US2106360A

US2106360A - Telephone system

Info

Publication number: US2106360A
Application number: US27340A
Authority: US
Inventors: Raymond Ralph
Original assignee: Bell Telephone Laboratories Inc
Current assignee: AT&T Corp
Priority date: 1935-06-19
Filing date: 1935-06-19
Publication date: 1938-01-25
Anticipated expiration: 1955-01-25

Description

Jan. 25, 1938. R. RAYMOND TELEPHONE SYSTEM Filed June 19, 1935 12 Sheets-Sheet 1 n S 6E m at v 6F r w 4 t at Q m at E 9 GI m 6E w 6R Gm ENE 33 3 w:

u mat n QC or I lulu I II. I l I I u v: at JHHIIL a at By V R. RAYMOND ATTORNEY Jan. 25, 1938. R. RAYMOND TELEPHONE SYSTEM Filed June 19, 1955 12 Sheets-Sheet 2 INVENTOR R. RAYMOND Q NR A 71.7'0 RNE Y TELEPHONE SYSTEM Filed June 19, 1935 12 Sheets-Sheet 3 'INVENTOR R. RAYMOND ATTORNEY Jan. 25, 1938; R. RAYMOND TELEPHONE SYSTEM Filed Jfine 19, 1955 12 Sheets-Sheet 4 INVENTOR I R. RAYMOND ATTORNEY v at Filed June 19, 1935 12 Sheets-Shet 5 lNl/li NTOR BY 1?. RA MONO ATTORNEY Jan. 25, 1938. I R RAYMOND I 2,106,360

TELEPHONE SYSTEM Filed Juhe 19, 1935 12 Sheets-Sheet 6 v INVENTOR By .5 R. RAYMOND ATTORNEY Jan. 25, 1938. R, RAYM ND 2,106,360

TELEPHONE SYSTEM Filed June 19, 1935 12 ShebS-Sh66t 7 INVENTOR R. RAYMOND By Q6.

FIG. 7

A TTORNE Y TELEPHONE SYSTEM Filed June 19, 1955 12 Sheets-Sheet 8 fa s M/VE/vm/P R. RAYMOND ATTORNEY- FIG. 8

Jan. 25, 1938. R. RAYMOND 2,106,360

TELEPHONE SYSTEM Filed June 19, 1935 12 Sheets-Sheet 9 INVENIDR R. RAYMOND FIG. 9

A T TORNE Y Jan. 25, 1938. R. RAYMOND TELEPHONE SYSTEM Filed June 19, 1935 l2 Sheets-Sheet 1O lNl/ENTOR R. RAYMOND A 7' TORNE Y Jan. 25, 1938. R. RAYMOND 2,106,360

TELEPHONE SYSTEM Filed June 19, 1935 12 Sheets-Sheet 11 A TTORNEY Jan. 25, 1938.

R. RAYMOND TELEPHONE SYSTEM Filed June 19, 1955 12 Sheets-Sheet 12 x Q Q lNl EN TOR R. RAYMOND ATTORNEY.

Patented Jan. 25,1938

UNITED STATES PATENT OFFICE Telephone Laboratories,

Incorporated, New

York, N. Y., a corporation of New York Application June 19, 1985, Serial No. 27,340

24 Claims.

This invention relates to telephone systems and more particularly to those systems in which telephone connections are established by means of automatically operative selector switches under the control of a sending mechanism common to a plurality of subscribers lines.

,It is the object of the invention to improve the common sending mechanism to render it more reliable in operation and less expensive to install and maintain in efllcient operating condition.

Heretofore in sending mechanism of this character such for example as is disclosed in the Patent No. 1,862,549, granted June 14,. 1932 to R. Raymond and W. J. Scully, switches of the wellknown sequence switch type have been employed for performing certain of the operating functions. These switches, of which there are three in each sender, require the installation of a driving motor and power shaft on each sender frame. Since all of the remaining apparatus of the sender frame is of the relay type, the elimination of these switches and the substitution therefor of relays to perform their functions would considerably simplify the maintenance of the sender and then the entire maintenance of the sender in good operating condition would be practically reduced to relay adjustment. The substitution of relays with their better contacts for switches having base metal contacts would give decidedly better circuit operating efllciency.

In accordance with the present invention relays have been provided for performing all of the functions of the sender, thus eliminating the sequence switches and the power installation for driving them. More specifically a train of sequentially operating relays is employed in place of the control sequence switch for controlling the selective operations of the selector switches in accordance with the setting of the registers of the sender. A group'of transfer relays and impulse generating relays is employed for generating and transmitting codes of impulses in accordance with the setting of the registers of the sender on calls to manual oiilces equipped with call indicator apparatus and on calls to tandem ofiices thus replacing a second sequence switch which formerly performed these functions and a group of relays is employed for performing timing functions to replace a third sequence switch. The impulse generating relays not only generate codes of impulses for the establishment of manual and tandem calls, but also serve for generating impulses for timing cer- 55 tain operations of the sender such as a delay interval during which the calling subscriber may dial a stations digit and a delay interval for making preliminary coin test for the deposit of a coin if the sender is equipped to serve calls from subscribers line having coin boxes. 5

A clearer understanding of the invention may be had from a consideration of the following description in connection with the accompanying drawings which disclose a complete register sender. In general Fig. 1 shows the coin test circuits,

Fig. 2 shows the pulse generating relays,

Fig. 3 shows the subscriber class and district frame recording relays together with certain general control relays,

Fig. 4 shows the timing and monitoring circuits,

Fig. 5 shows the transfer relays for call indicator pulsing,

Figs. 6 and? show the cross-bar switch used go as a dial register,

Fig. 8 shows the incoming recording relays and the locking relays of the dial register,

Fig. 9 shows the class and compensating resistance registers,

Fig. 10 shows the oilice registers,

Fig. 11 shows the selection sequence relays, and

Fig. 12 shows the selection control relays and the counting relays.

