US2187784A - Telephone system - Google Patents

Description

Jan. Z3, 1940. R. E. Hl-:RsL-:Y 2,187,784

' TELEPHONE SYSTEM Filed June 11,' 193e 4 sheets-sheet;

/NvE/vroR REHERSEY By ATTO/:WBV

R; E.HERSEY TELEPHONE SYSTEM A Filed June 17, 1958 Jm z3, 1940.v

4 Sheets-Sheet 2 F IG. 2 oFF/c5 nv/r Alva comvecfon.

IIHI- vf/vl//s/VTOR RE. HERSEY By www f4 T TORNEV Jan. 23, 1940. E. HERsEY TELEPHONE -sYs'rEu "Filed Ju'e 17, 195s l suina-sheet s /NVEA/ron.

Milf/P551 y @y Ww.

ATTORNEY RQ E. Hl-:RsEY

'rlamsraorm` SYSTEM Filed June '17, 1938 4 Sheets-Sheet 4 1wn`sNJPSJR-n hm R w m W SM1 A .Sm m ,En [L h fwn W we.. Pug MU ...la IWHILHF.. MS.

wa. Sh. 6:18.

- RLT/15955;

A T TORNE Y Patented Jan. 2,3, y1940 UNITEosTA'r-ss rAT ENT or eine; L

TELEPHONE SYSTEM I v 'i Ralph E. Hersey, Madison, N.`J., assignor to Bell'v Telephone Laboratories, Incorporated, New York, N. Y., a'corporation'of New York Application June 17, l1938,' 'semina 214,353

claims.

This invention'relates to telephone systems t and particularly to systems in. which automaticA switches are used for establishing conversational connections.

The vobjects of the invention areto obtain a more positive and complete test of they operative condition of the switches and connecting circuits used in establishing a talking connection; to test the condition of the connecting circuits both before and after ',the switches are operated to close the desired connection; to ycombine in the same control mechanism the function of pern formingthe verifying tests and the functionof operating the selective switches; and otherwise to secure improvements in systems `of this kind.

`The present invention is applicable to systems of the characterin which the selec-tive switches are operated under the control of register senders or markers located at the centraloffice,

and

.which receive the called designations either from a subscribers dial` or from an operators position.

Where cross-bar switches are used in thesev tems and common markers are associated temporarily'with the switch framesv vfor the purpose of testing trunks andlinks interconnecting the diierent switches and for the purpose of operating the switch magnets to closethe contact sets and establish the connection over the links trunks, Ait is particularly desirable to test and the

several circuits involved orgunstandard conditions and to test the connection after its establishment for continuity through the closed contacts of the switches and also for the presence of any unstandard conditions.

Since the common marker'that controls theestablishment of these connections lcauses the selective operation of the switch magnets, and since the success of finally established connection depends upon .the

.the

component connecting circuits vbeing free from any unstandard conditions and upon thev proper closure or" all of the switch contacts involved,

they

several verification tests can best be made .by mechanism located in the marker and which co--A operates with the mechanism that causesv operation of the switch magnets. If the 'various' tests are all successful, the marker proceeds in its regular manner with the establishment of the connection and'with its release from the switch frames after the connection has been completed.

0n the other hand, it trouble is encountered at` any stage, the marker is in Sa position to prevent any `further progress with the connection and to bring into operation trouble indicating devices the for making a record giving the details of trouble condition.

l iolowing specication.

. in which:

Acontro-l circuit and districtjunctor A feature of the invention is a system or' the general character above mentioned in whichl a common marker yserves to. operate a plurality of successive switchesto establish a connection by joining .in vtandem` a'plurality of serially lrelated link circuits; in which fthe linksare tested to determine if their conductors Aare continuous and are in. proper condition for operating the i.

switches; in which .the switches are operated to establish the connection, andthe operatedcontracts of all switches are then tested Ito determine if they have closed properlyyin which all links are .again tested to determineif they are free from `unstandard conditions; and. in. which the marker refuses to proceed with the normal es tablishment ofthe lconnection inwcase. any of these testsfprovesunsatisfactory. w .Another feature isa combined verifying and switch operating mechanism inwhich relays vare connected respectively to the successive links in-1 volved inaconnection to test the conductors o f said links, to control. the operation of the successive switches, to control the test of the closure of the successive .contacts in the established connection and to test .the connection after itsV esxtablishment for the presence rof any unstandard conditions. v

The foregoing and other features yof the in.y l

vention will be described more in detail lin the connection from a calling line;

