US1445258A - Testing system - Google Patents

Description

Feb. 13, 19 23.

s. B, WILLIAMS, JR, ET AL TESTING SYSTEM Filed w b. 5, .1919

fienen A. Boat/er.

l atented Feb. 13, 192

ts sales SAMUEL B. WILLIAMS, an, or BROOKLYN, NEW YORK, AND HERBERT njnos'ratrna, or WEST NEW YORK, New annsnr, nssrcnons To wnsrnan nnno'rrtrc'corirnny, INCORPORATED, on NEW roan, n. 35., A oonrona'rron or NEW YORK.

TESTING SYSTEM.

App1ication fi1cd February which the following is a full, clear, concise,

and exact description.

This invention relates to electrical testing systems, and more particularly to testing systems capable of use in connection with telephone systems employing connecting apiiaratus common to one group of apparatus, to connect an individual set thereof with an individual set of another group of apparatus. with which the connecting apparatus may be associated.

A telephone system employing automatic distribution of calls between calling subscribers and answering operators through the medium of line finders and selectors is shown, and one example of such a system is disclosed in a patent of Samuel B. Williams. Jr., No. 1,304,641, dated May 27, 191-9. In automatic call distributing systems it is usual to provide a terminal bank cont .ning multiple sets of a large number or subscr'ibers lines. Each line has a number of terminal sets individual thereto, located horizontally across the bank and available to a number or. diiiercnt line finders; the line lindci's being so arranged as to connect with the terminals of all the subscribers lines in the multiple bank. Each oi the line finders is connected to a particular selector. and a group of these selectors are arranged taining multiple terminal sets of a number oi cords or trunks extending'to diiferent op crators positions, a terminal set of each such cordor trunk being available to'each ot the selectors. Upon a subscriber removing his receiver from the hook switch in calling, an idle line finder is actuated to engage one of its brush sets with the terminal set of such line available thereto, and to extend the connection to the proper brush set of its associated selector. The selectorsearches over its terminal bank until such brush set en counters the terminals of an idle cord or to pass over a similar terminal bank con 5, 1919. Serial Macrame.

trunk terminating before an answering op orator, and'stops thereon, thus completing the connection of'the calling subscribers l ne to an answering positlon' The line finder involved and the particular selector connected thereto thus serve as connecting apparatus between the calling subscribers line and the cord or trunk extending to an answering operators position.

Each trunk has a signal associated there; with and operated on connection of a calling line with such trunk to indicate that a subscriber, is calling. Should a line he co n' nccted with a trunk at a time when such line is not in use due to an abnormal condition of line, the trunk signal would be operated in the same manner, although no response would be obtained to an operators challenge. The signal is known under these conditions'as a permanent signal. It is highly desirable that the line causing the trouble should be readily located and removed from service in such away that like difficulties will not recur pending the restoration of the line to its normal condition. It'is fur ther desirable that such location should be made quickly in order that the line finder, the selector, and the trunk involved will not be engaged for an excessive period; thus reducing the available equipment and impairing the efficiency of the system.

In absence of the present system it would be necessary in such cases to visit in turn each of the selectors having a multiple of the involved trunk until the selector connected to the terminals of such trunk were located; From th s selector the particular line finder connected thereto. would be found, and such line finder visited. The particular set of terminals on which this line finder rests would next be noted. and the numberof the line thus identifiedf Thisline is then removed from service, and prevented from eftion is to provide a testing system capable of application to telephone systems employ ing a plurality of sets of connecting appa.

ratus common toa group of sets off appii ratus in which each set of connecting zip-- paratus is arranged to connect with any set. of such group, by which any particular set of connecting apparatus connected with any set of such group-may be rapidly and accurately located. In accordance with this feature of the invention individual test terminals are provided for each set of connecting apparatus adapted to connect with the sets of apparatus oi the group, together with means by which testing current is supplied to the test terminal of a set of connecting apparatus connected to a set apparatus or the group, and it eans cooperating with the test terminals to determine the particular connecting apparatus involved in the connection. I

Another object of the invention. is to provide a testing system having a testing circuit associated with a circuit to be tested in which the flow of testing current such that the detection of the testing current is insured. p

In accordance with this feature of the i11 vention two transformer coils are provided and arranged tor unsymmetrical connection by three conducting paths in such a manner that flux produced in the core of the first transform-er coil will produce an efi'ective flu in the core of the second transformer coil by means oi currents flowing over three circuits, each includinga different pair of the three conducting paths and each of the three paths having current flowing thereover so long as all of these three circuits are maintained. The circuit arrangement is also preferably such that an effective flux will.

also be produced in the core of the second coil whether one two or three of these cir cuitsbe maintained at the same time.

Other objects and features of the invention, not speciiically mentioned above, will be ap txarent from the following specification and annexeddrawing illustrating diagrammatically one embodiment of the present invention as ai iplied to an automatic call distributing telephone system.

