US1907240A - Service observing equipment - Google Patents

Description

y 1933- 7 c. R. BROOKS El AL 1,907,240

SERVICE OBSERVING EQUIPMENT Filed Sept. 21, 1931 6 Sheets-Sheet 1 v IrTFFTcfi Charles H.Br-:mks Jul-11:1. E. UEHinE y 1933- c. R. BROOKS ET AL 1,907,240

SERVICE OBSERVING EQUIPMENT Filed Sept. 21, 1931 6 Sheets-Sheet 2 Charles H.Bruuks Ju 1.-|. E Els'TI-ine May 2, 1933.

SERVICE OBSERVING EQUIPMENT Filed Sept. 21, 1951 6 Sheets-Sheet 3 Char-'12s H.5rau1cs Jul-Ln E. Din-ins WWW May 2, 1933. c. R. BROOKS El AL:

SERVICE OBSERVING EQUIPMENT Filed Sept. 21, 1931 6 Sheets-Sheet 4 y 1933- c. R. BROOKS ET AL 1,907,240

SERVICE OBSERVING EQUIPMENT Filed Sept. 21, 1931 e Sheets-Sheet 5 E 6 mm H a m x; 0 m =5 EE 1 m m n m &1 S .MDY 6 EJ T N E T 1% U mmm on wn R e B w Ee mu cw E S s w \N. QILW%G n3 m; nun 8 Tan Patented May 2, 1933 warren stares PATENT QFFICE CHARLES R. BROOKS, GE CHICAGO, AND JOE-IF E.- OSTLINE, 9F BERWYN, ILLINOIS, S-

SIGNOB-S, BY MESNE ASSIGNMENTS, 'IG ASEQCIATED ELEGTRZC LABORATORIES, INC., OF CHICAGO, ILLINOIS, A COREORATIQN OF DELAW'ARE SERVICE GIBSERVENG EQUIPMENT Application filed September 21, 1931.

This invention relates to telephone systems in general, and particularly to arrangements for observing the quality of service aforded subscribcrs lines in such systems. The invention has for its object the provision of new and improved circuits and apparatus for the centralizedobservation of connections established in the various oflices of a multi-ofiice telephone system.

General description necessary for calling. When there are a number of offices in the system, it is ordinarily most economical to conduct the observing operations from a central switchboard. The centralization of observing facilities results in a considerable saving of equipment, and also permits the observing operator to Work in the most efiicient manner.

A centralized service observing system consists generally of a central switchboard located at some convenient point in the telephone exchange system. In each off ce of the exchange system there are a number of observation trunks which can be connected to the subscribe1"s lines or service trunks to be supervised. Switching apparatus atthe offices associate the various observation trunks with inter-office trunks extending to the can tral switchboard, and other switching apparatus associates the various inter-oflice trunks with the observing equipment at the switchboard. The various switching apparatus unitsare coordinated to prevent interference from lines calling simultaneously.

A service observing system of the above general type is shown in United States Patent No. 1,641,453, granted September 6, 1927, to John E.-Ostline, on which the present invention is an improvement. In prior systems, including that shown in the patent, it has been the practice to arrange the observing equip ment for connection to service trunk rather Serial No. 583,950.

than direct-lyto a subscribers line. This ar rangement has been generally satisfactory, although obviously it does not permit observation of the service of the primary line switches or finder switches which operate upon the initiation of a call. The present system is arranged so that the observation trunks may be connected directly to subscribers lines as well as to trunk lines, and thus provides for the observation of the service afforded by the non-numerical switches of the system. This is of particular importance in systemsemploying finder switches, as it enables the operator to determine the time required for the finder switchesto connect with the calling line after a call has been initiated. This arrangementconstitutes one of the main features of the invention.

Another feature of the present invention is the arrangement for reducing the transmission loss in a talking connection due to the connection of the observation equipment thereto. The talking conductors of the observation trunk are bridged across the talk ing conductors of the line in series with a. condenser of low capacity and the high impedance primary winding of a transformer. The shunting effect of this bridge on the talking connection isrelatively small, and, of course, the current flow in the bridge is feeble. This feeble current is amplified to the level necessary for the accurate supervision of the call by means of a vacuum tube amplifier associated with theobservation equipment.

A further feature of the invention is the provision of a designation sender which the description of the operation of the apparatus in a system embodying the invent-ion which is shown in the accompanying drawings comprising Figs. 1 to 7, inclusive.

Description 0 f drawings Referring now to the drawings, Fig. 1 shows a subscribers line and a part of the switching apparatus in the ot'rice in which the line terminates. Figs. 2 and 3 show that part of the service observing equipment located in the automatic office. Figs. l and 5 show service observing equipment located at the central observing oflice. Fig. 6 shows a portable observation set for use with the equipment shown in Figs. 2 and 3. Fig. 7 is a layout diagram showing the manner in which the various figures of drawings should be assembled to show the complete circuitsof a service observing system embodying the present invention. Switching apparatus in the outlying of/Zee Referring now to Fig. 1, the subscribers line from substation S terminates at an automatic otlice on the main distributing frame MDF and is cross-connected to the usual line and cut-0E relays. A group of lines, including the one shown, are accessible to the finder switch FA, which, together with other similar finders, is controlled by the distributor switch DA. Selector EA is individual to the finder switch FA and has access to the second selectors of the exchange. The finder switch, selector, and distributor switch shown are similar to those disclosed in United States Patent No. 1,688,588, granted October 23, 1928, to Clarence E. Lomax and Norman H. Saunders. The reference characters used in designating the various parts of these switches correspond, as far as practical, to the reference characters used to designate corresponding parts in the patent. One observation trunk is shown terminating 011 the equipment side of the distributing frame and is temporarily connected with a line to be observed by means of jumpers or a cord and shoe of any suitable type. While only one observation trunk has been shown in the drawings, it will be understood that there will be as many of these trunks as traffic conditions require, one trunk being supplied for each line to be observed.

Service observing equipment in the outlying ofiiee In Fig. 2 there is shown a number of observation trunks and their associated relays.

- The trunks are arranged in groups of ten for are associated with the tenth trunk of the second group. There may be as many additional groups of trunks as trafiic conditions require and these will be connected up in the manner indicated. Each group of trunks is provided with a pair of common relays of which relays CR1 are associated with the first group and relays CR2 with the second group.

To the right of the common relays is shown two groups of lamps. The lamps of the first group identify the position of the trunks in their respective groups, and the lamps of the second group identify the particular group in which a trunk in use is located. These lamps serve to identify the line and trunk under observation and are provided for use when the observation is made by means of the portable set shown in Fig. 6, as will be explained subsequently. WVhen calls are observed from the central observation switchboard the line or trunk under observation is identified by impulses transmitted over the interoflice trunk. These impulses are sent by the sender switch DS and its associated relays SR whose operation is controlled by conductors extending from the trunk and group relays to the lamps shown in Fig. 2 and to the banks of the rotary switch.

