US2119209A - Telephone system - Google Patents

Description

May 31, 1938. o. c. HALL ET AL 2,119,209

TELEPHONE SYSTEM Filed April 7, 1956 9 Sheets-Sheet l POLARIZED rou.

u/ve' o aca KERR 66 Sat: 9. K6

E 0. c. HALL INI/ENTORS J A TTORNEV May 31, 1938. o. c. HALL ET AL TELEPHONE SYSTEM Filed April 7, 1956 9 Sheets-Sheet 2 0. C. HALL INVENTORS J. F TOOMEV ATTORNEY F/aa May 31, 1938.

RING/N6 o. c. HALL El AL 2,119,209

TELEPHONE SYSTEM Filed April 7, 1936 9 Sheets-Sheet 5 MARC-INA L MARG/NAL T 0.6. HALL J.F TOOME) ATTORNEY May 31, 1938.

o. c. HALL ET AL TELEPHONE SYSTEM Filed April 7, 1936 THROUGH 9 Sheets-Sheet 4 .0. C. HALL INVENTORS- Jf TOOMEV BY W ATTORNEY May 31, 1938. o. c. HALL ET AL 2,119,209

TELEPHONE SYSTEM Filed April 7-, 1956 9 Sheets-Sheet 5 lmrll- .0.c. HALL I W J./-.' room-r B) i f I ATTORNEY May 31, 193 8.-

TELEPHONE SYSTEM Filed April 7, 1936 9 Sheets-Sheet 6 mes/1m- M MARC/NIL 0.6. HALL /NVENTOR$- 4E ATTORNEY o. HALL ET AL 2,119,209

May 31, 1938. o. c. HALL ET AL 2,119,209

TELEPHONE SYSTEM Filed April 7, 1956 9 Sheet s-Sheet 7 FIG. 7

. INVENTORS: ALL

ATTORNEY y 1938- o. c. HALL ET AL 2,119,209

TELEPHONE SYSTEM Filed April 7, 1936 9 Sheets-Sheet a 0. c. HALL J./T room-r ATTORNEY May 31, 1938. o. c. HALL ET AL TELEPHONE SYSTEM Filed April 7, 1936 9 Sheets-Sheet 9 Mom 0. C. HALL INVENTORS JJ-l' TOOMEV Patented May 31, 1938 UNITED STAT-ES iPA-TE NT o -FrcE ,TELEPHONE. SYSTEM 1 a oliver Ou HallyFair Lawn,.N. .J., and .JohnQF. .Toomey,Newy.York, N. Y., .assignors to,,B'ell 1' Telephone 1; Laboratories,

Incorporated, New

Y York, N. Y., a corporation of NewwYork Application April '7, 1936, Serial No. 73,110"

-, straightforward lines terminate in a single cord and plug at the inward or through position.

When the outward toll operator connects a calling line to the outgoing straightforward line the distant inward and through operator isautomatically connected, receives the. order and inserts the plug terminal ofthe line either in a trunk jack, in the case of a terminating connection or into the outgoing jack of another toll line. In the case of a terminating connection supervision received from the terminating local ofiice or called subscribers'station will be transmitted through the toll operators position back over the incoming line to the outward or originating toll. operators position without displaying any signals at the inward and through position. In case the call is to be routed to a distant city the inward and through operator plugs the callingline into a second straightforward line outgoing to. the .de sired point. In this case, also, any supervisory signals originating at the distant end of the connection are transmitted back over bothstraightforward lines to the outward operator without displaying any supervisory signals at the inward and through positions.

At the inward and through position outgoing ring-down toll lines are also terminated over which the operator may extend a calling straightforward line. In this case a reverting ring from the distant end of the line such as a ring-off passes through the intermediate operator's position and signals the outward operator without affecting the supervisory signals at the intermediate through ofilce.