In the paticular embodiment of theinventiou illustrated, a subscribcfs station It is sh wn having;- a pair of line conductors 10 and '11, extending); to a central oltice; A. line relaylfi, a cutoff relay 13, and a plurality er calling jacks, such as 14!, individual to the line are provided. The line relay 12 i 11, an

is ordinarily operated over a circuit extend mg from battery, left-hand winding of relay 2, lett-hand contact ofrelay 13, conductor l thence through the right-hand contact f relay 13, and right-hand winding of relav 2 to ground. 1 if V In call distributing; systems asapplied to large exchanges, it is usual for a calling line to be extended to an answering opera-- tor, through a line finder associated with a apparatus at substation A, conductor 10,

trated, and the line conductors 10 and llv and the test conductor 15 of the subscribers line are inultipled to an individual set or terminals in a multlple terminal bank ava1lable to a number of line finders, any one of which isdesigned to extend the particular subscribers line to an answering operator. Two such linev finders, LF and Ll or the usual type, are shown in the present instance. The closure of the contact of relay 12 causes the line Ll? to seize the termina s 18 01" the calling line substantially asdisclosed in the Williams patent above noted. As further disclosed in the above-noted patent, the cord selector GS is caused to seize an idle cord or trunk extending to an idle operators position herein shown as the associated circuit connected to the terminal set 21. The operators telephone set is next automatically connected to the trunl: through the contacts 24: and Qtiot sequence switch, termed for convenience SS when this switch is moved to position 7 as disclosed in the patent mentioned. A circuit is also closed from ground, interrupter 29, con tact 23 of sequence switch SS conductor 28, contact 26 or another sequence switch S5,, and lamp 27 to grounded battery. The lamp 27 is individual to the trunk concerned, and the flashing signal given by this lamp serves to identity the trunk over which a call has been extended to the particular answering}; operator. v

sequence switch SS, having a contact 10 is associated with the finder LF and its associated selector CS, and operates in such a manner as to close this contact 100 just subsequent to the stopping of the brush set 16 upon the terminal set 1.3 of line A. This closure takes place at position 4 and is maintained until. position 121-, and provides an operating); circuit for the cutoff relay 13, extending 'trorn grounded. battery, contact 100, sleeve brush of brush set 16 and sleeve terminal oi? terminal set 1.8, conductor 15, and winding oi relay 12-3 to ground. Busy potential is also placed upon the sleeve terminals of the multiple jacks and also upon the sleeve terminals of the multiples of, line A in the line finder contact banks. The operation of relay 13 opens the circuit of line relay 12, which releases.

On the engagement of the tip andrin a brushes of the selector C?) with the tip and ring terminals of set 21.,and' consequent movement of the contacts 24: and Le oi sequence switch SS, into their seventh posi-v tery, lower'lett-hand winding of repeating marines coil 36 winding of relay 69, contart 23 of sequence switch SS in position '7, cnga oil ring terminal and brush of selector cs. engaged ring brush and terminal of finder LF conductor 11. left-hand winding of induction coil. hook switch, and transi'nitter of station A, conductor 10, engaged tip tcrminal and brush ct finder Ll engaged tip brush and terminal of selector CS, contact 24 oi sequence switch Si in position 7. and upper left-hand winding; ot repeating: co l 56 to ground. A circuit is also pro-videiil through contact 98 of sequence switch or between positions 12- and 18 and often, the illun'iination ot the siuaerv-isory lamp {it when the supervisory relay (39 is deenergized during such interval, this circuit extending from gl'OlllldQd battery. resistance 42 lamp 60. and contact 98 of sequence switch SS between positions 1%} and 18;} to ground. On operation of relay (39, however. over the circuit previously mentioned, illumination of the lamp is prevented due to a short-cu cuit completed about this lamp by the closure of the contact of relay (S9. opening the operating circuit of: relay of) as tor example by restoring the receiver to the switclrhooiq at stat-ion A. the lamp .60 is. however, illuminated to indicate that disconnection is desired by station A.

In the present situation the relay (39 being energized prevents the illumination 0t lamp T he operator, under ordinary con ditions now obtains the number of the called line and completes the connection in the usual manner. It sometimes occurs, however, that the operator obtains no response either to her request. for Number please or to her subsequent challenge Are you calling although the lamp 60 is not. ligz'hted' The failure of the operator to obtain a reply indicates that something is the matter with this line. This condition is known as a permanent signal in stems of this type. This condition may ari. e. {for example. by the suliscriber leaving his receiver oil the hook. by cond 'ons prodi'icingr a short circuit between the line cam-ductors '10 and ll. or by grounding tl1erfl funder certain condition... It. is'ohviously desirable to determine what line in trouble in order to remove the trouble and to tree the line finder and selector involved in the connection so that they can be used in extending other calls.

in the absence of any special testing equipment. in order to locate the line causing the permanent signal, it would be necesto visit in turn each of the cord selecthe particular trunk orcord reported by the operator is found. From this selector it would be necessary to trace back to the particulsi r line finder connected thereto, and then to note the position of the terminal set frames until the selector connected to on which the brush set of such line Finder rests, and from this identi i. the line involved. flliis line maythen be removed :trom. service they use oi? a trouble cord, in the usual manner whichyserves to provide a trouble tcst for all the multiples of such line. To simplify this procedure and to save time as well to decrease the liability of error, the present invention contemplates the provision of a testing contact bank 85. Terminals indivii'lual to each of the line finders are arranged in this bank and connected to the tip and ring; brushes of the brush sets of their respective line finders. A brush set 36 is designed to pass over this contact bank and to engage one set of contacts at a time, the number or the line finder whose test terminals are engaged at any time being denoted by the number on a designation strip 3'? associated with the bank indicated by a pointer '38 movable with the brush set 36. flhis bank is for testing purposes and would in practice be located convenient to the switchman. an d a number of trunks would be provided hetween the answering positions oil the main switchboard and the switchnians desk. The terminal'set individual to line tinder LF is designated as 39.

