US1922192A - Telephone system - Google Patents

Description

J. 1. BELLAMY TELEPHONE sYsTEM Aug. 15 1933.

Filed Jan. 8, 1932 g5 weak-P P?? I'rcu' Era Tb 1- Jul-m I. Ballanj Patented Aug. 15 1933' UNITED. STAT-ES PATENT OFFICE 1,922,192 I TELEPHONE SYSTEM John I. Bellamy, Brookfleld, 111., assignor to Associated Electric Laboratories, Inc., Chicago, 111., a Corporation of Delaware Application January. 8, 1932. Serial No. 585,545

14 Claims. (01. 179-18 tioned amongst the trunk. groups accessible to.-

such selector.

' General description by side in groups or shelves, with a permanent.

multiple between thecontact banks of all the switches in a shelf, and with'arrangements for multiplying the banks of a number of shelves together and for connecting the bank multiple with outgoing trunks; as is explained in the McElyea Patent No. 1,633,118, granted June 21, 1927. The

number of shelves multiplied together as regards a given level depends upon the relative amount of tramc carried by the level in question.

In multi-oilice'telephone systems, the various groups of trunks accessible to an office selector often vary greatly in size amongstthemselves. Although, by using suitable grading, a trunk group can be formed which is in efiect a unitary group, but contains many more trunks than there are contact sets allotted to the group in the bank of any one selector, it is desirable, nevertheless, from the standpoint of securing the greatest possible efliciency in each individual installation, to be able to increase and decrease the number of contact sets allotted to a contact group to an extent dictated bythe relative size and cost-pertrunk of the trunk groups concerned, so that more than ten contact sets of a selector may to be expanded or contracted at will by including any desired portion of the contacts in an adjacent level in the same trunk group with the contacts in any given level. With this novel arrangement, any level may be divided into two parts, each part being indexed by a separate digit and belonging to a diflerent trunk group; one part is indexed by the digit normally assigned to an adjacent level while the other is indexed by the digit normally assigned to the level in question.

In order to enable the improved selector to search over allcontact sets assigned to a trunlr group when such contact set lies partly infone level and partly-in another level, the selector. in

addition to having the regular private wiper and 5 companion pair of line wipers is provided with an additional private wiper and companion pair of line wipers, so that two complete wiper sets are provided. .The additional'wiper set is preterably located on the shaft "either the space of one level above the regular wiper set or the space of one level below the regular wiper set, as will be pointed out more particularly hereinafter Then, when a trunk line group has contact sets assigned thereto in two adjacent levels, one wiper set searches in one otthe two levels at the same time .the other wiper set issearching in the other of the two levels, and either wiper set may find an idle trunk line reached through an idle contact set and cause the hunting operation of the '80 selector to stop and the idle trunk line to be seized. v

It will be understood, 0! course, that arrangements somewhat after the fashion or the ar- 1 trunk lines simultaneously.

A feature of the invention is that each contact set includes two test (or private) contacts, a 200- contact test bank beingprovided for this purpose, with the contacts arranged in pairs inthe manner oi the regular line-bank contacts, and that the regular test wiper oi the switch always tests over one contact only of a pair while the added test wiper always tests over the other contact of the same pairythe arrangement is such that the regular-test-wiper tests the lower'contact of each pair while the test wiper oi. the alternate set tests the upper testcontact 0! each testcontact pair. with this arrangement, a .contact set in any level may be assigned to the trunk group of the corresponding level by merely conmeeting the test conductor thereof to'the lower 1 test contact of the associated pair, and it may be assigned to the next adjacent level by merely connecting it to the upper test contact of the pair instead of to the lower.

With the arrangement above described, when a test wiper is being rotated over a level of contacts, the lower test contacts of the level are tested in case the test wiper in question is the alternate test-wiper,- whereby connection with a trunk line is prevented unless the wipers are rotated into association with the contact set assigned to such trunk line responsive to the digit assigned to the trunk line group containing the trunk line in question, as will be more particularly explained hereafter.

It will be understood, of course, that selectors which have two or more wiper sets, together with suitable switching arrangements for causing the connection to be automatically extended by way of whatever wiper set finds an idle trunk, are well known. Such prior selectors, however, employ separate bank-contact sections for each wiper set,

and the number of contact sets in the bank of a selector assigned to a trunk group is increased above ten only by duplicating the original bank arrangement for each added set of wipers. With the improved selector herein disclosed, the number of bank sections is not increased, but a more flexible use is made of the existing sets of bank contacts so that those trunk groups which require more than ten sets of contacts may be accommodated at the expense of other trunk groups not requiring as many contact sets.