Fig. 3 shows the common control relays CR associated with the trunk and group relays shown in Fig. 2. These relays terminate an interofiice trunk T over which all connections at the automatic exchange are observed from the central switchboard. The relays associated with this. trunk are also adapted to operate with the portable observation set shown in Fig. 6. In this figure there is also. shown an amplifier A which is an ordinary vacuum tube audio frequency amplifier and is used only when observing calls from the central switchboard.

Included in the common relay group is a sensitive polarized relay which operates in synchronism with the impulse relay of a, line under observation. The relay is connected to the line through a condenser and does not interfere in any way with the operation of the regular exchange switching apparatus. Impulses dialled by a calling subscriber are thus repeated tothe observation switchboard and recorded by means of a pen register.

Service observing equipment in the central oyfice Fig. 4 shows the interoflice trunk relays located in the same oflice as the centralized observing equipment. The relay group OTR is associated with the trunk T which extends to the automatic oflice in which the equipment shown in Figs. 1-3 is located. Therelay group OTRl is associated with the observation trunk T1 which extends to another automatic oiiice provided with equipment similar to that shown in Figs. 1-3. Both of these relay. roups are adapted to tlSSQCiett their respective trunks with. the trunk TO which extends to the first position of the observation switchboard. Relay groups OTR2 and OTB?) are associated respectively with trunks :T'and- T1 and are adapted to'associate these trunks with. thetrunk T01 which extends to the secondjposition of the observation switchboard. Additional relay groups may be pro.-.

which a call is being observed. The equip-- ment at the other position of the observation switchboard; will be exactly'thesame as that shown in this figure.

Portable observation set Fig, 6 shows the circuit of a portable observation set which can be associatedwith the apparatus in any of the automatic ofiices for the purpose of observing trafiic solely in that ofiice. Thisset includes the usual lamps and.

keys, an operators-telephone set, and a pen register PR. Thetrunk and group lamps for this particular equipment are associated with the exchange apparatus itself as shown in Fig. 2.

Detailed description The invention having been described generally, adetalled description of the operation of the-apparatus: shown will now be glVBILT For this purpose it will be assumed that the subscribers linetermmatingin substation S is the line to be observec Operation of the s'wz'tchz'ng appamtas in the outlying ofice Before proceeding with the detailed description of, the operation, of the serivce 0bservmg switching apparatus in the outlying exchange will beconsidered briefly. This apparatus as previously stated is similar to that shown n the Lomax and Saunders patent, and is described in detail in the patent. It will be assumed first that the subscriber at substation S initiatesa call at a time when-the service observing switchboard is not in service. The calling subscriber on lifting his rece ver-completes a circuit from battery, upper winding of; relay 19, contacts 20, terminal 4, line conductor 2, through the loop at the substationS, line conductor 1, terminal 6, and contacts 22, to ground. Relay 19 operates and marks the line as calling inthe banks of the finder switches by closing con tacts 23and opening contacts 25, and at contacts 2e connects groundby way of contacts two separate setsof: wipers, {These-wipers;

equipment the operation of the 21 andrconductorr to relay 520.15 the distributor switch. Assuming that no other calls. are inprog'reSs at this time,'rela.y' 52,

on operating, completes a circuit at contacts for relay 53 and stepping magnet-51 in series.v The wipers of the switch DA will be standing on the contacts associated with. an idlefinder, such as the finder FA, 'due 'to circuit conditions which, will be described subsequently, and, upon the closure of the above-mentioned circuit, relay 53' wilk opcrate andQopenv the stepping. circuit at-contacts 57 Magnet 51 does not operate at this time due to the high. resistance of relay 53.. As a resultrof the operation, ofrelay 53 a circuitis completed by way of contacts and 5S, wiper 63, conductors 163 and 150, con tacts 117, upper winding of line relayv 102 of selector EA, to battery. Relay: 102 operates and at contacts llficompletes a circuit forrelease relay 101; .Relay 101 operates, connects ground to release trunk conductor 151 at contacts 11.8, and prepares the impulsing circuit of'the selector at contacts 114. Relay 53 at contacts 59 also closes a circuit over wiper 64 and conductor162, which extends by way of. contacts 125,121, and torelay 107. Relay 107 operates and at contacts 129: extends the ground on. conductor 162fto verti-v cal magnet 105 of the finder switch. Magnet 105 operates to raise the wipers of the'switch one step, at the sameti'me opening the circuit of relay 107 at contacts 121. On the first verticalstep of the wipers vertical test wiper will engage a bank contact corresponding torthe first level of thebank and will'testthis level for the presence of acalling line. If the calling line isnot in this level there will be no further action until magnet 105 restores after the release of relay 107, whereupon. the

circuit for relay 107 willbe again closed at contacts 121 and relay 107 will again complete acircuit for themagnet. These operationswill be repeateduntil suchtime as test wiper 175 engages the contact corresponding to the level in which the calling line isaccessible. hen this level isreached, and. while a as 1nagnet105 is still energized, a circuit will'be I completed from ground applied to conductor, .80 at contacts 24 of the calling line, bankcontact 29', wiper 17 5, conductor 158, upper winding of relay 106, contacts 120, winding of relay 107, to battery.,-Rela'y 106, on 0pcrating, prepares the rotary; test circuit-.iat' contacts 122, completes a locking-circuit; for

itself at contacts 123, prepares a circuitfor rotary magnet-1104 at contacts 147', andat contacts "148 prepares the automatic stopping circuit. Magnet 104a-operatesim medi ately upon the closure of the-above circuit,-

opens the circuit o f relay'107', and'stepsthe wipers of'the' finder'in upon the first set of i contacts in theselected level; It will be noted that the finderswitch is provided with have access to two different groups of lines appearing in the corresponding levelsof their respective banks and the lines in these levels are tested alternately until the calling line is' found. Assuming that the calling line 1 upon connects test wiper 170 via contacts 143 and 131 to the stepping circuit which includes relay 107. Since this set of contacts is marked non-calling, wiper 17 0 will accordingly find ground and relay 107 will energize.

