US1568038A - Automatic telephone system - Google Patents

Description

Dec. 29, 1925. 1,568,038

5. B. WILLIAMS, JR., ET AL AUTOMATIC TELEPHONE SYSTEM Filed Sept. '7, 1922 13 Sheets-Sheet 1 #7 1. 5- .9. F/y. A7. F192. fly/a 5- /1 Dec. 29, 1925. 1,568,038

S. B. WILLIAMS, JR., ET Ah AUTOMATIC TELEPHONE SYSTEM Filed Sept. 7, 1922 13 Sheets-Sheet 2 MVen/ors: Samue/ 5. Wf/l/ams/k y far/ 6. G/fison.

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Dec. 29, 1925. 1,568,038

s. B. WILLIAMS, JR., ET AL AUTOMATIC TELEPHONE SYSTEI Filed Sept. '7, 1922 13 Sheets-Sheet 5 y M/Q Dec. 29, 1925. 1,568,038

S. B. WILLIAMS, JR., ET AL AUTOIATIC TELEPHONE SYSTEM Filed Sept. '7, 1922 13 Sheets-Sheet 4 1,568,038 ET AL Dec. 29, 1925' S. B. WILLIAMS, JR.,

AUTOMATIOTELEPHONE sys'rnu Filed Sept. 7,

1922 1 Sheets-Sheet 5 'far/ 5. 6725071. by M I -A/f y.

Dec. 29, 1925. 7 1,568,038

S. B. WILLIAMS, JR, ET AL AUTOMATIC TELEPHONE SYSTEM Filed Sept. 7, 1922 m/en -Samuel 5f WWW/775 J/t [ar/ 6/fi50/1.

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Dec. 29, 192:. 1,568,038

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Q NR bunk Filed Sept. 7, 1922 Smwn Dec. 29, 1925. 1,568,038

s. B. WILLIAMS, JR., ET AL AUTOMATIC TELEPHONE SYSTEM Filed Sept. '7, 1922 13 Sheets-Sheet 8 Dec. 29, 1925. 1,568,038

5. B. WILLIAMS, JR., ET AL AUTOMATIC TELEPHONE SYSTEM Filed Sept. 7, 1922 15 sheets-$115515 9 Deg. 29, 1925. 1,568,038

s. B. WILLIAMS, JR., ET AL AUTOMATI C TELEPHONE SYSTEM Filed Sept. '7, 1922 13 Sheets-Sheet ll ET AL AUTOMATIC TELEPHONE SYSTEM Filed Sept 7 1922 13 Sheets-Sheet 12 far/ 5. 6/fi50/7.

S. B. WILLIAMS, JR.,

n o o 8% a i um fi m g Dec.- 29, 1925.

Dec. 29,1925. 1,568,038

S. B. WILLIAMS, JR., ET AL AUTOMATIC TELEPHONE SYSTEM Filed Sept. 7, 1922 13 Sheets-Shet 13 m m 3 3 w 93 w 93 b Q w 93 m Pl 1 SQ @RT mum? mg Samue/ 6f WV/[amsk [ar/ 5. 5mm by My Patented 29, 1925.

v 1,568,038 UNITED, STATES PATENT orslcst,

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Applioeti on lled leptember 7, 1m. Serial-Io. saaaaa.

To all whomitmay' 'c omern:

Be it known that we, SAMUEL B, Wm

mans, Jr., and EARL S. GIBsoN, citizens of the United States of America, residing at Brooklyn, in the county of Kings and State of New York, and Bid ewood, in the county of Bergen and State 0 New Jersey, respectively, have invented certain new and useful Improvements in Automatic Telephone Systems, of which the following is a full, clear,

, concise, and exact description.

This invention relates to automatic telephone exchanges and-more particularly to what are known as community automatic exchan es; that is, systems for small towns and vi lages wherein various types of subscribers lines such as rural lines and party lines as well as individual lines terminate in the same exchange, the rural lines being local battery lines and the party and individual lines being commonbattery lines.

The object of the invention is to rovide a system of this character which wil be efficient in operation and cheap to manufacture.

In the circuit arrangement of this invention multi-contact relays instead of step-bystep switches are used to establish the con nections.

