US2183030A - Telephone system - Google Patents

Description

Dec. 12, 1939. Rlc ARDs 2,183,030

TELEPHONE SYSTEM Filed June 14, 1937 2 Sheets-Sheet 1 IN VE N TOR lDR/S TREVOR R/CHA RDS ATTY Dec. 12, 1939. l. T. RICHARDS TELEPHONE SYSTEM Filed June 14, 1937 2 Sheets-Sheet 2 IN VE NTOR vop R/CHARDS- I IDPIS TRE Z ATTY Patented Dec. 12, 1939 lTED srAres- PATENT OFFiCE signor to Associated Telephone & Telegraph Company, Chicago, 11., a corporation of Delaware Application June 14,.1937,.Serial'No. 148,013 In Great Britain-July 21, 1936 '7 Claims.

The present invention relates to automatic switches for use in automatic telephone or like signalling systems and while more particularly concerned with the provision of additional facilities on group selector switches, the invention is also applicable to final selector switches and other switches responsive to series of impulses.

Arrangements have already been made in which a group selector has access to either of two sets or groups of outlets. After stepping the switch vertically to particular levels the switch is caused to release thereby absorbing the first digit whilst at the same time outgoing leads in the switch are changed over to a second set of wipers so that after receiving the second digit the switch again steps vertically and then hunts automatically in a rotary direction for afree outlet in a group of the second set. Should the first digit dialled step the switch to any other level the switch will hunt automatically for a free outlet in a group of the p first set only.

According to one feature of the invention a switch having access to two different sets of lines is provided with circuit arrangements which cause access to be had to a line of one set'in response to one or more series of impulses of a predetermined number or numbers respectively and also in response to a series of impulses of another predetermined number different from that of the 30 first of these series followed by the aforementioned one or more series of impulses and cause access to be had to a line of the other set in response to a series of impulses of a further predetermined number difierent again from said 35 other predetermined number followed by one or more further series of impulses.

According to another feature of the invention a switch having access to two different sets of lines is provided with circuit arrangements which cause access to be had to a line of one set in response to two series of impulses of predetermined numbers and also in response to a series of impulses of a diiferent predetermined number from the first of these series followed by two further series 45 of impulses corresponding to the aforesaid numbers and cause access to be had to a line of the other set in response to a series ofimpulses of a third predetermined number 'difierent again from said different predetermined number fol- 50 lowed by two further series of impulses.

According to a further feature of the inven-- tion a group selector switch having access to two sets of groups of lines is provided with circuit arrangements which in response to a series of im- 55 pulses of a predetermined value or values cause values followed by a second series of impulses cause the switch to hunt for an idle line in a group of the other set.

The invention will be better understood from p the following description of one method of carrying it into effect, reference being had to the accompanying drawings which illustrate the circuitsof a group selector and comprise Figs. 1 and 2 which should be arranged side by side to form a complete circuit diagram. The diagram shows a circuit employing a switch of the twodirectional type arranged to have so-called rectangular motion.

For the purpose of the description it will be assumed that on dialling '7 as a first digit the switch performs a digit absorbing and wiper switching function while on dialling 5 as a first digit the switch performs a digit absorbing function only, while on other digits the switch functions as an ordinary group selector.

When the calling subscribers loop is extended across the incoming negative and positive conductors by way of a line finder or other nonnumerical switch relay A operates over its outer windings in series andat armature at operates relay B. Armature bl thereupon extends a guard earth on the incoming P conductor, armature b2 completes a locking circuit for relay B, armature bl completes a circuit to light the supervisory lamp LP which is connected to battery over common conductor I!) by way of equipment which is arranged to give an alarm if the switch fails to step oifnormal and open springs N2 within apredetermined period while armature b5 com pletes an operating circuit for relay C on its lefthand winding by way of resistance YD, contacts 5 NPAI, armatures b5- and b2, magnet VM (nonoperative in this condition) to battery. If the switch is functioning as a first selector the middle winding of relay A is connected to earth at armature b3 by way of a dial tone transformer over common conductor I2 so that dial tone is applied. to the incoming speaking leads in a balanced circuit by induction from the middle winding of relay A to the two outer windings so as to inform the calling subscriber that he may com- 5 mence dialling. Relay C in operating at armature cl prepares a circuit for the vertical magnet VM which however is non-operative in series with the winding of relay B.

