US1233870A - Automatic telephone system. - Google Patents

Description

C. L. GOODRUM.

AUTOMATiC TELEPHONE SYSTEM.

APPLICATION FILED MAY 24, 1916.

1 M33 WYUQ Patented July 17, 1917. 3 SHEET$-SHEET //7 ven/or:

C. L. GOODRUIVI.

AUTOMATIC TELEPHONE SYSTEM.

APPLICATION FILED MAY 24, I9I6.

//7 ve/v for: Char/e5 L. Good/um.

C. L. GOODRUM.

AUTOMATIC TELEPHONE SYSTEM.

APPLICATION FILED MAY 24. I916.

3 SHEETS-SHEET 3.

7n 1 y m J 0 e m LAW a D1 /7 n for: Char/es L. Good/ am.

and a 1: 1.11 ES L. GOUJDR'UM, OF NEW YORK, N. Y., ASSIGNOB '10 WESTERN ELECTRIC COM- PAINT, INCORPORATED, 015 NEW YORK, N. 1., A UORPORATION OF NEW YORK.

AUTOMATIC TELEPHONE SYSTEM.

aea'aeto.

Specification of ltetteraratent.

' Application filed Way 2%, 1916. Serial Ito. 99,58t.

New York, in the county of New York and State of New York, have invented certain new and useful Improvements in Automatic Telephone Systems, of which the following is a full, clear, concise, and exact description.

The present invention relates to automatic telephone systems in which the allotment of switches is controlled by a starter wire which is led through contacts associated with busy finders to the next idle finder.

The object of the invention isthe provision of means whereby, if the starter circuit through a switch is being used to control a selection at' the time the switch is released and restored to normal, the starter circuit will be maintained closed at said switch until the selection has beenefi'ected.

Referring to the drawings, Figure 1 shows apparatus individual to one subscribers line, ortion of the apparatus individual to anot ier subscriber in the same group, and apparatus common to the entire group of lines, that individual to the line being shown to the left, and that common to the group to the right, of the dotted line; Fig. 2 shows a line finder and a first selector, with their associated circuits and apparatus; and Fig. 3 shows the circuit arrangement by which the starter wire is always extended to an idle line finder.

The present invention is an improvement on the s stem described in an application of C. L. oodrum, Serial No. 87 2,743. The system of said application provides means whereby a switch cannot be released while the starter circuit therethrough is employed, thus preventing'the mutilation of a call. In

the system of this application, the mutilation of a call is prevented by providing a relay which is held energized while the starter wire is employed, and connects the starter wire extension to all the contacts of the side-switch wiper which is employed to extend the starter circuit.

The automatic switch described in the above noted application, Serial No. 872,743, may be used herein and may also, with slight modification, act as either a finder switch, a selector switch. or a connector. The terminal bank is of the panel type shown in U. S-

Patent No. 1,098,529, issued June 2, 1914, to

J. N. Reynolds and is made up a of strips of metal with interposed insu ting strips. Each metallic strip has ears projecting from. opposite faces of the bank, adapted to be wiped over by the brushes of automatic switches. Three of these metal strips located in adjacent relation are apportioned to each The brush rods of the several finders, in their normal positions, bear such angular relatlon to one another that the brush rod Patented July at, tart.

of the finder normally assigned to a given line has a brush set positioned so as to be ready to at once begin travel over the group in which such calling line is located.

Since all the finders are accessible to all the lines of all the divisions, the circuit arrangement herein described is such that if the finder normally assigned to any group is busy, another finder will be set in motion by the initiation of a call in such group. In this event, the brush rod of the idle finder is given a rotary movement to position a brush set into operative relation with the desired group, and is then started in a vertical movement to connect with the calling line in such group. For this purpose, a switch 509 is located at the top of each finder. Each group of lines is represented on this switch by a fixed contact 265. These contacts are adapted to be traversed by an arm 214 fixed to the brush rod 507. The initiation of a call in any group electrically distinguishes the contact 265 individual thereto on the switch 509 of tha preselected finder, so that, when the brush 214 reaches such contact, a circuit is closed to start the secondar movement of the brush rod. The relation etween the 'arm 214 and its associated rod 507 is such that when said arm reaches the contact in question, a set of brushes is positioned just below the group of terminals in which the call originated. Theupward movement of the rod causes this positioned set ofbrushes to wipe over the sets of terminals of this section until that of the calling line is found when a circuit is closed to stop such movement, and the calling line is connected through this finder to a selector (shown at the right in Fig. 2), which is then controlled from the sender at the substation to extend the connection to a connector, either directly, or, in caseof a large exchange, through a series of selectors.