These multi-contact relays consist of a number of bare wires running horizontally with which other bare wires are adapted to engage. A feature of this invention is the provision of a circuit arrangement for preventing sparking at the points wherethe bare wires engage when the contact between these wires is broken .upon the disestablishment of the connections, these wires not being provided with platinum contacts. In accordance with this feature of the invention, the circuits for maintaining the multi-contact relays energized to hold these bare wires in contact is not broken until after the circuits which lead through these bare wires have been opened. More specifically, the circuit is so.

arranged that upon the breaking down of the connection a relay 1s released which removes current from what may be termed for convenience the circuit relays. These relays in releasing remove current from the circuits Including the bare wires referred to.

After this current is removed the circuit ofthe relay which has been maintaining the multi-contact relays energized is opened and these rela s released, but inasmuch as no current is owing at this time through the points where these bare wires engage, no spark ng results. It will be readily apparent that this is a desirable if not a necessary feature where ordinary bare ,wire with no platinum contacts is used for otherwise the wire would be burned and rendered useless in, a very short-time.

Another feature of the invention is the provislon of a circult arrangement for reventing the calling subscriber from dia ing more digits than required to build up the particular. connection involved.

A further feature is the provision of a circuit arrangement wherein in the case of a revertive party line call the calling party dials the d rector number of the desired station and then dials the letter suffix of his own station and then replaces his receiver,

whereupon his bell and the called station bell will ring alternately until the called party answers, when the ringing will cease which is the signal for the calling party to remove his receiver and carry on the conversation.

. Another feature is the provision of means for preventing two or more lines calling simultaneously from getting the same link circuit.

Another feature is the provision, in a community exchange of the all-relay type, of a circuit arrangement whereby. the calling party, in addition to being able to build up local calls automatically, can select one of a number of trunk groups, whereupon an idle trunk in the selected group is connected to his line over which the call 1s extended to a desired main oflice.

Another feature is the provision of a circu-it arrangement wherein on a revertive call the connector relays are released and the finder relays are held set, thus eflecting a saving in current. This is a very desirable feature in systems supplied with current from a small storage battery.

A still further feature is the provision of a circuit arrangement whereby upon the selection of a trunk to one of the central offices, alternating current is momentarily applied thereto to operate a signal at the said ofiice as a calling signal, and upon the replacement of the receiver by the calling party said current is again applied to operate a disconnect signal at said ofiice.

A further feature is the provision, in a system of the type referred to, of a circuit arrangement for operatmg a si nal at the central office if all the links are busy or defective.

Another feature is the provision, in a system of the type referred to, of a circuit arrangement for automatically selecting another link if the one selected does not function and extend the calling line Within a certain interval.

A further feature is the provision, in a system of the type referred to, and wherein a line finder starting circuit is closed upon the removal of the receiver by the calling party, said circuit being then removed from his control and released when the line is extended by the finder, of means for .restorin the start circuit to normal in case the ca ing party abandons the call before the .finder has time to connect with the calling line.

A further feature is the provision of an improved means for generating the required ringing current by means of relays, and a code switch for applying this current to the rural lines, the code switch magnets being operated in sequence and not in unison so as to permit of a relatively small battery being used.

Another feature is the provision of an allrelay generator and a switching arrangement for selectively operating party line bells branched off the line to ground and operated by plus and minus current.

Other features will appear in the followin detailed description.

Referring to the drawings:

Fig. 1. shows the various types of subscriber circuits; Fig. 2 shows a trunk connector; Fig. 3 shows a local connector; Fig. 4 shows a line finder; Fig. 5 shows marker and allotter circuits; Figs. 6 and 7 show a link circuit; Fig. 8 shows a counting relay circuit; Fig. 9 shows a trunk selector; Figs. 10 and 11 show a trunk circuit and Fig. 10 also shows a trunk ringing control circuit; Fig. 12 shows a ringing circuit; Fig. 13 shows the tone and alarm circuits; Fig. 14; shows the substation dial, and Fig. 15 is'a view showing the manner in which the drawings should be arranged to trace the operation of the circuits.

The system shown in the drawings is particularly adapted to give full automatic service to small towns and the equipment shown provides for eighty subscribers lines and ten groups of trunks by means of which connections may be extended to other offices. These eighty lines are individual lines, party lines and rural lines. The individual lines are operated on a common battery basis.