An additional feature of the present invention is that the circuit arrangements of the selector have been improved and simplified by providing a simple and reliable control circuit for the slowacting release and series relays, which circuit is of the so-called slugless type and which is maintained entirely separate from the circuit of the operating magnet of the selector, whereby it is applicable to selectors having operating magnets of difierent characteristics without necessitating a change in the resistance or other characteristics of the slow-relay, control-circuits.

Description of drawing Referring now to the drawing, comprising a single sheet, they show a sufficient amount of apparatus in a telephone system embodying the features of the invention to enable the invention to be understood. More in particular, the draw,- ing showsthecircuit diagram of a selector constructed according to the invention, together with various views of the bank and wiper arrangement of the selector, so that the Way in which the novel wiper assembly cooperates with the contact bank will be readily understood.

Fig. 1 shows the circuit diagram of the selector, together with its regular wiper set comprising wipers 2123 and the alternate wiper set comprising wipers 24-26, and the first and second levels of the two bank sections 31 and 32.

Fig. 2 is a front view of the bank of the selector (with the contacts diagrammatically indicated), showing the wiper shaft and attached wipers, with an additional wiper set located one step above the normal wiper set.

Fig. 3 is a view taken along the line 3-3 of Fig. 2 in the direction indicated by the arrows, and it shows the normal relation of the wiper sets to the contact bank, with the alternate set of wipers off-set one step radially from the regular wiper set in order to avoid interference between the ends of the wiper arms when they enter the contact bank.

Fig. 4 is a view similar to Fig. 2 showing the lower part of the bank shown in Fig. 2, together with the bottom part of the shaft, and it discloses a modified arrangement wherein the alternate set of wipers is placed below the regular wiper set instead of above the regular wiper set as in Fig. 2.

Fig. 5 is aview taken along the line 5-5 of Fig. 4 in the direction indicated by the arrows, and it indicates that the alternate wiper set is off-set radially the space of one rotary step.

As indicated in Fig. 1, the selector illustrated is provided with line relay 5, release relay 6, series relay '7, switching relay 8, and wiperswitching relay 9. In addition, the selector is provided with the usual vertical, rotary, and release magnets, 17, 19, and 18; and it has the off-normal spring contacts 10 and 11 as well as the over-flow contacts 12 and 13, which latter contacts are preferably operated only when the selector takes its twelfth rotary step, by which time all contacts in the path of .the wipers will have been searched over. The dial-tone and busy-tone transformers 20 and 21 are provided common to the selector shown and other similar selectors for the usual and well understood purposes.

The selector, as illustrated, is of the so-called battery searching type in that it hunts for a trunk line having a battery connection on the test lead thereof.

It will be noted that, when relay 8 operates, the incoming conductors 2 to 4 of the selector are extended to wipers 21--23 in case the wiperswitching relay 9 is in normal condition, and are extended to wipers 24-26 in case wiper-switching relay 9 is in operated condition. The wiper 27 is paired with the wiper 21 merely for the mechanical purpose of maintaining a tension on the wiper 21, as can be seen best in Fig. 2, while the wiper 28 is paired with the wiper 24 for a similar purpose. It is to be noted that there is no electrical connection made to either of the wipers 2'7 and 28 from the selector.

The dial-tone source is associated with the selector under the assumption that the. selector is a first selector, to which connection is ex: tended automatically responsive to the removal of the receiver and in the well-known manner. It will be understood, of course, that the dialtone connection is replaced by a ground connection if the selector is used as a subsequent selector in the trunking system.

Referring now to Fig. 2, wherein the switch bank and the bottom section of the shaft, together with the attached wipers, are shown detached from the selector, it may be pointed out that the selector is mechanically of the general type illustrated in Fig. 62, page 62 of Automatic Telephony,"second edition, written by Smith and Campbell, and published by the McGraw-Hill Book Company Inc., 1921. Other views of switches employing similar bank arrangements and wiper assemblies are shown in Figs. 50, 55,

56, 5'7, 59, 65, and 66 of the Smith and Campbell book. The two regular wiper assemblies,

including wipers 21 to 23 and 27, Fig. 2, are

with which connection zis'made bythe regular set of wipers.