As the present invention may be employed i with switches of various kinds difiering widely from that diagrammatically indicated herein, and as the switch structure itself forms no part of the present invention, only such description as is necessary to understand the circuit arrangement of this invention will be given.

The brush rod 507 is rotated through suitable mechanisms actuated by the rotary magnet 205, and after it reaches the desired group, the circuit of the rotary magnet is opened, and the rod is elevated by suitable mechanisms operated by the vertical magnet 207. In moving upward, the arm 214 is raised out of engagement with the contact 265.

In the normal position of' the finder switch, the switch arms 210, 216, 232 and 233 are in engagement with the first set of contacts, as shown in the drawings. On attraction of the armatures of the escapement magnet 207, the switch arms are moved by suitable mechanism to engage the second set of contacts. The magnet, when denergized, moves the switch arms into engagement with the third set of contacts. This switch is 'restored to normal by the restoration of the brush rod.

A selector, the circuit arrangement of which is shown to the right of the dotted line in Fig. 2, has its circuit control switch arms 243, 252, 256, 257 and 258 controlled through suitable mechanism by the escapement magnet 241. This magnet does not move the arms on its first energization, but on deenergization moves them to the second set of contacts. On the next energization of the magnet 241, the circuit control switch arms are moved to the third set. Resetting is accomplished on actuation of release magnet 261, which restores the selector to normal and which, in restoring, resets its circuit control switches.

Referring now to Fig. 1, the subscribers line conductors 111, 112 terf'ninate in a pair of terminals 224, 225. The usual test ter minal 226 is associated with each pair of line terminals, and is connected by a conductor 114 with a cutofi' relay 120 individual to each line. Each subscribers. line is provided at the central office with a line relay 116, bridged across the conductors 111, 112, which becomes energized when the subscriber closes the line circuit by removing his receiver. The line and cut-ofl relays 131, 132,- respectively, of another line in the same group are also shown.

A number of finder switches are apportioned to the lines in such a manner that brushes to wipe over said group of terminals in search of the calling line. However, if this finder has been taken for use, a call from this grou willbe taken care of by the next idle line tinder, which must, however, first rotate to position a set of brushes be low the group of terminals containing those of the calling line.

Fig. 3 shows more clearly an arrangement whereby a line finder, having been started in motion by the initiation of a call, cannot be interfered with bythe initiation of a call in any other group, or by the restoration of any busy finders through which the driving circuit is extended.

Associated with the relays c, b of each group of lines is a relay 0.. Each of these relays a, when energized, opens at its right,- hand armature and back contact the driving circuit of the finder switch of the preceding group, and closes, at the front contact of its right-hand armature, a circuit from the first or second contacts to the third contact of a switch arm of the preceding finder. Forv example, the relay (1, when energized, closes a bridging circuit from the first or second contacts to the third contact of the switch arm 418 of the preceding finder, through conductor 416, right-hand armature and front contact of relay 0., conductor 415 to the third contact of switch arm 418 at the preceding finder. At the left-hand armature, the relay 0. cuts 011' at its back contact the lines from its group, to prevent actuation of its group finder while the relay (1' is energized.

Relay 0' is deenergized when the cut-off relay of the line calling in that group acts, but relay 6 is slow to fall back, in order to hold the starter wire circuit open at the back contact and right-hand armature of relay b until the circuit control switch arm has been moved to third position. The circuit control switch moves to third position as soon as the cut-off relay is actuated.

