelay 13 and its resting contact,

.conductor 11 being grounded at this time through the resting contact of armature 17 of cut-oli relay 13 and said armature and the common conductor 25. Upon energizing, line relay 14 disconnects ground from test contact 22 and its multiples in the banks of the finders at armatures 18 and 19; connects conductor 27 with private normal conductor 28 and cut-off relay 13 at armature 18; places ground on the signal start conductor 24 at armature 19; and at armature 20 places ground through armature 16 and its resting contact on the linder start conductor 26.

Assuming the operating mechanism C) of the finder allotter FA to be resting with the wipers 68 and 69 on the bank contacts 72 and 73 of the finder F, line finder 37 of the finder F energizes over the following circuit: from ground by way of the common start conductor 26, resting contact of armature 85 and said armature, spring 66 of the push button P and its resting contact, wiper 69, bank contact 73, and line relay 37 of the finder F to battery.

Upon energizing, line relay 37 closes a circuit for switching relay 36 and stepping magnet 35 in series at armature 47, and at armature 46 connects test wiper 390i the finder F to the junction of switching relay 36 and Steppingis `short-circuited by the `ground potential found by test wiper 39, and stepping magnet 35 is operated from this same ground potential, and the wipers of the finder are advanced step by step by the buzzer-like action of stepping magnet 35 in Search et the calling line.

lWhen the terminals of the calling line are reached, test wiper 39 encounters an ungrounded contact, and switching relay 36, being no longer short-circuited, energizes in series with stepping magnet 35. Sleppng magnet 35, however, does not energize at this time on account ot the high resistance of switching relay 36. Upon energizing, switching relay 36 connects the line conductors of the calling line with the corresponding conductors 48 and 53 yof the connector C at armatures 41 and t5; closes a point in the circuit of chain relay 83 at armature 42; prepares a locking circuit for itself and grounds conductor 51 at armature 44; and at armature 43 disconnects test wiper 39 from the junction of vits own winding and stepping magnet 35,

and connects it toground, thereby placing a busy potential on private normal conductor 28 of the calling line, and closing a circuit for cut-o relay 13 in serieswth the lower winding of line relay 14. Upon energizing, cut-olil relay 13 disconnects ground from start conductor 26 at armature 16, thereby opening the circuit of line relay 37 of the nder F. F

Line relay 37, however, being slow-acting, does not deenergize immediately. As a further result of the energiz'ation of cut-off relay 13, it disconnects the calling bridge at armatures 15 and 17. Line relay 1t, however, does not deenergize at this time but is held energized in series with cut-oil relay 13 by its own lower winding.

As a result of conductor 51 being grounded upon the energization of relay 36 of the finder as above explained, stepping magnet63 enerizes over the following circuit from ground y way of the working contact ,of armature 47 and saidarmature, working contact of armature 44 and said armature, conductor 51, resting contactof armature 130 and said ar-v mature, conductor 52, bank contact 72, wiper 68, resting contact of spring V65 and .said spring, armature 86 and its resting contact, and stepping magnet 63to battery. Stepping magnet 63 now advances wipers 68 and 69 from engagement with bank contacts 72 and 73, and continues to advance them by its buzzer-like action until wiper 68 comes into engagement with an ungrounded contact which denotes that an idle finder connector link is reached. The line relay of the allotted inder is not operated, however, until another call is A made for the reason that ground is removed from the start conductor26, prior to the new nder bein allotted, by cut-o relay 13 as explained a ove. During the time in which vthe wipers 68 and 69 are being rotated in other call being originated, before the next finder is allotted.

ln the connector C, line relay 102 energizes over the calling line in response to the previously described operation of switching relay 36 of the nder F, the lower winding of relay 102 being grounded through the common dial tone conductor 172. Upon energizing, relay 102 closes a circuit for release relay 103 at armature 120. Release relay 1.03, upon energizing, opens a point in the circuit of common signal 171 at armature 124 and prepares a circuitfor vertical magnet 112; places ground on locking conductor 17 5 at armature 123, and at armature 122 grounds holding conductor 52, thereby establishing a holding circuit' for switching relay 36 of the lnder F by way of armature 14 and its working contact before the'slow acting relay 37 has had timel to deenergize.

ies

' The calling subscriber now hearsthe dial I tone, which is placed on the common conduc-- tor 172 by the signalequiment shown in ig. 3 in a manner to be explained hereinafter, and knows that he maynow call the desired number.