- trunk groups above mentioned. As, indicated second column oi? the above table, it may be" In Fig. 3, it may be seen that the alternate wiper set is set one step behind the regular wiper set, radially, so as to avoid the ends of the wipers being forced into engagement with one another. when the wipers enter the contact bank.

The contact grouping The grouping of the bank contact will now be explained. Referring to Fig. 1, it is assumed that the trunk group to which the digit 1 is assigned is a group'of rather expensive interoijfice trunks, while. the trunk groups to which the digits 2 and 3, respectively, are assigned are either small trunk groups or else are relatively inexpensive groups not requiring the eiilcient. trunk-use demanded by the first group. A total of thirty contact sets, comprising the first three levels of the selector bank (all'three of the illustrated levels) have been assigned to the three by the following table, all contact sets in the first level, together with the first six contact sets in the second level, have been'assigned to group 1; the last four contact sets in the second level together with the first three contact sets in the third level have been assigned to group 2; and the last seven contact setsin the third level have been assigned to the third group;

Number Trunk groups 33233;? of contact 1 sets 11 to 10, 21 to 26 16 27 to 20, 31 to 33 7 34 to 30 7 In explanation of the information given in the pointed out that contact set number 11 refers to the first contact set in the first level, that the succeeding contact sets in the first row are designated 12, 13, 14, etc. to the ninth. set, which is numbered 19, and that the tenth set is numbered 10. The numbering 'of the contact sets in the higher levels follows the same plan.

It will be understood, of course, that the above indicated apportionment of contact sets amongst Detailed description The invention having been described general ly, a detailed description of the operation of the apparatus shown will now be given.- For this purpose it will be assumed that the selector is seized in the usual course of setting upa telephone connection. 1

Seizure of the selector When the selector is seized (by way of con- .ductors 2, 3, and 4), which seizure is made by way of a lineswitch, for example, because there is no ground potential on conductor 2, and conductor 2 is supplied with battery potential (negative potential) by way of resistance element 14, line relay 5 operates over conductors 3 and 4 and through contacts of switching relay 8. Upon operating, relay 5 closes a circuit for release relay 6 by way of resistance element 15. Relay 6 thereupon operates and closes a locking circuit for itself in series with relay '7, but relay '7 does .not operate as long as it is shunted by resistance element 15. Relay 6 also prepares a test circuit for the upper winding of switching relay 8 by placing ground potential on the left-hand .85 terminal thereof; it opens a, point in the circuit ofrelease magnet 18 and prepares a circuit for vertical magnet 17; and, .at its upper armature, it places ground potential on the incoming release trunk conductor 2 so as to provide a holding circuit. for the preceding switch (not shown). By the above described operation of relay 6, the selector is prepared to operate responsive to the first digit of a desired number.

Dial tone In order to inform the-calling subscriber that a first selector has been seized andthat he may now begin to dial the digits of the desired number, ground potential is normally applied to the upper terminal of the upper winding of line relay 5 through the secondary winding of the dialtone transformer 20, whereby a characteristic dial-tone current is transmitted back over the calling line to the calling substation. I

Directively setting the selector When the first digit is dialled, the circuit of line relay 5 of the selector is interrupted, at the callingdevice on the calling line a number of times depending upon the value of the digit. Each time its circuit is interrupted, line relay 5 deenergizes and closes a circuit for vertical magnet 17 by way of contacts of the unoperated switching relay 8 and contacts of the operated release relay 6. By the operation of vertical magnet 1'7, the wipers of the selector are raised stepby-step until they come to rest opposite the desired levels of contacts.

Responsive to the first restoration of line relay 5, relay '7 operates in series with release relay 6 because the shunt circuit including resistance element 15 is removed from around series relay "7 Upon operating, relay "7 connects resistance element 16 in shunt ofrelease relay -6,- thereby setting up a circuit condition which will enable relay 6 to release in spite of' its connection in series with relay '7 in case the receiver is replaced at the calling substation.