The jack 40 of one such switc'hmanls trunk has been indicated and an operator having a trunk giving a permanent signal indication may insert the plug 41 ot such trun lt into the jack 40. This act serves to efi'ect the movement of sequence switches SS and SS into position 14 and into ringing position, respectively, as disclosed for example, in the patent above referred to. The lamp 27 is thereuponarranged to burn steadily over a circuit from grounded battery, lamp 2?, contact 102 of sequence switch SS between pov the number oi I sitions 3 to 16 to'ground. .as disclosed in said patent and remains steadily lighted until theringing 'is completed as hereinafter described. The switchman. is now signalled through the application 01 alternatinging current to the tip and ring conductors of the plug 41, over a circuit including the source of ringing currentlOB, contact 104 in position 13, the tip contacts of plus; 41 and ack 40, conductor right-hand winding of relay 44. condenser 46, conductor 47. the ring contacts of the jack 40 and plug 41 and the contact 105 in position 13 to said source 103. The consequent operation of relay 44 illuminates the lamp 48 and provides a direct current lock'inggcircuit tor relay 44 extending from grounded battery; lamp 48,

contact and left-hand winding of relay 44.

with the jacks 52 and 53 of his trunk, the

switchman, on observing the illumination of lamp 48, inserts these plugs or plugs of a similar switchmans set therein and moves the key 49 to listening position.

This act automatically disconnects the ringing current, and moves the contacts of sequence switch S8, into position 17, in which position the lamp 2? is extinguished and the controlling circuit of the calling supervisory lamp 59 extended to the contact of relay 92. This relay was actuated upon the insertion of the plug 41 into jack 40 over a. circuit extending from grounded battery, winding oi relay 92, sleeve contacts of plug 41 and jack 40, and resistance to ground. The contact of relay 92 is thus closed during ringing, but completes no circuit until sequence switch contact 48 is moved into posi tion 17, upon the switchman moving the key 49 to listening position. As soon as this is done however a circuit is completed extending from battery, lower right-hand winding of coil 56, winding of relay 58, ring contacts of plug 41 and ack 40, conductor 47, upper contacts of key 49, right windings of transtlf'ormer coil 99, lower contacts of key 49, conductor 45, tip contacts of jack 40 and plug 41, and upper right winding of coil 56 to the other side of battery. Relay 58 is thereby operated thus short-circuiting lamp 59 and preventing its illumination so long as this circuit is maintained. The switchman can signal the answering operator however by opening and closing the listening key 49, thus alternately opening and closing the circuit through the relay 58. Its contact is correspondingly opened and closed, and when opened removes the short circuit about the lamp 59 to permit its illumination over a circuit from grounded battery, resistance 97, lamp 59, contact 43 of sequence switch SS, in position 17, and contact of relay 92 to. ground. The resulting flashing of the lamp 59 serves to indicate that the switchman desires to communicate with the operator, being substantially the same operation of the signals and their meaning as in a connection between'a calling and a called subscriber.

Although the insertion of the plug 41 into jack 40 effects the movement of the contacts of sequence switch S5, out of their seventh or listening-in position into their fourteenth or talking position, as disclosed in beforevmentioned patent, means are available to the operator as therein described which wlll upon operation efiect the movement of the sequence switch SS again to its llsteningin position and inasmuch as the key 49 is in its listening position'such an act by the operator will complete telephonic circuits for intercommunication between the operator and the switchman. On obtaining this connection the operator informs the switchman of the permanent signal on the trunk used.

inthe connection.

The operator would efiect the movement eas es of the contacts of sequence switch S3, again to its fourteenth or listening-out position, and

the switchman would establish connectionoi? plugs 50 and 51 of a switchmans set with the acks 62 and of a tone testing circuit, preferably common to all the switchmens trunks, in order to locate the line finder in yolved in the permanent signal connection. The same or another switchmans set can be used for this purpose, and the circuit of the switchmans trunk is such that the disengagement of the plugs 50 and 51 from the jacks52 and 53 does not disturb the circuit previously traced to maintain the supervisory relay 58 energized to prevent illumination of the lamp 59. The transformer coil 99 and jacks 52 and 53 may however be common to a number of switchmens trunks, and connected to the individual trunks by the movement of the key 49 in dividual to a particular trunk with which connection is desired.

In the present system it is possible for one switchman to answer calls over the switchnians trunk and another switchinan to simultaneously search for line finders in volved in permanent signal connections.

'The switchman answering a call over a switchmans trunk, on being informed of the permanent signal connection, and desiring to disconnect from such trunk, as for example to answer a call over another trunk, would move holding key 55 into its closed position and also move the key 49 of the trunk in use out of listening position. The

operation of key 49 disconnects the coil 99' from the trunk originally used and leaves it free to be connected to another switchmans trunk by movement of the key 49 individual to such other trunk. The closure of key 55 provides a holding circuit through the relay 58 to prevent-the lamp 59 giving a disconnect signal at this time; this circuit extending from battery, lower Ilglll) winding 0i coil 56, winding of relay 58, ring contacts of plug 41 and jack 40, conductor 47, upper contacts of key 55, Winding of retardation coil 5'2, lower contacts of key 55, conductor 45, tip contacts of jack 40 and plug 41, and upper right-hand winding out coil 56 to the other side of battery. Under these condi tions none of the lamps 27, 59 and 60 are lighted, and since this condition is maintained until after the involved line finder has been located, consequent"annoyance oi the operator by false signals during the testing operation is thereby prevented.

