US2222126A - Automatic switch for use in telephone or like systems - Google Patents

Description

, Nov. 19, 1940.

R. TAYLOR ET AL 2,222,126

AUTOMATIC SWI TCH FOR USE IN TELEPHONE OR LIKE SYSTEMS Filed June 22, 1938 IN VEN T0125 REGINALD TAYLOR GEOGE THOMAS BAKER Patented Nov. 19, 1940 UNITED STATES PATENT OFFICE AUTOMATIC SWITCH FOR USE IN TELE- PHONE OR LIKE SYSTEMS Application June 22, 1938, Serial No. 215,032 In Great Britain July 27, 1937 13 Claims.

The present invention relates to automatic switches for use in telephone or like systems and is more particularly applicable toelectromagnetically-operated step-by-step switches of the twomagnet vertical and rotary type which are arranged to have so-called rectangular motion, that is to say, release is normally effected by the advancement of the wipers beyond the end of the bank contacts after which they fall and are then l0 rotated back to normal under the bank by spring tension.

Where such switches are required to absorb a digit, it has hitherto been the usual practice for the wipers to be set and to restore to normal in response to the digit in question and for release to be satisfactorily effected in the interdigital pause it has been found preferable to provide arrangements whereby under this condition the wipers are restored to normal along the path over which they were set. The use of different methods of release according to the circumstances involves difliculties unless an auxiliary release magnet is provided and this is not altogether desirable since it renders switches of this type a non-standard item of manufacture. The chief object of the invention is to provide arrangements whereby on such switches the problems involved in digit absorption may be satisfactorily solved.

According to one feature of the invention in a two-directional electromagnetically-operated step-by-step automatic switch provided with two sets of wipers the eifect of the absorption of the initial digit transmitted to the switch coupled with a wiper switching operation is obtained 5 without a release operation by arranging that alternate impulses produce wiper switching and only alternate impulses efiect movement of the wipers so that only the first half of the bank is accessible in response to the first digit, only the second half of the bank being accessible in response to a further digit and only if the first digit is of such a value as to require absorption.

According to another feature of the invention in a two-directional electromagnetically-operated step-by-step automatic switch the primary movement of the wipers is effected in response to alternate impulses only of the first digit, the circuit arrangements being such that if the digit is of predetermined value the wipers are auto- 5 matically advanced in the primary direction to a particular position from which they are again advanced in response to a further digit.

A further feature of the invention is that in a two-directional electromagnetically-operated step-by-step automatic switch of the vertical and rotary type provided with two sets of wipers alternatev impulses only of the first digit effect vertical movement of the switch wipers and a wiper switching operation is also effected by alternate impulses, the circuit arrangements being 5 such that if the first digit is of predetermined value the wipers are automatically given a further vertical movement to a position representing a movement of half the height of the bank from which they are again moved vertically in response 10 to alternate impulses of the succeeding digit.

The invention will be better understood from the following description of one method of carrying it into effect, reference being had to the accompanying drawing. This shows a circuit dia- 15 gram of a digit-absorbing group selector of the vertical and rotary type provided with two sets of wipers each having access to one hundred outlets.

The circuit arrangements are such that each 20 alternate impulse received is absorbed, the vertical magnet and the wiper switching relay DA being operated on the. first and each subsequent odd impulse while on each even impulse relay DA is released and the magnet is not operated. 25 Hence one set of one hundred outlets may be accommodated on levels 1 to 5, each of which has twenty outlets, ten upper and ten lower. In response to digits of value 1 or 2, the switch wipers are raised to level 1 but in the former case access is had over operated armatures of relay DA to the upper set of outlets while in the latter case access is had over resting armatures of relay DA to the lower set of outlets. Similar considerations apply to other pairs of odd and even digits. 35

If the wipers are raised by the first digit to an ordinary level, the switch then performs a rotary hunting operation in a normal manner, the testing taking place on either the upper or lower set of outlets according as to whether the digit is odd or even. If the wipers are raised to the predetermined digit-absorbing level, no cut-in takes place and the switch hunts vertically to level 5 where it awaits the second digit which will in the manner already described carry the 4 wipers to the desired set of outlets in the other. hundreds group situated on levels 6 to 0.