In the Meszar et al. arrangement, due to the fact that the inward ends of the straightforward lines are plug-ended, separate inward and. through and outward switchboards are-required,

the inward. and through board. being used exclusively for terminating through calls and the 1 outward board,- which isequipped with-the usual double-endedcord circuit, being usedfor outward calls, i. e. calls originating locally for extension over toll lines to a distant point.

This" system is'veryefiicient and satisfactory fori large ofliceslbut may be undesirable, from;

i a cost standpoint, forsmallofliceswhere a small number of operators, operating as a single group, could handle all of the toll traffic both inward,

through andoutward were they'in a position to doso. An object of the present invention, therefore, is

to provide such an arrangement that a single operator can handle all types of toll calls.

A feature of the invention whereby the foregoing object is obtained resides 1113511011 an ar-;-

rangement of toll lines; trunk circuits and cord circuits, that all suchtypes'of lines, i. e., both I inward and outward trunks, straightforward toll lines andring-down toll'lines maybe terminated at a-single' operators position and interchangeably connected at will by means ofa universal double-ended toll cord circuit arranged to adapt itself for the proper kind of supervision, i. e., through or terminating depending upon the types of lines connected thereby.

"Anotherfeature resides in a novel method of controlling the exclusion of transmission loss pads from tolllines-whentwo lines, so equipped, are connectedtogether bymeans of a cord circuit whichmethod COIlSlStSril'l so connecting the pad. control'relay of each line to the line conductors in series with a battery, and so arranging the cord circuit that when' the. lines'are connected together, and .the cord circuit talking key is not operated, the talking conductors of the cord circuit are reversed with respect. to the two ends thereof, thereby connecting the tip of one line to the ring of the other lineand vice versa whereby the pad control relay of each'line will receive operating'current toexclude the respective pads from the lines.

Another feature resides in so arranging the cord circuit that when the operator plugs into a calling straightforward tollline and actuates the talking key, a zip order tone will be connected 4 cord Fig. 2 and a ring-down toll line Fig. 3 is disclosed-whereby ringing current is .connected to the toll line by means (relayr301) controlled by direct current connectedto the tip of the cord connections terminating at the toll office.

arrangement is standard practice at the present time, but has the disadvantage that the tip conductor of the line is permanently grounded through a retard coil and the ringing control means. As the ring conductor of the line is also used in a similar manner to perform other func tions such as transfer, which necessitates a similar permanent ground thereon through the lower winding of the retard coil andleft-hand winding of relays M5 and 3M, it will be noted that an impedance bridge exists across the line which may be traced from the tip through the upper winding of the retard coil, winding of relay 301 and resistance 308 to ground and from ground through relays 314 and 3l5 and lower winding of the retard coil to the ring of the line.

Another feature of the present invention, therefore, resides in a novel means for controlling the various desired signaling functions, over the tip and ring as heretofore, which obviates the necessity of a permanent ground connection to the line conductors.

Ringing is accomplished in this case by a marginal relay arrangement controlled over the sleeve of the cord and line, whereby, when the ringing key is operated the ringing relay is connected to the tip of the line only while the key is operated. Operation of the ringing key also connects ground to the tip of the line causing the ringing relay to operate. Other functions previously controlled over the ring are likewise controlled over the sleeve by the operation of keys in the operators position which connects the proper relay to the ring conductor which operates to ground simultaneously applied to the ring conductor by the actuation of the same key.

Another feature of the invention is a single lamp per line which serves both as an idle line indicating signal and also as a line or calling signal. When the line is idle the lamp burns steadily at reduced brilliancy. When a call is received the brilliancy increases and the lamp starts to flash.

