US1801301A - Telephone system - Google Patents

Description

April 21, 1931. c. E. BEALE 1,301,301

TELEPHONE SYSTEM Filed April 22, 1929 4 Sheets-Sheet 1 Iii-aim Charles Edmund Eialb 8 Q h NN o m P m ,w QT w a N M Mn 8 w I m w L m n x mu 7 v Em5 1llll| 3? il V a 3 J gm Mm wv Q|W|- Mm ll. g a h I. .2 mm mm at. ZN UN W.

April 21, 1931. c. E. BEALE 1,801,301

TELEPHONE SYSTEM Filed April '22, 1929 4 Sheets-Sheet 2 A? HERZA.

@ g Irwin-5* $15 EZ'LIF'ZE! Edmund Baal: Q

AprilZl, 1931.. 5 A E 1,801,301

TELEPHONE SYSTEM Filed April 22, 1929 4 Sheets-Sheet 3 Inn-11hr Eh r155 Edmund EEEZE 1 1 DE LAY ED 1135 M April 21, 1931.

Filed April 22, 1929 C. E. BEALE TELEPHONE SYSTEM co oa,

4 Sheets-Sheet 4 harlas Edmund Banzai Patented Apr. 21, 1931 UNITED STATES PATENT OFFICE CHARLES EDMUND BEALE, OF LONDON, ENGLAND, ASSIGNOR TO ASSOCIATED TELE- PHONE AND TELEGRAPH COMPANY, OF CHICAGO, ILLINOIS, A CORPORATION OF- DELAWARE TELEPHONE SYSTEM Application filed April 22, 1929, Serial No. 356,952, and in Great Britain June 27, 1928.

The present invention relates to telephone systems and is more particularly concerned with final selector switches for use in such systems.

i The object of the invention is to provide circuits for all classes of final selectors which shall be more efficient than those hitherto employed, having particular regard to the conditions of heavy traffic and other factors met with in modern automatic and semiautomatic telephone networks. These improvements have been attained without increasing the number of relays usually employed and without the use of special con tacts actuated by the switch mechanism other than the oif-normal and cam spring contacts generally in use.

According to one feature of the invention, the ringing relay is made more efficient by reducing its spring combination to a minimiun. Further, the application of ringing to a called line is sufliciently delayed to ensure the operation of the cut-off relay and thus prevent premature tripping of the ringing. A feature of the circuits in this connection is the arrangement of the rotary shunt relay which also controls the application of ringing current and which is also re-operated in circuit with the ringing relay to complete the speaking circuit when the called party replies.

According to another feature of the invention, the supervisory relay of the called party is disconnected from the lines whilst impulses are being transmitted to the switch in order to prevent any possibility of the speaking condensers adversely affecting the impulse accepting relay by reason of discharges and also in order to prevent any possibility of the operation of said relay in such circumstances.

A further feature of the invention consists of the guarding of the switch till a normal position is reached. The release trunk circuit is arranged to be opened momentarily on the release of the calling party to allow other switches in the connection to restore, and thereafter is immediately re-guarded till the normal position is reached. This is efiected by allowing the relay which normally operates when a busy line is reached, to re-operate in circuit with the release magnet.

In order that the invention may be better understood, and more readily carried into effect, a detailed description will now be given of methods of applying these features, reference being had to the attached drawings. It will be understood however, that this is given by way of example only and that various modifications may be made in the circuit details by those skilled in the art without departing from the spirit of the invention.

Referring now to the accompanying drawings, Fig. 1 shows a regular final selector circuit; Fig. 2 a circuit suitable for P. B. X. subscribers having from 2 to 10 lines in their group; Fig. 2A a typical testing bank arrangement for connectors such as that shown in Fig. 2; Fig. 3 a circuit for P. B. X. subscribers having groups of from 11 to 20 lines and Fig. 4 provides similar facilities for large groups of lines to P. B. X. subscribers. Referring now particularly to Figure 1, when the switch is seized over conductors 12 and 13, impulse accepting relay A will operate over the circuit: earth, back contact and armature 10, lower winding of relay A, springs controlled by armature 11, conductor 12, callingloop, conductor 13, springs controlled by armature 14, upper winding of relay A to battery. Relay A operates and closes the circuit of guard relay B at the front of armature 15. Guard relay B operates and earths the release trunk conductor 15 to guard the switch at armature 16; at armature 17 short circuits the lower winding of relay E to make that relay slow releasing; at armature 18 prepares a holding circuit for the switching, ringing or busy relays and operates relay C via oil normal contacts 19; and at armature 20 prepares the impulsing circuit to the magnets.