This sender is particularly designed to function in a telephone system employing cross-bar switches. Such a system isdisclosed in Patent No. 2,093,117 granted September 14, 1937 to W. W. Carpenter, and a general reference is hereby made to that patent.

Ten senders, like the one disclosed, are mounted on one frame and are associated together in a group. Of the twenty-nine conductors, by which the sender is connected to the link circuits, conductors 330 to 350 are multipled to all ten send- 40 ers, while conductors 325 to 320 and H2 to H4 are individual to this sender.

When the sender is idle, battery is connected to conductor 325 over the back contact of relay 0 and the outer right back contact of relay Iii. When a subscriber originates a call, a line switch control circuit and a link control circuit are taken into use and these circuits function to find a district circuit or junctor which has access to a group of. senders, preferably containing more than one idle sender.- The calling line is then connected to the selected district Junctor and the sender. 7

Assuming that the sender disclosed has been seizedfor service, the link control 'circuitconll nects ground to conductor 32]., completing a direct circuit for relay 3, and a circuit for relay 3l2 over the innermost normal contact of relay 3| 5. Relays 3H and H2 connect. conductors 333 to 349 through to the sender equipment. When the line and link control circuits operate the line and link switches, the talking conductors of the calling line are connected through to conductors H2 and 3. Conductor 2 extends to ground over the left normal contact of relay I04 and the right back contact of relay I01, while conductor I I3 extends over the right normal contact of relay I09, left normal contact of relay I01, conductor i i5 to battery through the right winding of relay 3l0. If the connection over the line and ,link switches and the subscriber's loop is complete, relay 3I0 operates, closing a circuit from ground at the inner right back contact of relay 303, front contact of relay 3I0, conductor 35I to the winding of relay 8 and battery. A circuit also extends from conductor 35l over the right back contact of relay 8l5, conductor 82'! to the winding of relay 3 and battery. Relay 314 closes an obvious circuit for relay 3l3, which in turn connects ground from the inner upper back contact of relay 809, conductor 828, middle right front contact of relay 3 i3 to conductor 352, thereby completing a circuit over the front contact of .relay 8 to battery through the winding of relay 8| 5. Relay M5 at its right armature transfers the circuit of relay 3 from the ground supplied by relay 3i to ground at the contact of relay 8l5. Since relay 3" is slow to release, it maintains its contacts closed during the transfer. Relay 3 connects ground from its inner right contact through resistance 365, innermost right back contact of relay 308, conductor 383, lower back contact of relay 932 to conductor 4 to control the district junctor.

Relay 3l3 in operating, connects battery through the winding of relay 3 l 5, over the middle left contact of relay 3l3 and the second lower contact of relay 3 to conductor 338 as an indi-' cation to the link control circuit that the line conductors have been closed. Ground from the link control circuit operates relay 3I5 which looks over its third left contact to ground at the inner left contact'of relay 3i 3. Relay 3|5 disconnects battery from conductor 325 to remove the idle indication, and closes at its middle right front contact a point in the all-senders-busy chain circuit. It also conects ground over its second left contact to conductor 350 to hold the line and link switches operated, independent of the line and link control circuits. In addition it connects ground over its innermost left contact and the lowermost contact of relay 3 to conductor 339 as a release signal to the link control .circuit. Furthermore it opens the circuit of relay 3l2 which releases, opening conductors 340 to 349. When the link control circuit releases in response to the release signal, relay 3 also releases, opening the remainder of the common conductors.

During the time that relays 3H and 3I2 were operated, a registration was made of the class of service of the calling line and the number of the district frame involved. This information is furnished by the link control circuit in the form of ground to one of the class of service leads v 330 to 333, one of the frame tens leads 334 and 353 to ground at the inner right front contact of relay 3|.

The frame units indication is registered on the cross-bar type dial register 800. To indicate the relationship between the select magnets and the 5 switch structure, they have been numbered M0 to 010 although they appear in Figs. 2 and 3. With conductor 343 grounded, select magnet 8l3 operates, preparing the contacts of the No. 3 level of the register. Magnet 5" also extends its op- 10 erating ground over its local contact, and conductor 2" to the winding of relay 8 and battery. Relay 3 closes a circuit from battery through thewinding of the frame hold magnet |0|, inner back contact of relay "I to ground at the outer left front contact of relay 8| I. Magnet '|0l operates, closing a locking circuit for itself through the winding of relay 80i, lower contact of magnet l0l to grounded conductor 353.

It also closes a circuit from battery through the winding of relay 828, left back contact of relay 825, to ground at the upper front contact of magnet l0l. Magnet IOI closes the contacts of cross-- point H2, at the No. 3 level prepared by the operated select magnet H3. The cross-point connects ground to conductor H i, which extends over the outer right back contact of relay 300 and the third left contact of relay 3i5 to the winding of relay M5 and battery, locking relay 3i5.

When relay 3|2 released as previously 'described, the circuit of select magnet 5l3 was opened and that magnet released in turn releasing relay 8 and permitting relay 80| to operate in the locking circuit of hold magnet 10!. Crosspoint H2 is maintained closed as long as magnet IN remains operated. 1

When relay 3 operated, a circuit was closed from ground at its outer right contact through condenser 354, left winding of relay 3| 0, outer right back contact of relay 405 to the source of 40 dial tone. A tone is thereby induced in the subscribers dialing circuit and is heard in the substation receiver as an indication that dialing may start.