Each time line relay 5 reoperates, it replaces 1 the shunt circuit around series relay '7 through the resistance element 15, which shunt circuit is of such low resistance that relay '7 is unable to remain operated more .thanmomentarily with this shunt applied. It may be pointed out here that the resistance element 16 preferably has a resistance low with respect to the resistance of relay 6. and that resistance element 15 has a re-' sistance low with respect to the resistance of element 16, and that by varying the resistances of elements 15 and 16 with respect to each other and to the resistances of relays 6 and '7 the holding effects of. relays 6 and 7 may be increased or decreased as desired; raising the resistance at 15 increases the holding effect of relay 1, and raising the resistance at 16 increases the holding effect of relay 6. By using this principle, diilerent weights or gauges of contact assemblies may be provided for.

As a further resultot the operation of relay '7,

a point in the circuit of rotary magnet 19 is opened at the upper contacts of the relay, whereby the premature operation of rotary magnet 19 responsive to off-normal spring 10. shifting to its alternate position upon the first vertical step of the switch is prevented.

Trunk hunting At the end of the vertical movement of the switch, line relay 5 comes to rest in an energized condition, following which series relay 7 shortly restores responsive to the resistance element 15 being shunted around its winding. When relay 7 restores, the circuit of rotary magnet 19 is completed, which circuit includes off-normal spring 10 in its alternate position, and an armature of relay 6. By the buzzer-like operation of the selfinterrupting rotary magnet 19, the wipers of the selector are rotated step-by-step over the selected contacts in search of an idle trunk line. It may be assumed that the digit 1 has been dialled, in which case the wipers 2123 have-been raised opposite the first level of bank contacts, while the alternate set of wipers, 24-26. has been raised opposite the second level of bank contacts. With the grouping as hereinbefore given, and as indicated in Fig. 1, both wiper sets pass over trunk lines of the first-level group while trunk-hunting until the alternate wiper set has advanced beyond the sixth group of contacts in the second level, following which only the lower wiper set, comprising wipers 21--23, is searching over first-level trunks, while test wiper 24 of the alternate set is passing over the disconnected upper test contact, of the last four contact groups in the second level.

Because of the angular displacement of the two wiper sets, the normally connected wiper set (which has been raised opposite the first level of bank contacts, under the previous assumption) engages the first set of bank contacts while the alternate wiper set is still one step short of engage ment with the bank contacts in the second level. As a result, the first set of bank contacts in the first level is always tested first, and relay 8 is operated by way of test wiper 21 to seize this set of bank contacts if the trunk line connected thereto is idle. If this contact set tests busy, however, the rotary movement continues and the alternate wiper set engages the first contact set in the second level at the same time that the normally connected wiper set engages the second contact set in the first level.

For the purpose of the following description, it will be assumed that the trunk lines connected to the contact sets now engaged by the two wiper sets both are idle, in which case a test circuit is closed for the upper winding of switching relay 8 by way of test wiper 21 and the lower test contact in the second set in the first level, while a test circuit is closed at the same time for the upper winding of wiper-switching relay 9 by way of wiper 24 and the upper test contact of the first group in the second level, the testcircuit of relay 9 being completed by wayof release trunk conductor 54 of trunk T11 of the first-level group.

operate fully without further aid fromtheir test.

circuits. Relay 9, in addition to opening a point in the circuit of rotary magnet 19 at its upper armature, disconnects the normally connected wipers 2123 and substitutes the alternate wipers 9 both restore.

24-26. Relay 8, in addition to opening a point in the circuit of rotary magnet 19 at its upper armature and a point in the circuit of vertical magnet 17 and release magnet 18 at its innerupper armature, applies ground potential directly at its middle upper armature to test wiper 24 by way of the operated inner-upper armature of relay 9; opens the test circuit of the upper winding of relay 9 at the normally closed contacts controlled by its inner-lower armature so as to prevent a subsequent operation of relay 9 in case this relay has not operated by the time relay 8 operates; and at its lower armatures it disconnects the incoming conductors 3 and 4 from the windings of line relay 5 and extends them by way, of

which contacts the talking conductors 55 and 56 of the trunkTll are connected.

The line and release relays (not shown) to which the trunk T11 extends now operate and bring about the grounding of conductor 54 so as to extend the ground potential back through wiper 24 and contacts of the operated relays 9 and 8 so as to hold relays 9 and 8 operated and to maintain the preceding portion of the connection established after the release relay 6 has fallen back. Responsive to line relay 5 being disconnected, this relay falls back and again removes the shunt from around series relay 7, whereupon relay 7 operates and shunts resistance 16 around relay 6, responsive to which relay 6 shortly restores and opens the circuit of relay '7, permitting relay '7 to restore also.