Figs. 3 and4 disclose part of a common switch controlling'rnarker; and

Fig. 5 is a block diagram showing the manner in vwhich the several figures of the drawings should be arranged. 1

` l fGenemZ description The 'invention is illustrated in anautomatic telephone system -in which automatic switches y of'thefcrossfbary typeare used as'the medium vfor extendingconnections from subscribers lines over trunksvto other subscribers lines. These cross-bar switching mechanismsI arel controlled by'register' sendersv at the central ofce, which receive 'the designations from the calling subscribersy dials, and by decoder markers, which are connectable to the senders for receiving information from the senders, and which are connectable to the proper switch frames for the purpose of testing the outgoing trunks and for testing the connecting links and for operating the magnets of the cross-bar switches to establish the connections.

While the system disclosed is not limited to the use of cross-bar switches of any particular type, reference may be had to the patent to Reynolds 2,021,329 of November 19, 1935, for an understanding of the construction and operation of a switch suitable for use in such systems. Because of the complicated nature of these systems, and since it is not necessary to an understanding of the invention that the system in all of its details be disclosed, much of the circuits and equipment has been eliminated in the present disclosure for the sake of simplicity. And in the following descriptions reference will be made to numerous operations which are not fully disclosed in all of their details. Wherever such references occur it will be understood that the circuits and equipment so referred to are already old in the prior art, and in particular reference is here made to the following for a detailed disclosure of all operations and equipment referred to herein but not specically disclosed: Carpenter Patent 2,093,117

of September 14, 1937; and Carpenter application Serial No. 214,356, filed June 17, 1938.

When the subscriber at station |00 initiates a call, a connection is established through the cross-bar switches |0| and |02 to the district junctor circuit |03, and to a subscriber sender |04, represented schematically by a box. Sender |04 is connected by a plurality of conductors, represented conventionally by conductor |31, to district junctor |03 and to junctor relay H3 by conductor |32. It is also connected by a plurality of conductors to the marker circuit shown in part by Figs. 3 and 4. This connection is indicated conventionally by the connection of conductor |30 to the marker boundary line |29. When the subscriber dials the office code, this is recorded in the sender, and then the marker in cooperation with the sender determines the pair of oflice frames upon which is located the group of trunks leading to the called destination. An idle trunk 200 of the district group, located on the secondary ofce switch 20| is then selected and the marker proceeds to select an idle connecting channel extending from junctor |03 to the trunk 200. This channel consists of a link 08, connecting prima-ry and secondary district switches |05 and |06, junctor H0 connecting secondary district switch |06 and oii'lce primary switch 202, and link 203 connecting primary and secondary ofce switches 202 and 20|.

Detailed description The aforementioned idle channel having been selected, this system will now be described in detail. After an available channel consisting of the link |08, junctor ||0 and link 203 has been selected, relay 400 which is identified with the selected channel, operates through a circuit from ground 40|. Relay 400 operated, locks through its lowermost contacts to ground on the innermost contacts of relay 402, which operates from ground 403, when a circuit is closed'indicating that the register relays of the marker have operated and registered the oiiice code, the district frame with which the calling district junctor |03 is associated and that certain other functions have been performed. Relay 400 operated now closes three circuits through its two upper, and its lower inner contacts, which closure initiates the performance of the following functions:

(l) The operative condition of the links |08 and 203 of the district link and connector circuit and of the oftce link and connector circuit respectively, which are identied with the selected channel, is checked.

(2) If the aforesaid links |08 and 203 are found to be in operative condition, then hold magnets ."Il, |09, 204 and 205 are operated.

(3) With the hold magnets all operated, a test is made to determine the continuity of the established connection through the operated contacts of the switches |05, |08, 202 and 20|.

(4) With the connection established from the calling district junctor |03 to the outgoing trunk 200, the marker before releasing makes certain tests to determine if any unstandard conditions exist. If any of these tests indicates an unstandard condition then the call is blocked, and the marker releases after a predetermined interval. The aforementioned tests are as follows:

(a) Checking the operation of a relay in the district junctor, which relay is operated when the tip party of a two-party line is calling.

(b) Checking the condition set up in the district junctor, when the call is other than a tip party call.

(c) Checking the condition of the district junctor for calls to an operator.

(d) Checking the district junctor circuit for the operation of a relay that establishes a talking charge condition.

(e) Checking a no-charge condition in the district junctor.

(f) Checking the registration of a zone-charge condition in the multiple registration circuit.

(g) Checking for the condition existing on a zone-charge call when all multiple registration circuits are busy in the case of district junctors arranged for message rate or time charging of local calls, or for no-message rate or time charging of local calls.