lin response to the calling ot the lirst digit in the desired number, line relay 102 is deenergized a corresponding number of times in response to the interruptions of its circuit at the calling substation. Upon each of the resulting deenergizations of the line relay 102,

an impulse of current is sent to vertical magnet 112, the first impulse of current being transmitted over the following circuit: from ground by Way ofarmature and its restlng contact, armature 124 and its working contact, contact of oE-normal spring 127 and said spring, relay 104, and vertical magnet 112 tobattery. By the operation of vertical magnet 112, the wipers 148-150, inclusive, of the connector are raised opposite the level of contacts in which the desired line terminates. Relay 104 is ener v' in series with vertical armrest magnet 112 and, being slow-acting, retains its armaturel attracted throughout the vertical movement. The energization of relay 104 serves, at armature 126, to maintain the circuit of relay 104 and vertical magnet 112 intact after the off-normal springs have shifted, as they do upon the first vertical step. As a further result of the energization of relay 104, it closes a circuit for relay 101 at armature 125. Upon energizing, relay 101 closes a locking circuit for itself atarmature 115; opens the point in the circuit of the common signal 171 and prepares a circuit for release magnet 111 at armature 116; places direct ground on the lower winding of line relay 102 at armature 119 and disconnects the dial tone conductor -172 therefrom; connects up the lower talking condenser to conductor 53 at armature 117, the lower talking condenser being normally7 disconnected to prevent a normal flow of dial tone through the lower talking condenser and 'through the lower Winding of impedance 105 to battery by way of the lower winding of ring-cut-off relay 109.

At the end of the Vertical movement. series relay 104 deenergizes; opens the initial circuit of relay 101 at armature 125, leaving y relay 101 energized over its locking circuit which includes armature 115; and at armature 126 opens the point in its own circuit and that of the vertical magnet 112 and extends the operating circuit to rotary magnet 113.

When the calling subscriber operates his calling device in accordance with the second digit of the desired number, the corresponding deenergizations of line relay 102 result in a corresponding number of impulses being transmitted to rotary magnet 113. The eircuit over which the first of these impulses is transmitted, is as follows: from ground by way of armature 120 and its resting contact, armature 124 and its working contact, normally open contacts controlled by offnormal spring 127, armature 126 and its resting contact, armature 137 and its resting contact, armature 146 and its resting contact, and ro tary magnet 113 to battery. By the operation of rotary magnet 113, the wipers 148-150, inclusive, are rotated into engagement with t-he bank contacts 151-153, inclusive, of the called line. Slow acting relay 107 is energized in multiple with rotary magnet 113 and retains its armature attracted throughout the rotary movement. Upon energizing, relay 107 disconnects test wiper 149 from the lower winding of switching relay 110, and connects it to busy relay 108 at armature 134, and at armature' 135 places a shunt around armature 137 and its resting contact. so as to prevent any energization of busy relay 108, which is likely to occur during the rotary movement while test wiper 149 is passing over grounded test contacts, from opening the circuit of relay 107 and rotary magnet 113.

.lt will be assumed first that the called line is busy, in which case test conductor 152 is grounded, and when test wiper 149 arrives on test contact 152, busy relay 108 energizes through the normally closed contacts controlled by armature 144, and armature 134 and its working contact; prepares the busy signalling circuit at armature 138; opens a point in the circuit of relay 107 and rotary magnet 113 at armature 137; and at armature 136 disconnects the locking' conductor 175 from the lower winding of relay 110 and prepares a locking circuit for itself.

Under these conditions, when slow-acting relay 107 deenergizes at the end of the rotary movement, it disconnects itself and rotary magnet 113 from the operating circuit at armature 135; completes a locking circuit for busy relay 108 at the normally closed contacts controlled by armature 134; and at the normally closed contacts controlled by armature 133 places the busy tone which is on the busy signalling conductor 174, on the lower heavy talking conductor 53 by way of the lower talking condenser and armature 117 and its working contact. By this operation, a busy signal is transmitted back to the calling subscriber to inform him that he cannot, for the time being, obtain the desired connection and, when the calling subscriber replaces his receiven, the partially established connection is released in the usual manner.