The subscribers sets of these lines equipped with the usual bridged arrangement of ringer and condenser for signaling. The party lines are also operated on a common battery basis and are equipped with the standard Bell party line ringing equipment; that is tosay an alternating current relay is bridged across the line at each station and when operated connects the associated biased ringer m a ground branch from one side of the line. One call number is assigned to each party line and a letter sufi'ix is used to indicate the station on the line. The directory number for a station on a party line is therefore the line number followed by a letter such as 32R. The rural lines are operated on a local battery basis. The automatic equipment at the central ofiice is controlled over a so-called simplex circuit from the subscribers dial, a ground connection being provided at the dial. One call number is assigned to each rural line and the station is indicated by a two digit sufiix. The directory number for a station on a rural line is the line number followed by a two digit sutlix, such as 21-18.

When the receiver is removed from the hook a distinctive dial tone will be heard as soon as the automatic equipment is ready to receive impulses. The time between the removal of the receiver until the tone is heard is very short.

Calls for stations not on the same party or rural line will be made bv dialing the directory number. If the wanted line is busy a distinctive busy tone will be heard when the dialing operation is completed, and the receiver should then be replaced, which releases the automatic equipment. If the station is idle, ringing tone will be heard and will continue until the call is answered. If the call is for a station on'the same line, whether party or rural, it is known as a reverting call. If a party line subscriber desires to make a reverting call he dials the listed number and the letter sufiix of his own number and then replaces his receiver. The bell of his own as well as that of the called station will ring alternately until the called party answers when the ringing ceases which is the signal for the calling party to again remove his receiver and conversation may proceed. If the calling party is on a rural line and desires to make a revertive call he will only have to dial the listed numher and then replace his receiver. All the bells on the line will then ring the code of the called station and will stop ringing when the called party answers, which is the signal for the calling party to remove his receiver and conversation may proceed. The calling party can readily identify a reverting'call since the first two digits are the same, the sufiix only beingdiiferent.

In making a trunk call the subscriber will the selection of a trun and the operation of a si nal at the central ofiice to which the trunk extends, whereupon the operator will,

plug in and'ascertain the number desired and then extend the connection. If allthe trunks in the desired group are busy the calling party will get a distinctive tone,

whereupon he should replace his receiver to restore the automatic equipment.

On incoming trunk calls to the community exchange the operator at the distant ma-in ofiice sets the automatic equipment at the said exchange to connect with the desired line. a

The ringing current on an incoming trunk call is automatically applied at the branch exchange. Due to the isolated location of the branch exchange a single low frequency ringing system maderup of relays is used. Provision is made for a maximum of twenty stations on a rural line and a code switch for twenty different ringing codesis provlded.

A detailed description will now be glven of the operations involved in buildlng up the various kinds of connections. In tracing these circuits it should be borne in mind that the hundreds or thousands and hurtdreds digit of the reference character Wlll indicate the sheet whereon such character will be found.

Individual line to individual Zine.

The removal of the receiver by the subscriber at substation 22 closes the circuit of line relay 500, which relay in attracting its armature 518 operates group relay 501 over a circuit including a normal contact of relay 502. Group relay 501 at its right armature closes a locking circuit for itself including group relay 503 and anormal contact of relay 504. To provide against two or more group relays: 501, 529, etc., operating simul taneously and thus seizing the same link, the locking circuit leads through series contact on all the intermediate group relays. Thus if, two or more group relays such as 501, 529 operate simultaneouslyonly one relay 501, can hold. Relay 503 operates group relay 502, which relay in attracting its right armatures removes ground from the group relays corresponding to 501 and grounds the starter wire to initiate the operation of line finder mechanism to extend the calling line to an idle link circuit. The startingc1rcuit includes the following elements: ground, 505, 506, 507, 508, 509, allotter relay 400 to batteryr Assuming the allotter control switch AC shown in Fig. 5 to be in position 3, the starter wire will be connected-"to allotter relay 400 of the third link through the normal contact of the advanced starter wire relay 401. Relay 400, in operating prepares a circuit for relay 504 in the starter circuit, but the latter cannot operate because it is short circuited by the normal contact of relay 401, as is evident from the circuit traced for relav 400. This short circuit will be removed when the calling line has been extended to the link circuit, when relay 504 will operate and unlockthe group relays 501, 503 to restore the control of the start circuit to the other lines. Relay 400 in operating, causes the operation of the link holding relays of Fig. 7 .as will be described, and connects thegroup relays of the line finder to the contacts of the group relays'in the group circuit toconnect the calling line to the seized link. More in detail, thecall being traced having originated in group No.; 1,