Call to panel om'ce Assume for the purposes of this description that the wanted number is Chelsea 3-5678. When the subscriber dials the first letter C, which is the equivalent of the digit 2, the circuit of relay 3l0 is opened twice, causing relay M0 to close its back contact twice. Relays 8 and M5 also release. Relay 8l4 is fast both to operate and release in order that it may follow relay 0 as closely as possible. Relay M5 is also fast to release.

At the first release of relay 0, a circuit is closed from battery through the winding of relay 825, back contact of relay 8| 4 to grounded conductor 352. Relay 825 operates and is sufficiently slow to: release to remain operated throughout the impulsing for the digit, in spite of the repeated momentary breaking of its operating path. Relay 825 in operating, opens the circuit of relay 828 which releases, remaining released throughout the reception of the digit impulses.

Relays 8l8, 8| 1 and M8 serve to transmit the dial pulses over

conductors

829 and 830 alternately to the pulse counting or recording relays 8|! to 824. At its first release, relay 3 l0 connects ground from the inner right back contact of relay 300, over the backcontact of relay M0 and the left front contact of relay 3 to conductor 355, right back contact of relay 3l8, winding of relay 8l8 to battery. Relay 8l3 operates, closing a circuit from battery through its winding, left winding of relay 8l8, back contact of relay 8", front contact of relay 8l8, over the front contact of relay 825 or the inner right back contact of relay 828 to grounded conductor 882. This circuit also extends to grounded conductor 882 over the outer right back contact of relay 828 and the normal contacts of relays 8H and M2. Relay 8l8 does not operate, being shunted by the operating circuit of relay 8l8. When relay 8l8 reoperates at the end of the first pulse, relay 8l8 operates, closing a circuit from grounded conductor 352, inner right back contact of relay 826, left front contact of relay 8l8, conductor 838, left back contact of relay 826, right back contacts of

relays

822 and 828, winding of relay 8l8 to battery. Relay 8l8 locks over its inner right front contact, normal contacts of relays 828, MI, 822, 823, M2 and 8 to grounded conductor 352, thereby recording one pulse.

Relay 8l8 in operating prepares a circuit from battery through the winding of relay 8, right winding and right front contact of relay 8l8 to conductor 355. When relay 3|8 releases in response to the second pulse, groundingconductor 355, relay 8l8 is held operated and relay 8" operates, opening the holding circuit for relay 816 which now releases. At the end of the second pulse relays 8H and 818 also release closing a circuit from grounded conductor 852, inner right contact of relay 826, left back contact of relay 8! 8, conductor 829, right back contacts of relays 823 and MI, outer right front contact of relay M9, to the winding of relay 828 and battery. Relay 828 looks over its left alternate contact and the normal contacts of

relays

8, 822, 823, M2 and St I to grounded conductor 352. Relay 828 also opens the locking circuit of relay 8l8 so that relay 828 alone of the pulse counting relays remains operated at the end of the digit. While relay 3l8 remains operated between digits, relays 8, M5 and 828 remain operated and relay 825 releases.

The cycle of operations described above for relays 8I6, 8|! and 8l8 repeats for every two start of each series of pulses and to .hold -"it steadily until well after the end of the series.

When relay 825 closes its left contact following the dialing of the first digit, a circuit is .closed from ground at the upper front contact of magnet 18f, left back contact of relay 828, left normal contacts of relays 8H and M2, right back contact of relay 828, inner right front contact of relay 828 to the winding of select magnet H2 and battery. Magnet 812 operates, preparing the No. 2 level of contacts and extends its iary magnet H8 to battery. Magnet I82 closes a locking circuit for itself, and the auxiliary hold magnet H8, through the winding of relay 882, upper front contact of magnet I82, outer front contact of relay 88l to ground. The operation of relay 8 opened the operating circuit of se- Magnet 182 t the next digit. Auxiliary hold magnet 'Il8 closes cross-point 1 ll in the corresponding vertical. In addition magnet H8 closes a circuit from ground at its front contact through the winding of relay 885 to battery, opening the dial tone circuit.

It will be observed from the foregoing that the release of relay 828 is ineffective to operate one of the select magnets M8 to 8l8 until hold'mag net 'l8l has been properly operated by the registration of the district frame number and there-' fore that the first digit dialed cannot be falsely registered on the first or frame vertical of the dial recorder.

If a false pulse is transmitted, or the digit on is mistakenly dialed for the first digit, relays 8l8- and 8l8 are operated as above described, in turn operating relay 8l8. When relay 828 falls back,

the select magnet circuit is closed as above traced Y to the back contact of relay 824 and thence over the inner left front contact of relay 8l8 to thewinding of the No.1 select magnet 8. This magnet extends its operating ground to the winding of relay M2. The locking circuit of re-- lay 8l2 extends over the front contact of magnet I82 and therefore cannot be closed until after the first digit has been registered. Likewise relay M2 is ineffective to operate magnets I82 and "8 since the ground supplied to the outer left contact of relay 812 for the purpose of operating the hold magnets is opened at the front contact of relay 88! and is not reclosed until magnet ll8 has closed one of thecross-points in its vertical. Relay 8l2 opens the holding circuit for relay 8l8 so that relay 8l8, magnet 6H and relay 8l2 restore in succession and the circuit is in condition to record the proper digit.

It may also be noted that relay 8l2 is effective to record the digit one on, the framevertical since a ground for operating the frame magnet "I is supplied over the back contact of relay 88!.