It will be assumed now that the line of substation A is idle when called as hereinbefore described. That being the case, busy relay 108 is not energized when the wipers of the connector come to rest on the terminals of the called line and relay 107, upon deenergizing, completes a circuit for the lower winding of switching relay 110 in series with cut-off relay 154 and the lower winding of line relay.

155 of the line circuit LC as follows: from ground by way of locking conductor 175, armature 136 of busy relay 108 and its resting contact, lower winding of relay 110, resting contact of armature 134 andl said armature, normally closed contacts controlled by armature 144, test wiper 149, testcontact 152, cutoff relay 154, and the lowerwinding of relay 155 to battery. Cut-off relay 154, upon energizing, clears the called line of its bridge at its upper and lower armatures. The energization of line relay 155, however, is merely incidental at this time and does not perform any particular function.

In the connector C, switching relay 110, upon energizing, closes a locking circuit for itself first at its lightly adjusted armature 145, and then disconnects rotary magnet 113 at armature 146 so as to prevent any further rotation of the wipers in case the calling subscriber again turns his calling device; disconnects ground from the upper terminal of relay 106 and places direct ground on test wiper 149 at armature 144; disconnects armature 134 of relay 107 from test wiper 149 at the normally closed contacts controlled by armature 144; and at armatures 143 and 147 connects up the line wipers 148 and 150, whereupon ringing current is intermittently projected out over the lower talking conductor to the called substation from the common ringing conductor 173, andreturns by way of the upper talking conductor to battery by way of the upper .winding of ring-cut-o" relay 109.

When the called subscriber responds to the ringing of his bell by removing his receiver, ring-cut-otl relay 109 energizes over the called line from ground on common ringing conductor 173, and closes a locking vcircuit for itself at its lightly adjusted armature 141, and then places a shunt around the resting contact ot' armature 130 and said armature at 2@ armature 140 for a reason which will be pointrent merely stops Howing through the talked out fully hereinafter; and at. armatures 139 and 142 disconnects the conductors of the e called line from the source of ringing current and its own upper winding. and extends them to the windings of batteryfeed impedance 105 by way ont armature 133 and its resting contact, and the working contact of armature 121 and said armature. rlhe called subscriber now receives talking battery through the upper winding ot impedance 105 and the return circuit to ground is afforded through the lower winding of impedance 105, armature 132 and its resting Contact, and the working Contact of armature 141 and said armature to the grounded lockingV conductor 175. The reasons for leaving the lower winding of impedance 105 ungrounded until ringcut-o relay 109 energizes is to give the calling subscriber an audible ringing signal due to the ringing current returning throughl the upper winding of ring-cutod relay 109, and inducing a tone by transformer action in the lower winding of relay 109 which is transmit- Ated to the lower talking conductor through the lower winding of impedance 105.

The calling and called subscribers may now converse with each other as desired and when the conversation is finished, they both replace their receivers. Y

When the receiver is replaced at the called substation A", no particular result is accomplished in the connector C except that curingfbattery-feed impedance 105.

When the receiver is replaced at substation ik, line relay 102 of the connector C de` energlzes and opens the circuit of slow-acty lng release relay 103 at armature 120, at the same time closing a circuit for slow-acting relay 107. Relay 107 energizes at this time, but does not perform any particular function. When slow-acting relay 103 lets go, `it removes ground from guarding conductor 52 and holding conductor 51 at armature 122, whereupon the finder connector link is renmaltese dered selectable to the nder allotter FA again and switching relay 36 of the nder F deenergizes; disconnects the conductors of the line of substation A from the line conductors of the connector C at armatures 41 and 42; and removes ground from testwiper 39 at armature 43. allowing relays 13 and 14 of the line circuit LC to deenergize. As a further result of the deenergization of release relay 103, it removes ground from locking conductor 175 at armature 123, thereby opening the circuit of relays 101, 109, and 110. Relay 110 deenergizes promptly. Relay 101 and relay 109, however, being slow-acting remain attracted for an interval. As a still further result of the deenergization of relay 103, a circuit for release magnet 111 is closed as follows: from ground by way of armature 120 and its resting contact, armature 124 and its resting contact, armature 116 and its working contact, and release magnet 111 to battery. Upon the energization of release magnet 111, the shaft and Wipers of the connector C are restored to normal position. When the normal position is reached, a point inthe circuit of the common alarm signal 171 is opened at oid-normal contacts 128. Shortly rafter its circuit is opened, relay 109 deenergizes and restores its armatures to normal. Relay 101 deenergizes after an interval, but in case the connector is in working order mechanically and has been restored to normal by release magnet 111, no particular result is accomplished. Assuming, however, that the switch Ashaft was not restored to normal, the od-normal contacts 128 are closed, and the common alarm signal 171 is sounded when armature 116 opens the circuit of release magnet 111 and comes into vengagement with its resting contact. An attendant may respond to the alarm and take the necessary steps to clear up the trouble.