Releasing the selector When the selector is to be released, ground potential is removed from release-trunk conductor 54 of the trunk T11, whereupon relays 8 and When relay 8 restores, it completes .a circuit at its inner-upper armature for release magnet 18 by way of contacts of the restored release relay 6 and oif-normal contacts 11. By the operation of release magnet 18, the selector isv restored to its normal position, whereupon the circuit of the release magnet is opened at off-normal contacts 11. At oil-normal contacts 10, battery potential is reconnected to release-trunk conductor 2 by way of resistance element 14 to indicate that the incoming trunk com prising conductors 2--4 is again in condition to be selected.

Additional description of trunk selection It may be pointed out at this time that relays 9 and 8 operate successively rather than simultaneously in the event that the contact set engaged by the alternate wiper group is idle and the contact set engaged by the normally conneetedgroup is engaged. Under this condition, no test circuit is'completed for the upper winding of relay 8 by way of test wiper 21, because of the lack of an idle-indicating battery potential on the contact engaged by wiper' about the wiper switching operation hereinbefore described, whereupon the circuit of relay 8 is switched from wiper 21 to wiper 24, and relay 8 then operates over wiper 24 and completes the seizure of the idle trunk engaged by wipers 2426.'

Still another case needs to be considered: the normally connected set of wipers, wipers 21-23, may encounter an idle contact set at a time when me contact set encountered by wipers 24-26 group of the calledlevel. For example, assume.

that the wipers 2123 have been rotated to the last set of bank contacts in the first level. In this case, wipers 24--26 are in engagement with the ninth set of contacts in the second level. In this case relay 9 cannot operate, as there is no connection to the contact on which wiper 24 is standing. When relay 8 operates under this condition, it extends the connection by way of wipers 21-23 to conductors 51-53 ml the trunk T10, whereupon the holding circuit for the selector and the preceding switch is established over-conductor 51 of the trunk T10, and release relay 6 of the selector falls back as hereinbefore explained. 17

All trunks busy in the selected group When all of the trunks in the selected group are busy, the group assigned to the first level of the selector for example, the wipers of the selec tor are rotated step-by-step until both sets of wipers have passed off the contact bank, which occurs upon the twelfth rotary step of the switch. This amount of rotation is necessary in order to insure that the alternate wiper settests each contact-in the level over which it is passing, as the alternate wiper set is angularly displaced one step behind the normally connected wiper set.

When the twelfth rotary stepis taken, overflow contacts 13 are operated to close an operating circuit for the lower winding of wiper-switching relay 9, whereupon relay 9 operates to open the circuit of rotary magnet 19 at its upper contact to prevent further-rotary movement. At the same time, overflow contacts 12 substitute busy-tone current from the transformer 21 for the dial-tone current from the transformer 20, thereby sending a busy signal back to the calling line.

When the calling subscriber responds to th busy signal by replacing his receiver, the deenergization of relay 5 results in the transmis-' sion of a momentary impulse to operating mag-- net 17 and in a momentary operation 013 relay '7, but relay 6 falls back after a short interval and opens the circuit of relay '1 and the circuit of magnet 17, at the same time closing the usual circuit for release magnet 18 to cause the selector to be released. At the same time, ground potential is removed from conductor 2 by relay 6, so as to bring about the deenergization or relay 9.

- Modified grouping arrangement only the first six as disclosed. When this is done,

it is merely necessary to disconnect the release trunk conductor of'the last four contact sets in the second level from the lower contacts and connect them to the corresponding upper con-' contacts in the second level; It is to be understood, o! course,that this does not cancel the second-level group, as this group may as many contact sets as desired in the third level, the test conductor of each second-level trunk line in such case being connected to the upper test contact so that it will be searched over and connected with by the alternate wiper sets, if idle.

It may be pointed out that the normally connected wiper set cannot connect with any trunk line group in the second level, for example, which is assigned forthe first-level group when the digit 2 is dialled, as the test contacts of the trunk lines so assigned are disconnected in the row then wiped over by test contact 21 of the normally connected wiper set.