:Relay 107 again completes a circuit for magnet 104 at contacts 129, thereby operating the magnet to step the wipers ahead to the next set of contacts of the level. When the calling line is reached, for example, the line from substation S, test wiper 173 will find battery on contact 27 instead of ground and as a result relay 109 will not energize. A circuit may now be traced from ground, contacts 113, conductor 151, winding of relay 108,

.' contacts 131, 138, and 128, conductor 157, test wiper 173, test contact 27, contacts 23, lower winding of relay 19, winding of relay 18, to battery. Relay 19 will remain operated over this circuit and relays '18 and 108 will en- 1 ergize. Relay 18 opens the starting circuit at contacts 21,'and at contacts 20 and 22 disconnects relay 19 and ground from the line conductors. Relay 108 is the switching relay of the finder and has numerous functions to perform. Upon the operation of this relay the calling line is extended through to the line relay of the selector by the closure of contacts 130 and 136. Wiper switching relay 109 is disconnected from the test circuit at contacts 132; The opening of contacts 131 disconnects relay 108 from the test wiper, and the closure of contacts 146 connects ground to'this wiper to maintain the line cut-off relay of the line in operated condition. Discrimlinating tone is applied to release trunk conductor 121 at contacts 133. A new holding circuit for relay 108, including the winding of relay 107, is completed at contacts 134. Relay 107 does not operate in series with rel lay 108, due to thehigh resistance of the latter relay. A circuit is closed at contacts 135 by way of conductor 164 and wiper 62 for relay 54 of the distributing switch. This relay on operating opens the circuit of relay 53, which restores, and at contacts 57 completes a circuit for stepping magnet51. Since the finder switch has been operated to an off-normal position, off-normal contacts v166 will -be closed, and groundby way of these contacts,

conductor 165;, wiper 61, contacts 57 and 56,

energizes'magnet 51 to step the distributor wipers to the next set of contacts. If the next set of contacts is also busy, a similar. operation will take place and in this manner the wipers of the distributor will 'be'stepped until an idle finder switch is found. 'The movement of the wipers of the distributor switch opens the previously described en-" ergizing circuit for-line relay 102 of the selector. This relay is now held operated over the calling subscribers loop. The calling subscriber may thereupon complete the connection by diallingin the usual manner;-

Since it has been assumed that the centralized observation switchboard is unattended at'this time, the group relays 210, 212, etc., will be in normal condition, as will be explain'ed in more detail hereinafter. The initiation of the call as above described will be without effect onthe observation equipmentat this time due to the normal condition of these relays. Then the finder switch connects with the calling. line, as above described, ground is applied over test contact 27 and relay contacts 23 to maintain relay 19 operated and to mark the line busy in the banks of the various connector switches. The test contact is connected by way of conductor 16 to relay 201, and this relay energizes upon the seizure of the calling line by the line finder. Relay 201, upon operating, opens a point in the circuit of relay 202 at contacts 223, the utility of which will be apparent as the description proceeds.

Observation of calls from the contra/1077706 The operation of the service observing circuits will now be described, first consideration being given to the observation from the central observing position of calls originating on lines terminating in the automatic ofi'ice such as the line for substation S.

Observing e guipwwnt placed in service plug and jack,'contac ts 536 of release key K4, 7

conductor 472, through "normally closed contacts419 of relay 401, and through similar contacts in the chain indicated by the dotted portion of conductor 483,'contacts 430,-conductor 478, contacts 463, and relay 409, to battery. Relay 409'operates, closes a circuit from ground'at contacts 461, conductor 477, normally closed contacts 514 and 515 of keys K6 and K7, thence'over two branch circuits, one of which includes conductor 467, contacts 41,4,conductor 356, upper right-hand winding.

of repeating coil E, Fig. 3, contacts 348, conductor 268, contacts 237 of relay 213 (Fig. 2'), conductor 267, contacts 329, high resistance lower winding of relay 305, to battery. In multiple with the above described circuit is a circuit including conductor'47 5, contacts 426, conductor 356 of the trunk T1 and thence over a path similar to that above traced in the service observing circuit in the exchange in which the trunk line T1 terminates. \Vhile only 'two circuits of this have been shown, it will be understood that there will be as many of the circuits as there are observing trunks coming in to the position under consideration. There will, of course, be a key such as keys K6 and K7 for each trunk, and there -will be a corresponding lamp L7 or L8 for each trunk. When it is desired to observe connections only in aparticular office or offi'ces, the trunk keys corresponding to the other offices will be operated. This will prevent calls originating in these other oiiices from beingotrunked to the'position under consideration.

As a further result of the operationof relay 409, a. circuit is closed from battery, resistance 411, contacts 462, thence over two parallel circuits, one by way of conductor 482, upper windings of relays 402 and 401, contacts 417, conductor 357, lower right-hand winding of repeating coil R Fig. 3) contacts347,

-winding of relay 311, conductor 255 to open contacts of relays 202, 204, 206, etc. A multiple circuit extends through the upper windings of relays 404 and 403, contacts 428, and conductor 357 or the trunlr line T1 to the observing equipment in the ofiice inwhich the trunk line T1 terminates. Only two ofthese circuits have been shown, but it will be understood thatthere is a circuit of this type for each trunk extending to an outlying of: fine. V l

'Referr'ing now to Fig. 3, it will be recalled that relay 305 operated upon the insertion of the receiver plugin the jack as just descrlbed. This relay completes a holdlng circult for itself at contacts 330, which renders it independent of the contacts 237. Ground is applied at contacts 328 to conductor 258, which extends by wa-y of contacts 2290f relay 203 and the chained contact of similar relays of the group to contacts 277 of relay 204, and thence through the chained contacts of the corresponding relays in all'other groups, the last contact group being connected to conductor 260 which extends-to relay 301. Belay 301 accordingly operates, opens the alarm signal circuit at contact 319, and closes a" circuit from ground at contacts 328 by way of contacts 320, conductor 254, to relays 210, 212,

and corresponding group relays of other groups. The group relaysoper'ate', and at their contacts 233, 279, 282, and 283, etc., connect the upper windings of the various trunk relays 202, 204, 206, 208, and other similar relays 'to conductors of the respective observation trunks. As a further result of the operation otrelay 305, a circuit is completed for relay 310, which relay prepares the ampli-v tier A for operation by closing contacts 338. A circuit is closed by way of contacts'339'and 351 for relay 309, and this relay operates. Relay 309 closes a circuit for relay308 at contacts 337. Relay 308 operates and pre. pares various circuits concerned withthe repeating of the impulses dialled by a calling subscriber. The observation equipment is. now in condition to receive calls from any of the exchanges equipped according toth'e ar rangement shown in the drawings;

The condition of the apparatus at this time may be summarized briefly, as follows: The group relays 210, 212, etc., in each office will be in operated condition and the trunk relays 202, 204, 206, 208, etc., of the various trunks will be connected'up on all trunks in which 'calls are not in progress. In the case of relaysi This arrangement prevents the extension to the observation switchboard of calls that are in-progress when the'e'quip ment is placed in service. In the commonre-' lay group GR (Fig. 3), relays 301, 305, 308, 309, and 310 are operated, and relay 302 has been connected through "to the normally open upper contacts of the various trunk relays.- 1m ul'se' repeating relay 314has its lower rig t-hand polarizing winding energized in series with resistances 369 and 370-andthe upper windings of this relay are bridged across theoperating conductors 256 and257 in series with condenser 367. The filament of vacuum tube 318 of a'mplifierA is lighted in series with the ballast'resista'nce lamp BL. The equipment is now inreadiness to intercept the first callinitiated on any of the observation trunks.