(h) Checking the continuity of the circuit through which the message register of the calling line operates.

(i) Checking for the presence of ground on the sleeve conductor of the outgoing trunk to make sure that the trunk will be held busy after the call is established.

The various features before outlined will now be discussed in order.

Checking the operative condition of the links of the selected channel Relay 400 operated closes two circuits for checking the operative condition of links |08 and 203 identified with the selected channel. If there is no ground on the winding terminals of associated hold magnets |01 and 205, and a battery potential is found thereon, it is an indication that these magnets are in an operative condition. If a trouble ground is connected or a cross ground from another operated hold magnet, which might for instance be connected through contacts of relay which are multipled to contacts of a similar relay not shown, it would be an indication that the link associated with this magnet is unavailable. If no battery should be connected to the winding, due perhaps to a blown fuse, or should the operating circuit be open for any reason, this also is a condition which the test about to be described would detect. Assuming that the magnet |01 is in operative condition, a circuit is accordingly' closed for polarized relayA 300.. The

upper and lower windings: of this rel'ay are, con-- nected?. differentially in: series, by the connection of ground on the upper innermost ccntacts'and battery on the lower contacts of relay h,` which; ope'ratesfroni ground 30.2; to. register anv oft-normal conditiony ofthe markerin a manner similar tolrelay 402, before discussed'. The lower wind-1 ing of relay 000 predominates magnetically.` and causes its contacts toarernain` closed. The oper.'m

' ating circuit for' relay; 30011 may betra'cedi yfiicrn sor' battery through the winding'of' magnet |01, left in-ner contacts of relays liti and' |10 over conductor H9" 'through upper inner operatedfcon the current in the upper winding of relayl 300 tov be increased 'due to the reduction of circuit resistance froml the multipled connection ofthe' lower winding of relay 300" and the winding of" magnet' E01. The current in the upper winding of relay v300 now predominates vand relay 30.0 operates, opening its break contacts. If, hoW-' ever, thereis a ground on the-windingof' hold magnet l 01 then the current in the lower winding of relay 300I is increased while the upper winding is shortcircuited by the direct ground connection. Relay 300iunder this condition; accordingly does not operate.

The functions of the several relays havingA con# tacts in the test circuit above discussed will nowbe mentioned in detail, these relays and their functions being the sameas those disclosed' in 'greater detail in the above-#mentioned application of`W. W. Carpenter Serial No. 214,356, filed June 17, 1938. Relay HI' is identified with thegroup of district iunctors in which junctor |03 is l'ocated vand is operated from groundy in sender |04-, through the outerl operatedcontacts of relay "I |32 Relays H2 and H4, connected in multiple, are marker connecting relays andl are furnished one per marker for each district link and corinect'fn` frame. These` relays operate whent ground is connected by the operation. of relay l5, whichin turn is operated when start battery 326 ispannected over conductor H6 by the marker which may be selected to handle the c all initiated by the` subscriber of station |00. Relay 404 is av relay that isheld operated from ground on thev contacts of relay 40T, which latter relay Operates'when the` channel test paths are closed. In order to insure that all hold magnets have ample time torelease fully, after the channel test is `made andbefore their operation is started, the opening ofmthe circuit of relay 404 is delayed for an interval'. During this delay relay 408 is connected to make a final test for ground on sleeve conductor v20G` of the selected trunk to. ymake sure. that this. trunk is then actually available. If the test ythen discloses the presence of ground on this sleeve conducton, then relay 40B operates and locks` and operates relay 6105. If relay 40.5 should thus be operated the circuit before traced for relay 300Y is not closed and relay 300 is not operated'. In other words, the link associated with district pri mary hold magnet I0l--is reported unavailable if' ground should thusl be found on' the sleeve con-r 3 duct-0r zneoff theI selected tnmk: zoo, with which is. associated link [08J of the channely selected: to

reach said trunk 200'. The. operation of relay 300 isl alsoblocked-if: relay 406. also fails to. operate andthereby close its lower contacts.. Relay 40.6 and relayr 4l16..in multiple therewith, operate: through r.upper break contacts of relay 411 and over '/cvonductor424, which is. extended through a circuiti and contacts'notshown, ofrelays. H12, l I li and H3, to?checktheoperation of these relays.