The relays a and a etc., of busy finders are energized in branches of the starter wire circuit. The relay a ofthe finder normally associated with the group in which the call originates is not actuated until the calling line has been seized.

The invention will be best understood by a detailed descri tion of the operations involved in extending the calling line through a first selector, from which point the usual operations would take lace to complete the connection with the ca led party.

When the subscriber at the substation 110 removes his receiver, a circuit is closed for the line relay 116, said circuit leading over the subscribers line 111, 112, and through the telephone set of substation 110. This relay thereupon closes a circuit for rela c to start a finder searching out the ca ing line, this circuit leading from grounded batnaaaevo tery through'the left-hand winding of relay 116, left-hand armature and back contact of the cut-ofi' relay 120, conductor 121, contacts 117 118 conductor (1, left-hand armature and-back contact of relay a, conduetor 134, inner left-hand armature and back contact of relay 1'), conductor 135, and winding of relay 0 to ound. The rela c thereupon locks itsel up in ser1es wit the line relay 116 in a circuit leadin from ground through relay 0, its left-ban armature and front contact, conductors 137 134', left-hand armature and back contact of relay a, conductor d, contacts 118, 117, conductor 121, left-hand armature and back contact of cut-ofi relay 120, and left-hand windin of line relay 116 to grounded batter hari d armature and back contact of relay 6, so that this circuit is new independent of this contact of relay b. Relay 0 closes at its right-hand armature and front contact an energizing circuit for a slow release relay 6' from grounded battery, winding of relay 0;, conductors 128 and 127, front contact and right-hand armature of relay 0 to ground. Relay 0', at its right-hand armature and front contact, also closes the circuit of escapem'ent magnet 217 to move the circuitcontrol switch of the line finder normally associated with the group in which the callin position. 11 this position the brush rod of the line finder is moved vertically to cause a brush set to test for the calling line. It has been assumed that the line finder normally associated with thestarter wire 130 is not in use. Under this assumption, the arm 214 of the finder brush rod is in engagement with the fixed contact 265 individual to this line group. The circuit of escape magnet 217 is as follows: grounded battery, magnet 205, (Fig. 2), conductor 212, magnet 217, conductor 218, arm 216, conductor 215, am 214:, contact 265, conductors 130, 127 and right-hand armature and front contact of relay 0' to ground. The magnet 205 is so adjusted and the circuit conditions are such that 1t does not operate when this circuit is closed.

In the second position of the circuit control switch arms, the circuit for the magnet 217 is maintained, this circuit being from grounded battery, magnet 205, conductor 212, magnet 217, conductor 218, arm 216, now in its second position, conductor 287, conductors 202, 201, back contact and righthand armature of relay a of the next finder switch (see Fig. 3), conductor 231, arm 200, now in second position, conductor 129, righthand armature and front contact of relay 6, conductors 128, 127, and right-hand armature and front contact of relay 0' to ground. At the same time, the relay 220 is energized by a circuit extending from his circuit shunts out the inner leftline is located, into its second grounded battery relay 220, conductors 213, 201 and to ground by way of the circuit just traced. Relay 220 pulls up and prevents a circuit being completed to the release magnet 203 until the circuit control switch has 207, conductors 268, 266, right-hand armature and front contact of the magnet 217, conductors 267, 204, right-hand armature and back contact of release magnet 203, conductors 202, 201, and to ground by way of the v circuit previously traced. When the brushes 221, 222 and 223 arrive on the terminals 224, 225 and 226 of the calling line, the cut-0d relay 1% of such line is ener ized over the followin circuit: grounded attery, relay 120, con uctor 114, terminal 226, brush 223, conductor 113, contacts 228, 273 of magnet 217, conductor 271, resistance 272, conductor 201 and to ground by way of the circuit already traced. Cut-off relay 120, at its lefthand armature, opens the circuit of relay 0 which, in deenergizing, opens the circuit 0 driving magnet 207, the finder being thus brrlmght to rest upon the calling line termina s.