Second position the switchboard placed in service The foregoing operations are those which' take place when the first position ofthe observation switchboard is placed in service. In the event that the second position had been placed in service instead of the first position, I

the operations involved would be substan tially-the same, exceptthat in'this case, since 7 thepositionapparatus is connected'to the trunk TOl, ground is extended over conductor 472 instead of conductor 472. This ground, by way of chained contacts 442, 454,

relays of the observation equipment of the various ofiices in the manner previously described. The trunk relays 405, 406, 407, 408, etc.,associated with the second position, will be placed in operating condition by the connection ofbattery through resistance 413 and contacts 464, to the upper windings of the respective relays.

lt'will be seen from the foregoing thatthe first position to be placed in series will be assigned the first intercepted cell due to the operation of its associated relay, such as 409 or 410. It will also appear presentlythat when two positions are in service at the same time the intercepted calls will be assignedto the respective positions alternately.

' O'aZZ initiated on a subscribers Zine The description of an intercepted call will now proceed on the basis ofboth observation positions having been placed inservice with the first position having precedence as regards the first call. Assuming that-the subscriber at substation S initiates the first call after the observation equipment is placed in service, the line relay equipment, finder switch, distributor, and selector will operate in exactly the same manner as previouslydescribed for'calls made with the service observing equipment out 01 service, Under v.the'se conditions, however, relay 202 of the trunk relaysTRl is'connected in parallel with the upper winding of line relay 19, the circuit extending by way of contacts 233 and 223 and conductor 17, which is jumpered to terminal 4 in multiple with line conductor 2. Relay 202 will accordingly energize in parallel with the-line relay immediatey upon the initiation of the call. The talking con- *duc'tors 14 and 17 of the observation trunk are accordingly extended through to thecomtacts 229 and the circuit for the associated trunk lamp is closed at contacts 228. Relay 202 remains energized over the above-traced holding circuit, and relay;209 energlzes and closes a circuit for the associated "group lamp at contacts 232. Relay 209 also-closes a cir cuit from ground zit-contacts 231,.conductor 253, winding of relay 302, to battery. The opening of the chain circuit permits the group relays to restore, thereby disconnecting the various observation trunk relays 204, 206, 208, etc., from'their associated trunks so that calls over the lines to which these trunks are connected will not beintercepted. The

group and trunk lamps, in this case the trunk lamp 1 and the group lamp 1, are lighted,

, although this is without any particular utility in the present instance since the call is to be observed at the central oflice. The conductors over which these lamps are energized-1 however, extend, respectively, to the second and tenth contacts of the banks of switch DS andidentify the observation trunk, as will be explained hereinafter.

Referring now to the common relay circuit of Fig. 3, relay 302 operates upon the closure of the above-traced circuit, opens a further point in the alarm signalling circuit at contacts 321, closesv a point in the starting circuit of thev designation sending switch at contacts322, and at contacts 323 closes an obvious circuit for slow-to-operate relay 303.v

During the slight interval requiredfor relay 303 to operate a circuit is closed from ground at contacts 323, contacts 326, winding of re,

lay 311, contacts 347, lower right-hand winding of repeating coil R, conductor 357, contacts 417, upper windings of relays 401 and 402, contacts 462, and resistance 411, to battery. Relays 401 and 402 operate and lock to ground by way'ofcontacts 420 and conductor 472. Relays 401 and 402 are .soadusted that contacts 422' are closed before contacts 416 are opened, and as afresult an ,impulse ground is transmitted by way of thesecontacts, lower left-hand windingof repeating coil R1, conductor 470, lower highresistance winding of relay 505, to battery. Relay 505 energizes momentarily and at contacts 530 connects ground through the re-' lease key contacts 536 to relay 502. Relay -502 operates, locks byway of contacts 516,

clear by the time the connection is extended through, and consequently relay 505 will restore and open the original energizing circult of relay 502. The latter relay, however, will remain" energized over the previouslytraced locking circuit and lamp L6 will continue to glow. Asa further result of the operation of relay 401 the chain circuitindicated by the dotted section of conductor 483 is opened at contacts 419, thereby permitting relay 409 to restore and at contacts 462 disconnect battery from the upper windings of the various trunk relays associated with the first position. The release of relay 409 also completes a circuit at contacts 412 for trunk relay 410 associated with the trunk of the second position, and this relay operates to prepare the trunks for extending intercepted calls to the second position.

To proceed with the intercepted call under consideration, a further result of the operation of relay 402 is the closure at contacts 421 of a circuit for the office identifying lamp L7. This lamp glows to indicate to the'operator that the intercepted call is from the particular oiiice designated by the lamp, in this case the otfice in which the subscribers line from substation S terminates. The supervisory conductors 355 and 358 of the trunk T are extended by way of contacts 424 and 425 toconductors 473 and 474- of the trunk TO. The condition obtaining at this time may be summarized as follows: The calling subscriber has initiated a call and the finder switch FA has started in search of the calling line. A momentary signal has been transmitted over the trunk T to switch the trunk through to the first position of the observation switchboard and guard lamp L6 has been lighted to indicate the interception of a call upon initiation. The operator at this position will accordingly note the time at which lamp L6 operated.

hen the finder switch FA. connects with the calling line, ground will be applied to test conductor 3 of the called line, and this conductor, being multipled with conductor 16,

relay 201 of the trunk relay group will operate in theusual way. Relay 201 closes a circuit which may be traced from ground at contacts 222, contacts 224, conductor 255, thence over the previously traced circuit to relay 505, which relay will again operate and close a circuit at contacts 529 for lighting the subscribers pilot lamp L4- The interval between the li hting of lamps L6 and L4 represents the time taken by the finder to connect with the calling line after the initiation of the call. Relay 311, which is connected in series with the lower winding of relay 505, is not operated at this time due to the high resistance of the latter relay. As aresult of relay 311 remaining in normal condition, the amplifier A will be connected in operating condition between the observation trunk T111 and the interotiice trunk T. The circuits over which the voice current from the calling and called lines are transmitted will be described subsequently.