Referring to the testing operation, the in sertion oi plug 50 into the jack 62-completes a governing circuit for a tone generator 64, this circuit extending from grounded battery, winding of a relay 65, conductor 66, and upper contacts of jack 62 to ground. The energization of relay 65 completes a'cir-1 cuit to operate the tone generator 64, this ll D i tor of the motor, to conductor (38 and contact of relay 6:") 'tothe ground.- switch may be provided to do operating circuit tor the tone generator (it,

it it desired to ope enerator independently ot the The tone generator 64; developsalternating current, the frequenc 1: not being preier- Y ably such asto produc a tone which can be readily distinguished from currents of other frequencies which may be encountered in testing over the multiple terminals of line finders engaged at the time; the altm'uating current thus developed flowing tin primary Winding of a transformer inducing corresponding currents in the secondary Winding thereof.

Each of the switchrnairs truni-is'has a tone he; '72 individual thereto, and in testing over such trunk this key is closed. Undeut conditions the insertion of the pl J the jack 63 completes a tone cir ut extending from the grounded secondary inding of repeating coil 71, conch-rotor 73, resistance 74, lower contacts of jack 63, lett-hand'contacts of tone key 72, conductor 41-7, ring contacts oi jack 40 and plug 41, winding of supervisory relay 58, and lower right-hand winding of repeating coil 56 tln'ouglr irrattery to 'ound. A parallel branch of this circuit extends from the conductor '73, through the righthand contacts of tone key 72, conductor 45, tip contacts of jack l0 and plug l1, and upper right-hand vindingot repeating coil 56 to ground. 7 The resistance 74 inserted in the parallel branch including the ring contacts of the jack 4-0 and plug 41 to prevent too great a lieu of direct current over a circuit completed upon the insertion. or plug 41 into jack 4:0 and extending from battery, lower right-hand Windingot coil 56, Winding of relay 58, ring co; acts of plug all and jack 40, conductor l7, 3 contacts of key 72, lower contacts of 1 G53, resistance 74:, right hand contacts of key 2, conductor 45, tip contacts of jack 40 and plug 41, and upper right-hand winding of coiloo to battery. The several windings of the transformer or repeating coil 56, preterably contain substantially the same number of turns. on account of its use tor two way telephonic transmission as well as for testing currents, although this particular relation between the dili'erent windings is not essential to the present invention.

A transformer coil 76 has its primary Winding arranged in a circuit connection bridged across the tip and ring brushes of the brush set 36, and condensers 77 and '78 are positioned in this counection'intermediate the primary winding and the respective brushes. The primary winding of the 7 Exit relay Ga.

coil 76 is non-'symmetrically' "divided lay being "grounded at an "intermediate- P011113 ct its Winding sons to. include a. considerably greater nuirnber of turns in the tip'side,

51. and jack 6% back to the secondary Winding of the repeating 'coil '76, The trans initter S0 of the switchmans set profs-r ably left out of circuit during testing as there is no reason tense it'during the actual testing. W Y

The switchinan in searchingtor the line finder connected to the involveclsubscribers line. moves his brush set 36over the testing bank 35 until it encounters the terminal set 39 of: line finder LF having testing current thereon, which tact Wlll be ndicated to the switchman by the production of a charac-v teristic tone in his receiver 79 corresponding, in frequency to the frequency of the testing currents developed by the tone generator 64. I Upon the engagement of the brush set 36, with the terminal set 39, thesecondary windings of the repeating coil 56 ill be connected with the dividedprimary= winding of the transformer coil-76' by three conducting paths lee-tor line finder, test tenninal, brush; and condenser 77 the ring conductor of the trunk selector line finder, test terminal, brush, and condenser 7 8, and ground; Three fluctuating current circuits'are accordingly possible between the secondary windings for alternating current, namely, the tip conductor of the-trunk use of the repeating coil 56 and the primary winding of transformer coil; 76," the first including the upper secondary Winding of the repeating co il 56, the tip conducting path, upper portion of primary Winding of transformer 7 6, and ground to the other side of such secondary Winding, thesecond circuit including the battery and other'seo onda-ry Windingof coil 56. the ring conducting path, the lowei portion of such primary winding, and ground to theot-her' side of such battery, and the third circuit in -cluding both secondary windings of coil 56 and intermediate battery in series with the tip conducting path, entire primary- Windof coil 76 and the ring conducting path.