Considering now the circuit operation, on the seizure of the switch from a preceding switch the loop extended across the incoming negative 50 and positive conductors operates relay A which in, turn operates relay B. This relay locks over armature bl and at the same armature lights the switch supervisory lamp LP. Relay B also at armature b2 operates relay C on its right-hand winding in series with resistance YB, at armature b1 applies guarding earth to the incoming P conductor, and, assuming that the switch is functioning as a subscribers first selector, at armature b6 connects up a dial tone transformer over common lead 12 to the middle winding of relay A whereupon dial tone is extended by induction through the windings of this relay to the incoming speaking conductors in a balanced circuit. Relay C upon operating, at armature c4 prepares an impulsing circuit for the vertical magnet VM in series with its low resistance left-hand winding, the magnet however being non-operative in series with the winding of relay B.

On receipt of the first train of impulses relay A responds and on its first de-energisation an energising circuit is completed for the vertical magnet VM as follows: earth, armatures bl and al, rotary off-normal contacts NR6, left-hand low resistance winding of relay C, armatures daZ and a l, rotary off-normal contacts NR4, magnet VM to battery and accordingly the switch wipers are raised to level 1. The off-normal springs N are now mechanically operated and at contacts N3 short-circuit the right-hand winding of relay C to enable it to hold operated during the train. At contacts N4 an operating circuit is completed for relay H over its right-hand winding from earth, contacts NPBZ, armature c5, off-normal contacts N4 and armature b4 and this relay thereupon looks over its other winding to the earthed P conductor.

On the re-operation of relay A at the end of the first impulse, the vertical magnet remains held over the following circuit: earth, armatures bl and al, off-normal contacts N2, vertical magnet interrupter contacts um, armature ht, lefthand winding of relay DA to battery via the vertical magnet. Relay DA now operates and at armature daZ disconnects the impulsing circuit to the magnet VM in readiness for the absorption of the next pulse.

On the next release of relay A in response to the second impulse, the vertical magnet is released while relay DA now remains held over its middle low resistance winding in series with the left-hand winding of relay C. At the end of the second impulse relay A re-operates and releases relay DA since it will not hold operated in series with the comparatively high resistance relay B.

Hence it will be seen that after the dialling of an odd digit the vertical magnet and relay DA will remain energised while after an even digit they will both be released. During the impulse train relay B is intermittently short-circuited by armature al but it remains operated due to the slugging effect of the short circuiting. The presence of the metal rectifier MBA in the energising circuit of relay B prevents the slowing up of the magnet operation which would otherwise result by the direct connection of a comparatively low value non-inductive resistance in parallel with its winding. It will be readily understood that neither the magnet VM nor relay C will hold operated in series with relay B and moreover the inductance of the latter relay is such that it has no appreciable effect on the magnet performance.

It will be assumed first that the wipers are raised to an ordinary level, that is, a level not set aside for digit absorption so that the switch will function as an ordinary group selector.

At the end of the impulse train relay A remains operated and maintains relay B while after a circuit is completed from the earthed P lead to hold relay DA over its right-hand and middle windings in series if the train has comprised an odd number of impulses. The initial operating circuit for relay H is also disconnected and also its holding circuit over its left-hand winding but this relay now remains held on its right-hand winding by way of armature b6, the rotary magnet interrupter contacts rm, armature h3 and the critical level normal post spring contacts NPAI. An energising circuit for the rotary magnet RM is also completed from the same earth by way of off-normal contacts N4 and armature c5 and the wipers are thereupon rotated into engagement with the first set of contacts in the level selected, while the magnet interrupter contacts T'ITL are opened. The rotary off-normal springs NR are mechanically operated on the first rotary step and at contacts NR5 maintain the locking circuit for relay DA independently of armature cl, at contacts NR6 disconnect any impulsing circuit to relay C and at contacts NR5 prevent the completion of any further circuit for the magnet VM over armature 04.

The switch now hunts for a free outlet in the level selected, access being had over the negative 1, positive 1 and Pi wipers to the upper set of outlets on the level if an odd digit has been dialled and access being had to the lower set of outlets if an even digit has been dialled.

If the first outlet encountered by the test wiper Pl or P2, as the case may be, is engaged as indicated by the presence of earth or booster battery potential, relay 1-1 will be held operated over its left-hand winding and the disconnection of its right-hand winding by the contacts rm is therefore without effect. The rotary magnet deenergises however and on the closure of its interrupter contacts the magnet is re-energised to advance the wipers to the second set of contacts in the level selected. This stepping operation continues until an idle outlet is reached or alternatively the wipers are advanced to the 11th position.