The invention will be more fully understood from the following description in which; Fig. 1 represents the line end of an automatic toll line together with Fig. 1A representing a pad circuit for transmission purposes; Fig. 2 represents the toll office end of the automatic toll line; Fig. 6 represents the toll office end of another automatic toll line identical with Fig. 2 for the purpose of more readily tracing a call from one line to another of said lines, Fig. 7 represents a two-way ring-down toll line; Fig. 8 represents a two-way trunk circuit for use in recording and completing calls-originating from subscribers in manual offices and for completing connections to subscribers on connections terminating at the toll office; Fig. 9 represents an out-dialing trunk circuit for completing calls on a dial basis to subscribers on A description of the initiation and completion of calls over these circuits in conjunction with a toll operators cord circuit of Fig. 3, the operators position circuit of Fig. 3A, a position dial circuit of Fig. 4, an operators telephone circuit of Fig. 5 and order tone circuit of Fig. 5A will serve to illustrate the various features of this invention wherein Fig. 10 represents the arrangement of Figs. 1 to 9 of the drawings. For convenience the reference characters used have been chosen in groups of I00, those from I00 to I99 referring to Fig. 1, 200 to 299 to Fig. 2, etc.

'by operation of the ringing key. This general General description of operation Inge'neral the operation of the present system maybe briefly outlined as follows: Both the automatic toll line and the ring-down toll line in this system are arranged to function on calls in either direction. When therefore the front plug of the toll cord of Fig. 3 at an outward position is plugged into the outgoing jack 661 of the toll line of Fig. 6 extending to a distant ofiice, the relays of these circuits function; to extinguish the associated idle line indicating lamp (H9 thereby enabling the next idle line indicating lamp to light; to light the associated cord supervisory lamp 344; and to send out a voice-frequency signal over the talking conductors to the distant oflice. This signal is received at the distant office by a circuit organization such as shown in Figs. 1 and 2 and which functions; to return an acknowledgment signal to the originating office after the calling condition is registered, in order that the connect signal may then be cut off; to start the associated trunk lamp Hi to flashing for indicating an incoming call to the inward toll operator. The first inward operator answers by inserting the rear plug of her toll cord into the associated jack 248 and at the same time operating her talking key on the toll cord which results in; extinguishing the flashing line lamp 22 I automatically causing the toll cord of Fig. 3 to be associated with the common toll signal equipment shown in Figs. 3A, 4, 5 and 5A; and automatically sending zip tone back over the talking conductors to the calling operator as an indication that the second operator is ready to receive the number of the called subscriber.

When the calling toll operator passes the wanted subscriber number the incoming operator then plugs the front end of the toll cord into jack 661, if the call is required to be completed over another automatic toll line or jack 100, if the call is to be completed over a ring-down toll line, jack 800 if she completes the call over a toll switching trunk, or jack 900 if the call is to be completed to a dialed subscriber in the local ofiice. In the case of the call being extended over another automatic toll line the same action takes place as when the first operator originated the call on the previous toll line, namely, extinguish the idle line indicating lamp, light the associated cord lamp and send on a connect signal to the next toll office. The next inward operator answers the incoming flashing signal, and the same action takes place as described for the previous operator except that now the original operator hears the zip tone from the last operators telephone and order tone circuit. The first operator again passes the wanted subscriber number and the connection is then assumed to be completed over a standard toll switching trunk to the wanted number.

When the called subscriber answers, the toll line circuit then automatically sends back a receiver-off-hook signal which passes through the toll cord at the intermediate toll office, and is received by the originating toll line which returns an acknowledgment signal to the line and causes the first operators toll cord lamp 344 to be extinguished. If the called subscriber hangs up for any reason, a receiver-on-hook signal is similarly transmitted to the originating toll line circuit where it is acknowledged and cord lamp 344 again lighted. If the called subscriber flashes-in the calling operator then the above noted signals are transmitted over the toll line alternately and the by giving the through operator a steady cord lamp 304 and sending back an acknowledgment signal to the originating toll line which in turn terminates the disconnect signal and the circuits I restore to normal. The through operator in turn disconnects her plug in a similar manner which causes the toll line to send a disconnect signal to the terminating operator. The toll operator at the terminating office therefore receives a disconnect signal by noting a steady light 304 and she also then disconnects her toll cord and an acknowledgment signal is returned to the inter-' mediate toll line causing the disconnect signal to cease and the apparatus all to restore to normal.