The second letter of the office code, H, is the equivalent of the digit 4 and the relays 8l8, 811.

and 8l8 perform two complete cycles. Relays 8l8 and 828 operate in response to the first two pulses as previously described. After the third pulse relays 8H and 8l8 are held operated, grounding conductor 888 and closing a circuit over the left back contact of relay 828, right back contact of relay 822, outer right front contact of relay 828 to the winding of relay 82l and battery. Relay 82l locks over its inner left front contact and the normal contacts of

relays

822, 823, 8 l2-and 8 to grounded conductor 352, at the same time opening the locking circuit of relay 828 which re-- At the end of the fourth pulse relays 8l8,

leases. 8H and 8l8 are normal, connecting ground to conductor 828, to complete a circuit over the right back contact of relay 823, outer right front contact of relay "I to the winding of relay 822 and battery. Relay 822 locks over its inner left front contact and the normal contacts of relays 823, M2

and 8 to grounded conductor 882, releasing recult of relay 8 and magnet 814.

relay 828 is released as above described connecting ground from the front contact of magnet 10! over the left back contact of relay 825, left normal-contacts of relays 812 and 8, right back contact of relay 824, inner right front contact of relay 822, to the winding of select magnet 8 and battery. Magnet 814 prepares the contacts in the No. 4 level of the switch and extends its operating groundover conductor 218 to the winding of relay 8| l. Relay 8 looks itself and magnet 8 l4 over its front contacts, normal contact of hold magnet 103, left back contact of relay 813, lower front contact of relay 802 to ground. At its normal contacts it opens the locking circuit of relay 821 and the operating circuit of magnet 814 and at its outer left front contact closes a circuit from ground, over the inner front contact of relay 80l, upper front contact of relay 802, right back contact of relay 813, back contact of relay 803 to the winding of hold magnet 103 and battery. Magnet 103 closes a locking circuit for itself through the winding of relay 803, front contact of magnet 108, left back contact of relay 8l3, front contact of relay 802 to ground. When magnet 103 has fully operated it opens the locking cir- Magnet 103 holds cross-point 620 closed.

In recording the third code digit three, relay 82l is operated and locked, and, on the release of relay 825, operates select magnet 6l3 which prepares the No. 3 level of contacts. Magnet 613 operates relay 8 which, since relay 803 is operated, locks under the control of magnet 104 and operates that magnet. Magnet 104 locks in series with relay 804, locking cross-point 115 and releases relay 8| I and magnet 6l3.

For the thousands digit 5, relays H9, 820 and 821 are operated and released as before by the first four pulses, the fifth pulse operating relay 823 over conductor 830 and the front contact of relay 822. Relay 823 locks in a circuit from battery through its winding, back contact of relay 819, inner left front contact of relay 823, normal contacts of relays 812 and 8| 1 to grounded conductor 352. Relay 823 also releases relay 822 and when relay 825 falls back operates select magnet 6I5. Relay 8, hold magnet 105 and relay 805 function to close cross-point 62L When the hundreds digit 6 is recorded, the first five pulses cause the successive operation and release of

relays

818, 820, 821, and 822, relay 823, being operated alone at the end of the fifth pulse. The, sixth pulse causes the grounding of conductor 829, operating relay 824 over the front contact of relay 823. Relay 824- locks over its outer left contact and the normal contacts of relays 812 and 8 to grounded conductor 352.

Since relay 823 locked over the back contact of relay 8l8 it is also operated when relay 825 releases at the end of the digit and a. circuit is closed from ground at the upper front contact of magnet 101, back contact of relay 825, left normal contacts of relays M2 and 8, right front contact of relay 824, outer left frontcontact of relay 823 to the winding of select magnet 6l6 which prepares the contacts of the No. 6 level of the register. Magnet 106 and relay 806 are operated under the control of magnet 616 and relay III to close cross-point 622.

In recording the tens digit '7, relays M8 to 822 are operated and released and

relays

823 and 824 operated and locked by the first six pulses as for the hundreds digit. The seventh pulse reoperates relay 8" over the back contacts of 9,106,880 lay 021. Since this is the 1m pulse of the digit,

relays 820 and 822. Relay 818 releases relay 823 and locks over the normal contacts of relays 820 to 823 as before. Since relay 824 locked inde-' pendently of the other counting relays it remains operated, and when relay 825 releases, the select magnet circuit extends over the right front contact of relay 824 and the outer left front contact of relay "9 to the winding of select magnet 811. Magnets 811 and 181 and relays 8H and -801 cooperate to operate and lock cross-point through the winding of relay 403 to battery. Thefunction of relay 403 will be described after.

When the ofllce code had been completely received, as indicated by the operation of magnet 104, the sender is ready to summon a decoder. For this purpose, magnet 104 closes a circuit from ground at its lower front contact, conductor 889, winding of relay 930, normal contact of relay 832, lower back contact of relay 833 to bathereintery. Relay 930 connects battery directly to conductor 940, and over the normal contact of relay 93l to conductor 84]. The decoder connector responds to this signal to connect the sender with the decoder over a large number of conductors as indicated.

Conductors

940, 941, 810 and 8", and 321 are control conductors. Conductors 322 to 324 and the conductors shown at the upper left corner of Fig. 6 are for transmitting to the decoder the code, subscriber class and frame identification which has previously been recorded in the sender. Conductors 944 to 948, 951 to 951 and 961 to 863 and the group shown on Fig. 10, are for receiving the decoded information from the decoder. The decoder and decoder connector function as described in the above identified Carpenter patent.