If the test wiper encounters a free outlet, that is, one unmarked by earth or booster battery potential, relay I-I quickly restores and at armature h3 further opens the magnet driving circuit while at armature h2 it applies earth to the test wiper to guard the outlet seized. A circuit is now completed to re-operate relay C over its right-hand winding by way of armatures hi and b2 since the short-circuiting earth has already been removed therefrom at contacts NR3. Thereupon at armature cl, c2 and 03 the incoming leads are extended through to the succeeding switch, relay A is disconnected from the speaking leads and at the same time relay H is re-operated over its righthand winding. Relay A on releasing short-circuits relay B and during the release time of the latter relay the loop extended forward over the negative and positive wipers operates the A and B relays in the succeeding switch whereupon a guard earth is returned over the test wiper so that when relay B subsequently restores relay H will be maintained on its left-hand winding and also relay DA on its right-hand and middle windings in series if it has been operated.

In response to the dialling of subsequent digits trains of impulses are transmitted straight through the switch to route the call to the wanted party.

If all the outlets in the level selected prove busy, the wipers are rotated to the 11th position where the cam springs S are mechanically operated. At contacts S3 the left-hand winding magnet as follows:

of relay H is disconnected from the test wiper so that on the opening of the interrupter contacts rm relay I-I releases as previously described and opens the magnet driving circuit and reoperates relay C which in turn re-operates relay H. The incoming speaking leads are extended as before through to the wipers which however now connect by way of the multipled 11th step contacts back again to the upper and lower windings of relay A which therefore remains held over the incoming loop and maintains relay B. Contacts S2 disconnect the dial tone circuit and -at contacts Si and S2 connect relay A in circuit with the busy flash and tone cam assemblies BF and BT over common leads l3 and II respectively whereupon busy tone and flash are applied to the incoming speaking leads in well-known manner. Contacts S3 also extend earth over the test wiper to operate an overflow meter which may be connected to the 11th outlet of that particular level for trailic observation purposes.

Considering now the case in which the first digit dialled raises the switch wipers to the digit absorbing level, the normal post springs NPA are arranged to be mechanically operated by the switch shaft. If it is desired that these springs shall be effective only on the odd digit corresponding to this level, a strapping, shown bya circle and dash connection, is taken from the contacts NPAI to armature dai so that in case the even digit is dialled the release of relay DA will shunt the contacts NPAI to render them ineffective; similarly if the dotted connection is utilised, the normal post springs will only become effective as regards" the even digit.

On the release of relay C in the usual manner at the end of the impulse train, relay H releases since the holding earth is removed at the .operated contacts NPAI while for the same reason no energising circuit is completed for the rotary magnet RM. Relay H on releasing completes a self-interrupted driving circuit for the vertical earth, armatures bl and al, oiT-normal contacts N2, vertical magnet interrupter contacts om, armatures 11.6 and c4, rotary off-normal contacts NR4, magnet VM to battery and the switch wipers are accordingly raised vertically step-by-step.

When the switch shaft reaches level 5, another set of normal post springs NPB is operated and at contacts NPBi a circuit is completed by way of the protective resistance YA to maintain the vertical magnet in an energised condition while at contacts NPB3 the short-circuit is removed from the right-hand winding of relay which now re-operates. This relay releases relay DA at armature cl if it has already been operated in response to the dialling of an odd digit and at armature c4 releases the vertical magnet and again connects it to the iinpulsing circuit in readiness for the second train of impulses which will follow at the conclusion of the interdigital pause.

By the above arrangement the time available even in the shortest interdigital pause is ample for the purpose of digit absorption, particularly since digit 7 is usually allocated as the digit to be absorbed so that the switch will have to make one step only to reach level 5 in readiness for the next digit.

On the dialling of the second digit the switch steps vertically from level 5 and in the manner previously described each alternate impulse is absorbed. The switch then performs an automatic rotary search for a free outlet in the selected group of outlets.

When the connection is released at the conclusion of the conversation, earth is removed from the P conductor at the controlling switch in the train thereby releasing relay H and also relay DA if it has been operated. Relay H disconnects the holding circuit for relay C which previously existed over armatures c6 and h! and on the release of relay C a self-interrupted driving circuit is completed for the rotary magnet RM from earth supplied to common conductor Iii by way of delayed alarm equipment, armatures b3 and h3, interrupted contacts rm, off-normal contacts N4, armature c5 and magnet RM to battery. Accordingly the wipers are rotated clear of the banks after which they fall and rotate by spring tension back to their normal position where the off-normal contacts N4 open and disconnect the release circuit.