The operation of relay C removes earth from the lower winding of relay D at armature 21 so that this relay does not adversely affect the impulses by causing the speech condensers to charge and discharge and at the same time the possibility of this relay operating during the transmission of impulses to till -' ture 25 the switch is completely avoided. At the front contact of armature 22 relay C short circuits its upper winding to make it slow to release; at armature 23 a circuit for the busy relay G is prepared; while at armature 24ia holding circuit for itself is prepared so that relay C will remain in the operated position during impulsing of the vertical series, when the off-normal springs are operated. When the calling subscriber dials the next digit of the wanted subscribers numb r, or alternatively when the register controller forwards the necessary impulses, relay A will impulse in synchronism and at each restoration will complete circuit: earth, armature and back contact, armature 2O and'front contact, armature 24; and front contact, armature 25 and back contact, vertical magnet V to battery. The] vertical magnet operates and raisesthe wipers one step each time it operates. On the first vertical step the off normal springs close, thus making circuit of relay C now dependent on the impulsing circuit. during the impulsing-due to their slow release feature. V] hen the impulse series is completed the wipers will be opposite the required level and relay C will rel-ease following its slow-to-release pause. Belay E thereupon operates over the circuit: earth, front contact and armature '18, off-normal springs 26, armature 2'2' and back contact, back contact and armature 22, upper winding of relay E to battery; relay E operates and at arma the impulsing circuit is now transferred to the rotary magnet R. At armature 28 relay E closes a locking circuit for itself which is independent of relay C. When the next impulse series is received, relay A will impulse as before and the rotary'magnet R will be operated over the circuit: earth, armature 15 and backcontact, armature and front contact, armature29 and back contact,

armature is and back contact, armature and front contact to the magnet R. A parallel circuit also extends from theback contact of armature e'land off-normal springs to relay C which operates and renders itself slow-to-release at armature 22 and at armacalled subscribers cut-0E relay (not shown) to battery.

Relay H operates and closes a locking circuit foritself at its armature 32 and at the the holding Relays B and C hold up.

stores and at the back contacts of armatures 35 and 36 the ringing circuit is completed. This ringing circuit may be traced from ringing currenton conductor 37, upper winding of ringing trip relay F, back contact and armature-35, armature 33 and front contact, line-wiper 38, called subscribers line, subscribers bell and condenser in series, line wiper 39, front contact and armature 34, armature 33 and back contact, resistance 40 to battery. I 1

Under these conditions the ringing relay F does not operate, and'the wanted subscriber will be signalled. It will have been noticedthat the application of ringing current to the wanted subscribers lines is slightly delayed after the switching of relay H due to the releasing time of relay E and therefore there is no possibility of premature operation of relay F, as the wanted subscribers cut-off relay is given ample time to operate and dis connect the line relay. An indication to the calling subscriber that ringing current is being applied is alforded by means of the leak condenser 41 which is connected between the outgoing line and the calling circuit by armature'4c2. 1

As soon as the called subscriber removes his receiver to reply to the call he places a direct current path across his loop and relay F thereupon operates and at armature 43 provides a holding circuit for itself from earth at armature 18 in series with the upper winding of relay E. Relay E alsooperates in this circuit and completes the talking circuit between the two subscribers at the-front contacts of arinatures 35 and 36. Back bridge relay D now operates over the called subscribers loopand at armatures 14 and 11 causes the direction of current flow to the calling circuit from relay A to be reversed. This reversal is used for metering and signalling purposes. Conversation may now take place. t may be noted that the further operation of the calling subscribers calling device or a momentary operation of the switchhook is'rendered ineffective to step the switchby the opening of the impulsing circuit at armature 4L4.