Trunk designation transmitted to the obsercation switchboard Referring back to the operation of relay 202 upon the initiation of a call, as above described, we find the following starting circuit completed for the sender switch. Relay 301 having restored upon the opening of the chain circuit by relay 202, ground at contacts 328 by way of contacts 319, 322, and 324, conductor 269, contacts 234 and 244, pulsing relay 216 and magnet 218, to battery energizes the relay and. magnet. Relay 216,. .on operating,connects the grounded starting circuit to the pulsing circuit which may be traced from contacts 242 and240, conductor 266, contacts 350, conductor 358, contacts 425, conductor 474, contacts 538, conductor 540, and relay 509, to battery. Magnet 218, on operating, steps wipers 219221 ahead one step and, by opening contacts 245, removes the short circuit from the winding of relay 2'17. Relay 2,17 opcrates and opens the circuit of relay 216 and the magnet at contacts-244. The relay and magnet restore, the former removes ground from the pulsing circuit, and the latter again closes the short circuit for relay 217. Relay 217 releases slowly, due to the short circuit of its winding, and after an interval recloses the circuit for the pulsing relay and magnet. Upon the switch wipers reaching the second position a circuit for relay 213 is completed from ground on the bank contact engaged by wiper 220. It may be noted that all contacts accessible to'wiper 220, except the normal po-.

nal starting circuit and is controlled by wiper 220, as long as the same is away from its normal position. Relay 213 also completes a holding circuit for its lower winding at contacts 236 to maintain the relay operated until the'observing operator releases the connection. The original energizing circuit of relay 305 of the common relay equipment is opened at contacts 237 to prevent the reoperation of this relay in case theobserving operator releases one connection and a new call arrives before the sender switch has returned tonormal position.

With relay 213 operated, it is obvious that the pulsing relay and stepping magnet will continue to operate until the switch wipers return to their normal positions. Relay 216 will accordingly close the pulsing circuit at contacts 242 for each step ofthe wipers.

lViper 221, on encountering the contact associated with the group in which an engaged trunk is located, will find ground on, the contact to energize relay 214'. Relay 214 operates and locks to the off-normal ground circuit at contacts 239 and opens the pulsing-circuit at contacts240. In the present case it is assumed that thefirst trunk of the first group is the one. in use, and consequently conductor 221 will find ground on contact 261, and relay 214 will operate after the first impulse has been transmitted over the pulsing circuit. As relay 214 is locked up, the energization and deenergization of relay 216will be ineffective starting circuit of the sender.

the sender.

to transmit any further impulses until wiper 219 engages the ninth contact of its bank, whereupon a circuit is completed for relay 215. Relay 215 operates and opens the circuit to relay 214 at contacts 241. Relay 214 restores, and again closes the pulsing circuit at contact 240. The next step of the wipers brings them into engagement with the contacts associated with the first trunk designating contact, and relay 216 will again transmit impulses until wiper 221 engages a contact marked by ground. In the present-assumed connection, the first trunk contact is the one marked, and consequently relay 214 will again operate following the transmission ofone impulse by relay 216. Relay 214 will remain locked up until the wipers of the switch reach their normal position, and consequently no further impulses will be sent during the present connection. lVhen the wipers reach normal position the oil-normal ground circuit is opened and the stepping operation of the switch ceases. Relay 214 releases and extends the previously-described pulsing circuit by way of contacts 240 and 243 and conductor 265 to relays 306, 307 in series. Relay 213 will remain energized over its lower winding to ground on the original Thus the sender is prevented from further operation as long as the connection between the observation trunk and the central switchboard is maintained.

It will be noted that three vacant contacts appear between the group designating contacts and the trunk designating contacts. These vacant contacts are for the purpose of creating a pause between the two series of impulses of sufficient length to allow the necessary switching operations in the receiving switch. It will be apparent that in case more than five groups oftrunks are required, additionalcontacts will be allotted to these groups and the trunk designating contacts will be moved over to later positions in the switch bank. A twenty-five point switch of the type shown can be arranged to handle ten groups of ten trunks each in this manner. \Vhen more than ten groups of trunks are required it is only necessary to provide a double set of banks containing the necessary additional contacts.

Referring now to the receiving switch RS, Fig. 5, relay 509 operates in response to each impulse transmitted by pulsing relay 216 of The first series of impulses, i. e., the series designating the trunk group, are repeated by way of contacts 547, relay 510, magnet 513, to battery. Relay 510 and the magnet operate in response to the impulses and relay 510, being slow to release, remains operated throughout the series of impulses. Magnet 513 advances wiper 559 step-by-step in accordance with the impulses received. In the case under consideration it is assumed that the sender switch transmitted a single impulse to identify the group, and, therefore, wiper 559 is operated into engagement with contact 562. During the pause which follows the transmission of the group-idem tifying impulses, relay 510 restores and a circuit is completed from oil-normal contacts 555, which operated on the first step ofthe wiper 559, contacts 548, relay 511, to battery. Relay 511 operates, completes a locking circuit for itself at contacts 553, and switches the impulsing circuit over to magnet 512 at contacts 552'. Relay 509 repeats the next series of impulses as in the preceding case, and magnet 512 responds and advances wiper 558 step by step in accordance with the number of impulses received. In the present instance it has been assumed that the trunk-identifying digit consistsof a single impulse, and wiper 558 accordingly engages contact 560. Relay 510 again operates in series with the stepping magnet, and, shortly after thelast impulse of the series, thisrelay releases and completes a circuit for the selected lamps. 'Tliis circuit may be traced from ground on contacts 546, contacts 549, wiper 559, contact 562, conductor 565, group lamp 1, to battery, and also by way of wiper 558, contact 560, conductor 563, and trunk lamp 1, to battery. The selected lamps are now lighted to indicate to the operator the particular group and trunkto which the observing equipment is connected,

and oiiice lamp L7 is likewise lighted to indicate the office in which the connected trunk is located. Guard lamp L6 and subscribers pilot lamp L4 are both lighted and the operator is awaiting the dialling of the called number by-the calling subscriber.

The calling subscriber dials The progress of the connection has been described up to the point-at which the calling line has been connected through to the first selector, an observing connection has been extended to the first position of the observing switchboard, and the trunk-identifying digits have been sent over the observation trunk to light the trunk-identifying lamps at the central switchboard. These operations take place very rapidly and will ordinarily be completed before the subscriber starts to dial the called number, although there will be no interference even though the subscriber turns the dial before the sender switch has completed its sending operation.

The calling subscriber dials the first digit of the called number by interrupting the loop circuit for line relay 102 of selector EA in accordance with the value of the called digit. Condenser 367 (Fig. 3), which is bridged across the line conductors in series with the upper winding of polarized relay 314, as previously described, is charged during the interval that the loop circuit is closed and discharges at each interruption of that circuit. Upon the first interruption of the line circuit and consequent discharge of the condenser a current how is set up in the upper winding of relay 3%, which opposes the current flow normally existing in tne lower rightehand winding of the relay, and the relay moves its armature to close contacts 352 and open contacts 351. A circuit is now closed by way of contacts 339, 352, and resistance 371, lower-left-hand winding of relay 314, to battery. T is left-hand winding of the relay is energized in this circuit an l tends to maintain the armature of the relay in its operated position. An impulse is also transmitted. by way of contacts 339, 352, and 32 i, resistance 368,0ontacts 3&6, conductor 355, contacts 42 i, conductor 4:73, to magnet 501 of the'pen register PR1 (Fig. 5). The impulse is accordingly recorded on the tape by the pen register in the usualgmanner. At the end of the impulse the impulse contacts of the subscribers dial complete the loop circuit and condenser 36'? is re-charged. During the recharging of the condenser current will flow in the opposite direction in the upper windings of the polarized relay, thereby causing the armature of the relay to be moved to its normal position, as shown in the drawings.