The function of the jack d will now be explained. llt sometimes'becomes necessary to temporarily remove the finder connector link Vfrom service and when such an occasion arises, a Hat piece of conducting material about the size of a five-cent piece is insertedv between the springs of the jack d', thereby closing a circuit for the lower winding of relay 106. Relay 106, upon' energizing under these conditions, separates conductors 51 and 52 at` amature 130, and places ground on conductor 52 so as to render the finder connector link non-selectable to the finder allotter FA, and at armature 129-places a shunt around the chain contacts 42 of the finder 1F so as to impose the same condition on the chain circuit asis there when the finder connector link is in actual use.

1t may occur occasionally that all the linder connector links become busy, and that a subscriber attempts to originate a call at this time and is unsuccessful because no finder connector link is available; Assuming that all aveces@ the finder connectors become busy, all the contact points, such as armature 42 of switching relay 36 and its working contact, in the circuit of chain relay 83 are closed and chain relay 83 energizes; disconnects stepping mag- 'nets 63 and 64 at armatures 86 and 87 so as to preventuseless hunting operation at this time; and at armature 89 closes a circuit for relay 62. Relay 62 thereupon energizes and connects the all trunks busy tone conductor 54 with the common conductor 25 and disconnects ground therefrom, so as to give a dis`- tinctive tone to any subscriber who happens to take olf his receiver at this time. It may be stated that this tone is taken from the ringing current lead through a small condenser as may be seen in Fig. 3. rlhis small condenser cuts down the loudness of the tone considerably, but allows a tone to pass which is very much louder than either the ordinary busy signalling tone or the dial tone ordinarily received soon after the subscriber removes his receiver. For this reason, the subscriber, upon hearing the all trunks busy tone, is able to distinguish that tone by its loudness, and is informed thereby thatall the connecting links are busy. The subscriber may now replace his receiver and wait a while for a trunk to become idle, or he .may leave his receiver off the hook and wait until his line is found by a finder.

Assuming that all the yfinder connector links are busy, and that several subscribers have their receivers off waiting for dial tone and are listening to the tone placed on by relay 62 of the finder allotter FA, all the subscribers who are waiting for the dial tone note the cessation of the all trunks busy tone when a trunk becomes idle and relay 62 deenergizes due to the deenergization of chain relay 83. However, all the waiting subscribers, except the one whose line is found by the finder which becomes idle, hear the all trunks busy tone again when the switching relay of the finder corresponding to switching relay 36 of the finder F energlzes and closes the chain again upon nding one of the calling lines. rThis process, of course, is repeated until all the waiting lines have been taken care of, and the intermittent interruption of the all trunks busy tone may be exceedingly puzzling to the subscribers who hear it several times before their respective lines are found or it may even be the source of considerable annoyance. lln order to furnish a means to prevent the all trunks busy tone from being interrupted while two or more subscribers are waiting at such a time,.the locking push-button P has been provided and may be operated, when desired, to connect the working contact of armature 84 of relay 62 to the common start conductor 26. When this is done, `relay 62 becomes locked up independent of chain relay 83 through armature 84 and its working Contact and the normally open contacts of the pushbutton P tostart conductor 26 and, consequently, does not deenergize again until the lines of all the waiting subscribers have been found, or until all the subscribers have hung up their receivers and thereby removed ground from the start conductor, in which case relay 62 deenergizes in case chain relay 83 has fallen back.

The working contact of armature 84 is not permanently connected with start conductor 26 for the reason that it may at some time be desirable to have relay 62 fall back each time the chain circuit is opened, so that an observer who is making a call may have some fair idea as to the Way in which the trac is being handled, as is determined by the frequency at which the all trunks busy tone is interrupted.