Assuming now, in the call described above, that the number had been such as to require completion at the intermediate toll oilice over the ringdown toll line of Fig. 7 instead of over a second automatic toll line. In this case the intermediate toll operator inserts the front toll cord plug into jack 100 instead of jack I561.

Connection between two automatic toll lines For the purpose of describing the through supervisory features, ringing, transfer, and other signaling and control functions on toll lines of this character a call will be traced; as it originates in one toll office, referred to as office X; as it is carried through an intermediate toll office. referred to as ofiice Y; and as it terminates in a third office, referred to as ofiice Z. Since the detailed description of the automatic toll line represented by Fig. 2 on such a call depends on whether the call is being described in an inward or an outward direction, Fig. 2 will be referred to when the call is inward and Fig. 6 will be referred to when the call is outward in direction. Thus on calls originating at office X a toll cord the same as in Fig. 3 is assumed as being plugged into a toll line the same as Fig. 6. The line end Fig. 1 of the toll line then is assumed to connect with a similar Fig. 1 at oflice Y and which in turn connects with Fig. 2. The toll cord of Fig. 3 in this ofiice then serves to illustrate its use on through supervision. In extending the call outward to office Z the operator in office Y thus is I assumed to plug into the toll line of Fig. 6 and I again the line end Fig. 1 of the extended toll line is assumed to connect with a similar line end at office Z and which in turn connects to Fig. 2.

Before proceeding to trace the call outlined above it should be observed that the transmission and reception of high frequency signals over telephone lines for supervisory purposes is not new.

To facilitate this description however reference may be had to Patent No. 1,860,446 to R. S. Bailey et al. which describes in detail that part of the toll line shown in Figs. 1 and 1B. Briefly this arrangement involves transmitting an acknowledgment signal of predetermined frequency back over the line whenever an incoming signal arrives. The receipt of the acknowledgment signal at the sending end resultsin cutting off the signal being sent. When the incoming signal ceases at the receiving end of the line it causes the acknowledgment signal to cease. Since this necessitatesa circuit arrangement that both sends and receives high frequency signals simultaneously there is interposed in line L a directional selection circuit composed of coils I I 03, I04, I36, and condenser I31 which is of the nature of a hybrid I transformer.

Such an arrangement is disclosed and claimed in the patent to George Crisson No.2 1,755,243 issued April 22, 1930 and as it forms no part of the present invention, it is deemed sufficient to merely statethat it prevents'the voice frequency signal applied to the line L by relay I20 from becoming effective over 1eads'I38 and I39 in operating the signal receiving apparatus of Fig. 1B Without interfering with incoming high frequency signals whichmust be registered by the apparatus of Fig. 1B. To facilitate this selection,

whenever an outgoing signal of 1400 cycle carrierl 05 frequency is being sent, relay I44 remains in its normal position, thus tuning the incoming leads I33 and I39 to receive signals having a frequency of 1000 cycles. When signals of 1000 cycles are being sent relay I 44 is in an operated position- 0 which by connecting coilI45 and opening the condenser I40 tunes the incoming circuit to receive signals having a 1400 cycle carrier frequency.

High frequencies of any suitable values may 5 be used in signaling of this character. For the system here described high frequencies of 1000 cycles and 1400 cycles are employed as the carrier frequency. Three separate signals are then obtained when cycle, cycle or cycle cur-" rent is superimposed on the carrier frequency of 1000 cycles. The acknowledgment signal has 20 cycle current superimposed on a 1400 cycle carrier frequency. The receiving apparatus shown in Fig. 1B for identifying the incoming 3 signal includes transformers I05, I06, and I01; an amplifier vacuum tube I08 and a rectifier tube I00 for separating the low frequency current from the carrier frequency; and a vibrating polar relay IIO for responding to the low frequency lfi component. The output of this network connects over leads III and H2 with three low frequency tuned circuits designated A, B and C. Tuned circuit A responds to 20 cycle frequencies and consists of a tuned coil II3 connected inskifi serieswith a condenser IIII, rectifiers H5 and direct current relay H6. Similarly, tuned circuit quencies of 45 cycles for operating relay 8.050