The'circuit for relay 309 1S opened at contacts 351 during the impulsing, but due to the slowacting characteristics of this relay its armatures aremaintained in operated position hroughout the series of impulses. Subsequent impulses to the calling subscribers dial are repeated in the manner previously described until all of the called digits are recorded on the tape the pen register.

The observing operator will now listen in on the connection to determinewhether or not the called subscriber answers, and also to ascertain the quality of the transmission. The voice currents to the calling line are amplified by amplifier A which is connected between the observation trunk and the interoffice trunk. It will be noted that the lefthand winding of the transformer 316 is bridged across conductors 256-and 257 series with condensers 373 and 367. The above conductors, as previously described, are connected to the talking conductors of the line under observation, and voice currents impressed on this line are accordingly transmitted through the transformer and coin denser. Transformer 316 is coupled with transformer 317, the latter of which is connected to the gridof vacuum tube 318. The plate of this vacuum tube is connected through the primary winding of transformer 366 and to vthe grounded positive side of the exchange battery. The secondary winding of transformer-366 is connected in the loop circuit including contacts 3stOand 3%, contacts 3 15 and 3529,.and the left-hand winding of'the repeating 0011 R. A further loop c1rcuit may be traced from the condenser and right-hand windings of repeating coil R, conductors 356 .and 357, contacts 415, 418, and 423,.to the left-hand windings and condenser of repeating coil R1. The right-hand windings to this repeating coil are 'connected'by way of conductors 468 and 469, contacts 524 and 528, contacts 533 of the key K3,contacts of the jack and plug of the .operators receiver set to the receiver. The operator'is enabled to clearly overhear the conversation between the calling and called subscriberover the connection just described, while, due to the low capacity of condensers 367 and 373 and the high impedance of the transformer winding, relatively little current is taken from the talking connection,

Obsemin-g operator intercepts .a call 7 In casethe calling subscriber fails to get thecalled subscriber, due either to errors in calling or to faulty operation of the switch ing apparatus, the observing operator upon noting this'condition may enterlthe connection and converse with the subscriber. The operator may hold up a partially extended connection independent ofthe calling subscriber and may signal the attendant in. the outlying exchange in order to call his attention to the condition; Byway of example, it will be assumed thata call from substation S to another subscriber in the same'oflice has failed to get through while under observation, as described in preceding paragraphs.

a On noting the subscribers difiiculty, the observing operator will actuate key K3, there-.

closing contacts 3 lland 343.

The operator may now converse with the calling subscriber and call his attention .to the improper manner in which thecalling device was operated, i1 such wasthe cause of the trouble,:or, in case the switching apparatus operated in ,a faulty ,manner the operator may advise the subscriber :thatthis condition will be corrected and thathemay call the wanted subscriber after a shortinter val. The operator will then actuate key K4: to the right, thereby connecting ground through contacts 541 and the release circuit of the position equipment, zresistance 5ll7,

contacts 537, conductor 174, contacts 425, con

ductor 358, contacts 350, conductor 266, contacts 240 and 24:3, conductor 265, relays 306 and 307 in series, to battery. Relay 306 will operate in this circuit, but due to the inclusion of resistance 50? in the circuit relay 307, which is marginally adjusted, will not operate. Relay 306 bridges impedance 315 across the talking conductors of the observation trunk at contacts 331, thereby completing a holding loop for the exchange switching apparatus which will be eftective to maintain this apparatus in operated condition after the calling subscriber hangs up. I11 order to call the attendant at the outlying ofiice the observing operator will now momentarily actuate key K5, thereby short-circuiting resistance 507 by the closure of contacts 539. Relay 307 now operates due to the increased current flow in the circuit, and .at contacts 332 closes a circuit for the buzzer which audibly signals the oflice attendant. The attendant on noting the alarm signal will plug 7 into the test jack TJ with the usual test telephone and may then converse with the observing operator to ascertain the cause of the signal. The attendant may then trace the call over the exchange switching apparatus and repair the faulty condition as required. I

Release of the observation connection hen the operator has satisfied herself that a connection has been completed satisfactorily, or after having called the ofiice attendants attention to an unstandard condition, she will release the observation connection and thus. condition the observing equipment for receiving a new connection. In the case of an intercepted call, the operator will first restore the talking key K3 to normal position, thereby removing the shunt from the lower winding of relay 505 with the consequent release of relay 311. Relay 311 will restore and open thecircuit of relay 312, which will also restore. The operator will then restore key K4 to normal position, opening the circuit of relays 306 and 307, and these relays will restore. 'Relay 306.0pens the bridge across the talking conductor of the trunk at contacts 331, which permits the switching apparatus of the outlying office to release, providing the calling subscriber has restored his receiver. If the calling subscriber has not yet hung up, the switching apparatus will remain operated and the condition of the observing equipment will be exactly the same as it was when the obser-" vation of the connection was started. The release of the observing equipment will be the same from this point on regardless of whether the subscriber has hung up or remained in connection with the calling subscriber. This release is brought about by the operation of key Kelto the left, thereby opening the holding ground circuit at confrom ground at oil-normal contacts 555, con-.

tacts 545 and 557, to the magnet. The magnets accordingly operate buzzer-like, and advance the wipers step by step to their home positions, whereupon the oft-normal contacts open and relay 508 restores. Relay 511 also restores and switches over the impulsing circuit to the magnet of the lower receiving switch.

As a further result of the removal of ground from the release circuit upon the operation of key K4, trunk relays 4.01 and 1-02 restore and again close the chain circuit for the trunk group relays 409, 410, etc. In case the second position of the switchboard has been placed in service, relay 410 will be operated and relay 109 will be prevented from operating so that the next call received will be routed to the second position. In the common relay equipment CR, relay 305 restores upon the opening of the release circuit, and at contact 328 removes ground from the circuit over which relays 303, 310, 202, and 209 have been held operated. These relays restore, followed by the restoration of relays 303 and 309. Relay 209 on restoring opens the circuit of relay 302, which restores and opens the circuit of relay 213 of the sender switch. The latter relay restores and the observing equipment is now in condition to receive the next call.