At the commencement of release an unguard period on the incoming P conductor which is represented by the sum of the release times of relays H and C is provided to enable preceding switches to restore. On the release of relay C following the release of relay H earth is replaced on the P conductor over armature c6 and ofi-norrnal contacts NI until the switch has completely restored to normal when the earth is removed by the opening of the off-normal contacts NI We claim:

1. In a telephone system, an automatic switch having a plurality of sets of wipers and corresponding groups of contacts, means in the switch responsive to received impulses for alternately operating the sets of wipers and switching from one set to another, said means operated in response to a first digit to select a contact only in a portion of the contacts of each group, the contacts in another portion of each group being se-' lectable only when the switch is operated in response to more than one digit.

2. A telephone system as claimed in claim 1, wherein the contacts in the other portion of each group are selected only when a particular first digit is received by said switch.

3. In a telephone system, an automatic switch having a plurality of sets of wipers and means responsive only to alternate received impulses of a first digit for moving the wipers, means responsive to the receipt of a particular digit to automatically move the wipers to a particular position, and means responsive to a further digit for further moving said wipers.

4. An automatic switch of the two directional type having a plurality of sets of wipers, a bank of contacts for each set, means responsive to alternate received impulses for alternately operating the wipers vertically and switching from one wiper set to another, means in the switch operated responsive to received impulses corresponding to a particular digit for automatically oper-. ating the sets of wipers vertically past one group of contacts in each bank, said first means thereafter responsive to a succeeding digit to operate the wipers vertically only by each alternate impulse thereof.

5. An automatic switch as claimed in claim 4 wherein said first means is also responsive to each alternate impulse of a succeeding digit to switch from one set of wipers to another.

6. In a telephone system, an automatic switch having vertical and rotary movement, a pair of wiper sets therefor, a bank of contacts for each wiper set, means in said switch responsive to a first digit to select a contact in only the first half of each bank of contacts, said means responsive to a particular first digit to prepare for selection of contacts in the second half of each bank of contacts and thereafter responsive to a second digit delivered to the switch to select any contact set in only the second half of each bank of contacts.

7 In a telephone system, an automatic switch having vertical and rotary movement and a plurality of sets of wipers and contacts for each set arranged in levels, a vertical magnet and a switching relay in the switch, means in said switch responsive to alternate impulses of a first digit received by said switch to operate the vertical magnet to raise the wipers and to alternate impulses to switch from one set of wipers to another to select contacts only in particular levels, means in the switch responsive to a particular first digit received thereby to cause the wiper sets to prepare the switch for selection of contacts only in another group of levels, said first means responsive only to a second digit to select a set of contacts in said other group by means of either set of wipers.

8. In a telephone system, an automatic switch having vertical and rotary movement and having a plurality of wiper sets each having access to a bank of contacts, means in the switch responsive to a first digit received by the switch for selecting a line in only a portion of the banks accessible to each wiper, means responsive to a particular first digit for preparing the switch to select contacts in another portion of the banks,

for switching from one set of wipers to the other,

means in the switch responsive to the receipt of one impulse of a digit received by said switch to operate both the magnet and the relay, and means responsive to the next impulse of the digit to deenergize both the relay and magnet.

11. A telephone system as claimed in claim 10 wherein the relay and magnet are thus operated by a first digit to select trunks in one group and are similarly operated in one instance by a second digit to select trunks in a second group.

12. In a telephone system an automatic switch having vertical and rotary movement and having a plurality of sets of wipers, a vertical magnet in the switch for operating said wipers, a relay in the switch for switching wipers, means in the switch responsive to impulses of a received digit to operate the magnet and relay in response to odd numbered impulses and responsive to even numbered impulses to cause deenergization of both, whereby a line may be selected over any wiper set.

13. A telephone system as claimed in claim 12,

wherein there are two groups of lines accessible to each wiper set and means for absorbing a particular first digit to cause odd and even impulses of a subsequently received digit to select a line in a second of said groups only.

REGINALD TAYLOR. GEORGE THOMAS BAKER.

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