At the conclusion of conversation the release of the switch takes place when the calling subscriber replaces his receiver. Relay A thereupon restores and at armature 15 opens the circuit of relay B which after its slow-to-release period also restores. The

locking circuit of relays H, F and E is now opened at armature l8 and these relays release; also at armature 16 earth is removed from the release trunk conductor 45 allowing the other switches in the connection to be released. A circuit is also completed from earth,armature 15 and back contact, armature 20 and back contact, off-normal springs 64, release magnet RM and lower winding of relay G in parallel, to battery. The release magnet RM operates and causes the restoration of the wipers to normal in known manner while the operation of relay G closes a circuit at armature 46 for the re-guarding of the release trunk. This circuit is from earth, front contact and armature 46, back contact and armature 47 to the release trunk conductor 45. l/Vhen the switch is in its normal position off-normal springs 64 open allowing the deenerigization of the release magnet and relay G thus removing the guarding earth. The switch may now be taken into use for other calls.

It will have been noticed that when the switch is released the release trunk conductor circuit is momentarily opened after relay B restores and before relay E restores and relay G operates. This period is long enough to allow other circuits to restore and the release trunk is then re-guarded till the switch has restored to normal. This arrangement prevents the switch being taken into use during heavy trafiic periods by another calling switch whilst it is restoring to normal without unnecessarily holding other apparatus.

If the called partly replaces his receiver before the calling party a delayed alarm circuit is closed, and becomes operable after a pre-determined time interval if the calling subscriber fails to replace his receiver. This alarm circuit is from battery through the lamp 52, front contact and armature 48, front contact and armature 49, back contact and armature 50 of relay D, which restored when the called subscriber replaced his receiver, conductor 51 to the delayed alarm arrangements. The glowing of the lamp 52 indicates to the maintenance oflicer which switch is being held so that if necessary-he can effect the release of the connection.

The operation of the switch if the desired subscriber is found busy willnow be considered. In this case, as soon as the wipers reach the correct contacts the test'wiper 31 will encounter earth andthis will cause the operation of busy relay G via armature 23 and front contact before relay O releases. When relay C restores, relay G remains locked via the springs controlled by armature 23, front contact and armature 30 to earth at armature 18. Switching relay H is unable to operate because its circuit is opened at the back contact of armature 30, and relay E therefore remains energized. At

armature 10 of relay G, earth is removed from the lower winding of relay A and busy flash and tone are substituted, from conductor 53, armature S 1 and front contact, back contact and armature 55, front contact and armature 10, in order to provide a lamp signal in an originating ofiice as well as a tone, this busy signal may consist of alternate battery and earth periods, the tone being also on during one of these periods. During the battery period, when relay A will restore, battery is also connected to conductor 56 and guard relay B is held from earth, back contact of armature 15, armature 20 and front contact, armature 29 and front contact, upper winding of relay B to battery connected to conductor 56.

The calling subscriber hearing the tone or alternatively the operator seeing the lamp flash if the call is through a manual office, will release thereby allowing relay A to restore and relay B then releases and is followed by relays E and G. The release of the switch then takes place as previously described. If the subscriber hangs up his re ceiver or if the operator releases, during the battery period of the busy signal relay B remains held till the conclusion of the period when the release then takes place. This arrangement prevents unguarded periods on junctions if the call has passed through several exchanges.

Referring now particularly to Fig. 2, when the switch is seized by the preceding switch, impulse accepting relay A operates over a circuit similar to that previously described and at armature 10 extends earth to operate the guard relay B. The operation of guard relay B earths the release trunk conductor at armature 11 to guard the circuit, while at armature 13 it extends earth to operate relay C and further prepares the impulsing circuit to the magnets at armature 14:. Relay C upon operating removes earth from the lower winding of relay D at armature 15, to prevent that relay from interfering with the impulsing and prepares various circuits which will be more readily obvious as the description proceeds. Among these relay C prepares a circuit from the test wiper 23 to the busy relay G at armature 16 via the resistance 17 and at armature 18 disconnects the circuits to relay E and short circuits its own lower winding thereby rendering it slow-to-release.

When the calling subscriber proceeds to dial the next digit of the desired subscribers number, relay A will impulse in synchronism, whereat earth impulses are connected to the vertical magnet thus causing the shaft and wipers to be raised to the predetermined level. It will be noticed that relays B and C hold up during impulsing due to their slow releasing features. At the completion of the vertical train of impulses, relay C will release after its slow period so that the following circuit is now completed to relay earth, armature. 13 of relay B, operated olfnormal springs 19, back contacts of armaiures 20 and 18, lower winding of relay E to battery.