. When'relay. 4200.0peratesa second circuit isalso "closed for operating-relay 304i. to test the avail. v

ability oflink 200 between oflice primary switch` Z02- and cnice secondary switch 20|. Relay 3.04 is a polarized; relay similar to` relay 300A before described'. Its windings are connected differentially series, the `upper winding .being conF nected Ito groundonfthe upper middle contacts and its lower winding to battery onr the lower contacts: of" relay 301;A Thefoperatin'g circuit for re-'r lay 304 maybe traced from'y battery through the winding' of secondaryoifice hold magnet 205, contacts of relay 201, right inner contacts of relay 208', over conductor 2l 2 through lower inner con- "tacts of relay 400, lower innerjbreak contacts ci` lrelay 404, lower contacts of relay 405, lower inner contactsofrelay'4l0, lower contacts of relay 4l l, lower outer break contacts of relaylll 2*, over conductor 3|4 to the center point of the connection betweenthe upper and lower windings of relay- 304-. As in the case ofY relayv .300; if therev is no ground on the winding of magnet 205,A the shunt` ing effect of this winding on the lower winding of relayy 304 reduces the current in this winding,`

while at the same. time, the current. in the upper; windingv is increased so that relay 304 operates, If, however, there is a trouble ground on the winding of magnet 205,. the current in the lower winding of relay 304' is increased by the direct ground connection, while theupper winding is short-circuited., The effect of. this iste cause relay 304 to maintainjits contacts closed. ,If no battery should be connected to the winding of' magnet' 2.05., then, of course, relay 306i' fails also tov oper-4 ate for this type of trouble condition. Relays i. il? and 41|, through the lower break contacts of which the operatingv circuit for relay 30.4 was traced, are relays that are` operated and held when two markers select the same trunk and then test the same; sleeve conductor 209'. In. other words, if the condition of a single trunk being` selected simultaneously by each of two markers occurs, then the operation of. the test relay 304 is prevented by the `operation of relays M0 and 4H.. The operating ycircuit. .for relay 304 was tracedl through contacts of relays 20'? and 208.. Relay 200. is operated from marker ground M3 through right outer contactsk of associated relay 210,l and over conductor 2 l0 when relay 'M0 operates` due to the selective operation of relay lli! by marker battery 0|@ over conductor 2.20. Relays 208.,v 210 and 2H arer operated,.sinc,e these relays are associated with the oifice frame `on which is locatedthe `selected trunk 20,0. Relay 207 is selectively operated from marker ground` M5, ove." conductor 22+' and through left contacts of relay 2013 and is identiiied with the particular switch of' the selected oflice frame upon which Athe selected link 203 terminates. v

` The operation of relays 300 and 304 to check the availability of the links between the primary and secondary district switches E05 and 06, re-A l spectively, and between the primary and second-l ary ofiice switches 202 and Elli, respectively, has been just discussed. Ii' as before described, one

of these links has been found unavailable dueto the improper grounding of the associated-hold magnet |07 or 205, or due to the absence of battery potential and relay 300 or 304 did not operate, then the call is blocked as to be hereinafter described. The call is also blocked if the operation of relay 300 lor 304 is prevented by non-continuous circuits through the contacts of the several relays, as hereinbefore described. When for any reason relay 300 or 304 fails to operate, resulting in the blocking of the call, a trouble release signal is given to the subscriber sender, as described in the aforesaid' Carpenter application Serial No. 214,356, filed June 1'7, 1938, the marker releases and the subscriber sender selects another marker for a second trial. If, however, the links |08 and 203 associated with relays 300 and 304 respectively, are satisfactory for use as indicated by the operation of these relays, they and associated apparatus function as now to be described.