Since subscriber class relay 303 and frame tens relay 301 were operated, ground is connected to

conductors

323 and 324 to transmit this information to the decoder. With cross-points H2, H3,

620 and 1 I 5 closed in the dial register,

conductors

631, 032, 642, 653, 661 and 662 are grounded to transmit the units digit of the frame indication and the code designation to the decoder. It is to be noted that the ungrounded conductors are connected by the relay or cross-point to one of

conductors

625, 626 and 621. These conductors are used by the decoder in making a testof the continuity of all of the registering conductors each time that the decoder is used.

Assuming that the wanted number represents a subscribers line'in a panel type ofllce reached by direct trunks from the originating ofllce, after the decoder has completed its decoding operation, class relay 821 is operated. None of the ofllce register relays of Fig. 10 will be operated, but conductors 841 and 848 will be grounded by the decoder, operating the

skip offlce relays

831 and 938. Since short direct trunks are to be used, compensating resistance relays 903, 804 and 805 are operated. Since this call is to a' full me-' from the sender establishes a connection with the district frame and then connects ground to conductor 82I operating relay 90I. Relay 90I extends this ground over its left front contact to conductor 828 leading through the link switches to the district junctor where it operates a relay which in turn extends the lead through the district frame connector to another point in the decoder where another ground is applied to it. This second ground holds relay 80I operated after the direct connection with the decoder, by way of conductor 82f, has been broken.

Having closed this indirect hoiding'circuit for relay 80I, the decoder connects ground toJconductor 910, closing a circuit throughthe winding of relay 88I to battery at the inner upper front' contact of relay 990. Relay 99I locks to ground at its inner upper front contact and at its upper normal contact opens the ground connected to start conductor 9, thereby P rmitting the release of the decoder connector and in -turn of the decoder. At its lower front contact relay 98I connects ground to conductor 912 which supplies locking ground for the class and a part of the compensating resistance relays, for the offlce register relays of Fig. 10, and over the back contact of relay I I I1 for compensating resistance-

relays

908 and 901. In addition, ground over conductor 912 extends over the back contact of relay IIi to the right winding of relay I08 which operates and locks to conductor 912 independent of relay III. The closure of these lockingcircults is thus delayed so that the register relays may be released and set up in a different pattern if the decoder reroutes the call.

The selection of an outgoing trunk and the connection of the district junctor to that trunk take place under the control of the decoder, as described in the above identified Carpenter patent, and when these functions are completed the decoder removes the ground by which relay 90I was held operated. While relay 80I was operated it connected ground to conductor 888, front contact of, relay 931, conductor 914, winding of relay II06, conductor 918, to battery at the outer upper contact of relay 990. Relay H08 operates in this 'circuit and closes a locking circuit for itself through the winding of relay I II 8, outer lower front contact of relay H09, to ground at the upperback contact of relay IIII. Relay III8 does not operate, being shunted by the operating circuit of relay II08. When the decoder releases relay 90I, it is an indication that the connection has been completed as far as the outgoing trunk and that the sender may assume control of the further extension of the connection. Relay III8 then operates to close the fundamental circuit for trunk test.

When relay 930 operated. connecting battery to conductor 918 as above described, relay I2I9 operated from ground at the lower back contact of relay I2I 2; relay I2II operated from ground at the lower back contact of relay I2I0; relay I209 operated from ground at the outer upper back contact of relay I208 and relay I285 operated over the back contact of relay I282 from ground at the inner upper back contact of relay I208.

For a call to a panel type oflice, the trunk test circuit should not be closed until after the thousands digit has been registered and therefore, the operation of relay II08prepares a circult from battery, through the winding of relay I201, inner upper front contact of relay II08, conductor II22, fourth right contact of. relay 908,

conductor 888, lower back contact'of relay 808 to ground, holding relay I201 operated until relay 808 has been operated. With relay I201 operated,

-relay -90I, conductor 351, lower back contact of relay I208, upper fro'nt contact of relay I209,

conductor I240, outer upper from contact of relay I I08, conductor I'I20, inner upper back contact of relay 924, conductor 918, outer upper back contact of relay I208, winding of marginal trunk test relay I 200, conductor I 24I, lower front contact of relay 900, conductor 911, right back contact of relay 2l8, conductor 2I9, resistance 918,, outer upper back contact of relay 924, conductor 919, inner upper front contact of relay III8, conductor II2I,' front contact of relay 904, through resistances 9H and 9I0, front contact 'of relay 908, conductor 980, right back contact of relay 80I-to the fundamental ring conductor 829., f

Whenthis circuit is established and the trunk and incoming selector are ready, relay I200 operates, connecting ground over conductor I242 to the winding of relay 209 and battery. Relay 209 in turn closes a circuit from battery. through the winding of relay 208, left front contact of relay 209, outer left back contact of relay 2I8, conductor 220 to ground at the inner lower contact of relay I209. Relay 208 at its contact closes a holding circuit for relay 209 to ground at the left back contact of relay 809. Relay 209 also closes a circuit from battery at the outer upper contact of relay 990, conductor 915, winding of relay I222, windings of relays I220 and I22I in parallel, conductor I248, inner lower back contact of relay 924, conductor 981, inner lower front contact of relay H08, conductor H28, inner right front contact of relay 209, conductor 22I, back contact of relay I209, conductor I244 to ground at theouter right front contact of relay 8I8. Relays I220, I22I'and I222 look over the front contact of relay I222 to ground at the outer lower contact'of relay I209. Relay I22I in operating closes a circuit from battery on conductor 918, winding of relay IIOI, lower back contacts of relays IIII, III2, III8, III4 and III8, back contact of relay I204, inner. upper back contact of relay I2I0, front contact of relay I22I to ground over conductor I244. Relay'l IOI closes a locking circuit for itself through the winding of relay IIII, lower front contact of relay |IOI, to ground at the upper back contact of relay III2, but relay I III does not operate, being shunted by the operating circuit of relay IIOI. Relay Il0l closes a circuit from battery through the winding of relay I208, upper front contact of relay IIOI, outer upper front con- ,tact of relay III6,-to ground at the'upper back contact of relay III9. Relay I208 opens the circuit of relay I209 which releases, opening thewhich releases relay 209. At its outer lower contact relay I209 opens the locking circuit of relays I220, I22I and I222 releasing them.