' connect the line conductors 111, 112 through to the stepping relay 234 of the selector. It will, of course, be understood that the operations involved in connecting the callin line with a connecting circuit, just trace take only a fraction of a second. The stepping relay 234, at its armature and front When the cut-ofi relay 120 operates and deenergizes the relay 0, the escapement magnet 207 also is denergized, whereupon contact, closes a circuit for a slow-acting relay 235. The subscriber will not operate his sender to transmit the first series of impulses. The relay 234 is adjusted to respond to every interruption of the line circuit, but the relay 235 is made slow to release so as to remain energized during such interruptions. When the armature of the relay 2 34 closes its back contact, an impulse is given to the rotary driving magnet 236 to cause the brush rod of the first selector to be rotated to position the proper set of brushes below the group of trunks terminating in connectors serving the desired group of subscribers. The circuit is as follows: grounded battery, magnet 236, conductor 269, bottom contact of: spring 237, which is closed as long as the brush rod is in its normal vertical position, conductors 238, 239, armatureand front contact of slow-acting relay 235, armature and back-contact of relay 234 to ground. At the end of this series of impulses, which, in the system shown, represents the hundreds digit of the wanted line, a relatively long closure of the line circuit occurs, which causes the slow acting relay 240 to become deinergized. It will be noted that this relay is energized upon the first de'e'nergization of relay234, by a circuit leading through armature and front contact of slow relay 235. The relay 240, at its front contact, closed a circuit for the escapement magnet 241 of the circuit control switch of the selector, which, however, would not permit the circuit control switch to move. Upon the termination of the impulses, the relay 234 is maintained energized, whereupon the relay 240 is deenergized, thus opening the circuit of escapement magnet 241. This permits the circuit control switch to move to second position, causing the set of brushes 246, 247, 248 to hunt over the selected group of trunks for an idle connector.

As soon as the circuit control switch arrives in the second position, a circuit is closed for the vertical driving magnet 242 of the selector. This circuit is from grounded battery, magnet 242, its armature and back contact, control switch arm 243 and its second contact, conductors 244, 245, armature and front contact of relay 234 to ground. The magnet 242 thereupon makes and breaks its own circuit, thus causing the brushes 246, 247 and 248 to wipe over the terminals 249, 250 and 251. -An idle trunk is represented by ground battery on its test contact 251. Therefore, when the test brush 248 reaches the contact 251 of an idle trunk, a circuit is closed from grounded battery, escapement magnet 241, arm 252 and its second contact, conductors 253, 254, brush 248 and test contact 251, to ground. Thereupon, the escapement magnet 241 is energized and permits the circuit control switch to move to third position. The arm 243 opens the driving circuit for the vertical magnet 242 to stop the brushes on the idle trunk thus selected. The contacts 249, 250 and 251 are connected to the next selector or connector,

' and through these the line is extended to the called party, either directly or through additional selectors in any desired manner.

As the circuitcontrol switch moves into third position, its arms 256 and 257 extend the calling line circuit through to the next switch. The interruptions of the line circuit now caused by the subscriber operating his sender, operate the succeeding switch means to secure connection to the called line in the usual manner.

Assuming that the called party is not busy, and the connection has been completed, conversation will take lace and, on completion, the parties will a up. Ground is put on conductor 255 in any well-known manner, completing release circuitsfor the selector and finder. The selector release circuit is as follows: grounded battery, release magnet 261, off-normal contact 260, conductor 259, arm 258 and its third contact, conductor 254, brush 248 and contact 251 to grounded conductor 255. The finder release circuit is as follows: grounded battery, re-

lease magnet 203, off-normal contact 262 conductor 263, back contact and armature of relay 220, conductors 264, 259 arm 258 and its third contact, conductor 254, brush 248 and contact 251, to grounded conductor 255. The finder and selector switches in restoring, also restore their-associated circuit control switches.