Since, the finder allotter is common to several finders, it is extremely important to guard against any mechanical trouble that may arise in the finder allotter from time to time, especially since the finder allotter must operate each timev a call is made and, for that reason, receives considerable use. Inorder to guard against the service from being tied up owing to a mechanical failure in the finder allotter, a second operating mechanism, which is shown inside the dotted rectangle denoted by the reference character 0', has been provided and, when it is desired to do so, the push-button P may be operated with the result that the operating mechanism shown in the dotted rectangle indicated by the reference character O is disconnected at spring 65 and the substitute operating mechanism is connected up at spring 67. Also, the start conductor 26 is shifted from wiper 69 of the first operating mechanism to wiper of the second operatlng mechanism at spring 66. lt may be pointed out that relay 6l is operative when the second operating mechanism is used owing to the fact that it has a second winding in multiple with the second operating magnet which allows it to operate just as though the first operating mechanism were in use.

ll`he operation of the common signalling equipment shown in Fig. 3 will now be described. Of this equipment, the ringing interrupter relays 201,-205, inclusive, and the associated marginal relay 206 will be considered first. The ringing interrupter relays 201-205, inclusive, are provided for the purpose of interrupting the supply of ringing current so as to project ringing current out on a calle-d line intermittently, ard also to distribute the ringing periods of the ve ringing leads so as to lower the maximum demand for ringing current in order to allow a source of ringing current of a smaller capacity to be used than would be necessary were` the ringing current supplied to all the ringing leads simultaneously.

- of in this case merely 'opens a point in the circuit For the purpose of the following description, it will be assumed that a call is'made.

This results in the signal start conductor 24 being grounded as hereinbefore described. When this occurs, the rst interrupter relay 201 energizes through the resting contact of armature 242 and said armature, and in series with the low wound marginal relay 206. Marginal relay 200, however, does not energize in series with one of the interrupter relays alone, and, consequently, remains incrt for the time beingfw In order to time the operation of the interrupter relays properly, they are made slow to deenergize by the wellknown expedient of placing a copper collar around the core, and are made slow to energize by placing the copper colla'r around the armature end of the core rather than the opposite end. 'llhis means of maki 0' a lrelay slow tol pull up is, of course, wellliown to those skilled in the art, and is taken advantage to slow up the cycle of operation still more. lln the drawings those relays which are slow to pull up are indicated by solid black portions at the upper ends of their cores in order to distinguish them from the ordinary slow to release relays which have Pthe lower ends of theircores cross hatched. "-When relay 201 energizes, it disconnects the lirst ringing current lead from ground and connects it with the secondary winding of the ringing current transformer T. As a fur ther result of the energization of relay 201, it i opens a point inthe circuit of relay 203 at armature 226,.and at armature 227 closes a circuit for relay 202 by way of the resting contact of armature 234 and. said armature. When this occurs, the marginally adjusted relay 206 energizes and opens the circuitof relay 201 at armature 242. Relay 201, however, remains energized for an interval, ow-

ing to the fact that it is slow-acting and main\ tains vthe circuit of relay 202 closed until the latter relay energizes. Upon energizing, relay 202 s ifts the ringing lead controlled thereby to the secondary winding of the ringing current transformer at armature 222; ofl relay 204 at armature 228; and at armature 229 prepares a circuit for relay 203.

When relay 201 deenergizes, it connects the ringing lead which it co'nt-rolslbaclr to ground again at armature 221; opens the circuit of the slowacting relay 202 at armature 227; and at armature 226 completes the circuit of *I relay 203. Relay 203, upon energizing,

prepares a circuit for relay 204 at armature 231;-opens a pointin the circuit of relay 205 at armature 230; and at armature 223 shifts its ringing lead in the usual manner.

When relay 202 denergizes, it, among other things which are apparent, completes the circuit of'relay 204 at armature 228, and relay '204, upon energizing, prepares a circuit kfor relay 205 at armature 233, opens a point in the circuit of relay 201 at armature 232, and at armature 224 shifts its ringing lead to the secondary winding of the ringing current transformer.

When relay 203 deenergizes, it completes the circuit of relay 205 at armature 230, and relay 205, upon energizing, closesl a point in the circuit of relay 201 at armature 235; opens a point in the circuit of relay 202 at armature 234; and at armature 225 shifts ringing lead 173 from ground to the secondary winding of the ringing current transformer.

When relay 204 deenergizes, it opens the circuit of relay 205 at armature 233 and completes the circuit of relay 201 at armature 232.- When this occurs, relay 201 energizes again with the results hereinbeiiore described.