The release of relay I22I permits relay IIII to operate in the locking circuit of relay II M. Re-

lay II II in operating opens the locking circuit of relays H06 and III6 and these relays release. When relay III6 opens its outer upper front contact relay I208 releases, permitting relay I209 to reoperate. Relay IIII also closes a circuit from ground at its inner lower front contact through the winding of relay I206 to battery over conductor 915. Relay I206 locks to ground on its upper front contact and closes an obvious circuit for relay I205. These relays prepare the sender for incoming and final selections.

With relays I 209 and I205 operated, the fundamental circuit is closed for incoming brush selec-' tlon and extends from the fundamental tip conductor 328 to the upper front contact ofrelay I209 as previously traced and thence through the lower winding of polarized relay I203, winding of stepping relay I202, back contact of relay I220, outer upper front contact of relay I205, conductor II2I and thence to the fundamental ring conductor 329 as before.

Relay I202 operates in series with the selector relay, but the current flow is not in the direction to operate polarized relay I203. In addition the winding of relay I203 is shunted by a circuit over conductor I240, upper back contact of relay II06, conductor H24 and resistance I246.

The counting relay circuit for incoming brush selection, closed by relay I202 extends from ground over the contact of relay I202, front contact of relay I2II, back contacts of relays I233 and I223, conductor I248, inner upper front contact of relay IIII, over conductor II25 to the first left contacts of the thousands vertical of the dial register 600, over the contactclosed at cross-point 62I, conductor 612, back contact of relay I225, winding of relay I226, to battery over conductor 915. Relay I226 operates, looking through the winding of relay i225, front contact of relay I226, back contact of relay I234 to ground at the inner lower contact of relay I209, but relay I225 does not operate.

When the selector at the terminating ofilce sends back the first revertive pulse by shunting the sender relay, stepping relay I202 releases permitting relay I225 to operate and transfer the counting relay circuit over the front contacts of relays I225 and I 235 to the winding of relay I224 and battery over conductor 915. When the revertive pulse ends and relay I202 reoperates, relay I224 operates and looks through the winding of relay I223 to ground at the outer lower contact of relay I209. The second revertive pulse permits relay I223to operate. The counting relay circuit then extends as traced to the back contact of relay I233, front contact of relay I223, conductor 610, middle lower front contact of relay I205, conductor I241, outermost right contact of relay 306, conductor 359, lower back contacts of relays H05 and H04, conductor H26, winding of relay I222 and to battery over conductor 915. Relay I222 locks through the windings of relays I220 and I22I in parallel, front contact of relay I 222 to ground at the outer lower contact of relay I209. When relay I202 releases in response to the third revertive pulse, relays I220 and I22I operate.

Relay I220 opens the fundamental circuit to terminate the brush selecting operation of the incoming selector. Relay I22I closes a circuit from grounded conductor I244, front contact of relay I22 I, inner upper back contact of relay I2 I0, lower back contact of relay I204, lower back contacts of relays III5, III4, III3 and III2, outer lower front contact of relay IIII, winding of relay II02 to battery on conductor 915. Relay II02 looks through the winding of relay III2, lower front contact of relay I I02, to ground at the upper back contact of relay III3. Relay II02 also closes a circuit from ground at the outer upper front contact of relay I I I I, conductor I I21, upper front contact of relay II02, winding of relay I208 and battery. Relay I208 releases relay I209 and these relays further open the fundamental circuit.'. Relay I209 also opens the locking circuits for the counting relays, which thereupon release. The release of relay I22I permits relay III2 to operate in the locking circuit of relay H02. of relays HM and II II and these sequence relays release. Relay II02 prepares an additional circuit for relay I208 which extends from conductor II21 over the middle right back contact of relay 308, conductor 360, back contact of reinner upper front contact of relay III2, conductor II28, to the left row of contacts of the hundreds vertical, over. the contact closed at crosspoint 622, conductor 680, third left contact closed at cross-point 62I, conductor 613, back contact of relay I221, winding of relay I228 to battery on conductor 915. Relays I228and I221 respond to the first revertive impulse while relays I226 to I220 respond to the next three impulses in the same manner as for incoming brush selection.

When relays I220, I22I and I222 operate, the fundamental circuit is opened as previously described. Since relay III2 is now operated, relay I22I operates relay II03 which in turn looks through the winding of relay III3 to ground at the back contact of relay II I4. Relay II03 closes a circuit from ground at the upper front contact of relay III2, lower front contact of relay II03, to the winding of relay I201 and battery.

Relay I201 in turn operates relay I209 which releases relay I209, thereby releasing the counting relays and permitting relay III3 to operate. With relay III3 operated, relays H02 and III2 release in turn releasing relays I201 and I208 and reoperating relay I209 to establish the circuits for final brush selection.

For this selection, the counting relay circuit extends to conductor I248 as before, over the inner upper front contact of relay III3, conductor II29, second left contacts of the hundreds vertical, contact closed at cross-point 622, conductor 6", front contact of relay I235, winding of relay I224 to battery on conductor 915. Relays I220 to I224 function as previously described in response to two revertive pulses.