When the circuit control switch of the finder of the first group has moved to third position, if another call comes in from that group, relays c' and b are energized, and a circuit is completed from ground, front contact and right-hand armature of relay 0, front contact and right-hand armature of relay 6', conductor 129, switch arm 200, in its third position, conductor 270, conductors 423, 424, outer left-hand armature and back contact of relay b conductor 425, and relay a", to grounded battery. a pulls up and breaks the line normally extending from the first and second contacts of switch arm 200, conductor 231, right-hand armature and back contact of relay a, and conductor 201 to the finder switch of its own group. At the same time, the starter wire from the first group is extended to the second group by arm 200, in its third position, conductors 270, 423, and 426, back contact and righthand armature of relay b conductor 411, and switch arm 412, in its first position. If the finder of the second group is also busy, its arm 412, and third contact extend the starter wire 129 to-the third group by way of conductors 413, 427, 428, right-hand armature and back contact of relay b, to arm 418, and thence through the conductor 416, right-hand armature and back contact of the relay a, and conductor 420, to the finder switch of the third group. Relay a pulls up in this case.

Assume that the finders normally associated with the first two line groups are busy.

Under such conditions, the arms 200, 412 of their circuit control switches will be in their third positions, extending the starting conductor 129, through to the drivin magnet of the finder normally associate a with the third group of lines. The relay 131,upon its energization, due to the closure of the line circuit upon the initiation of a call at the substation connected to conductors 401, 402, closes a circuit for the grou relay 0' to start the preselected finder. T is finder is the third one from the left as shown in Fig.

2. The circuit is as follows: grounded battery, left-hand winding of relay 131, conductor 405, left-hand armature and back contact of cut-ofi' relay 132, conductor 406,

contacts 403, 404, conductor 407, contacts 408, 118, conductor d, left-hand armature and back contact of relay a, conductor 134, inner left-hand armature and back contact of relay b, conductor 135, relay 0' thereupon becomes energized and closes the circuit of.

.ductors 413, 427, 428, right-hand armature and back contact of relay 6 conductor 421, arm 418 and its first contact, conductor 416, right-hand armature and back contact of relay a' and conductor 420, which leads to grounded battery through the driving magnet 205 of the line finder. Circuit is also completed to the relay a by the shuntleading from conductor 423 over conductor 424, outer left-hand armature and back contact of relay 6, conductor 425, and rela a to grounded battery. A similar circuit from conductor 427 is also completed for relay 0; over conductors 430, 431 and relay a to grounded battery. These circuits energize these relays to open the group conductors d and d, to prevent calls coming in on these groups until the call originating in the first group has been put through the finder switch of the third group. Relays a and a on pulling up, complete bridgin circuits from the first and third contacts 0 the preceding finder switch arms 200 and 412, respectively through the right-hand armatures and front contacts of sald relays, so that resetting of the finder switches of groups one and two will not afiect the starter wire extendin through said switches. a

The circuit of the rotary stepping magnet of the selected finder is completed at this time from grounded battery, magnet 205, conductors 212, 275, arm 210 and its first contact, conductors 209, 208, armature and back contact of magnet 207, conductors 268, 206, armature and back contact of magnet 205, conductor 204, right-hand armature and Mr contact of magnet 203, conductor 202, conductor 420 corresponding to conductor 201 of the first der) and to ground at the right-hand armature and front contact of relay 0' over a circuit previously described. The magnet 205 interrupts its own circuit, thus rotating its brush rod until its arm 277 engages with the metallic contact 278, corresponding to this line group. A ground magnet out of circuit, and cut in the vertical magnet 207 of said finder. This circuit may be traced by way of contact 278, arm 277,

".to a conductor 283 of this finder, which corresponds to conductor 215, through an arm corresponding to arm 216 of the finder circuit of Fig. 2, conductor 218, escapement magnet 217, magnet 205, to ounded battery. It will thus be seen t at relay 205 remains attracted on the last impulse, thus positively positioning the brush rod 507, and preventing overthrow thereon. From this point on, the operation is the same as that already traced.

When the relay 1; closed at its right-hand armature and front contact, the circuit just traced to the rotary driving magnet of the said finder, it opened at its outer left-hand armature and back contact, the line extending from conductor 415 through said armature and contact to relay a while relay 6' remains energized; that is, while a call coming in over the first group is being extended by the preselected finder switch, and until said finder switch is connected with the callcalling line operates. The relay 220 would be energized as before described to prevent premature actuation of the release magnet 203.