Relay .E thereupon operates and at its armature 21 provides a locking circuit for itself which is independent of relay C; at armature 22 the impulsing circuit is transferred to the rotary magnet R. l Vhen the next series of impulses is received, relay A will again impulse as before and the rotary magnet and relay C will nowbe operated in parallel, whereupon the wipers to be stopped round to the first contact of the group dialled. It will be noticed that do the period that the wipers are stepping round the bank, a circuit is prepared to relay G at armature 16 of relay C, as previously described, and should the private wiper 23 encounter earth while passing over busy connections, the limitation of current in the circuit due to the comparatively high value of resistance 1? causes relay G to make its armature 24 only, the operation of which is in effective at this stage.

At the conclusion of the impulse series, the Wipers will be resting on the first line in the group dialled. and should this be busy, test wiper 23 will encounter earth, and wiper 25 will encounter battery connected through a resistance, so that it will be seen when relay C releases at the completion of the rotary series of impulses, the resistance 17 is short circuited at armature 26, thus enabling relay G to fully operate over the circuit: earth at armature 13 of relay B, light armature 24, resting contacts of armatures 16- and 26, upper winding of'relay G to battery. A typical view of the testing bank arrangement referred to, is shown in detail at the bottom left hand corner of the figure. The hunting start relay HS will now be energized from earth at wiper 23, armature 16 and back contact, armature 27 and front contact, upper winding of relay HS, armature 28, wiper 25, resistance similar to 38 to battery, after which a locking circuit is provided over the path: earth at armature 13 of relay B, armature 29, interrupter springs 30, lower winding of relay HS to battery. The operationof relayHS also completes a circuit to the rotary magnet R from earth at armature 13 of relay B, armatures 31 and 22, winding of the rotary magnet R to batter, and parallel there-- to over the operated elf-normal springs 19, upper winding of relay C to battery. Both relay C and the rotary magnet H are therefore operated in parallel, and as soon as the rotary interrupter springs 30 break, the circuit of the lower winding of relay HS is disconnected causing it to release, and in turn breaks the circuit to the rotary magnet R and relay 0 at armature 31, so that the wipers will be moved on to the next set of contacts. It will be appreciated that relay C will not release immediatelyits circuit is disconnected, due to IiLS slow releasing feature, and should this next set of contacts test busy, earth will be encountered on wiper 23 and via the strapped testing bank contacts to wiper 25 so that a circuit is thus connected for relay HS from earth at wiper 25, armature 28, upper winding of relay HS, armature 32, interrupter springs '30, lower winding of relay H to battery. The hunting start relay HS is therefore operated over both, windings in series and the rotary inagnet and relay C are again energized over the circuit previously described. This cycle of operations will continue so long as the wipers 23 and 25 encounter busy, contacts, and the'wipers will accordingly step from contact to contact until afree trunk is found.

lnthe event of all the lines testing busy, the switch wipers will eventually reach the last contacts in the group, which it will be noted are not strapped, whereupon wiper 23 only will encounter earth, and it will be appreciated that relay HS will not re-operate and the circuit to relay C is now definitely opened. After a-short pause relay C will release and at armature 16 the locking circuit to relay C will again be transferred to earth at armature 13 of relay B; The so-called busy flash and hold circuits thereby eX- tended over conductors 36 and 37 on relay B and function in similar manner to that described more fully in connection with Figure 1. Assuming however, that a free trunk is encountered in the particular group dialled, wipers 25 and 23 will encounter battery via the cut-off relay of the line selected. Corr sequently, relay -HS will not re-operate and relay G which has been holding from the earth on wiper 23 also releases, so that upon the release of relay C after its slow period a circuit may now betraced for relay H from earth at armature13 of relay B,upper winding of switching relay H, back contacts of armatures 2? and 16, wiper 23, to battery via the winding of the cut-off relay. Relay H operates over the circuit described and closes a locking circuit for itself at its armature 33 to earth at armature 13, and also connects a direct earth at armature 20 to wiper 23 to ensure the full operation of the cut-off relay and to mark the selected line busy. The cirare cuit to the slow releasing relay E is also opened at armature 20 of relay H, so that after a short pause relay E releases and ringing current is thereby connected to the called subscribers line substantially as described in connection with Fig. 1.