The unbalancing otthe'primary windings 18 to produce a non-symmetrical circuit arrangement between the repeating coil 56' and the transformer coil 76, and is such as to insure a resultant flow of fluctuating current to operate the receiver-79, solong as fluctuating currents continue to tlow in any one or more of the three circuits. As a result of the non-synnnetrica-l arrangement, so long as none of the tliree conducting paths are open or shortcircuited to fluctuating currents, and fluctuating currents are developed in the secondary windings of the re eatin coil 56 corres ondin current resistance of Which was of low value.

will flow over'each of the three conducting paths, and each of the three mentioned circuits Will be maintained. Short circuiting between any two of the three conducting ,paths will still leave at least one of the.

three circuits operative to produce an effective flow of current 1nv the secondary Winding of the transformer coil v'76 to operate the receiver 79, and it is only ivhen all three of these conducting paths are directly short circuitedtogether by a connection of practically negligible resistance that all three of these circuits can be effectively de-- currents flowing over each of these three conducting paths, so long as tWo or all of the three circuits are effectlvely maintained. 4 The tip and ring conductors and the ground connection of the trunk line are in.-

v olved in the three conducting paths noted, and the tip and ringv conductors of the trunk lineinvolved are, under these conditions, connected through the corresponding brushes and conductors of the selector and line finder involved With the tip and ring terminals to which the line conductors 10 and 11, respectively, are connected. Should the permanent signal be caused by a grounding of the ring line conductor 11, the ring and ground conducting paths mentioned are short circuited together, and While the second and third circuits are thus effectually destroyed, the first circuit over the tip and ground conducting paths is effectively maintained, and flux isdeveloped thereby in. the core of the transformer 76 by the passage of fluctuating currents through the upper portion of the primary Winding thereof. This flux develops a fluctuating current in the secondary Winding of the transformer 76, and'thus effects the operation of the receiver 79 so that the engagement of the brush set 36 upon the terminal set 39 of the line finder itlis desired to locate will be readily detected. On some types of lines it is possible to obtain a permanent signal paths is effectively maintained and flux is developed thereby in the core of the transformer '76 by the passage of fluctuating currents through the lower portion of the primary Winding. This flux similarly effects the operation of the receiver 79 to detect theengagement of the brush set 36 with the terminal set of the line finder involved. A permanent signal may also result from a short circuiting together of the line conductors l0 and 11, and in such cases the tip and ring conducting paths are short circuited together. Thisto all intents effcctually destroys the third circuit, but the first and second circuits are still effectually maintained, the first over the tip and ground conducting paths, and the second over the ring and pound conducting paths. The passage of the fluctuating currents in the first circuit through the upper portion of the primary Winding of transformer 76 develops flu}; in the core thereof, Whilethe passage of the fluctuating currents in the second circuit through the lower portion of this primary Winding develops flux in the core thereof which is always opposed. to the flu): developed in the upper portion of this primary by the current in the second circuit. Due however to the unsymmetrical arrangement previously described, these fluxes are unbalanced, and the resultant flux vdevelops a fluctuating current in the secondary winding of the transformer 76, Which in turn operates the receiver 79 in accordance With the impressed frequency. When the permanent signal arises from a subscriber leaving the receiver of his set removed from the hook switch, the situation is for all practical. purposes, the same as that existing when the line conductors l0 and 11 are short-circuited, and accordingly no special explanation is considered. necessary.

It may however occasionally happen that the condition causing a 'iermanent signal will clear itself subsequent to connection to the testing position, but before the brush set 36 has been engaged with the terminal set of the line finder involved. In this event all of the three circuits between the secondary windings of the repeating coil 56 and the primary Windingof the transformer coil 76 are effectually established With the engagement of the brush set 36 With the terminal set of such line finder.

No short circuit exists between any two or more of the three conducting paths, and the passage of the fluctuating currents over each of these circuits through such portion or portions of the primary Winding of transformer 76, as are included in the respective circuits, results in the production of corresponding flux in the core of this trans former. The flux produced by two of these circuits Will lead a direction opposite to that possessed by the flux which the other one or" the three circuits develops at the same instant, but a preponderance of this: exists in one direction at such instant, and provides resultant flux effective to develop fluctuating current in the secondary Winding 01:? the transtormer'io to operate the receiver 79, in accordance with the trequency of the testing Ctlll'l'l.t, thus indicati the engagement of the brush t a. terminals of a line tin it is desired to locate as previously descrii'ied. I

The unsymmetrical circuit arrangement described thus insures alternating signaling current reaching and operating the receiver irrespective 01" whether the permanent gnal arises from the receiver being off the hook switch, the short-oircuiting of the conductors it) and 11, or the grounding of one or the other oi these conductors, and also in eventoi the removal of the condition causing such permanent signal prior to the location of the line tinder involved.

The number indicated on the designation strip 37by the pointer 38 at this time shows the line tinder identified LF on the drawing, to be the one involved. This line finder is at once visited and the number of the terminal set on which its engaged brush set rests noted. From the position of this terminal set in the contact bank, the number or theline represented thereby may often be directly determined or the number may be tound by consulting a list or chart of line finder terminals. As soon as the number of this line is determined, the switohman has a plug S t of a trouble cord 85, having its sleeve conductor associated with a suitable source of alternating current inserted into a multiple jack 87 of the line A. In practice the tone generator 6-it can serve this source, in which case another transformer 86 is preferably provided, having its primary Winding arranged in the output circuit with the generator 64:, and its secondary winding connected to the sleeve of the plug 8st. 7 On the insertion of the plug 84; into the jack 87, tone current is placed upon all the sleeve multiplesot line A, and produces a distinctive tone in an operators' receiver, upon testing the sleeve multiple of line A. with the tip of a calling plug of a cord or trunk circuit to determine Whether or not line A is in proper condition to receive a call. The character of the tone received indicates line A to be in trouble, and Warns operators against connecting therewith. Obviously, a separate tone generator can be used to supply current to the trouble cords 85,. if desired. The sleeve terminals of the line finder. multiples of line A alsohave this current placed on thennbut inasmuch as the cut-oil relay 13 or line 'A is operated upon the insertion 0]": jack 4: into jack 87, over a circuit extending from at with grounded battery, secondary Winding of transformer 86, conductor 88, resistance 89, sleeve contacts of plug S-Ztand jack 87,0011- ductor l5, and Winding of .relay l3 to ground, to disconnectthe line relay l2 and the battery associated therewith from the conductors l0 and 11, line A, will not :in-