Relay I220 opens the fundamental circuit to stop the final selector. Relay I22I operates relay II 04 which looks through the winding of relay III4 to ground at the upper back contact of relay III6. Relay II04 operates relay I208 Relay III2 opens the locking circuit pulse, therefore, operates relays I234 and I233,-

aioaaeo which releases relay I209 to further open the fundamental circuit and release the counting relays. With relay I22I released, relay-I I I4 operates, releasing relays H03 and III3. A-further holding circuit for relay I208 may be traced from the outer upper front contact of relay II04, inner lower front contact of relay I205, conductor I249, second right contact of relay 308, conductor 36I, lower back contact of relay 801 to ground. Therefore, the circuit for final tens selection cannot be established until the tens digit has been recorded.

When the fundamental circuit is reclosed for this selection, relay I202 reoperates closing the counting relay circuit which extends as previously traced to conductor I248, inner upper front contact of relay III4, middle upper front contact of relay I205, conductor I250, to the left contacts of the tens vertical, contact closed 'at cross-point 623, conductor 812, back contact of relay I225, winding of relay I226 to battery on conductor 915. The first two revertive pulses operate relays I228, I225, I224 and I223. Relay I223 extends the counting relay circuit over its front contact, conductor 610, middle lower front contact of relay I205, conductor I241, outermost right contact of relay 308, conductor 359, lower back contact of relay I I05, lower front contact of relay II04, conductor II30, second left row of contacts of the tens vertical, contact closed at cross-point 623, conductor 616, winding of relay I234 to battery on conductor 915. The third and locks them to ground at the inner lower contact of relay I209. Thereupon the counting relay circuit is extended over the front contact of relay I 233 to the back contact of relay I23I and the winding of relay I232. In addition, the operation of relay I234 opens the locking circuits of relays I225 and I226 and these relays release. The, next pulse operates relays I 232 and I 23I which lock to ground at the inner upper contact of relay I208. Relay I232 opensthe circuit of relay I 235 which releases. The next three pulses operate relays I 230 to I225, inclusive, and since relay I235 is released, relay I225 extends the counting relay circuit over its front contact and the upper back contact of relay I235 to the winding of relay I222. The eighth revertive pulse operates relays I 220 and I 22I in the locking circuit of relay I222, terminating the tens selection.

Relay I22I operates relay H05, which locks through the winding of relay III 5, inner lower front contact of relay II05, upper back contact of relay III6, to ground at the upper back contact of relay III3. Relay II operates relay I201 which in turn operates relay I208, releasing relay I209 and the counting relays. The release of relay I22I permits relay II l5 to operate and release relays H04 and III4; Relay I201 is held operated after relay III4 releases over the inner upper front contact of relay I205, conductor I25I, outer left back contact of relay 308, conductor 362, outer lower back contact of relay 924, conductor 98I, lower back contact of relay 809 to ground if registrations have not been completed.

It will be remembered that magnet 108 in operating operated relay 403, and that the decoder operated delay relays 934 and 935, indicating that neither five digit numbers nor stations letters were to be expected. Therefore, as soon as relay 403 operated, a circuit was closed from battery through the windings of relays 509 and 5I9 in series, over the upper front contact of relay 934,

ductor ms, to the windings of relays I220 conductor 982, fourth left contact closed at crosspoint 62I, conductor 88I, inner left front contact of relay 403, conductor 4I4, outer lower back contact of relay 92I, outer upper front contact of relay 93I to grounded conductor I244. Relays 509 and 5I9 lock over the outer lower front contact of relay 509 to grounded conductor I244 and close a circuit from battery through the winding of relay 809, conductor 83 I, inner lower front contact-of relay 509 to ground. Therefore, relay 809 operates to permit the closure of the fundamental circuit for final units selection'as soon as the units digit is registered. Relay 809 also removes the ground from.conductor 352 to prevent false regis tration in case of belated dialing or switchhook manipulation.

The counting relay circuit for final units selec-' tion extendsto conductor I248, inner upper front contact of relay III5, outer lower front contact of relay I205; conductor I252, left contacts of the units vertical, contact closed at cross-point 624, conductor 613 back contact of relay I221, winding of relay I228 to battery. Relays I228 to I223 are operated under the control of the first three revertive pulses. Relay I223 extends the counting relaycircuit as traced for finaltens selection to conductor 359, over the outer lower front contact of relay II05, conductor II3I, second left contact of the units vertical closed at cross-point 624, to conductor 816. The following six pulses operate relays I234 to I225, and relays I222, .I22I, and I220 as previously described.

Relay I22 I, when operated, closes a circuit from grounded conductor I244, front contact of relay I22I, inner upper back contact of relay I2I0,

lower back contact of relay I204, outer lower front contact of relay I I I5, conductor 913, front contact of relay 938, conductor 914, winding of relay II06 to battery on conductor 915. Relay 06- operates and closes a circuit for relay I201 over its inner upper front contact, lower back contact of relay II03 to ground at the outer upper front contact of relay II I5. Relay I201 operates relay I208, releasing relay I209 and the counting relays, thereby permitting the operation of relay- III6 in the locking circuit of relay II06, releasing-- relays II05, II I5, I201 and I208 and reoperating relay I209.

When relay I208 releases and relay I209 reoperates to reclose the fundamental circuit, the incoming selector at the terminating ofiice transmits a single long pulse of reversed battery over the fundamental circuit to the sender. Relays I202 and I203 are both operated in responseto the reversed battery. Relayl203 looks over its upper front contact to grounded conductor I244.