When the called subscriber removes his receiver to answer the signal his line is looped and the ringing relay F operates in known manner, thus completing a circuit for its lower locking winding in series with the Lil lower Winding of relay E. The operation of relay E, at this stage disconnects the ringing feed and causes the speaking connection between the two subscribers to be completed at the front contacts of armatures 34 and 35, while the called subscribers loop closes a circuit for the back bridge relay D which operates and reverses the. direction of current flow in the calling loop for metering or supervisory purposes.

It will be appreciated by those familiar with the art, that the supervision and release of the connection is substantially as described in connection with Figure 1. 7

Referring now particularly to Fig. 3, when the connector is selected by apreceding switch, the impulse accepting relay A operates in known manner and at armature 10 extends earth to operate the guard relay B. The operation of guard relay B connects earth to the release trunk conductor 12 at armature 11 to guard the switch, while at armature 13 earth is extended to relay C by way of resting contacts of off-normal springs 14, upper winding of relay C to battery and also to relay E via' armatures 15 and 16 winding of relay E to battery. The operation of relay E controls the extension of ringing at its armatures 17 and 18, while relay G prepares a holding circuit for itself at armature 19 and also connects both windings of shunt fifeld relay G in parallel over the circuit earth at armature 20 of relay B, armature 22 and front contact, armature 23 and front contact, left hand winding of relay.

G, interrupter springs 24 of rotary magnet R to battery and via armature 22 and front con-tact, right hand winding of relay G, interrupter springs 24 to battery. Relay G operates and prepares a circuit for the initial rotary kick when relay C releases. When the calling subscriber proceeds to dial the next digit of the desired number, relay A will impulse as previously explained and the first impulse will follow the path, earth at armature 10 of relay A, operated armatures 25 and 19, winding of vertical magnet V to battery, so that the shaft and wipers will be raised one step and the off-normalsprings 14 will be operated, thereby causing the initial energizing circuit of relay C to be disconnected, thisrelay however does not release immediately'du'e to its slow-to-release feature and when the next impulse is transmitted the following parallel path may be traced to relay C, earth at armature 10, armatures 25 and 19, operated off-normal springs 14, upper winding of relay C to battery. Consequently, relay C will be heldoperated during the remainder of the vertical impulses, and when the wipers of the switch finally arrive opposite the level dialled, relay C will release after a short pause, thereupon operating the rotary magnet over the circuit:

earth at armature 20, armature 22 and back contact, front contact and armature 26, winding of rotary magnet R- to battery. It will be appreciated therefore that the wipers of the switch will be moved on to the first set of contacts and the circuit of both windings of relay G will be opened at the rotary interrupter springs 24. Assuming now that the first set of bank contacts test busy, wipers 27 and 28 will both encounter earth so that relay G will re-operate via both its windings in parallel over the circuit: earth, wiper 27, back contacts of armatures 29 and 30, right hand winding of relay G interrupter springs 24, to battery and earth, wiper 28, armatures 31 and 32, resting contacts of cam springs 33, left hand coil of relay Gr interrupter springs 24, to battery. Accordingly, the shunt field relay G operates and locks up over its armatures 34 and 35 to earth at armature 20, whereupon the wipers will be moved on to the next set of contacts by a similar circuit arrangement to that already described.

It should be mentioned that armatures 34 and 35, besides completing a locking circuit for relay G, also short circuit the windings of the switching relays HA and HB until the correct time arrives. This short circuit may be traced from earth at armature 20, ar matures 34 and 35, through the windings of relays HA and HB and armatures .36 and 37 respectively, operated contacts of off-normal springs 14, resting contacts of cam springs 33 and back to earth at armature 20. Assuming now that testing wiper 28 encounters a free trunk, the busy earth previously mentioned will be replaced by battery via the cut-off relay of the called subscriber, so that the circuit is only completed for the right hand winding of relay G, and as is well known to those skilled in the art, the magnetic flux produced in the right hand coil of shunt field relay G will now pass through the closed iron circuit provided by the core of the deenergized left hand winding, thereby diverting the operating power of the relay so that it becomes in-operative. The short circuiting earth is accordingly removed from the winding of relay HA at armature 34 of the relay G and the following operating circuit is completed earth at armature 20, resting contacts of cam springs 33, operated contacts of off-normal springs 14, armature 36, winding of relay HA, left hand winding of relay G, interrupter springs 24 to battery. The operation of relay HA completes various circuit functions, among which is the connection of a direct earth to wiper 28 over armatures 32 and 31, thereby ensuring the operation of the cut-ofi' relay of the called subscribers line switch and also marks the trunk in use busy to other callers.