Incoming signals therefore operate relay I I6, I I! or II8. If relay II6 operates it connects ground to winding of relay I I9 thence to battery at break contact relay I20 thereby operating relay I I9 and connecting 48 volt battery I2I through high re-c sistance I22 to lead I23. If relay II'I operates it connects ground to winding of relay I24, thence to battery at break contact I20 thereby operating relay I24 to connect ground through resistance I25 to lead I23. If on the other hand relay -BO II8 operates, it connects ground through the back contact of relays I24 and H9 direct to lead I23. The three different kinds of incoming signals therefore are transformed into three ,corresponding conditions that are connected to lead I23 as above described and these conditions will be referred to in the description that follows without repetition of the above explanation.

While the function of. the apparatus shown in Fig. 1B is to receive and transform incomingwo signals from the toll line to battery or ground signals on lead I23 to Fig. 2, the function of relays I26 to I32 inclusive of Fig. 1 is to convert battery or ground signals on lead I33 coming from Fig. 2 to high frequency carriersignalss7 for transmission over the toll line. Lead I33 is connected in series through relays I26, I21 and I28 to negative 24 volt battery. Relay I26 being polarized responds by operating when negative 48 volt battery through either a high or low resistance is connected to lead I33 but does not operate on ground signals. Relay I21 is both sensitive and marginal and operates whenever direct ground, ground through a low resistance, or 48 volt battery through low resistance is connected to lead I33. It does not operate however when 48 volt battery is connected through a high resistance to lead I33. Relay I28 is marginal but not very sensitive and only operates when direct ground is connected to lead I33.

Fig. 1A represents a transmission pad circuit of the usual type controllable over lead I34 from Fig. 2 for reducing the transmission equivalent of the toll line at originating and terminating toll oflices but removed from the line on through connections at intermediate offices. Lead I34 in this invention in addition to controlling the transmission pad also affects incoming signals to lead I23 depending on the type of circuit to which the automatic toll line is connected. This is accomplished by the addition of relay I20 connected from 24 volt battery in series with the pad control relay I35 to lead I34. Relay I20 being marginal operates for example when direct ground is connected tolead I34 by the toll line of Fig. 2 as will later be described, thus indicating that said toll line is connected to another automatic toll line. If, however, said toll line is connected to a ring-down toll line arranged for transmission pad control, then the ground to lead I34 is through a resistance which permits pad control relay I35 to operate but does not allow marginal relay I20 to operate. In the latter case the incoming signals are not altered. In the former case, however, when relay I20 operates it removes battery from the windings of relays H9 and I24 thus permitting only a disconnect signal to be received as will later be described. When the automatic toll line is connected to a ring-down toll line not arranged for transmission pad control, no ground will be connected to lead I34 thus preventing either of relays I20 or I35 from operating and in this way the transmission pad remains in the circuit and the incoming signals function the associated two-way automatic toll line relays of Fig. 2. Whenever the connection is interrupted, as will later be described, by the operation of a talking or splitting key in the toll cord of Fig. 3 or by the removal of a plug from the jack, ground will be removed from the lead I34 causing relay I35 to release also relay I20 if same had been operated.