When the first series of impulses is received relay A responds and each time it releases a circuit is completed to energise the magnet VM as follows: earth, armature b2, resting armature ai, low resistance righthand winding of relay C in parallel with resistance YA, contacts NR4, armature ci, magnet VM to battery, and accordingly the switch wipers are raised to the level dialled. During the impulse train it will be noticed that relay B is intermittently short-circuited by the resting armature a! but this relay will remain held due to the slugging eifect of the short-circuited winding. The presence of the metal rectifier MBA in the energising circuit of relay B prevents the slowing down of the vertical magnet operation which would otherwise result by the direct connection of the comparatively low value non-inductive resistance YC in parallel with its winding. It will be readily understood that neither the vertical magnet nor relay C will hold in series with relay B and moreover the inductance of the latter relay is such that it has no appreciable eifect on the performance of the magnet.

On the first vertical step the off normal springs N are mechanically operated and at contacts N2 the supervisory lamp LP is extinguished whilst at contacts N4 an operating circuit for relay H is completed on its lefthand winding. Armature hi thereupon connects the righthand winding of relay H to the test wiper Pl, armature 71.2 disconnects the energising circuit of relay C over its lefthand winding while armature 723 extends an earth to short-circuit this winding and the slugging eiiect thus produced enables relay C to hold satisfactorily during the train of impulses received.

Assuming now that any digit except 5 or '7 has been dialled, at the end of the impulse train relay A remains steadily operated and holds relay B. After a short interval relay C releases and completes an energising circuit for the rotary magnet RM from earth, armature h5, rotary magnet interrupter contacts rm, off normal contacts N i, armature c3 and the magnet RM to battery whereupon the wipers are advanced into engagement with the first set of contacts in the level selected. The rotary oif normal springs NR are mechanically operated on the first rotary step and at contacts NR4 disconnect the vertical magnet W from the impulsing circuit to prevent any further actuation. On energisation of the magnet the rotary interrupter contacts rm are opened also.

If the test wiper Pl encounters an engaged outlet which is indicated by an earth or booster battery potential, relay H will be held operated over armature dr2, contacts NPBI armature dafi, contacts Si and armature hi on its right hand winding and the disconnection of its original holding circuit by the interrupter contacts rm is therefore without eiiect. However the rotary magnet RM is de-energised and on closure of the interrupter contacts the magnet is re-energised to advance the wipers on to the second set of contacts. This stepping operation continues automatically until an idle outlet in a group of the first set of lines is found or alternatively the wipers are advanced to the 11th position.

If the Pi wiper encounters a free outlet, that is, one unmarked by earth or booster battery p0- tential, relay H will quickly restore and at armature h5 opens the magnet driving circuit while the selected outlet is immediately busied from earth, armatures bl, h and dafi, contacts NPBi, armature (U2 and the Pi wiper. A circuit is now completed to re-energise relay C on its lefthand winding in series with resistance YD, contacts NPAl, armatures b6 and 712 and the vertical magnet to battery and this relay in operating at armatures c5 and c6 switches the incoming speaking leads through resting armatures dad and (Z to the first choice negative and positive wipers. Armature c3 disconnects any circuit to the rotary magnet and at the same time reoperates relay H over its lefthand winding whereupon it holds on its other winding by way of armatures hi and 04 to the carthed P conductor. Relay C in operating at armatures c5 and 06 also releases relay A which in turn at armature a! short-circuits and releases relay 3. Meanwhile, however, the loop extended over the negative and positive wipers operates the A and B relays in the succeeding selector whereupon a guard earth is returned over the P lead to maintain relay H when subsequently relay B releases after its slow release period. Relay B in releasing at armature b5 disconnects the lefthand winding of relay H which remains held on its righthand high resistance winding to the earthed P lead.

On dialling the second and subsequent digits, trains of impulses are extended over the negative and positive leads to succeeding switches to route the call to the wanted subscriber.

Assuming now that all outlets in the level selected prove busy the wipers are rotated to the 11th position where the cam springs S are mechanically operated. Since the P! wiper fails to encounter any earth potential relay H will release quickly as described in the previous paragraph and open the driving circuit and re-operate relay C. Armatures c5 and c5 switch the incoming leads as before through to the negative and positive wipers which connect by way of the inultipled 11th step contacts to the outer windings of relay A. Relay A therefore remains held to the incoming loop and maintains relay B while relay H is re-operated at armature c3. Cam contacts S2 connect up the busy tone transformer over common lead l3 to the middle winding of relay A whereupon busy tone is induced in the outer windings and is applied in a balanced circuit to the incoming speaking leads. Cam contacts SI extend an earth over armature b1, contacts Si, armature daii, contacts NPB! and armature drZ on to the test Wiper Pl to operate an overflow meter which may be connected to the 11th outlet of that particular level for trafiic observation purposes.