The circuits to relay HB and the testing wiper 27 are opened at armatures 37 and 29 respectively, and the ringing circuit to the called subscriber is prepared at. arniatureS 1 rent to the called line at its armatures 17 and 18, the circuit details of which will now be generally well recognized. When the called subscriber removes his receiver to answer the call his lines are looped via the switchhook spring and the ringing relay F is operated in known mannerand completes a circuit for its upper locking winding in series with. relay E. The operation of relayE disconnects the main ringing circuit and also completes the speaking connection betweenthe calling and called parties at armatures 17 and 18. The closure of the loop via the called subscribers instrument causes the back bridge relay D to I operate, thereby reversing the direction of current flow around the calling loop for metering or supervisory purposes.

Upon the release of the switch, earth will be extended over resting contacts of armatures 10 and 25, operated off-normal springs 14, winding of relay C and the release magnet Z in parallel to battery, thus causing both to operate, so that the switch will be guarded during its releasing period from earth at operated armature 41 over the release trunk conductor 12. Individual supervision and a delayed alarm scheme are also incorporated in a similar manner to that already fully described in Fig. 1. p 1

Should all the lines in the group test busy, the switch wipers will continue to rotate until they pass beyond the last contact of the group, whereupon cam springs 33 will be operated thereby disconnecting test wiper 28, so that the circuit to the left hand coil of re lay G is opened and the relay will not reoperate. Moreover, the operating circuit to both switching relays HA and HE is also opened at the left hand contacts of the cam springs 33 and the busy hold circuit is completed to the lower winding of relay B while at the centre contacts of the cam springs, busy flash and tone is connected to the lower winding of relay A, via armature 42 of relay B. The function of the busy circuit is more fully described in the foregoing description of Fig. 1.

for the left-hand winding-of relay G. Re-

lay G will restore, as previously explained and remove the short-circuiting earth from the windings of relays HA and HB. Re-

lay HA does not operate since its winding is short-circuited by the earth encountered by wlper 28. Relay HB, however, operates over a circuit extending from earth at armature 20, resting contacts of cam springs 33, op-

rupter contacts 24. The operation of relay,

HB completes various circuit functions among which is the connection of a direct earth to wiper 27 over armatures 30 and 29 to insure the operation of the called subscribers cut-off relay and to mark the trunk busy. Relay HB also connects up the upper set of talking wipers, opens the circuit of relay HA at armature 36 and disconnects wiper 28 at armature 31. The holding circuit ofrelay E is opened at armature 16 and that relay releases and completes the ringing circuit as previously described. The operations involved'when the call is answered and the connection is released are the same as those described for a call completed over wiper 28.

Referring now. particularly to Figure 4, when the switch is selected by a preceding switch, impulse accepting relay A operates over the calling loop in known manner and at armature 10 extends earth to operate the guard relay B. The operation of guard relay l3,'earths the release trunk conductor 11 at its armature 12 to guard the switch; prepares a circuit at armature 13 for the driving magnet DM, and further completes a circuit to relay E over the path: earth, armature 14, back contact of armature 16, winding of relayE to battery. The operation of relay E opens points in the ringing circuit at its armatures 17 and 18 and also prepares the 7 initial stepping circuit for the automatic rotation of the rotary switch at armature 19. Normally on this type of switch the subscriber would dial one impulse only, and when relay A releases upon the reception of this impulse, relay C is operated via earth at armature 14' of relay B, resting springs of armatures 15 and 20, upper winding of'relay C to battery. Relay G operates and completes a circuit to its lower winding from earth at armature 14 ofrelay B,armature 19, home contactof bank 20, wiper 21, armature 22 and front contact, lower winding of relay C to battery and parallel thereto via frontcontact andarmature :13 of relay B, interrupter H springs 23, winding of driving magnet DM to battery. 7

The, driving magnet therefore energizes and opens-its own circuit at the interrupter springs 23, so thatthe wipers will be moved on to the next set of contacts in a manner which is well known. Should the next set of contacts test busy, earth will be extended via wiper 21 over a similar path to that previously traced, so that the driving magnet will again energize, while relay 0 remaini held during its open circuit periods under connected at armature 24, to prevent this re-' lay flicking during impulsing.