In case the line under observation has not been released, trunk relay 201 will remain operated so that upon the subsequent operation of relay 210, which occurs upon the closure of the chain circuit by the trunk relays, the trunk relay 202 will not be con-' nected to the trunk. This condition will pre-.

vail likewise on trunks connected to lines on which calls were lnitiated when the service observmg equipment was 111 use in the preceding connection. These lines, therefore, will Metering operations The observation equipment of the present application is arranged for the supervision of the two classes of metering commonly used, 1. e., the so-called booster battery metering in which the metering current is applied to the release trunkor holdingconductor of a connection, and forimetering over a separate. Emetering, conductor. The observation trunks are accordingly provided with a fourth conductor, which, in the present instance, is shown connected-to:the;holding conductor by a strap at :the distributing frame. ihenobserving calls on .lines arranged {for the separate wire :metering, this sfourth conductor will-be connected torthe metering conductor of the line, and resistance 353 (Fig. 3) will be shortcircuitedby astrap;354. 1n this casethe relay-20.4 .willbeoperated upon the application .of ground to :themetering conductor, which takes place .upon :the .call beinganswered by the called subscriber. In the arrangement .showninthe drawings, however, the metering conductor of :the observation trunk is ;tied :to the holding conductor which is grounded upon-the seizure of the calling line by a line-finder. Under these conditions, relay 304 isprevented from operating due to resistance 353 in the-circuit, but when the high voltage meteringcurrent .is

' applied 'to the holding conductor of the line the relayoperates.

It will :be recalled that when .the .service observing equipmentwas ,placed'inservice relay 305 of the common relayequipment was operated and looked over acircuitwhichanay be traced from battery,lower high resistance winding of .relay'305,.contacts 330 and 348, upper right-hand winding of repeating coil R, conductor 356, contacts 4l5, upper lefthand winding of repeating coil R1, conductor 471, relay 504, through contacts of the release key to ground at contactsfi tl. It will also be recalled that relay 504 was notoperated in the above circuit due to the high resistance of the lower winding of relay 305. It will be apparent that upon-the operation of relay 30Las the result of the applicationof metering current to the meteringcon'ductor of the line under observation the lower high resistance winding of relay 305 will be 'shunte'd'by the upper low resistance winding of the relay, upon the closure ofcontacts 327. Relay 504 operatesdue to-the increased current flow 1n its circuit, connects metering tone to the operators telephone circuit'by wayof contacts518 and 525,.closesa circuit for slow-tooperate relay 503at contacts526, and connects-the tone return, ground to the operators receiver circuit by way of contacts .523 and 5:27. Relay 503 operateszatter ashort delay and reestablishes the connection of the receivertothe talking conductors of -the observat-ion trunk by closing contacts 519and 522, and at contacts 518 and L3 disconnects the itself at contacts 521, and at contacts 520 closes a circuit for metering lamp L5. The

lamp glows to givethe ope-rator-avisualinill- 1 dication-that the metering operation wascompleted successfully.

Observation of calls with ZfihflOfltGbZ obseroation set 'The portable observation .set provided-for observing connections .in the outlying ofiices is substantially the .samev as that provided at the:centralcbservation switchboard. As this set is-adapted for supervising in a single ofiice only, the otficedesignating lamps andoflice keys have :been omitted, and the receiving switch and associated lampbank hasalso-been omitted. "Identification of the trunk in use is made by means of the lamp bank which ing parts in the centralized equipment shown in Fig. 5. .F or example, relays 602,603,604, and605 correspond to relays 502,503, 504, and 505, respectively, and ha've exactly the-same functions to perform; Keys K,'i K*1, and K2 correspond to 'keys K3, K4, and-K5 ofthe' centralized equipment. Lamps L1, L2, and

L3 correspond to lamps L4,'L5, and L6; etc.

The portable observation set is connected with the observation equipment of an e2;- change by means of a terminal strip and-j ack of the type commonly used for connecting selector and connector switches oftheStrowger type with their associated self-wiring;

The service observing equipment is placedin service by connecting up thep rta-bleset and 1 inserting the plug P of the operatords receiver set into'thejackzl. v-Uponconnecting up the portable se t,fa circuit is completed from ground on the jack contacty-con'ductor360,

relay 313, to battery. Relay 31'3 operates and disconnects the observing equipment'ofthe outlying o'fiice from the interofiice trunkl by opening contacts 345 350. 'A circuit 'is closed from groundby way of conductor;63 1, springs and contacts of the jack and plug,

release key contacts 626, relay 604, conductor 634, j ack contact, conductor 363, and thence to the lower winding ofrelay305 as previously 7 described for calls observed atzthecen-tral switchboard. Battery is-normally connected to the twowindings ofrelay 6Q5{so;;thatjthis relay will operatein the same manner in 1 which relay 505, previously described foperated upon the initiation of a calllonea :line equipped for observation. :Thetalking conductors ofthe observation trunkare extended to the portableset by way of conductors 361 and 365 which are permanently connected with thetrunk conductorsat thB COHIITIOII relay equipment. The pulsing circuit over which dial impulses are repeated to the pen register is connected to the portable set by way of conductor 359. A circuit over which relay 306 is operated to hold up a connection is connected to the portable set by way of conductor 36%. A momentary application of ground to conductor 362 upon the initiation of a call energizes relay 602, and the seizure of the calling line by aline finder energizes relay 605 to light the respective supervisory lamps L3 and L1. The various operations, such as establishing a talking connection with a calling subscriber, holding of a connection, and release thereof is obtained by the operation-of keys K, K1, and K2 in the same manner as previously described for the central observation switchboard. lVith the foregoing explanation in mind, it will be readily seen that the operations involved for observing and supervising a call by means of a portable set is the same as that described for observing calls at the central switchboard.

that is claimed is: v I 1. In a multi-office telephone system, a central oihce, an outlying OfiICQ, an observation switchboard at the central oflice, a subscribers line terminating at the outlying office, non-numerical switching apparatus for connecting the line with an automatic switch, an observation trunk connected with said line, an interoiiice trunk connecting said two offices, means responsive to the initiation of I a call on said line for starting the operation of said switching apparatus and for extending a connection from the line to, said switchboard via the interofiice trunk, and means responsive to the completion of the operation of said switching apparatus for operating a signal at the switchboard.

2. In a multi-ofiice telephone system, a central: oflice, an outlying ofiice, an observation switchboard at the central office, a sub- I scribers line terminating at the outlying of- 45 a call on said line for starting the operation of said switching apparatus and for operating a signal at the switchboard via said observation trunk and said interoffice trunk, and means responsive to the completion of the operation of said switching apparatus for operating a second signal at the switchboard.

3. In a multi-oifice telephone system, a central office, an outlying ofiice, an observation switchboard at the central oifice, a subscribers line terminating at the outlyingoffice, a finder switch having access to said line, an observation trunk associated with said line, an interoflice trunk connecting said two oflices, means responsive to the initiation of a call in said line for starting said finder to hunt for the line and for establishing a con nection from the line to said switchboard via said observation trunk and said interoflice trunk, andmeans responsive'to said finder connecting with the line for operating a signal at the switchboard.

4. In a telephone system, a central oifice, a plurality of outlying offices, a plurality of observation trunks in each outlying oiiice, each of said'trunks being directly connected to a subscribers line terminating at the office, a trunk line extending from each outlying oflice to the central ofiice, an observation switchboard at the central office, means responsive to the initiation of a call on a subscribers line terminating at any of the outlying offices for connecting the associated observation trunk with one of said trunk lines and for connecting the trunk line to said switchboard, and means thereafter effective to prevent any further connections to the switchboard as long as said first connection said position, and means at said position forindicating the time between the initiation of a call on a line and the instant when the same is extended to a further point.