Assuming now that the toll operator at the originating ofiice X inserts the front cord plug in jack 661, a path is closed for lighting the cord lamp over a circuit traced from battery through cord lamp 344, contact 345, relay 300 which is assumed to be normal at this time, lead 343, contact 346 on key 341, sleeve lead 348, thence through plug and jack to sleeve lead 635 and 636, thence to ground both through right winding relays 631 and 038 in series, and to ground through the left windings of said relays and right front contact relay 655. The cord lamp 344 now remains lighted until the called subscriber in the distant office answers as will presently be described. The circuit thus traced causes relays 631 and 638 to operate and the latter relay in turn connects ground over lead 639 for operating relay 640 to battery. Relay 640 then closes a path for operating relay B50 traced from ground at left back contact relay 006, contact 601 on relay 640 to battery through winding relay 050. Relay 640 at its left inner contact closes a path for operating relay 655 traced from ground at left back contact relay 600, contact 652 on relay 540, to battery through winding relay 055. Relay 640 also operates relays 508 and 601 from battery at its left outer armature and contact to ground through lower winding relay 600 and winding of relay 601 in multiple. The operation of relay 601 thus opens the winding of relay 5I4 causing its contact to open thereby extingm'shing idle indicating trunk lamps 6I9 and 62L The operation of relay 650 closes a path for causing 2. connect signal to be sent to the distant toll ofiice Y which may be traced from ground through resistance 649, left back contact and armature relay 605, front contact and armature relay 650, contact 65I on relay 0I3, contact 621 on relay 028, right back contact and armature relay 629, thence over lead I33 and through wind ings in series of relays I26, I21 and I28 in Fig. 1 to negative 24 volt battery. Relay I21 operates and closes a path for operating relay I3I over a path traced from ground at right contact relay I26, bottom armature and back contact I20, lower front contact relay I21 to battery through winding relay I31. Relay I3I operating at its bottom inner contact connects ground to winding of relay I44 thus tuning the receiving circuit of Fig. 1B for an acknowledgment signal having a carrier frequency of 1400 cycles. Relay I3I at its top inner contacts also operates relay I20 for sending out a connect signal of 1000 cycles 20 cycles which is connected to the front contact of relay I29 by relay IN.

The connect signal is registered by the automatic toll line at office Y which then returns an acknowledgment signal to ofiice X as will presently be described. The receipt of an acknowledgment signal at the originating office X causes negative 48 volt battery I2I through a high resistance I22 to be connected to lead I23 as pre viously described. This causes relay 600 to operate and connect ground through contact 604 on relay 005 to winding relay 606 to battery. The latter relay in operating at its left armature and break contacts opens the ground path previously traced for operating relays 050 and 655. Relay 050 releases thereby opening the circuit to lead I33 and terminating the connect signal being sent to distant office Y. Termination of the connect signal at office Y in turn terminates the acknowledgment signal which will presently be described, thus releasing relay 500 which in turn removes ground for holding relay 606. The latter relay continues, however, to be held by ground traced at right back contact relay 632, leads 63I and 030, contact 609 on relay 606, thence through winding relays 605 and 606 in series to battery. Relay 005 operates in this circuit and thus prepares the circuit for further signaling which will later be described.

When the connect signal, on the call here being traced, comes in at office Y it may come in on toll line which is not the first idle line or it may come in on a line which is the first idle line. For the purpose of this description the latter case is assumed and relay 2! is accordingly shown in an operated position. Loops 2I9 and 223 at this time are burning dimly on low alternating current voltage extending from ground on transformer 2I6 over common lead 2I1, through front contact and armature; directly to lead H8 and through left break contact and armature relay 2J2 to lead 220for lighting lamps-2M at the inward toll position.

The connect signal, upon first being received at oflice Y results in connecting 48 .volt battery l2] through resistance I 22 to leadl23 which' may further be traced throughwinding of polarized relay 200 in series with slow operate relay 20| and marginal relay 202to 24-volt battery. Relay 7:30 i i being marginal doesnot operatebecause of the high resistance I22. Polarizedrelay 200 is poled so that it operatesatthistime thereby connecting ground'to lead- 203 which is traced further through contact 204- on relay 205,

then throughwinding relay 206 to battery. Theoperation of relay 206 at its left outer make contactconnects battery to the winding of relay 201 and to the bottom winding relay 20B causing both relaysto operate. Relay 206-at. contact 203 prepares a path -for operating relay 205-when battery isremoved from lead 123. Relay 205 at contact 2H) connects ground to the armature of relay 2! I, whichpathtraced through the back contact of relay 2| lisusedto energize winding relay 2 l2 andrightwinding relay 2l3 in multiple tobattery. r