Assuming now that wiper 21 eventually en counters an idle line, battery in place of earth is found connected to the testing contact bank 20'so that the magnet is not re-operated and relay C is short circuited, thus causing this relay to release whereupon a circuit is then completed to the switching relay H from earth at armature 14 of relay B, front contact and armature 19, upper winding of switching relay H back contact and armature 22, wiper 21, to battery via the cut-off relay of the line selected. Relay H operates its armature 25 over this circuit and completes the circuit for its lower locking winding to earth at armature 14 of relay B, whereat relay H operates fully and at armature 15 connects a direct earth to the testing wiper 21 in order to guard the connection and ensure the op eration of the cut-elf relay of the line selected. It will be noted that the holding circuit to relay E is opened at armature 16, and after a short pause due to its slow feature this relay will release, whereupon ringing current will be connected to the called subscribers instrument over the circuit, ringing feed over conductor 26, winding of ringing relay F, armatures 27 17 and 28, wiper 30 and bank contact, called subscribers instrument, bank contact and wiper 31, armature 32, armature 18 and back contact to ring return battery. In response to the ringing circuit thus completed the called subscribers bell will ring, and when he removes the receiver'to answer the call,thelinewi"ll be looped via the switch hook springs, and the ringing relay F will be operated as described in connection with the previous figures. The operation of relay F completes the circuit for its lower locking winding at armature 33 in series with relay E, and the latter relay operates and completes a speaking connection between the calling and called subscribers at armatures 17 and 18. At this period the back bridge relay D is operated over the called subscribers loop and here again current flow in the calling loop is reversed for metering or supervisory purposes.

In the event of all the lines in the QTOU} testing busy, the wipers will be automatically rotated to the 25th contact, or if double banks are used the 50th contact, whereupon relay G willbe operated in series with relay H over the circuit: earth, armature 14 and front contact, armature 19, upper winding of relay H, back contact and armature 22, testing wiper 21, last bank contact in the group, upper winding of relay G to battery. Relays G and H operate in this circuit and cause a busy flash and tone over conductor 34, to be extended by way of armatures 35 and 36 to the lower winding of relay A, while a busy hold circuit is connected via conductor 37, upper winding of relay B, armature 38, to earth at armature 39 of relay B.

The function of the busy flash and hold circuit has already been fully described in connection with the previous figures, and suflicient is indicated herewith to enable its application to be readily appreciated for this particular circuit. It should be mentioned that although the necessary circuit functions to produce a ringing condition have been performed, the last contacts in the group are open, so that wipers 30 and 31 are switched through to a dead line and consequently the ringing circuit is ineffective.

On the release of the connection when the calling subscriber replaces his receiver, relays A and B are restored, and consequently earth is removed from the main holding circuit at armature 14 of relay B, thereby releasing the various relays which have been locked thereto. It will be seen that when all the; relays have released, a homing circuit will then be completed from earth at the back contact and armature 14, homing plate 40, wiper 41, back contact and armature 13, interrupter springs 23, winding of driving magnet DM to battery, and parallel thereto via the lower winding of relay G to battery.

The self interrupter circuit thus connected will cause the wipers of the switch to be stepped to the first bank contacts whereupon earth via the homing plate is disconnected and the wipers come to rest in the home position. It will be noticed during the period that the'wipers are rotating to the home position, relay G will be operated over its lower winding, and the release trunk conductor 11 will be guarded over the circuit: earth at armature 42, back contact and armature 43 to conductor 11 thereby ensuring that the switch mechanism is completely restored to normal before the switch is freed for engagement on other calls.