'teri ere with the operation of line finderLF after such line finder is restored to its normal position; nor with other line finders, inasmuch as the o fieration of relay 13 prevents subsequent actuation ot' relay 12 and consequent closure of the starter wire circuit. The restoration of the involved line tinder, selector, and operators and switchmens trunks to their normal condition may be accomplished in any suitable manner. One such method is for the switchm an to see that his set is connected to the jacks 52 and-58 and that the tone key 72 ot' the trunk involvcd is open. He next opens the holding key of the switchmans trunk used in the connection, and; alternately closes and opens the key d9 of this trunk to flash the operator through the medium of the lamp 59 as earlier described. The operator, in response, effects the connection of her set with the trunk connected with the selector, as before explained, and the kev 49 is now maintained in listening position. The switchman, then directs the operator to Withdraw the plug ll from the jack 4.0. The operator thereupon takes down the connection and the selector 9:, as Well as the operators and switchinen s trunks involved therein, are restored to normal condition ready for subsequent use as disclosed in the previouslynoted copending patent application.

9 The above-described method is suitable under ordinary operating conditions, but in order to further economize the time of the answering operators during periods of very heavy trafiic, a number of tone jacks 90 may be provided, convenient to the answering operators. Any trunk having a permanent no signal thereon would have the plug 41 thereof inserted into a tone jack 90, thereby operating a relay 91, over a circuit extending from grounded battery, winding of relay 92, sleeve contacts of plug 41. and ack 90, conductor 93 and Winding of relay 91 to ground. The operation of relay 91 in turn effects the illumination of a lamp 94 at the sWitchma-ns position, thereby indicating that atrunk having a permanent signal thereon hasbeen 20 plugged into tone jack 90; While the operation of the relay 92 prepares a circuit for the lamp 59, as. previously explained.

This relay 9]. and lamp 94 may, if desired, be common to a large number of tone jacks 90. Plugging into jack90 completes a tone circuit extending, from the grounded secondary winding of repeating coil 71, conductor 95, resistance 96, ring contacts of jack 90 and plug 41, Winding of supervisory rewinding of relay 58, ring contacts ofplug gized under these conditions.

i l and jaclr 90, resistance 96, conductor 95, and secondary Winding of transtorn'ier '71, to ground. Upon the insertion of plug 4.1 into jack 90, ringing current is automatically applied. as previously described but due to the completion of the dii ct current circuit just mentioned. 1

tne contacts of the sequence switch SS, moved into their position l7, but without lighting the lamp 59, inasmuch the supervisory relay 58v is ener- The lamp 27 is extinguished on the movement of contact N2 of switch SS, into position 17, leaving the lamps, all extinguished during subsequent testing operations.

'lhe switchman observing the illumination of the lamp 9%, would see that plugs 50 and- 51 of a switchmans set were in the aclzs 62 and 63, as previously described, to insure the actuation of the relay 65 and consequent operation oi? the tone generator 64 and generation of :liuctuating testing currents in the secondary winding of the repeating coil 71, as previously described. The switchman then searches over the contact bank 35 to locate the line finder connected to the line causing the permanent signal, and on determining this line finder, proceeds to find the number of: the line represented by the terminal set engaged by the brush set thereof. He then proceeds to have trouble tone as well. asdirect current placed on the sleeve terminals of this line, in order that such line will test in trouble, and in order that the line relay oi. such line will. be operated, as previously described.

The line findermay then be manually re stored to its normal position which effects the restoration of the selector CS to normal and the movement of the contacts of sequence switchSS, to position 1. A disconnect signal. results from the opening of the operating circuit ol. the relay 69 on disengagement oi? the finder and selector brush. sets 16 and 19 from the terminal sets 18 and 21, respectively, and the consequent illumination of the lamp 60 to indicate disconnection is desired, as disclosed in the copending Williams patent application. The lamp 59 is not lighted under t iese circumstances, but the operator on noting that the plug 41 of the involved trunk is in a trouble jack 90,

disconnects therefrom, extinguishing lamp 9-4 at the switchmansposition, provided no other trunks are engaged in corresponding tone jacks 90 and eiiecting the restoration oi the trunk to normal condition.

The line finder Ll selector CS, and the apparatus used in locating the involved line finders are now in their normal condition ready for subsequent use, and line A is arran "ed to test in trouble, and prevented from a; ,in connecting with any or the line finders until the trouble has been located and line restored to its normal condition.