Going back to the operation-of relay20l itwill be observed thatthis relay functions as a'busyrelay because at its-break contact it opens the, circuit of relay- 2l4wand: that.its make contact extends battery 2I5 :throug-h-to the armature of relay 2M- of .thenext automatic toll line: Battery 2l5 therefore operates relay 214- of-the first toll linethat is .idle, that is,- whoserelay 201is normal. Thev operation. of relay 20! causes relay 2|4to release andopenthe low voltage current: path. Atthe same" time relay 2I2. having operated, ahigh voltagecycle currentthrough a flashing interrupter 222iis connected; through the leftfront contact relay-2l2 to lamps 22I-in front of inward operator positions; Lamps 219 in front of the outward positions however,- remain out due. to the left break-contacton-relay 2l2= If instead ofassuming an incoming call on this toll line. we were to have-assumed it to" be taken for. use by-a tolloperator then relay 201-."would-have operated as before. but 212 would remain: normal. Inthis case. all lamps 2l9wand22l would be extinguished. Again if this toll line had-been assumed to be some intermediate idle toll-line thelamps 2 l9..and 22!. would alsobe out: It will therefore be apparentthat the use of a single lamp. .perline appea-ranceserves as an idle indicating lamp. for outward calls andalso as aflashingline. lamp on incoming calls.

The incoming or connect signal in addition to lighting lamp. 22L causes an-acknowledgment signal to be sentbackto thecallingatoll line:

further traced through'the right frontcontact of the operated .relay.2l2, leftback contact and armature relay 205,.left.back.contact and armature relay. 225,. leftback contact and armature relay 226, contact 223. on .relay '-2l3,- normal contact 22.1. on relay 228, thence through left back contactand armature relay- 229. to lead I33.-

As previously described polarized relay "I26" operates under this. condition and in turn operates relay I29 tosenda 20.,cycle signal superimposedaon 1400.cyc1ecarrier frequency. This constitutes an. answer. backor acknowledgment This path is traced from battery through wind-- ingrelay 206,- right winding relay 205, contact 209 on relay 206, conductors 230 and 23! to ground at left inner break contact relay 232.- The operation of relay 205 at its left outer break contact then opens the 48 volt negative battery path previously traced to lead I 33, thus cutting off the acknowledgment signal to the-distant ofiice.