Due to the bridging circuit about the circuit control switch arms of the finders through which the starter wire is extended, release and restoration of such intermediate finder or finders takes place without interference with the extended starter wire circuits. Resetting of intermediate circuit control switch arms from their third to first positions does not affect the starter wire circuit, as this circuit is maintained bridged around the first and. third contacts of the arms of busy finders through which it was extended by a circuit passing through the front contact and right-hand armatures of the a. relays which were actuated. Switch arms 200, 412 and 418 and their second and third contacts are so arranged that the arms engitge'their second contacts before disen- 5- gaging their third contacts so that the starter wire is maintained continuously closed during the release of said busy finders. Let .us suppose the finder of the second group restores. The starter wire from the 1 first group to the finder of the third group is still maintained by a circuit extending from grounded battery, relay 6 and its righthand armature and front contact, conductor 129, arm 200 and third contact, conductors V 5 270, 423, 426, right-hand armature and back contact of the relay b conductor 411, arm 412 and first contact, conductor 422, righthand armature and front contact of relay a l that group, and that if any line relay should become energized after relay 0 had been energized and started a line finder, but before said finder has reached the terminals of the line initiating said call, these terminals will be passed over by the line finder brushes. This is true, since the relay 0 is energized by a circuit closed at contacts 117, 118 of line relay 116, which cannot be deenergized until the cut-off relay of this line operates,

ileenergizing said relay and consequently re- Inorderto prevent sparking at the contacts, due to the self-induction of the primary and secondary magnets, a condenser 274 is provided, which is connected through the armature and back contact of the release magnet 261 of the selector and conductor 275 to arm 210 of the finder control switch. This feature, however, forms no part of the present invention and need not be further described.

A contact 281 is associated with the finder brush rod in such a manner that it will be closed when the selector brush rod is moved 56 vertically over more than ten steps. The closure of this contact closes a circuit for the release magnet 203 as follows: grounded battery, release magnet 203, off-normal contact 262 closed upon the first rotary or vertical *0 movement of the brush rod, conductor 282, contact 281 to ground. This prevents a finder. from being held in an off-normal position if, for any reason, it failed to be arrested upon arriving on the calling line termin'als.

Referring to that point in the operation where the brushes 221, 222, 223 of the finder are wiping over contacts of the group containing the calling line to connect with said line, it is possible that the test brush 223 will pass over the test contact of a non-calling line which is busy as a called line. The release magnet of the busy connector might in this event receive enough current for its energization and consequently release such connector. To prevent this, a resistance 272 is included in conductor 271.

-A stepping circuit for the rotary magnet 205 leads through the armature and back contact of the finder release magnet 203 to prevent a ground placed upon conductor 129 by the initiation of a call from completing the circuit of said driving magnet while the finder is being restored to normal.

What is claimed is:

1. In a telephone system, the combination with telephone lines, finders to which said lines are multipled, a starter circuit for said finders, means actuated upon the initiation of a call for closing the starter circuit, said circuit leadingthrough contacts open during the release of busy line finders, and release means for said finders, of means to preserve the continuity of said starter circuit during the release of said busy finders.

2. In a telephone system, the combination with telephone lines, finders to which said lines are multipled, a starter circuit for said finders, means actuated upon the initiation of a call for closing the starter circuit, said circuit leading through contacts open during the release of busy l1ne finders, and release means for said finders, of means to preserve the continuity of said starter circuit subsequent to release of said busy finders.

3. In a telephone system, the combination with telephone lines, finders to which said lines are multipled, a starter circuit for said finders, means actuated upon the-initiation of a call for closing the starter circuit, said circuit leading through contacts open during the release of busy llne'finders, and release means for said finders, of means to preserve the continuity of said starter circuit during and subsequent to the release of said busy finders.