Assuming now that '7 is dialled as a first digit thus raising the switch vertically to discriminating level, giving both wiper switching and digit absorbing facilities, the normal post springs NPA are operated by the switch shaft when the switch is set to the seventh level. At the end of the impulse train relay C releases after a short interval and completes an energising circuit for the rotary magnet at armature 03 in the normal manner and as a result the wipers are advanced into engagement with the contacts of the first outlet in the level selected. On this particular level the P contacts are left disconnected and since the Pi wiper picks up no potential relay H quickly releases and at armature 71.5 disconnects the magnet driving circuit. It

should be stated here that this particular level 75 of outlets in the first setof lines irrthe particular of relay DR a circuit isalso completed from: earth; arrangement described cannot be utilised for routing to succeeding selectors since it is. neoessary to disconnect the first P contactin order-to enable the switchto be released over the same path as it has been set in a manner. tobe: de scribed. Relay H in releasing-completes a'cir-' cuit to operate relay DR from: earth, lefthand winding of relay DR, armatures (1115 and da3; operated contacts N'PA-l, armatures b6 "and h2 and the vertical magnet to battery whereupon armature dr3 extends an earth over off normal contacts NI, right hand low resistancewindingof relay DR which is shunted by'resistance- YB for spark quench purposesand armatures b6 and 112 to operate the vertical magnet VM. The vertical magnet pawl when operated. is arranged'to engage with an extension arm ofthe rotary detent and move it out of engagement with the rotary ratchet member to initiate the full release of the switch along. the path over which it has been set. This arrangement reduces the releasetime to a minimum and.enablesstheswitchto be 7 This relay in operating at a make-first light armature da! looks over itsiother-windingtor the earthed P conductor, at armature da23disconnects dial tone, and at armatures da4, 5 and 6 switches over the negative, positiveand P leadsthrough to the second set of. wipers, i. e. the wipers having accessto the groups of lines of the second set.

Vi henthe switch commencesto release vertically the normal post springs restore and when it releases completely the off normal. and: rotary off normal springs will be restoredtov the. normal. condition. Contacts Ni thereupon open.-thever-- tical magnet energising circuit and at the-:same' time release relay DR since its'other" winding is disconnected at armature daS:

R2, and the magnet VM to battery inorder to prepare the switch. for receiving further dialled impulses.

On dialling the second digittheswitchsteps vertically and then performs an automatic rotary search for a free outlet in the manner described at the commencement of the specification but in this case however the search takes place over contacts of lines of a group of the second set of outlets only. It will be noticed that any further operation of the normal post springs N'PA or NPB is made inefi'ective at armatures da3 and drzii and it will be appreciated that any digit from lfto 0 may thus be dialled as a second digit.

Assuming now that 5 is dialled as a first digit the switch will be raised to the digit absorbing level whereupon the normal post springs NPA and NPB will be mechanically operated. At the end of the digit relay C releases after its slow release period and energises the rotary magnet which causes the switch to make one rotary step in the normal manner whereupon relay H quickly releases since a circuit tothe test wiper PI is disconnected at contacts NPBl. Relay H releasing opens the driving circuit and at armature 7L2 operates relay DR over its lefthand winding as before whereupon at armature 0373 the vertical magnet is energised in series with the righthand Winding of relay DR. On operation Relay C. now re-operates on its lefthand winding in series with resistance YD, contacts NPAl, armatures b6 and armature bl, M and dat; operated contacts NPBI and armature drl tooperate relay DB on its righthand winding. This relay in operating at armature dbl locks to the earthed P conductor, at armature ca /b3 prepares an alternative circuit to the NPBi contacts, at armature dba disconnects dial tone while at armature dbS the lefthand winding of relay DB is disconnected. On energisation of the vertical magnet-as previously described the switch restores to normal over the: path over whichit has been set-whereupon-a alllmechanically operated spring sets are restored to the normal condition and atoifnormai contacts Nithe vertical magnet and'relay DR are released. A circuit isnow completed to= operate relay C over its lefthand winding inuthe normal manner in ordertoprepare for th'e second digit;

On reception of the second digit the switch steps vertically and hunts in a self-interrupted circuit for an idle line in a group-of the first set. Since relay DB remains looked, any further operation of thenormalpost springs will b'e ineifective and any digitexcept 7 may thus be dialled as a second digit;