group relay 501 having been operated as described causes the operation of group relay 402 corresponding to this group in the line finder shown in Fig. 4 when relay 400 operates as described. This circuit includes the following elements: battery, 402, 403, 510, 511, 512, to ground. Relay 402 connects the ten lines including the calling line to the cross wire multiple shown in Fig. 4. Relay 400, in operating, also operates group relay 513 over the following circuit: battery, 513, 514, 404,405, 406, 407, 440, 515, 516, 507, 506, 505 to ground. Relay 513 places the units relays in the line finder under the control of the line relays of the calling group and causes the operation of the particular units relay in the line finder which corresponds to theposition of the operated line relay 500 in the group. The calling substation 22 being the second line in the first group, relay 408 will be operated, as follows: battery, 408, 409,410, 560, .517, 518, 519, 565, 566 to ground. It will be noted that when relay 513 operated, it completed an obvious circuit for relay 520.

Resistance 567, connected between battery and the front contact of relay 500, is to prevent the ground applied at the armature 566 from being connected directly to battery when relay 513 operates as described; it is a protective resistance.

, Slow to release relay 700 in the link circuit (Fig. 7 operates when relay 400 operates, the circuit being as follows: battery,

700,701, 600, 300, 411. 412 to ground. Relay T00 operates relay 702. The latter operates relay 703. Relay 702 provides holding ground for all the ordinary circuit relays such as 761 while relay .7 03 provides holding ground for all the multi-contact relays such as 402. 408. Relay 703 releases after relay 702 when the connection is broken down, so that no circuits will be broken by the, wire contacts of the multi-contact relays when the latter release. tlzus avoiding sparking at the contacts. When the link circuit is connected to the calling line by relays 408, 402,115 de- 522 to battery. Relay 522 cuts off the line relay 500 in the well known manner. I Relay 401 transfers the start wire 516 from link 3 pare for testing the called line.

which has just been taken for use to conduc-,

tor 441 leading to link 4, and removes the short circuit from relay 504, which now operates over conductor 527, and in attracting its left armature opens the locking circuit including group relays 501 and 503. Relay 504 in attracting its right armature removes ground from the start wire 516 to prevent this ground from causing the seizure of link 4 to which relay 401 has extended to start wire as described. At its left armature relay 504 transmits an impulse to motor magnet 539 of the allotter control switch AC to advance its brushes :1 step to vary the point of ingress of the starting conductor 51.6 with respect to the allotter A, (Fig. 4) in order to distribute the load uniformly among the links. The release of relay 503 releases relay 502 which restores the control of the group relays corresponding to relay 501 to their respective groups. Relay 502, in retracting its armature 505, releases relay 504 reconnecting the start wire 516 to armature 505 of relay 502 which may now be operated by another calling line to cause the seizure of the link to which relay 504 extended the start wire 441. At this time relay 400 also releases, since its locking circuit is opened by the release of relay 502.

Relay 702, in operating, operates slow to release relay 706 to prepare the ringing circuit, and slow to release relay 707 to pre- The circuit for relay 7 07 is as follows: battery, 707,708, 603, 306, 304, 613*, 709, 710, 766, 711, 712, 713, to ground. The circuit for relay 706 is as follows: battery, 706, 714, 740, 788, 710, 766, to ground over the path traced for relay 7 07.

Upon the operation of the group and units relays 402, 408, the impulse relay 715 is operated over the subscribers line circuit, this circuit including the following elements: battery 715, 716, 717, over the talking conductors traced in heavy lines and including contacts of the operated tens and units relays and the telephone set at substation 22, returning over 718, .719, to ground. When the calling line is extended as described to the link circuit, tone is transmitted to the calling line to inform the subscriber that the equipment is ready to receive the impulses from the dial. It will be remembered that relay 702 operated when the calling line was connected to the link. This relay at its inner left armature closed a circuit for the dial tone relay 1.322 which in operating energizes relay 13 20. This relay interrupts its own circuit, and creates a tone current in the primary of the induction coil'1323, which is transmitted over the following circuit which is the original energizing circuit for relay 1322: ground, 1322, 1323, 528, 433, 37:, 374, 609", 728, 729, 775, 7202-721, 722, 710", 786, to battery, The tone transformer 716 transfers this tone by induction to the calling line over the circuit traced for the impulse relay 715.'