From. the above description it will be apparent that it a number of difi'erent operators trunlrs having permanent signals thereon are plugged into tone acks 90, the sw tchman can locate all. the line finders 1n- .voived bv testing over the terminal sets in the bank 35 and noting all of the line finders lidflllf tone current on their terminal sets in the bank 35. These line finderswould be visited, and the particular lines involved noted, and removed from service as previously explained. This arrangement is of aid in quickly locating a number of lines having permanent signals thereon, and preventing these lines tying up line finders and cord selectors, which serve as percentage apparatus for a number of other lines. It will be further apparent that with the present system it is possible to simultaneously search for line finders associated with trunks connected to switchmens trunks and for line finders associated with trunks directly en gaged with. tone jacks 90; thus insuring a flexibility of operation desirable in systems of this character.

lVhat is claimed is:

1. An electrical testing system comprising pairs of banks of terminals, selectors permanently connected in pairs and adapted to cooperate with said banks respectively, a test terminal for each pair of selectors, means to supply testing current to the test terminal of a pair of operated selectors, and means cooperating with said test terminals to indicate the particular pair havingtesting current upon the test terminal thereof.

with said test terminals to indicate the particular set of connecting apparatus involved in such connection.

3. An electrical testing system comprising a group of lines extending to a plurality of diii'ereut positions, a plurality of sets of automatically operated connecting apparatus common to said groups, and each arranged to selectively connect with any line or said group, a test terminal individual to each of said sets, means to supply testing current to a line of said group with which one of said sets is connected at the position at which such line terminates, and means cooperating with said test terminals to indicate the particular one or? said sets involved in such connection.

l. An electrical testing system comprisis a group of calling lines, a group of trunk lines, a plurality of sets or automatic con necting apparatus common to each oi: said groups and selectively operable to connect any one of said calling lines to any one of said trunk lines, a test terminal individual to h or said sets, means to supply testing current to the terni'iruil ot' a set connecting a calling line to trunlr line, and means cooperating with said test terminals to indicate the particular set involved in such connection. l

an electrical testing system comprising a group of calling lines, a group of? trunk lines, a plurality of sets of automatic con necting apparatus common to each of said groups and selectively operable to connect any one of said calling lines to any one oi said trunk lines, a test terminal individual to each of said sets, means to supply testing current to a trunk line with which one oi saidsets is connected, and means cooperating with said test terminals to indicate the particular setinvolved in such connection.

6. An electrical testing system comprising a group of calling lines, a plurality of automatic line finders common to said group and selectively operable to connect any selected one oi said finders to any one of said'calling lines, a plurality of trunk lines, a plurality of selectors common to said group of trunk lines associated with said plurality ot tinders and each operable to connect with any selected one of said trunk lines upon connection otthe finder with which said selector is associated with a calling line, a test terminal. individual to each oi? said finders, means to supply testing current to a trunk line connected to a trunk selector, and means cooperating with said test terminals to indicate the particular tinder involved in such connection.

7. An electrical testing system comprising a group of subscribers li es, a group of trunk lines extending to an operators position, a plurality of sets of connecting appa ratus common to both of said groups and each selectively operable to connect any line of one group to any line of the other group, a test terminal individual to each ot said sets located at a testing position. connecting means to extend said trunk lines to said testing position, means to supply testing current through said connecting means to a trunk line extended to said testing position, and means cooperating with said test terminals to indiate the particular set connected to a trunk line extended to said testing position.

8. An electrical testing system comprising a group of subscribers lines, a group of trunk lines extending to an operators position, a plurality of sets of connecting apparatus common to botho'l' said groups and each selectively operable to connect any line of one group to any of the other group, a test terminal individual to each of said sets located at a testing position, a plurality of connecting circuits between said operators position and said testing position to connect said trunk lines to said testing position, means individual to each of said connecting circuits to supply testing current to a trunk line connected therewith, and means cooper ating with said test terminals toindicate the particular set connected to a trunk line connected with a connecting circuit.

9. An electrical testing system comprising a group of subscribers lines, a group of trunk lines extending to an operators position, a plurality of setsot connecting apparatus common to both of said groups and each selectively operable to connectany line of one group to any line of the other group, a test terminal individual to each of said sets located at a testing position, a plurality of connecting circuits between said operat'ors position and said testing position to con nect said trunk lines to said testingposition, means individual to each of said connecting circuits to supply testing current to a trunk line connectedtherewith,and means common to said connecting circuits andcooperating with said test terminals to indicate the particular sets connected to trunk lines connected with said connecting circuits.

10. An electrical testingsystem comprising a group of subscribers lines, a group of trunk lines extending to an operators position, a plurality of sets 0t coi'inecting apparatus common to both of said groups and each selectively operable to connect any line of one group to any line of the other group, a test terminal individual to each of said sets located at a testing position, a source of testing current, means at said 'operators position available to said trunk lines through which testing current is applied to a trunk line connected therewith, a signal at said testing position associated with said lastnamed means and actuated upon the connection of a trunk line with such means, and means cooperating with said test terminals to indicate the particular set connected to a trunk line connected with the means through which testing current is applied to a trunk line. Y

11. An electrical testing system comprising a group of subscribers lines, a group of trunk lines extending to different operators positions, a plurality of sets of connecting apparatus common to both of said groups and each selectively operable to connect any line of one group to any line of the other group, a test terminal individual to each of said sets located atatesting position, asource of testing current, means at the operators positions and available to said trunk lines through which testing current is applied to trunk lines connected therewith, a signal at said testing position associated with last mentioned means and actuated upon C 11UOC- tion of a trunk line with such means, and

means common to said means through which testing current is applied and cooperating with said test terminals to indicate the par ticular sets connected to trunk lines connected with the means through which testing current is applied.