What I claim as new and desire to secure by Letters Patent is 1. In a connector switch having access to subscribers lines, a switching relay energized responsive to the extension of a connection to an idle line, and means including a second relay controlled by said switching relay for delaying the application of signalling current to the called line for a predetermined time after the line is connected with.

2. In a connector switch having access to subscribers lines, a switching relay energized responsive to the extension of a con nection to an idle line, and means including a relay energized during the setting of the switch and released responsive to the operation of said switching relay for delaying gized responsive to the extension of a con-' nection to an idle line, arelay through which the application of signalling current to the called line for a predetermined time after the line is connected with.

3. In a connector switch having access to subscribers lines, a switching relay enerized res onsive to the extension of a connection to an idle line, a slow-to-release relayreleased responslve to the operatlon of said switching relay for completing the'signalling circuit of the switch, and means for re-operating said slow relay to open said signallingcircuit when the call is answered.

5. In a connector switch having access to subscribers lmes, a switching relay enerringing current is applied to a called line, said relay operating responsive to the answering of the call, a. cut-off relay for con trolling theapplication of ringing current to the called line, an initial operating circuit for said cut-off relay including normally closed contacts of said switching relay, and a subsequent operating circuit for said outoff relay including operated contacts of said second relay.

6. In a two-directional connector switch equipped with primary and secondary step-- ping magnets, a relay energized during the setting of the switch for effecting a changeover from the primary magnet to the secondary magnet, a switching relay energized responsive to the extension of a connection to an idle line, and means controlled by said switching relay for releasing said, first relay.

7. In a two-directional connector switchequipped with primary and secondary stepping magnets, a slow-to-release relay energized during the setting of the switch for eiiecting a changeover from the primary magnet to. the secondary magnet and for opening the signalling circuit of the switch, a switching relay energized responsive to the extension of a connection to an idle line, and means controlled by said switching relay for releasing said slow relay to complete said signalling circuit.

8. In a two-directional connector switch equipped with primary and secondary stepping magnets, a slow-torelease relay energized during the setting of the switch for effecting a changeover from the primary magnet to. the secondary magnet and for opening the signalling circuit of the switch, means for releasing said relay responsive to'the extension of a connection to an idle line, and means for re-operating said relay responsive to the answering of the call.

9. In a connector switch, a relay through which ringing current is applied to a called line, a second relay for disconnecting the ringing current from the called line, and an operating'circuit for said second relay including the windings of both relays in series.

10. In a connector switch, a relay through which ringing current is applied to a called line, a second relay for disconnecting the ringing current from the called line, means for operating said first relay responsive to the answering of the call, and means controlled by said first relay for operating said second relay.

11. In a connector switch, a double wound relay, a circuitincluding one winding of said relay for applying ringing current to a called line, asecond relay for opening said circuit, and means for operating said second relay in series with the other winding of said first relay. p I

12. In a connector switch, a double wound relay, a circuit including one winding of said relay for applying ringing current to a called line, a second relay for opening said circuit, means for operating said first relay responsive to the answering of a call, and means controlled by said first relay for connecting its other winding in series with said second relay to energize both relays,

13. In a connector switch, a relay through which ringing current is applied to a called line, a second relay for disconnecting the ringing current from the called lineand'for completing a talking connection thereto,-a circuit for energizing both of said relays in series, and means controlled by said first relay for completing said circuit.

14. In a connector switch two relays, a ringing circuit including a winding of the first relay and contacts of the second relay, and an operating circuit for thesecond re lay including a second winding of said first relay and contacts controlled by that relay.

'15. In a two-directional connector switch equipped with primary and secondary magnets, a relay energized at the end of the primary operation of the switch for effecting a changeover from the primary magnet to the secondary magnet, means for releasing said relay when a connection is extended to an idle line, and means for re-operating said relay responsive to the answering ofthe call.

16. In a'two-directional connector switch equipped with primary and secondary magnets, a relay energized at the end of the primary operation of the switch for effecting a changeover from the primary magnet to the secondary magnet, means for releasing said relay when a connection is extended to an idle line to complete a circuit for signalling over the line, and means for reenergizing said relay responsive to the answering of the call to open said signalling circuit and to complete a talking connection with the line.

In testimony whereof I have signed my name at Liverpool this th day of March,

CHARLES EDMUND BEALE.

Images