When relay 205 deenergizes, relay 202 energizes again as before described.

'llhis cycle of operation is repeated over and over as long as conductor 24 remains grounded, and the ringing leads are connected to the secondary winding of the ringing current transformer one by one in order. There is, however, an overlapping or a time interval during which two ringing leads are connected to the secondary winding of the ringing current transformer. rlhis, however, does not cause any trouble for the reason that the ringing current transformer T and the associated vibrator are designed to supply ringing current to two leads simultaneously.

The operation of the vibrator magnet 211 and pendulum 238 will now be taken up. As a further result of the ground potential be.- ing placed on conductor 24, a circuit is closed for the high-wound slow-to-energize relay 207. rJlhis relay, however, does not become suciently energized for a moment to attract its armature. As a further result of the ground-potential being placed on conductor 24, a circuit is closed for magnet 211 in series with the lower winding of impedance 208, and in series with both windings of the choke coil impedance 212. Upon energizing, magnet 211 attracts its armature and the pendulum 238 swings to the left and short circuits magnet 211, whereupon the magnet swings of the pendulum 238, the cycle of op) eration becomes steady, and the time required for one complete swing is determined by the weight attached to the pendulum.

Aiter'a time which is sucient to allow the pendulum to pick up speed and yibrate at its full amplitude, the slow to energize relay 207 energizes and places ground on the mid-point of the primary winding of the ringing current transformer '.l by way or the left-hand winding of the choke coil impedance 212. After this is done, eac-h backward swing of the pendulum results in a circuit being closed for the upper section of the primary windlng of the transformer 'll`, and each forward/MV swing of the pendulum results in a circuit being closed for the lower section of the primary winding and, consequently, an alternating current is driven through the secondary winding of the transformer T. rlhe choke coil 212cand the condenser 243 are used to smooth out the How of battery current so as to prevent the battery from being noisy, and causing unpleasant noises while the subscribers are conversing.

` Since, the lower winding of impedance 208 is in series with the winding of vibrator magnet 211, the current in the former fluctuates owing to the intermittent short-circuiting of the latter by the vibrating pendulum 238.

This fluctuating current in the lower winding of impedance 208 causes a corresponding fluctuating electromotive Jforce to be applied to the dial tone conductor 172 and through the upper winding of said impedance 208. rlhe small condenser 2,09 which is connected between the right-hand terminals of the upper and lower windings, respectively, allows some of the fluctuations in the E. M. lfd". applied to the termina-ls of the lower winding to pass directly across to conductor 172 so as to strengthen the dial tone without adding more turns to the upper winding of impedance 208 and, consequently, without increasing the resistance of impedance 208 to a point at which the operation of the line relays of the various associated connectors might be aected. i

As a still further result of the ground potential being placed on conductor 24, a circuit is closed for the busy interrupter relay 214 by way of armature 243 of relay 212 and its resting contact. Upon energizing, relay 214 closes a circuit for relay 212 at armature 240, and relay 212, upon energizing, opens the circuit of relay 214 at armature 243. After an interval, relay 214 deenelgizes and opens the circiut of relay 212', and relay 212, upon deenergizing, again closes y the circuit ot relay 214. This cycle of operation is repeated over and over as long as conductor 24 remains grounded. lt will be noted that each time relay 212 energizes, it closes a circuit for the lower winding of relay 213. Relay 213, upon energizing, closes a circuit for its upper winding at armature 239, which upper winding is wound in opposition to the lower winding. Consequently, relay 213 immediately deenergizes again and, as a result, buzzes at a high rate of speed as long as relay 212 is energized and start conductor 24 grounded. Obviously, since relay 212 deenergizes at intervals, as pointed out above, the buzzingof relay 213 is interrupted at intervals, of which the time depends upon the adjustment lof the relays 212 and 214. The operation of relay 213 causes an intermittent buzzing tone to be placed on the busy signalling conductor 174 through the condenser 24.4. t f

level and to repeat impulses in order to provide for such services. ln order to give an understanding of the functions of the connector C when raised to the tenth level and broughtinto engagement with one of the set of contacts in that level, reference may be had to the co-pending application of Jones, Serial No. 443,654, tiled February 9, 1921, which shows a private automatic exchange connector having access on a certain set ot contacts to a conference call connector.