Operation of hold magnets Magnets E01 and 205 start their operation in series with the windings of relays 300 and 304, respectively. Relay 300 in operating opens with its break contacts a locking circuit for relays 305 and 30G, which circuit is traced from battery through the windings of relays 305 and 306 in multiple, upper outermost make contacts of relay 305, contacts of relay 300, lower innermost make contacts of relay 305 to ground on the upper middle contacts of relay 402 over conductor 3|3 which ground operated relays 305 and 306 over conductor 3|3 through a circuit, not shown but indicated by the broken lines 323. `Relay 304 in operating also opens a second locking circuit for relays 305 and 30G. This circuit is traced from the windings of relays 305 and 306 through upper, innermost make contacts of relay 305, break contacts of relay 304, and lower outermost make contacts of relay 305 to the operating ground on conductor 3|3. Relays 305 and 30B accordingly release. It should be observed here that to effect the release of relays 305 and 305, both relays 300 and 304 must operate; if only one relay operates, indicating that only one of the tested links is available, then relays 305 and 306 do not release and the circuit for the subsequent operation of relays 303 and M2, is kept open at the lower inner and outer break contacts of relay 305. respectively, and the operating circuit for magnets |09 and 204 is open at the outer break contacts of relay 306. Relay 306 released closes a circuit from ground on the upper outermost make contacts of relay M5, operated as hereinbefore described, through lower inner normally closed contacts of relay 4| 2, over conductor 3|5 to junction point 324 and in multiple with this circuit path another circuit path from ground on the lower outermost contacts of relay 4|E over conductor 3|3 through lower inner normally closed contacts of relay 303 to said junction point 324, thence through break contacts of relay 325, upper outer break contacts of relay 306, over conductor 300, through upper outermost contacts of operated relay 400, over conductor Eil, through contacts of relays ||4 and |20 to the multipled windings of hold magnets |09 and 204 of the district secondary and omce primary switches which magnets are now operated. The purpose of relay H0 has already been described. Relay |20 is operated through the right contacts of relay H2, over conductor |2| from ground 32T in the marker circuit and is one of a number of similar relays in the district link and connector circuit, leach one of which is connected through individual contacts on the marker connecting relay H2. The proper relay |20 is selectively operated by the marker route relays and its selective operation gives access to the junctors, for example, junctor ||0, which connect the calling district frame with the ofce frame upon which is located the group of trunks extending to the called location. Relay 325 is controlled over conductor 32|, through a circuit connecting with the lower break contacts of relay 4|'|.

Relay 4|1 is arranged to check the continuity of the path for the subsequent operation of line message register |22. The operating circuit for relay 4|? is traced from ground through winding of message register |22, lowermost switch contacts of line link switches |0| and |02, left operated contacts of relay H3, resistance |23, left outermost contacts of relays and ||2, overconductor |24, through inner contacts of relay 300 over conductor 322 and through winding of relay 4| 1 to battery. If the circuit path just traced is closed, indicating that register |22 can be subsequently operated, relay 4|`| operates, but not register |22. If for any reason relay 4| 'l should fail to operate, indicating that the circuit for-the register |22 is open, then relay 325 operates subsequently from ground M8 and opens with its break contacts the operating circuit for magnets |00 and 204.

Assuming now that the circuit path for operating magnets |09 and 204 is closed, these magnets operate and close the associated crosspoints of switches |06 and 202, it being understood that the select magnets |25 and 2| 3 were previously operated, through circuits not shown here in detail. If magnets |01 and 205 are now not yet completely operated through the circuits just traced through the windings of relays 300 and 304 respectively, their operation is now insured and completed by the direct ground connection extended to the left through operated innermost switch contacts of magnet |09 towards magnet |01 and to the right towards magnet 205 through operated innermost switch contacts of magnet 204, provided, however, that magnets |09 and 204 have actually operated and closed properly their associated contacts.

Checking the continuity of the circuit through operated switch contacts With all hold magnets |01, |09, 204 and 205 energized and presumably operated the means for checking their actual operation as evidenced by a continuous circuit through their respective associated innermost operated switch contacts, will now be discussed. With relay 300 operated as before described, when magnet |09 operated its operating ground was extended through its associated innermost operated switch contacts to the winding of magnet |01. This operating ground now acts, over the operating circuit for relay 300 before traced, as a shunt on the upper winding of relay 300, which accordingly releases, responding only to the effect of its lower winding.` Similarly, the same operating ground is extended through associated innermost switch contacts of magnet 204 to the winding of magnet 205, causing the release of relay 304 by reason of the shunting of its upper winding. The release of relays 300 and 304 is evidence of the satisfactory closure of the switch contacts associated with magnets |09 and 204, respectively, and said release closes circuits for testing the satisfactoryclosure ofthe switch contacts fasseciated with magnets |07 and 205 (it vbeing understood that select magnets 2'| and ,2|8,. have been previously operated through f circuits not shown) (and. at the 4same time determines Whether*- certain standard circuit conditionsnecl, essary for the'successful functioning of th-e'established connectionexist.

vlo

The functioning of thecircuits'tor'testing the closure of' the switch 'contacts' associated .withjmagnet'swl and 205 will vbe 'described' lrst.' Ground connected through theinnerm'ost' operated switch contacts y of. magnet' |0'l1 `is 'extended through' right oper.-

Iated innermost contacts of-relay: I3, left middle vope-rated contacts` of relays lli' and H2, over.`