The .nzodifled wiper setting From the foregoing description it willjbe understood that a trunk group indexed by any digit from 1 to 9 may include trunk lines connected to the contact sets in the-next higher level and wiped over by the alternate wiper set when the digit indexing the trunk group is dialled. But, the trunk group to which the digit 0 is assigned cannot have more than ten trunks therein with the arrangement disclosed in Figs. 1 to 3, unless an, additional level of bank. contacts is provided above the tenth level, because the alternate wiper set is raised above the tenth level of bank contacts when the digit 0 is dialled. The modified wiper setting of Figs. 51 and 5 may be used instead of the wiper setting indicated in Figs. 1 to 3 in case it is particularly desired to' have more than ten contact sets in a selector bank assigned to the trunk line group indexed by the digit 0. As indicated in Figs. 4 and 5, the alternate wiper set, including line wipers 25 and 26, is positioned the space of one level of bank contactsbelow the normally connected wiper set including wipers 2123. With this modified setting of the wipers,

the alternate wiper set does not engage a given ninth level, whereby as many of the 'ninth level contact sets as desired may be assigned to the 0 level group.

It will be understood, of course, that the assignment for any level with the modified arrangement is such that additional contacts assigned to the group indexed by a given digit are located in the next lower level instead of the next higher level as in the embodiment oi. Figs. 1 to 3.

A special feature of the selector when constructed in accordance with Figs. 4 and 5 is that the first level of bank contacts may be completely utilized in giving access to trunks in the second-level group when the digit 1 is not assigned. In explanation of this statement, it I may be pointed out that it is common'practice to leave the digit 1 unassigned as the first digit in subscribers numbers because of the prevalence of so-called preliminary impulses caused by the careless removal oi the receiver, and the like. Sometimes the first level of bank contacts of a first selector is left disconnected, in which case the first selector merely releases in case the digit 1 is inadvertently dialled as the first digit or in case a preliminary impulse equivalent to the digit r is generated as the receiver is being removed. If trunk lines are connected to the contacts of the first level of the selector herein disclosed and constructed in accordance with Figs. 4 and 5, and the release-trunk conductors of these trunk lines are connected to the upper test contact in each case, the first level tests open to the normally connected wiper set when it rotates over the first level responsive to the digit 1 being dialled, in which case the wipers advance to the overflow condition, causing a busy-tone signal to be sent backto the calling subscriber. However, when the digit 2 is dialled the alternate wiper set rotates over the first level of bank contacts (while the it"a'rnally connected wiper set is rotatingover the second level), and the entire first level of bank contacts may be utilized for trunk lines of the second-level group.

If desired, the trunking flexibility of this latter situation may be secured when the full ten trunking digits are utilized by providing eleven bank levels, in which case the wiper sets are adjusted on the shaft so that each encounters a bank level responsive to the dialling of each of the ten assign ed digits.

it is evident that considerable modification may be made of the trunking arrangement herein disclosed. For example, the two wiper sets of the selector may be set more than one level apart in order to meet conditions which may arise from time to time. If this is desired, the alternate wiper set may be provided in different assemblies from the assemblies of the normally connected wiper set and located lower on the shaft than the regular wiper set, in which case the angular displacement of the two wiper sets is unnecessary, as there is no danger of interference between them when they are more than one level apart.

It is apparent that all levels of a standard bank may be. utilized when less than ten and more than four trunk groups are needed, as the trunking digits may be so assigned with respect to the wiper setting that one wiper set searches over an unassigned level while the other wiper set is searching over an assigned level.

What is claimed is:

1. In combination, a selector having bank contact sets arranged in groups, each group normally correspcmoing to a separate digit designation, the contacts in one of. said groups being divided between two trunk groups bearing different digit designations, means for bringing said selector into association with said contact group as a result of control being exercised over the selector in accordance with either of said digit designations, means thereupon effective for starting said selector searching over the contact sets in said groups successively, said selector-having two test wipers arranged to cooperate differently with thetest contacts of said contact groups, and means including said two test wipers and automatically effective dependent upon the digit in accordance with which the selector receives its control for preventing the selector from making connection with any trunk line of one group and for permitting the selector to make connection with any idle trunk line in the other group.