4. In a telephone system, the combination with telephone lines, finders to which said lines are multipled, a. starter circuit for said finders, means actuated upon the initiation of a call for closing the starter circuit, said circuit leading through contacts open during the release of busy line finders, and release means for said finders, of means to preserve the continuity of said starter circuit during the release of said busy finders and until the preselected finder is connected with the calling line.

5. In a telephone system, the combination with telephone lines, finders to which said 1 i i win lines are multipled, starter circuits therefor, means for extending said circuit to an idle finder, a circuit control switch for. each finder, said starter circuit leading to an idle finder through contacts of the circuit control switches of busy finders open during the release-thereof, release circuits for restoring said finders, and means actuated by said finders in their restoring movement to restore said circuit, control switches, of means to preserve the continuity of said starter circuit during the restoration of said busy finders to normal.

6. In a telephone system, the combination with telephone lines, finders to which said lines are multipled, starter circuits therefor, means actuated upon the initiation of a call for closing the starter circuit of one of said finders, a circuit control switch for each finder, said starter circuit leading to an idle finder through contacts of the circuit control switch of busy finders open during the release thereof, release circuits for restoring said finders, and means actuated by said finders in their restoring movement to restore said circuit control switches, of means to preserve the continuity of said starter circuit during the restoration of said circuit control switches to normal.

7. In a telephone system, the combination with telephone lines, finders to which said lines are multipled, starter circuits therefor, means for extending said starter circuit to an idle finder, a circuit control switch for each finder, said starter circuit leading to an idle finder through contacts of the circuit control switches of busy finders open during the release, of release circuits for restoring said finders, and means actuated by M0 said finders in their restoring movement to restore said circuit control switches, of means to preserve the continuity of said starter circuit during the restoration of said busy finders to normal and until said finder is connected with the calling line.

8. In a telephone system, the combination with telephone lines, finders to which said lines are multipled, starter circuits therefor, means for extending said circuit to an idle '50 finder, a circuit control switch for each finder, said starter circuit leading to an idle finder through contacts of the circuit control switches of busy finders, release circuits for restoring said finders, and means I actuated by said finders in their restoring movement to restore said circuit control switches, of relays controlling the finder release circuits, and means to preserve the continuity of said starter circuit during the W restoration of said circuit control switches a lines are multipled, a starter circuit for said and until the pro-selected finder connects y with the calling line.

10. In a telephone system, the combination with telephone lines, finders to which said lines are multipled, a starter circuit for said finders, and means for extending said starter circuit to an idle finder, of a relay associated with each finder switch, a bridging circuit for each finder normally open between certain contacts thereof, said starter circuit extending throu h contacts of busy line finders and actuatmg certain of said relays to close the bridging circuits of said busy finders until the selected finder connects with the calling line.

11. In a telephone system, the combination with telephone lines, finders to which said lines are multipled, a starter circuit for said finders, and means to extend said circuit to an idle finder, of a bridging circuit for each finder normally open between certain contacts thereof, release circuits for said finders, a relay associated with each finder and controlling the bridging circuit of the preceding finder,\said starter circuit extending through certain contacts of busy line finders and actuating said associated relays ing actuation of the relay of the finder normally associated with the line on which the calloriginated, said starter circuit extending through certain contacts of busy line finders and through contacts of the finder next beyond the selected finder an'l actuating the relays controlling the bridg ing circuits of said busy line finders.

13. In a telephone system, the combination with telephone lines, finders to which said lines are multipled, said lines being normally associated with idle finders, a starter circuit for said finders, and means to extend said circuit to. an idle finder, of

a relay associated with each finder, a bridging circuit for each finder normally open between certain contacts thereof and under control of the associated relay of the 'next succeeding finder, release circuits for line to the finder normally associated theresaid finders, said starter circuit extending with opened on ener 'zation of the relay through certain contacts of busy line finders associated with such der.

and the contacts of the associated relays In witness whereof, I hereunto subscribe 10 5 controlling the bridging circuits of sand my name this 23rd da of May A. D., 1916. busy finders, and a circuit extending from a CHARL S L. GOODRUM.

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