`lay 305, break contacts of relay 300 released as described, lower inner breakl contacts of` relay 305 andv to'battery through the winding of relay l303, whichfoperates, indicating that-'the circuit through theiswitch contacts'associated With mag- -netL |01 has-been satisfactorilyclosed.- Another -fcircuit, to test the .contacts of magnet` 205,'- is tr'acedvthroughthe winding of relay M2 fromthe y operating ground of magnet 2051through'itsfin- 'ner associatedswitch contactsiand-'through in.-

nercontacts of relay 2 |4 Which'is oneof a'num- 'ber of similar relays of the oice linky and connector circuit which is selectively y operated ythrough left contacts of relay2|0, over conducltor 2l5,' from vground 4|9` in themarker. `The particular relay# ZM whichl is operated depends upon the level of' the Vswitch horizontal' upon `which the selected trunk is found. From the inner-contacts ofrelay 2|4 the circuit being traced f .continues thro-ugh right outer contactsof relay V208, over conductor 2 |6, upper operated contacts of relay 420, over `conductor30'l, through upper inner break contacts of'relay 305, breakcontacts of relayl 304, released as-described, lower-outer.

lbreak contactsof relay 305, over conductorv 3|6 and vto battery through winding of relay 4| 2,

bwhich operatesif the circuit is complete. Relay -420 through the rupper contacts of` whihfthe circuit for relay 4|2 was traced, is operated in response tothe selection of the idle trunk 2,00. n YRelay 303jin operating opens with its upper contacts one of three holding circuits for they multi- `pledrelays 405 and 4|@ by disconnectingconductor 300 from conductorr 3|2. The other circuits are opened by relays 4|| and `42| `Relay 4|1 in operating as before described disconnects with its upper break contacts conductor"13`|2 from the windings of relays 4|@ and 406. The 'operation of polarized relayr 42| will no'W be discussed. Normally the upper windingof relay 42| 'is connected over conductor 3 to ground on the upper outermost contacts of relay 30|and the lower Winding over conductor 3H to battery on ythe lower vcontacts of relay'30l`. Ground is also connected to the center point of the upper and lower windings of relay 42| through lower inner normally closedr contacts of relay 'M2 to ground n on the'up'p'e'r outermost contacts of vrelayf4|6,

' and also over conductor 3I5 through'lower inner normally Yclosed contacts of relay"30.3,' over conductor. 31.8, t0 smiled 911th? We? Qiiwnf 'ing terminals of relays 300 and 304 wherrrelays4 operated, relay 332, Which is operated as herein@ itacts of relay`4||i..` When vrelays 303 and M2 operatejthroughthe lcircuits before traced, the

ground shuntA yis removed from thecommon winding terminal of relay 42| which then operj atesl from ground on` the upper. outermost contacts ofrelay 30 l, overconductor 3l lthrough Aupper winding of relay.42|,"over conductor 3|5, thence through the circuit path hereinbefore 203. Theupper winding of vrelay i525 is also energizeol` (c) through its lower" windingl to bat` ltery, (b) through the` windings of magnets E01 land 205 and switch contacts of magnets |03 and .traced forv the operation of hold magnets l|03 and 234, (c), through windings of relays 303 and M2,

connected by way of 4switch 'contacts' associated with magnets |03 and 205.6 Relayf02| does ynot vbeen removed by the operation of; relays 303 and` M2., vthere still remains a trouble ground, con, nected to the windingeterminals, of hold mag# nets `|09 and 2.04which would continue to shunt f v the upper winding of-relay 42|, thereby preventving its operation.` If, however, relay 42| oper ates, then 'all holding circuits for relays 410B and 4|6 are opened and these'relays release.

L operate, however, rir Aafter the grounds on the y upper and lowermost contacts of relay'4l5 hayev Relay;-303 in operating connects ground on the lower outer make contacts of relay34| 6, over conductor fll,I through lower inner .makecontacts make contacts of relay 406, overconductorv 320 to the center-'winding terminal of relay 300, thereby:v maintaining this relay non-operated. A similar `connection is made for relay 304 when relay M2' i' operates and connects ground on the upperv outermost make contacts of relay 4 IG, through its low-er make-before. break contacts to conductor o 3|4, thereby holding `relay y301| knonfoperated. This arrangement of grounding the center Wind- 'c 303 and 4|2Y operate insures that the operating circuits Vof relays 30.3 and`o4|2 are satisfactorily maintained through the contacts ofrelays 300 connect with their lower outer break contacts the operating'-circuitsbeforer traced for relays 300 and 304, respectively. Relay4|2 in* operating also vfunctions with its upper transfer contacts Ato hold ltrunk'2|10b1'1s'y and to effect the' normal release of the marker' as 'to be hereinafter dei scribed. o' c o.