2. In combination, an automatic switch having a bank of contacts divided into groups, said switch having two sets of wipers, operating means efiective to operate said selector to bring-one of said wiper sets into association with a group of said contacts by a movement of one extent, said means being effective to operate said selector to bring the other set of wipers into association with the same contact group by movement of a different extent, means for causing said selector to advance either set of wipers over the contacts in said group, each contact set in said group comprising two test contacts, a test wiper in the first wiper grouparranged to cooperate with the first test contact of any of said contact groups, and a test "wiper in the second wiper group arranged to cooperate with the second test contact in any one of said contact groups.

3. In combination, a selector having a bank of contacts divided into groups, each group including a row of line contacts and two rows of test contacts, means for bringing said selector into association with a group of contacts as a resultof either of two imparted movements, means for advancing said selector over the contacts in the group successively, means effective when one movement has been imparted to the selector for causing the selector to make successive electrical connection with the contacts in one of said rows of test contacts, and means effective responsive to the other movement having been imparted to the selector for causing the test contacts in the other of said rows instead of the first.

4. In combination, an automatic two-motion switch having a single contact bank divided into groups and having two sets of contact wipers, and means for variously positioning said selector so as to cause either of said wiper. sets to comelnto operative relationship with any one of a plurality of groups of said bank contacts.

5. In combination, an automatic switch having a bank of contacts arranged in parallel coextensive rows, said switch having two sets of contact wipers and means for bringing either wiper set into engagement with any one of a plurality of 11 said rows and for operating it over such row, the

second set of wipers being so positioned relative to the first that the second wiper set engages the adjacent contact row when the first wiper set is caused to engage a contact row to which it is directed, and means for securing said two wiper sets at a suitable angle with each other so as to prevent' their making electrical contact with each other as they are being advanced over adjacent contact rows.

6. In combination, an automatic switch having contact sets arranged in rows, said switch having two sets of wipers, means responsive to a control of one value being exercised over said automatic switch for causing it to associate one set of wipers with a contact row, means responsive to a control of a' difierent value being exercised over said switchfor causing it 'to associate the other wiper set with the same contact row, and means effective in either case to cause the associated set of wipers to be driven over the said contact row.

'7. In combination, an automatic switch having wipers, a bank of contacts accessible to said wipers and divided into groups, means in said switch refor causing saidselector to extend a connection v to a trunk line reached by way of the said desired group ofcontacts or by way of a trunk line reached through the immediately preceding group oi! conacts.

8. A circuit arrangement for controlling the release and series relays of an automatic switch wherein the two relays are operated in series with each other, two resistance elements, means con-,

trolled by the line relay of the automatic switch.

for connecting one of said resistance elements in shunt of the series relay, and means controlled by the series relay for connecting the other of said resistance elements in shunt of the release relay.

plurality of rows, a pair of wipers, one of said" wipers having access to only one contact of any of said pairs of contacts and the other wiper having access to only the other contact of any of said contact pairs, and means for advancing said wipers over two rows of contact pairs, respectively, at the same time. f

11. In an automatic switch, a contact bank in which the contacts are arranged in pairs in a plurality of rows, a pair of wipers, and means for moving said wipers to a position so that one of them engages one contact of a pair in a given row, while the other wiper engages the non-corresponding contact of a pair located in another row.

12. In combination, an automatic switch having abank of contacts including pairs of contacts arranged in-rows, said switch having a pair of progresslvely movable contact makers, means for maintaining said contact makers in a fixed position relative to one another, means for selectively operating said contact makers to associate either desired one oi them with a given contact row and for advancing them so that the desired one passes over the selected row of contact pairs, said contact makers being so positioned and adjusted that one contact maker engages a given contact of any pair when it is being advanced over a row of contact pairs, while-the other contact maker engages the other contact of the same pair when the said other contact maker is being advanced over the v same row of contact pairs.

13. In combination, a selector having two test circuits, two wipers included in said test circuits, respectively, a bank of test contacts in whichthe contacts are arranged in pairs in a plurality of rows, and means for moving said wipers so that when one engages a contact of a pair the other engages the non-corresponding contact of a pair in another row.

- .14, In combination, a selector having two test circuits, two test wipers included in said test circuits, respectively, a bankof test contacts over which the test circuits may be completed, said contacts being arranged in pairs, one wiper having access to only one contact of any of said pairs and the other wiper to only the other contact, and means for operating said selector to advance, said wipers over two rows of contact pairs, respectively, at the same time, whereby said test circuits are variously completed.

- JOI-IN I. BELLAMY.

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