6. In a multi-ofiice' telephone system comprising a central oflice and a plurality of outlying oi'hces, an operators position at the.

central oihce, lines terminating at the outlying ofiices, means controlled by the operator for rendering said position connectable to any of said lines, means. for connecting one of said lines to the position, means controlled by an operator for disconnecting said line from the position, means responsive to the initiation of a call on another line for connecting that line to the position, and means for rendering said last connecting means ineffective in case the first line is disconnected from the position subsequent to the initiation of the call on said other line.

7. In a telephone system, a line, means for extending a talking connection from the line, an operators position, a voice current amplifier, means for establishing a monitoring connection from said first connection to said position via said amplifier, and means controlled by the operator for excluding saidamplifier from the connection.

8. In a telephone system, a line, means for extending a talking connection from-the line, a local operators position, a remote operators position, a voice current amplifier, and means responsive to the establishment of said talking connection for extending a monitoring connection either to said local. position independent of said amplifier or to said remote position via said amplifier.

9. Infatelephone system,aline, means of extending talking connections from the line, an operators position, a voice current amplifier, means responsive to the establishment of said talking connection for extending a monitoring connection to said position via said ampliiier, and means controlled by the operator for converting said monitoring connection into a talking connection and for excluding said amplifier therefrom.

10. In a telephone system, lines, a local observation position for observing calls on said lines, a remote observation position for observing calls on said lines, means for rendering either position connectable to said lines, an amplifying device, and means for rendering said device effective only when said remote position is connectable to the lines.

11. In a telephone system, a. line, means for extending a talking connection from the line, an operators position, a transmitter and a receiver at the position, an amplifier, means for establishing a monitoring circuit from said connection to said receiver via said amplifier, and means controlled by the operator for connecting the transmitter to said circuit and for excluding said amplifier therefrom.

12. In a telephone system, a plurality of branch oflices, subscribers lines terminating at said ofiices, line indicating and supervisory equipment common to said oiiice. common means and means individual to each of said lines for associating the same with said equipment responsive to the initiation of a call on the line, and means for preventing a second line from being associated with said equipment while the first line is still associated therewith.

13. In a telephone system, a plurality of outlying oflices, a central office, a plurality of subscribers lines at each outlying oifice, means for extending connections from said lines, a trunk line extending from each outlying oifice to the central oiiice, means at each outlying ofiice responsive to the initiation of a call on a line for connecting the line with the trunk extending to the central office and for signalling an observing operator, and means responsive to the extension of a connection from the calling line to a further point for signalling the observing operator.

14. In combination, a trunk line, subscribers lines and means for connecting them to the trunk line, an indicator at the originating end or" said trunk line for indicating in any given case which of said lines is connected to the trunk line, a similar indicator at the distant end of said trunk, an impulse sending switch at the originating end of the trunk line operating from normal position to transmit impulses over the trunk line to control the distant indicator, common apparatus for controlling said first indicator and said sending switch, and means controlled by the sending switch for preventing the connection of a line to the trunk line unless the sender switch is in normal position.

15. In a service observing system, service observing equipment, service observation,

trunks normally disconnected from said equipment, lines to be observed, means responsive to the initiation of a call on any one of said lines for connecting the same to an observation trunk and for connecting the trunk to said equipment, an impulse sender operated from normal position responsive to the operation of said connecting means for transmitting impulses over the observation trunk to identify the particular line connected thereto, and means for preventing the reoperation of said connecting means until said sender returns to normal position.

In witness whereof, I hereunto subscribe my name this 15th day of September, A. D.

CHARLES R. BROOKS. In witness whereof, I hereunto subscribe my name this 15th day of September, A. D.

J OHN E. OSTLINE.

DISCLAIMER 1,907,240.O'harles R. Brooks and John E. Ostline, Chicago and Berwyn, Ill. SERVICE OBSERVING EQUIPMENT. Patent dated May 2, 1933. Disclaimer filed December 13, 1934, by the patentees, the assignee, Associated Electric Laboratories, Inc, consenting.

Hereby enter this disclaimer to claims 4, 6, 7, 9, 11, 12, and 13 of said specification which are in the following words, to-wit:

4. In a telephone system, a central office, a plurality of outlying offices, a plurality of observation trunks in each outlying office, each of said trunks being directly connected to a subscribers line terminating at the office, a trunk line extending from each outlying office to the central office, an observation switchboard at the central office, means responsive to the initiation of a call on a subscribers line terminating at any of the outlying ofiices for connecting the associated observation trunk with one of said trunk lines and for connecting the trunk line to said switchboard, and means thereafter effective to prevent any further connections to the switchboard as long as said first connection is maintained.

6. In a multi-office telephone system comprising a central office and a plurality of outlying ofiices, an operators position at the central office, lines terminating atthe outlying offices, means controlled by the operator for rendering said position connectible to any of said lines, means for connecting one of said lines to the position, means controlled by an operator for disconnecting said line from the position, means responsive to the initiation of a call on another line for connecting that line to the position, and means for rendering said last connecting means ineffective in case the first line is disconnected from the position subsequent to the initiation of the call on said other line.

7 In a telephone system, a line, means for extending a talking connection from the line, an operators position, a voice current amplifier, means for establishing a monitoring connection from said first connection to said position via said amplifier,

and means controlled by the operator for excluding said amplifier from the connection.

9. In a telephone system, a line, means for extending talking connections from the line, an operators position, a voice current amplifier, means responsive to the establishment of said talking connection for extending a monitoring connection to said position via said amplifier, and means controlled by the operator for converting said monitoring connection into a talking connection and for excluding said amplifier therefrom.

ll. In a telephone system, a line, means for extending a talking connection from the line, an operators position, a transmitter and a receiver at the position, an amplifier, means for establishing a monitoring circuit from said connection to said receiver via said amplifier, and means controlled by the operator for connecting the transmitter to said circuit and for excluding said amplifier therefrom.

12. In a telephone system, a plurality of branch offices, subscribers linesterminating at said offices, line indicating and supervisory equipment common to said office, common means and means individual to each of said lines for associating the same with said equipment responsive to the initiation of a call on the line, and means for preventing a second line from being associated with said equipment while the first line is still associated therewith.

13. In a telephone system, a plurality of outlying offices, a central office, a plurality of subscribers lines at each outlying office, means for extending connections from said lines, a trunk line extending from each outlying oifice to the central office, means at each outlying office responsive to the initiation of a call on a line for-connecting the line with the trunk extending to the central ofiice and for signalling an observing operator, and means responsive to the extension of a connection from the calling line to a further point for signalling the observing operator.

[Ofiicz'al Gazette January 8, 1935.]

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