When' the connection between'v the j district` junctor |03 and the selectedl trunk 200. hash-een -i and`3l04. Relays "303 and '4|2 in operating dis-r` established, the marker circuit then testsror certain standard.v conditions lbefore releasing These will now be discussed as before outlined. i n Checking the't'z'p party. relay in the district In order to insure that a calling tip vpu'artyfon, i 60. a two-party selective subscriber line is properly* charged and not the ring party the operation of relay 333 is effected by applying ground Ain the lsende'ar |04' to the conductor 335 and in operating'y causes a relay, not shown, inthe district junctor |03, to operate. This latter relay when operated," causes a ground indication to be returned to the marker effecting the ca oerationof` the tip party check relay 334. With relays 333 and 334 thusy after described for calls other than-tipparty calls, must not'be operated. With relays 333 kand 334 operated the operating circuit for relai/'303,

yhereinbefore traced, passesv through make contacts" of relays334 andv3'33 and break contacts f of relay 332. Should anfunjstandard condition exist as would be indicated by relays 332, 333, 334 all not operated or relays 332 andl 333 both operated, or relays 332 and 334 both operated, or only relay 333 or relay 334 either alone operated, then relay 303 would not operate, the holding circuit for relays 4I@ and 406 would not be opened and the marker circuit would be released only after a time interval, the sender selecting another marker to complete the call. In the case of an operator class call from a tip party line, the ground-indication is not returned to the marker from the district junctor. In this class of call, accordingly, the marker must cancel the test for the tip party line and cause the operation of relays 333 andv 334 so as to close partially the circuit for the operation of relay 303.

Checking for a call other than a tip party call For a call other than a tip party call a circuit is closed for operating relay 332, but neither relay 333 nor 334 is operated under this condition. The circuit for relay 303 is accordingly taken through break contacts of relays 334 and 333 and make contacts of relay 332. If relay 332 should fail to operate under this condition the 'call would be blocked.

Checking for an operator class call For an operator class call a relay in the district junctor circuit, not shown, is operated and locked and the locking ground is returned to the marker operating relay 330. Under this condition the operating circuit for relay 303 passes through make contacts of relay 330. Ii relay v-330 should fail to operate under this condition the call would be blocked.

- Checking the district junctor for a talking charge condition The district junctor |03 is arranged so that a talking charge relay, not shown, is operated,

Whenever the message register |22 is to be operated once for each call, or once for each predetermined timed interval, when the call over the jselected trunk 233 is completed.y The operation of the aforesaid relay causes a ground tojbe returned to the marker which operatesrelay 330.

The circuit for relay 303 accordingly passes through make contacts of relay 330 and upper v.break contacts of relay 328. Relay 328, which jisoperated for a zone charge condition as hereinafter described, must not be operated when relay 330 is operated. Accordingly should relay 330 not be operated with relay 328 not operated, or should relays 330 and 328' both be' operated then relay 303 cannot4 operate and the call would be blocked. ,f

Checking a 1ro-charge condition in thedist'rict junctor In the case of calls for which the message register |22 should notbe operated, the talking charge relay of district fjunctor |03 is not operated and the no-cliarge relay 33| is operated in response to the operation of a certain route relay, not shown, which is operated when the call is .directed to a destination for which there is to condition, then relay 303 would not operate and the call would be blocked.

Checking the' registration of a zone charge condition Whenever the calling subscriber initiates a call to, a zone beyond the local area for which one or more operations of register |22 is required, district junctor |03 calls into service a multiple registration common control circuit, not shown. When the zone charge condition has been properly registered in the common control circuit, relay 328 is operated and the circuit for relay 303 is then completed through make contacts of relay 328. For this condition relay 330 should not be simultaneously operated. Ii relay 328 should fail to operate, or should both relays 330 and 328 be simultaneously operated, then the circuit for relay 303 would be open and the call would be blocked.

Checking for a zone charge call when all multipleregistration circuits are busy When all multiple registration circuits are busy, relay 329 is operated which causes the operation through a circuit, not shown, of the talking charge relay of district junctor |03, of which relay theoperation was hereinbefore discussed. With this arrangement the calling party may be undercharged, but suffers no delay because of the all-busy condition of the zone registration circuits. Relay 330 is accordingly operated, and the operating circuit for relay 3D3 is completed through make contacts of relay 330 as described under Checking the district junctor for a talking charge condition, There is also another circuit path through contacts of relay 329 which .is not necessary when a talking charge relay is furnished in the district junctor, but which is required When no talking charge relay is furnished as described in the following paragraph.