The subscriber at'substation 22 now 0pcratcs the dial 100 to transmit the tens digit of the wanted number. The impulse relay 715 at the first interruption of the line circuit, operates counting relay 800 over a circuit including the following elements: ground at the armature 720 of relay 764, 721, 722, 723, 724, 801, (normal contacts of the upper counting relays) 800, 802, 832, to battery. Relay 800 connects the ground on conductor 801 to the slow releasing relay 803, which in turn, operates relay 804 as follows: battery, 832, 804, 815, 805, 709, 710, 766, 711, 712, 713, to ground. Relay 804 looks to conductor 805. Relay 800 prepares a circuit for relay 806, but this relay cannot operate as long as it is short circuited by the ground applied to conductor 801 by the armature of the impulse relay 715 in its retracted position. When the impulse relay 715 operates at the end of the first interruption, relay 806 operates in series with relay 800 over a circuit including the inner right armature of relay 800 to ground on conductor 805, and these relays lock up to this grounded conductor and relay 806 connects grounded conductor 805 to counting relay terminal 1. lVhen the dial interrupts the impulse circuit the second time and again closes the circuit, relays 807 and 808 operate, releasing relays 800 and 806 and relay 808 connects grounded conductor 805 to counting relay terminal No. 2. When counting relay 809 operates, relay 810 is operated-from grounded conductor 805 and holds in series with relay 811 which operates when relay 809 releases. The cycle is then repeated for these counting relays if the digit is larger than 4. 1f relay 809 operates a second time, the relay 812 operates and holds in series with relay 813 which operates when relay 809 releases, and a third cycle for the counting relays may be started. By means of these relays the impulses received from the impulse relay 715 are recorded. At the end of the series of interruptions for the first digit of the desired number and assuming this digit to be 3, slow relay 803 releases due to ground being permanently removed from conductor 801 by the continued energization of the impulse relay 715. Relay 803 in releasing closes a circuit for the tens relay 305 in the local connector control switch LOGS (Fig. 3). This circuit includes the following elements: grounded conductor 805, 815, 824, 816 725, 694, 306, 334, 365, 305 to battery. litelay 305 66nnects the countin 'relay terminals of Fig. 8 to the group re ays in thelocal connector circuit LC and the articular group relay, in this case relay 30 7, the, tens digit 1 not being used, operates over 307, 311, 375, 828, 834. 805, to ground, and locks to holding conductor 308 now groundedby relay 703. This locking circuit is as follows: battery, 307, 303, 309. 606, 726, 740-, 727, 723, 729 to ground. Relay 307 also operates relay 310 over the following circuit: ground, 713,

315, 364, 310, battery. The operation of relay 310 removes a short circuit from relay 817 which now operates in series with relay 305, this circuit including the following elements: battery, 305, 388, 312, 607, 730, 818, 817, 824, 815 to grounded conductor 805. The short circuit referred to may be traced as follows: 365, 306, 694, 725, 816, to 324.

Relay 817, in operating, releases the countingrelays and also release relay 804 which releases relays 817 and 305.

Conductor 306 over which the tens relay 305 was operated is now extended to units relay 316 by the armature 384 of relay 310 so that when slow relay 803 releases at the end of the series of interruptions corresponding to the second digit, relay 316 operates, connecting the counting relay terminals to the units relays in the local connector, and assuming line 31 is being called, relay 317 operates over the following circuit: battery,

317, 318, 319, counting relay terminal 1, to grounded conductor 805. Relay 317 locks to grounded conductor 308 as described for tens relay 307.