In order to explain the operation of the connector C when used as a repeater, it will be assumed that a subscriber has initiated al call; is using the connector C; and has operated his calling device in accordance with the lirst digit 0 in the desired number, which is the digit dialled when any special service is desired. The variousv relay operations which take place when the lirst digit in a .number is called, occur at this time as described hereinbefore, and vertical magnet 112 raises the associated wipers opposite the tenth level of bank. contacts, whereupon the tenth level springs are operatedand contact 114 is closed, thereby closing the following circuit tor ringcut-off relay 109: from ground by way of armature 144 of switching relay 110 and its resting contact, contacts 114 of the tenth level springs, and the upper winding of ring-cutoff relay 109 to battery. Upon energizing, ringlcut-off relay places the circuits in such a condition that no ringing current will be projected when the wipers are moved into engagement with the desired set of contacts. and also places a shunt around armature 130 of relay 106 and its resting contact to prevent the ground potential from being removed from holding conductor 51 upon the energization of relay 106, which occurs subsequently,

Upon the next operation of the calling subscribers calling device, the wipers 148-150, inclusive, are brought into engagement with the desired set of bank contacts and the usual busy test is made. Assuming the trunk terminating in these contacts to be idle, switching relay 110 energizes through test wiper 140 from battery on the test conductor ot trunk as shown in the J ones application above referred to, and connects up the line wipers and performs the other operations hereinbefore described. When armature 144 breaks away from its resting contact, the shunt is removed from the upper winding of relay 106, whereupon relay 106 energizes 'in series with the upper winding of ring-cut-of relay 109, and at armatures 131 and 132 disconnects battery and ground from the windings of the battery feed impedance 105 and connects the windings together, thereby closing a Aholding bridge across the line conductors of the seized trunk, whereupon the line and release relays of the seized trunk energize in the usual manner.

Upon each of the subsequent operations of the calling subscribers calling device, an interruption is produced in the circuit of the line relay of the seized trunk at armature 1 21 of line relay 102, thereby operating the seized switch in the usual manner. Also, the usual impulses of current are sent over the operat-v ing circuit to slow-acting relay 107 with the f result that this relay is maintained energized during each series of impulses which are repeated, and at armature 133 disconnects the upper line Wiper from lthe upper talking condenser and closes the bridge across the line wipers by a moredirect path which is exclusive of the windings of impedance 105. rl`his is the usual expedient made use of in order to obtain a better repeating circuit.

When the calling subscriber replaces his receiver, the connector C is released in the usual manner, and the seized switch is released in response to the opening of the bridge across the line Wipers of the connector C at armature 121 of line relay 102.

What is claimedV is 2 1. In a telephone system, groups ot connectors, a transformer having a primary winding and a secondary Winding, aV start conductor, a source of current, means for connecting said current source to said start conductor, means responsive thereto for connecting said current source intermittently to said primary Winding of the transformer for inducing alternating current in the secondary Winding, means operated responsive to the connection of said current source to said start conductor for distributing said induced cur-V rent to each connector group in sequence.

2. 1n a telephone system, calling lines, means for extending said calling lines, said means including line switches and groups of connectors, a source of current, a trans- 1to1-mer having a primary winding and a secondary Winding, circuits for supplying cur rent to said primary Winding, an electromagnetic vibrator or controlling said circuits'ior supplyingcurrent intermittently" to said primary Winding, said intermittent application of current to the primary winding `inducing alternating current in said secondary winding, a start conductor for said vibrator common to all of said line switches,

means in the line switches for connecting said currentsource to said start conductor upon the initlation of a call by any of said calling lines, said vibrator operating responsivel to said connection to control said primary winding circuits, and means operated responsive .to said connection of the current source to the start conductor for distributing said induced alternating current to each connector group in sequence for signalling purposes when the initiated call is extended by any connector in any group.

3. 1n a telephone system, calling lines, groups of connectors, means for generating ringing current, means for distributing said current t6 each connector group successively, a busy tone generating device, a'start conductor, a source of current,- and means responsive to the extension of one of said lines connectors, two relay type alternating current generators, a relay group for distributing the current generated by one of said generators successively to the groups of connectors, a start conductor common to said generators and said relay group, and means operat'ed responsive to the initiation of a call over one of said lines 4for operating the two generators and the relay group simultaneously.

In witness whereof, 1 hereunto subscribe my name this 18th day of October, A.. D.

CLARENCE E. LMA'

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