For district junctorsthat are arranged so that the message register |22 is operated only when a multiple registration circuit is called into service, a talking charge relay is not furnished. Consequently when relay 329 is operated due to all multiple registration circuits being busy as before described, no ground is returned to operate relay 330 and'it is accordingly necessary that the check for the operation ofthe district talking charge relay be canceled. This is accomplished when relayl 329 operates and short-circuits the make contacts of relayf330, thereby preparing the operating circuit for relay 303. If relay 329 should fail to operate under this condition, the call would be blocked.

Checking ,for the continuity of the message register circuit When relays ||2 and ||3 have operated and When an idle channel between the district junctor |03 and the selected trunk 200, has been selected and relay 306 has released, a circuit is closed for operating relay 4|I which was described in connection with Operation of hold magnets. Should relay 4|'l fail to operate indicating that the message register circuit is open, then relays 4|6 and 406 are not released. Relay 406 in not releasing prevents the release of relay locked through its right contacts over conductor H8. District junctor relay ||3 is also held to the same ground through its right outer contacts. The marker would accordingly not release until timed out. If relay 4|`| should operate, however, relays 406 and 4|6, would then release, assuming that relays 303 and 42| operated.

Relay 406 in releasing, releases relays Ill and H3. Relay H3 in releasing connects ground through its break contacts to the Winding of magnet |01 through the lower switch contacts associated with magnet ll'i. This ground is extended to hold also magnets H39, 2M and 205 after the holding ground furnished by the marker is removed when the marker subsequently releases.

Checking for ground on sleeve conductor of outgoing trunk When trunk 200 was selected and relay 420 operated as before discussed, a circuit was closed for immediately grounding sleeve conductor 25d v'so as to make the trunk test busy to panel selectors, which may also have access to this trunk, prior to the final connection of ground 225. This circuit is traceable from conductor 299, through outer contacts of relay 2|4, right inner contacts of relay 2li), over conductor 2H, through lower operated contacts of relay 420, upper break contacts of relay MD, to ground 422 through the upper break contacts of relay M2. When relay 4|2 operates, it transfers with its upper contacts the circuit for sleeve conductor 299 before traced fromground 422 to the winding of relay 423, the con-tacts of which are not shown here. Relay 523 operates, if ground 225 has been properly connected by the operation of its associated switch contacts, and then the normal release of the marker circuit is effected, assuming that all .other tests hereinbefore described have indicated the existence of standard conditions.

After the marker releases and the sender has completed its functions, the sender eiects the operationI through a circuit, not shown, of relay |28 which completes the transmission circuit between the subscriber station Ilm and the selected trunk 20D.

What is claimed is:

1. In a telephone system, a plurality of serially related switches, link circuits interconnecting said switches, means for testing said link circuits for an unstandard condition thereon, means for operating said switches to establish a connection over all of said links in series, means for testing the continuity of the established connection through said links, and means for testing the established connection for thel presence of an unstandard condition thereon.

,2. In a telephone system, a plurality of serially related switches, link circuits interconnecting said switches, means including test relays and circuits therefor for testing said links for unstandard conditions thereon, switch magnets operated over said test circuits for establishing a connection through said switches and including said links in series, means controlled by said test relays, for Verifying the operation of said switch magnets, and means for testing the. connection thus established for unstandard conditions.

' 3. In a telephone system, a plurality of serially related switches, link circuits interconnecting said switches, a common controlling and testing mechanism having means therein including test relays and test circuits for testing the condition of said links preparatory to the establishment of a connection, switch magnets operable over said test circuits to close contacts of said switches and establish a connection over said links in series, means including said test relays for verifying the operation of said magnets and the closed condition of the switch contacts, means in said common mechanism for testing the estabiished connection for the presence of an unstandard condition thereon, and means for releasing said common mechanism for use in establishing other connections.

4. In a telephone system, three serially related links, switches for connecting said links to each other, two relays and circuits therefor for testing'resfpectively two of said links, means dependent upon said test for causing the operation of all of said switches to establish a connection over said links in series, means including said relays for testing the continuity of the established connection through said switches, and a third relay for testing all of the links in the established connection to determine if an unstandard condition is present.

5. In a telephone system, first, second and third link circuits arranged in series, means for testing said first and third link circuits to determine whether an unstandard condition exists thereon, automatic switches for establishing a connection over said links in series, operating magnets for said switches. and means dependent upon said test for closing operating circuits for said magnets, means for verifying the operated condition of said magnets and the continuity of the connection extending over said link circuits, and means connected to the second one of said link circuits for testing the established connection including all three of said link circuits to determine whether an unstandard condition exists thereon.

RALPH E. HERSEY.

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