The link is now connected to the called line through the 0 erated group and unlts relays 307, 317 in t 1e connector. When the units relay 317 operated, relay 320 operated over the following circuit: battery, 320, 321, 609, 1000, 610, 322, 377, 323, 313, 608, 764, 766, 711, 712, 713, to ground. Relay 320 removes the, short circuit from about relay 817, as described, which now operates in series with relay 316 as follows: battery, 316, 389, 312, 607, 730, 818, 817, 824, 815,805 to ground. Relay 817, in operating, releases the counting relays, and also releases relay,

804, which releases relays 817 and; 316. The sleeve conductor 324 of the called line No.

' 31 is now connected through the right winding of relay 731 to battery to test the condition of the called line. If the line is idle or ungrounded'this relay will not operate and 7033738, 712, 713, to ground. Relay 707 released when relay 320 operated. The attraction of th left armature of relay 733 operates relay 7 06 over its lower winding to prepare the talking circuit and the attraction of its right armature releases relay 706 to prepare the ringing circuit. Relay 733, in operating, operates rela 739, this circuit being as follows: battery, 39, 714, 740, 7 88,

710, 766, 711, 712, 713, to ground. When slow relay 706 releases a short interval after its circuit is opened by relay 733 as described, it closes the following circuit tostart the ringing generator (Fig. 13)- in operation: ground, armature 741 of relay 706, 742, 615, 373, 379, 330, 630, 1200, 1300, start relay 1301, to battery. Relay 1301 at its armature 1314 operates relay 1302, which in turn operates relay 1303. Relay 1303 in turn operates relay 1304. Relay 1301 at its tially wound and the relay did not operate.

Relay 1.301, in operating, grounded the upper half of the rimary winding of trans former 1308. W en relay 1307 operated, it opened the circuit through the upper half of the primary winding and closed a circuit throu h" the lower half, thus reversing the direction of the flow of current in the primary winding and producing alternating current in the secondary winding of the transformer 1308. This operation continues, thus producing current of the proper character to ring an alternating current bell. The alternatin current produced in the secondary win ing is controlled by brush 1201 connected to conductor 1202. It will be remembered that rela 1304 operated upon the operation of re ay 1303. Relay 1304, in operating, opens the circuit of relay 1302, which after an interval retracts its armature, opening the circuit of slow relay 1303, which after an interval retracts its armature. Retraction of the armature of relay 1303 closes the following circuit to operate the magnetv 1203 of the first row of brushes of the switch shown in Fig. 12: bat- 1381'), 1203, 1204, 1309,1315, 1311, 1312, 1373, 1314, to ground. Magnet 1203, in operating, removes the short circuit from about relay 1205, which operates in series with magnet 1203. Magnet 1203 cannot hold in series with relay 1205, and therefore retracts its armature, advancing thebrushes of the first row one step. \Vhen magnet 1203 releases, it closes its back contact, and conductor 1204 is now extended conductor 1206, whereupon magnet 1207 operates and this cycle continues until magnet 1208 operates and releases. When relay 1209 operates 'on the operation of magnet 1208 and magnet 1208 releases, grounded wire 1247 is extended to" conductor 1248 and thence to conductor 1340 to short circuit relay l304.- Relay 1304 thereupon releases, starting a new cycle of operations, this cycle continuing as long as start relay 1301 re operated. The. ringing current is interrupted by the brush 1201 in order to avoid continuous ringing of the subscribers bell. For simplicity of illustration the ringing conductors 1235 and 1236 are shown as terminating in a circle marked A. A similar-cincle marked A in Fig.7 indicates these ringing conductors in Fig. 7. They are shown connected to the left armatures of relay 706. The path for ringing current may be traced as follows: (Fig. 7) 743, 744, 745, 746, 747, 748, 749, 750, 751, 752, 753, 754, 755, 743. The current in the primary winding 748, 750, of the transformer 789 induces alternating current in the'secondary winding 756 and 757 to operate the bell at the called substation 31 (Fig. 1). This circuit is as followsi ground at the right armature of relay 714, 771, 756, upper talking conductor shown in heavy lines (Figs.'7, 6, 3, 2, 1) through the bell at substation 31, (Fig. 1) returning over the lower talking conductor (Figs. 1, 2, 3, 6, 7) 769, 757, 758, 759, 760, 792, 761, 762, to battery. A portion of this ringing current flows from the lower talking conductor 769, throu h condenser 724, con ductor 723*, 720, wlnding 721 of transformer 716, conductor 7 22, 710 786 to battery. Coil 716 transmits this ringing tone by induction to the calling line over the normal contacts of relay 764. In response to the ringing of the bell, the subscriber at substation 31 removes his receiver, thereby operating the marginal ringing cut-off relay 7 63 through its right winding 761. Relay 7 63 in attracting its armature 766 cuts off the ringing current by releasing relay 739, and in attracting its inner left armature locks up to grounded conductor 711. In attracting its armature 766 relay 763 opens the circuits previously traced for relays 310 and 320 in the local connector control switch (Fig. 3). Relay 320 in retracting its armature 379 opens the circuit traced for start relay 1301 in the ringing circuit (Fig. 13) thus stopping the operation of these relays and-the ringing control switch, (Fig. 13) to economize on current. In attracting its armature 7 66, relay 763 operates relay 764 as follows: battery, 764, 765, 766, 711, 712, 713 to ground. Relay 764 connects talkin conductors 751 and 747 to 718 and 71 res ectively and cuts off the impulse re- ..lay bri ge. Relay 739 in releasing, connects relay 767 to the lower talking conductor'747 in circuit with the calling line and ground for this circuit is connected at armature 768 of relay 711 to the, upper talking conductor 751. The circuit for feeding talking current to the called line leads from battery at the front contact and armature 759 of relay 763 to the lower talking conductor 769, ground being supplied to the upper talking conductor 770 at armature 771 of relay 714. A substitute holding circuit for slow release control relay 700 is closed by relay 7 67 so as to hold relay 700 operated after relay 715 is cut off due to the operation of relay 7 64.