12. An electrical testing system comprising a group of subscribers lines, a group of trunk lines extending to an operators position, a plurality of sets of connecting apparatus common to both of said groups and each selectively operable to connect any line of one group to any line of the other roup, a test terminal individual to each or said sets located at a testing position, a source of testing current, means at the operators position to which said trunk lines extend and available to such trunk lines through which testing current is applied to any of said trunk lines connected therewith, a signal at said testing position associated with said lastmentioned means and actuated upon connec tion of a trunk line with such means, and testing means common to said means through which testing current is applied and cooperating with said test terminals to indicate the particular sets connected to trunk lines connected with the means through which testing current is applied.

13. An electrical testing system comprising a group of lines, plurality of sets of connecting apparatus common to said lines and each selectively operable to connect with any of said lines, a test terminal individualto each of said sets located at a testing position, a source of testing current, connecting means to extend said lines to said testing position, means available to said lines through which testing current is applied to a line connected therewith, a signal at said testing position associated with said last named means and actuated upon connection of a line with such means, means to apply testing current through said connecting means to a line extended to said testing position, and means common to said connecting means and to said means available to said lines cooperating with said test terminals to indicate the particular sets connected to lines connected with said connecting means and with said means available to said lines.

An electrical testing system compria ing a. group of sets of apparatus, a plurality of sets of other apparatus common to said group and arran ed to selectively connect with any set of said group, a test terminal individual to each'of said plurality of sets, contact means to selectively engage said test terminals, a source of testing current, means to apply testing current to the test terminal of a set connected with a set of said group, detecting means associated with said contact means to dctc at the engagement thereof with a test terminal having testing current applied thereto, and means to directly idei'itify the particular set upon the test terminal of which testingcurrent is detected.

151 An electrical testing system comprising a first and a second transformer coil each having a core and a winding operatively associated with its respective core, three conducting paths to connect three different points of the winding of the first coil to three different points of the winding of the second coil to join said windin s in nonsymmetrical electrical arrangement, three circuits each including a different pair of said conducting paths and different arrangements of each of said windings, and means to develop flux in the core of one of said coils to produce a flow of current in each of the three circuits, said flow of current serving to develop a resultant flux in the core of the other coil.

16, An electrical testing system compri ingfirst and a second transformer coil, each having a core and a winding operatively associated with its respective core, three conducting paths to connect three different points of the winding of the first coil to three different points of the winding of the second coil to join said windings in nonsymmetrical electrical arrangement, three circuits each ii'icluding a. different pair of said conducting paths and different arrangements of each of said. \vindii'igs, and means to develop flu); in the core oi one of said coils to produce a ("low of current in such ot'the three circuits as are effectively maintained; the flow (it current in such circuits as are effectively maintained serving to develop an effective flux in the core of the other coil.

17. An electrical testing system comprising a first and second transformer coiheach having a core and a winding operatively associated with its respective core, three con-' ducting paths to connect three different points of the winding of the first coil to three different points of the winding of the second coil to join in nonsymmetrical electrical arrangement, three circuits each including a difierent pair of said conducting paths and different arrangements of each of said windings and arranged in such a way that at least one of said circuits is effectively maintained on short circuiting together of any two of the three conducting paths, and means to develop a flow of current in such of the three circuits as are effectively maintained on short circuiting together of two of the three conducting paths; the flow of currents in such of the circuits as are effectively maintained serving to develop an effective flux in the core of the coil.

18. An electrical testing system comprisinga first and a second transformer coil, each having a core and a winding operatively associated with its respective core, three conducting paths to connect three different points of the winding of the first coil to three different points of the winding of the second coil to join said windings in nonsyminetrical electrical arrangement; three circuits each including a different pair of said conducting paths and different arrangements of each of said windings and arranged in such a way that at least one of said circuits is effectively maintained on short circaiting together of two of the three conducting paths, and means to develop flux in the core of one of said coils to develop a flow of current in such of the three circuits as are effectively maintained on the short circuit ing together of two of the three conducting paths; the flow of current in such of the circuits as are effectively maintained serving to develop an effective flux in the core of the other coil.

19. An electrical testing system comprising a first and a second transformer coil, each having a core and a winding operatively associated with its respective core, three conducting paths to connect three different points of the winding of the first coil to three different points of the winding of the second coil to join said windings in nonsymmetrical electrical arrangement, three circuits each including a different pair of said conducting paths and different arrangements of ach of-said windings and arranged in such a way that two of said circuits are each having a. core and av winding opera tively associated with its respective core,

three conducting paths to connect three different points of the first coil to three different points of the winding of the second coil to oin said windings in nonsymmetrical electrical arrangement, three circuits each including a different pair of said conducting paths and different arrangements of each of said windings and arranged in such a way that one of said circuits is effectively maintained on short circuiting together of two of three conducting paths, and means to develop flux in the core of one of said coils to develop a flow of current in the circuit effectively maintained on the short circuiting together of two of the three conducting paths; the flow of current in the circuit effectively maintained serving to develop an effective flux in the core of the other coil.

In witness whereof, We hereunto subscribe our names this 30th day of January, A. D.

SAMUEL B. WILLIAMS, JR.

HERBERT L. BOSTATER.

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