On release of. the connection at the end of the conversation, earth is removed from. the release trunk conductor P thus releasing relay: HI and either relay DA or DB' whicheven-is operated and thereupon relay H in releasing at armature ht disconnects the holding circuitfor relay C on its left-handwinding. On release of relayC- a selfinterrupted driving circuit is completed. for the rotary magnet RM from earth supplied to common conductor H by way of equipment which is arranged to' give a delayed: alarm in case of failure: to release; contacts N l; armaturect, ro-

tary magnet RM to 'eb'attery' and accordingly thewipers are rotated clearof the'banks-after which they fall and rotate under the banks under spring tension back to their normal positions where the oil normal contacts. N l open ancl disconnect the homing circuit. Preferably the-rotary magnet is mechanically prevented fromopening its interrupter contactsduringthe release movement so that there is no tendency'forit'to=chatter.-

At the commencement ofirelease an'initial unguard'period on the incoming Peonductor which is represented by the. sum of. the release times ofrelays H and C is provided to enable preceding switches to restore. On release of relay C following the release of relay H earth will be extended by way of operated off normal contacts N3 and resting armature 04 on to the P conductor to guard against premature seizure during release. When the switch reaches normal, contacts N3 open and remove the guarding switch I thus freeing the switch from further use.-

A test buzzer connected to test jack T over common lead I l and armature dal enables the set of wipers in use to be determined without removing the dust cover from the switch.

It will be appreciated that while numerous facilities are oifered by this switch, the number of levels which cannot be extended to succeeding switches is reduced to a minimum. In the example described in this specification level i of the first set of groups of lines will be the only level which cannot be utilised.

I claim:

1. In an automatic switch, a plurality of sets of wipers, means for causing a connection to be extended over one of said sets of wipers responsive to the receipt of impulses comprising a predetermined digit followed by impulses comprising any digit, and means for causing a connection to be extended over another of said sets of wipers responsive either to the receipt of impulses comprising a predetermined digit different from first said predetermined digit followed by impulses comprising any digit except first said predetermined digit, or to the receipt of impulses comprising any one of a plurality of predetermined digits different from first said predetermined digit and second said predetermined digit. 7

2. In an automatic switch having access to the lines of each sub-group of a plurality of groups of lines, means for operating said switch to extend a connection to an idle line of any desired sub-group of one group responsive to a train of impulses comprising a predetermined digit followed by a second train of impulses designating the desired subgroup, and means for operating said switch to extend a connection to an idle line of any desired sub-group of another group responsive either to a train of impulses comprising a predetermined digit difierent from first said predetermined digit followed by a second train of impulses designating the desired sub-group or to a single train of impulses designating only the desired sub-group.

3. In an automatic switch having access to a plurality of groups of lines, means for operating said switch to extend a connection to any line of one of said groups responsive to the receipt of a train of impulses comprising a predetermined digit followed by a second train of impulses designating said one line, and means for operating said switch to extend a connection to any line of another of said groups responsive either to the receipt of a train of impulses comprising a predetermined digit difierent from said first predetermined digit followed by a second train of impulses designating last said line or to a single train of impulses designating only last said line.

secondary wipers having a normal position, a primary group of lines accessible only to said primary wipers, a secondary group of lines accessible only to said secondary Wipers, means for extending a connection to any line of said primary group responsive either to a single digit directed movement of said Wipers or to two digit directed movements of said wipers wherein a predetermined first digit causes said wipers to be returned to said normal position following the first of said two movements, and means for extending a connection to any line of said secondary group responsive only to two digit di rected movements wherein a predetermined first digit different from last said first digit causes said wipers to be returned to said normal position following the first of said two movements and also causes said secondary wipers to be effective.

6. In an automatic switch for absorbing certain digits, first-choice wipers and second-choice wipers having a normal position, a group of lines accessible to each set of wipers, means responsive to impulses for moving said wipers from said normal position, means effective if said impulses comprise any one of a plurality of predetermined digits for causing said first-choice wipers to be effective in searching for an idle line designated by said one digit, means effective if said impulses comprise a predetermined digit difierent from first said predetermined digits for causing said wipers to be returned to said normal position and for preparing for further impulse directed movement of said wipers in which said first-choice wipers will be effective, means effective if said impulses comprise a predetermined digit difierent from first said predetermined digits and different also from second said predetermined digit for causing said wipers to be returned to said normal position and for preparing for further ill'lpulse directed movement of said wipers in which said second choice wipers will be effective.

'7. In an automatic switch as claimed in claim 6, wherein said third means and said fourth means also prevent a second return of said wipers to said normal position after said further impulse directed movement of said wipers even though said further movement is responsive to impulses comprising either of last two said predetermined digits.

IDRIS TREVOR RICHARDS.

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