' Upon the termination of the conversation, the replacement of the receiver by the calling party releases relay 7 67, which releases slow relay 700, which 1n turn releases relay 702, which releases relay 703. Relay 702, in releasing its armature 713 removes ground from the locking circuits of the energized circuit relays, whereupon they release, and relay 703 in retracting its armature 729 removes ground from the multi-contact relays 402, 408, and 307, 317, releasing them. Relay 703 releases after relay 702 so that no circuits will be broken by the wire contacts of the multi-contact relays when the latter release, thus "preventing destruction iiue to sparking at the contacts of these reays. I

Assuming now that the called line was busy, busy test relay 731'wil1 operate over its right winding from ground, on the sleeve of th called line. This circuit is as follows: battery, 731, 732, front contact and armature 772 of slow to release relay 707, 734, 612, 367, 327, 366 to ground on sleeve wire 324 applied by the armature 713 of relay; 703 if the line is busy as a called line, or through a relay such as 401 if the line is busy as a calling line. Relay 731 locks to ground at 713 over its left winding and armature 738 and connects busy tone to the calling line through the medium of the tone transformer shown in Fig. 13. Relay 731 in operating operates 1317 as follows: ground, 1317, 1316, 1210, 616, 773, 774, 775, 720 721 722, 710*, 786 to battery. Relay 1317 operates start relay 1318. The operation of relay 1318 causes a self interrupter relay 1320 to operate, andenergizes relays 1302 and 1303 to operate and 1304 to function as described. The operation of relay 1304 operates relay 1319 and causes relays 1302 and l303 'to release one'at a time as described. Relay 1319 connects tone from relay 1320 to the busy tone lead 1341. When relay 1303 closes its back contact relay 1304 is short circuited and released, removing the short circuit from the left-hand winding ofv relay 1321. Relay 1319 holds in series with th left winding of 1321 which operates removing the short circuit from its right winding. The release of relay 1304 also causes relays 1302, 1303 and 1304 to go i throu h a second cycle, of operations. The

. circuited and released by the release of relay 1303, relay 1321 is released. This sequence of operations will then .be repeated as long as start relay 1318 is operated, causing an interrupted tone tobeconnected to the busy lead 1341. This tone conductor-is connected through tone transformer716 to battery at 786, and gives a bus tone to the calling line. The calling su scriber will thereupon replace his receiver, releasing re lay 715 which by releasing slow relay 700 brings about the releases of the connection asdescribed in the case of a successful call.