It also extends this locking ground over the lowerfront contacts of relays III6 and I206 to the winding of relay I204 and battery. With relay I204 operated, the operation of relay I202 closes a circuit from ground over the front contact of relay I202, front contact of relay I2II, outer" of relay I209. Slightly after the closure of the circuit ofrelay I222, relay I204 closes a circuit from groundatthe upper back contact of relay I2I2, inner upper contact of relay I204,,conductor I253, outer'upper, contact of relay '90 nand I222. The purpose of this circuit is to insure the operation of these relays in case the reverse battery impulse is too short to permit relay I222 to operate in the manner above described. It is also carried over the contact ofrelay 905 so as to be ineffective for calls over long trunks where relay I202 may operate late.

At an interval following the reverse battery pulse from the incoming selector, direct battery is connected to the trunk and the selector awaits ink closure by the district junctor. The removal of the reverse battery releases relay i202 permitting relays I220 and I22I to operate. Relay I220 opens the fundamental circuit in the sender to prevent a false trunk closure signal. Relay I22l closes a circuit from ground on conductor I244, front contact of relay I22I, inner upper back contact of relay I2I0, lower front contact of relay I204, conductor I294, winding of relay 909 to battery. Relay 309 locks over its left contact to grounded conductor 393, marking the completion of the sender's function on the call.

Relay 309 at its inner right contact closes a shunt around resistance 305, thereby operating a marginal relay in the district junctor, which establishes the talking circuit and holding circuits for the line switches, district and office switches.

Relay 309 also disconnects ground at its inner .right back contact from the armature of relay 3I0, thereby releasing relays 9I4, 9I5, 3I4 and 3I3. Relay 3I4 disconnects ground from conductor II4. With relay 309 operated and relay 3I3 released, relay 3I9 also releases, opening the link in the senders-busy chain, disconnecting ground from conductors 393 and I244, thus removing the off-normal grounds and releasing the locked relays of the sender. It likewise reconnects the idle battery to the fourth lower contact of,relay 3. Furthermore, it disconnects ground from conductor 390 and the lowermost contact of relay 3| I. The disconnection of ground from conductor 390 releases the sender link switches and so disconnects the sender from the district junctor.

Call to cross-bar omce This type of call diilers from the call to a panel type oflice in only a few minor details since the incoming sender in a cross-bar oiilce transmits simulated revertive pulses, which cause the subscriber's sender to function in the same manner as do the selectors of the panel office. For a call to a cross-bar oflice, class relays 92l and 923 are operated. Relay 909 is not operated and therefore the trunk test employs relay I20I instead of relay I200.

The call also diifers in that trunk test may not be made until the hundreds digit has been recorded. It will be remembered that relays H09 and I I I9 are operated for trunk test. With class relays MI and 923 operated the operation of relay I I09 closes a circuit from battery through the' 'when relay 93I operates. on the release of the decoder, from grounded conductor I244, outer 2,1os,sso

upper front contact of relay 93 I, outer lower front contact of relay 92I, windings of relays i 3 and 003 in series to battery. With these relays operated an additional holding circuit exists for relay I20'I extending from conductor 399 over the left front contact of relay 929, which is held operated between digits, conductor 932, inner lower. front contact of relay 92 I, outer lower contact of relay 923, conductor 4, outer lower contact of relay 903, outer upper front contact of relay 93I to grounded conductor I244. The trunk test circuit, therefore, cannot be established until after the first pulse of the tens digit has been received to operate relay 929 and release relay 929.

Call through tandem ofllce In tracing the operation of the sender in controlling the completion of a call through a tandem oflice, it will be assumed that the call originates at a substation equipped with a coin box, that the wanted ofllce is reached through two distant omce selectors, that the wanted oillce employs party line designations and five-digit numbers between 10,000 and 10,499 and that Walker 5-1078 is the number of the wanted subscriber.

The seizure of the sender results in the operation of relays 3H and 3I2, whereupon the frame relay and the subscriber class relay are operated. Frame relay 399 and class relay 309 may be assumed to be operated. When the tip and ring conductors are completed through the line and link switches relay 3I0 operates, in turn operating relays 9I4, 3I4, 3I3 and 9I9. Relay 3I0 is operated over conductor 339 and locks under the control of relay 3I3. Relay 3II releases the link control circuit, 'holds' the link and line switches and releases relay 3I2, relay 3 being released by the link. The units digit of the district frame is recorded as previously described, and assuming it to be thesame as before, results in the closure of cross-point H2 and the operation and locking of magnet "I and relay "I and the operation of relay 929.

The recording of the wanted number takes I place in the manner previously described, resulting in the closure of cross-points 990, N9, 09l, H1, H9, 923, 924 and 992 accompanied by the operation and locking of magnets "I to I09 and H0 and relays "I to 909, inclusive. Relays 409 and 403 are operated by magnets H0 and 109, respectively. The seizure of a decoder and the transfer of the recorded information also take place as previously described.

Under the conditions assumed. the decoder grounds certain conductors 'so that neither of t the stations delay relays 934 and 939 are operated; compensating resistance relays 902, 903 and 901 may be operated, but relay 900 is not operated, being used only with calls to panel omces. Class relay 922 is used for this type of call. Relay 939 is operated but relays 931 and 939 are not operated. For controlling selections by the distant omce selectors, relays IO0I, IOI3, I022, I03I, I032 and I094 may be operated. These relays look under the control of relay 93I with the exception of relay 901' which is further controlled by relay III'I. With class relay 922 operated, relay 924 operates over the lower front contact of relay 922 and grounded conductor 912.

Since the stations delay relays indicate that a fifth digit may be expected, but none is actually dialed, the operation of relay 909 to indicate that dialing has been completed is delayed. When relay "I is operated by the release signal from the decoder, a circuit is closed from grounded