1 Party lines.

If the called number represents a station of a partyline, the calling party will dial the tens and units digits of such line, and

, in addition a third or party line digit, L,

M, R or W, Which representdigits 6, 7, 8 and 9 respectively. (Fig. 14.) Referring to Figs. 3 and 8, counting relay terminals 6 to 9 inclusive are used in connection with party line signaling. If a station of a party line is called, a ground will be connected to one of the counting relay terminals 6 to 9 due to the transmission of the third digit, which in the present embodiment of the invention is always either 6, 7, 8 or 9 impulses, as stated. It will .be remembered that relay320operated when the units relay 317 o erated in the connection traced. The party ine being shown asNo. 32, the operating circuit for relay 320 instead of being closed by units relay 317 is closed by units relay 382 since the units digit is 2 instead of 1 as just described in the case of the call to line 31. lay 320 is as followszbattery, 320, 321, 609,.

The circuit for re- 1000, 610, 322, 383, 323,313, 608,764, 766, 711, 712, 713 to ground. Relay 320, at its armature 368, transfers conductor 306 leading from the counting relay circuit, to .re-

selected by lay 328. Relay 328 operates uponthe termination of the third or party line set of 803 releases as described in connection with relays 305 and '316.- Its circuit is as follows: battery, 328,

368, 384, 306, 694, 725, 816, 824, 815, 805, 709, 710, 766, 711, 712, 713 to ground. The called number is 32R, and since R is the transmission of eight impulses, (1* 1g. .14) artyline ringing control relay 618 will be operated over the following circuit due to the operation of relay 328: battery, 631, 618, 619, 331, 332, 381,

819, (Fig. 8) to ground on conductor 805, through the operated counting relay contacts as described. Relay 618, in operating,

looks over the following circuit: battery, 631, 618, 646, 633, resistance 655, 624, 776, 797, 777, 77 9, 729 to ground. Relay 618, in operating, operates relay 620. as follows: battery, 620, 621, 333, 335, 334, 622, 623, 641, 624,776, 777, 779, 729, to ground. Relay 620 at its contact 634 locks to holding conductor 633 through resistance 655.

Relays 618 and 620 000 eratcto prepare the link circuit for app ying the proper character of' ringing current to signal the party line; station 32R, and relays 733 and 739 operatein the manner hereinbefore described. When connection is established vwith the party-line, relay 710 operates from ground on the test conductor 556 (Fig. 5)

line having a similar resistance included in its test conductor. The test conductors of the individual lines are open, as for example conductor 557. Relay 710 operates as follows: battery, 710, 714*,(which is marginal and does not operate in series with said resistance), 726, relay 706 being operated 745 727, 611, 391, 392, 393, 394, 435, 556, 555; to ground. Relay 710" closes the following circuit for holding slow relay 706' operated to prevent the application of individual line ringing current to the selected party line: grounded conductor 711, 766, 710, 756, 706 to battery. Relay 620 in operating as described operated relay 329 as follows: battery 329, 350, 670, 640, 624, 776, 777, 779, 729 to ground. Relay 329 looks over the following circuit: battery, 329, 613, 709, 710,766, 711, 712, 713 to ground. Relay 329 closes the following'circuit for ringing start relay 1301: battery, 1301, 1300, 1200, 630, 330, to ground at the armature 395 of relay 329. Relay 1301 starts the ringing circuit of dividual line. When brush 1211 reaches the eleventh contact 1212, pull-up relay 780 will operate. The circuit'is as follows: ground, 1211, 1212, 1237, 636, 625, 626, 27, 628, 679, 629, 680, 781, 732, 733,- 730, to battery. Relay 7 80 locks up over the following circuit: battery, 7 80, 787 788, 710, 766, to ground on conductor 711. Relay 7 80 prepares the ringing circuit. When brush 1213 reaches the eleventh contact 1214, relay 784 operates over the following circuit: ground, 1213, 1214, 1233, 637", 630, 631, 632, 633, 785, 734, 786, to battery. VVhen brush 1215 reaches the twelfth contact 1216, alternating current is applied over the following circuit to the primary of the transformer 789: lower end of the secondary of the transformer 1308, 1202, 1215, 1216, 1232, 638, 634, 635, 636, 637, 699, 638, 790, 742 754, 753, 752, 751, 750, 749,- 743, 747, 746, 745,743, 791, 639, 640, 641, 642,.643, 644, 645,1217, to the other

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