The inward toll operator at ofiice Y noting the flashing of toll line lamp 22I picks up the rear plug of a toll cordcircuit such as shown in Fig. 3 and inserts it in jack 248 of the calling toll line of Fig. 2. This action causes a-zip order tone to be transmittedto the calling toll operator at distant office X which is an indication to her that the toll operator at oflice Y is ready to receive the wanted subscriber's number: The insertion of the rear plug in jack 248 connects cord conductors 30l and 302 with toll line conductors 233' and 234-respectively. Also in like mannertoll sleeve conductor 303 is connected with line sleeve 235. If it be assumed that the toll operator has not as yet thrown talking key" 300, then the sleeve condition may. betraced from battery through cord lamp 304; contact 305 on relay 306-, lead 301, lower contact on ringing key 308, thence over sleeve 303 of plug a'ndsleeve 235 of tollline jack, through rightlight. Relay 238 closes ground to lead 239 for operating relay 240 to battery. Relay 240-at its left outer contact connects ground to winding relay 2, causing it to operate, whichin turn releases relay 2l2 to extinguish-line lamp 22I.- Relay 2l3 .which'previously operated in multiple with relay 2l2 does not release due to battery througlrmiddle locking winding, contact 24! to ground .at left inner armature relay 232. Therefore, contact 242. on relay 2l3 connects positive 24 voltbattery 243 through relay 244 to break contact 245 on relay 246 and-thence through lower winding of impedance coil 24'! and lower contactrelay208 to ring conductor 234. When the toll operator throws her talking key 300 positive battery 243 connected to ring conductor 234 may further be traced over the ring 302 of the toll cordin Fig. 3, contact 309 onringing key- 308, conductor 302A, contact 3| 0 on operatedrelay 3H, thence over lead 312 and bottom break-contact on relay 3l3, lead 314, bottom break contact relay 500, through winding 50! on repeating. coil 502 over lead 503 and through windingpolarized relay 504 to ground. Relay 504' operates. and connects groundto winding 505, thus closing a circuit for zip order tone po-- tential through winding- 505 traced over leads 506, .501 and 508. Thistone induced in windings SM and 509 is then -heard by the calling leads 3|2 and. 3Mand because talking conductor 30|A.isconnected through contact 315 on operated relayjllltolead.316, thence through of relays 231 and contact 3" on operated relay 3I8, lead3I9 and top break contact on relay 3I3, to lead 320, thence through top break contact relay 500, to winding 569. Talking conductor 30I is traced through plug and jack over conductor 233, through pad circuit windings I40, conductor I42 and top break contact relay I29, directional selection coil I03, and conductor IOI to distant end of the toll line circuit similar to Fig. 1. Talking conductor 302 is similarly traced through plug and jack over conductor 234, through pad circuit windings I4 I, conductor I43 and bottom break contact I29, directional selection coil I04 and conductor 102 to distant end of the toll line.

A further description is here given of other actions that follow the throwing of talking 'key 360 mentioned in the previous paragraph. In the first place contact 3 2I on key 300 closes a circuit for operating relay 306 traced from ground at contact 322 on relay 323. Relay 306 at its inner left make contact, closes ground for operating relay 3II direct to battery; at contact 324 it transfers the sleeve lead 301 from lamp 304 to lead 325, which is further traced through relays 326 and 32I in series to battery on lead 328. The direct battery s pply to lead 328 is further traced through contact 400 on transfer key 40I, contact 402 on key 405, lead 403, thence through contact 329 on relay 3 I3, lead 330 to lead 328. 7 Battery through a high resistance 33I is also connected to lead 328 but has no function at this time. The grounded sleeve 235 of the toll line therefore is connected through relays 326 and 321 to battery. Relay 326 being marginal does not operate because the left-hand winding on sleeve relays 231 and 238 of the toll line have too high a resistance. Relay 321, however, does operate and therefore connects ground to winding relay 3I8 to battery, causing the latter to operate and close contact 3I'I.

Another action takes place when relay 306 opcrating on its left-hand winding closes the looking circuit at its right-hand inner contact through a separate winding, said winding being included in a path from ground on talk key 300 traced over lead 332, winding relay 366 and winding relay 323 to battery. The latter relay operates in this path and at contact 333v connects ground to lead 334, which may be traced to lead 5I0 of Fig. 5, thence through normal contact on relay 5| I, lead 5I2, inner bottom break contact relay 500, lead 5I3 to battery through relay 5I4. The operation of relay 5I4 at its bottom make contact closes ground to winding of slow operate relay 5I5, causing it to operate and open the zip order tone circuit to induction coil 502. At the same time at its left makecontact the operating ground is extended to winding of slow operate relay 5I6 which again restores the zip order tone circuit and at its left make contact extends ground to winding to slow operate relay 5 I I. Relay BI'Ioperates and again opens the ziptone circuit at its left make contact, operates slow operate relay 5I8 which again restores the zip tone circuit and at. its left make contact connects ground to winding. slow operate relay5I I. Relay 5I I operates and at its bottom make contact extends ground to winding relay 500, which thenoperates and opens the induction coil winding 50Iand 509 from the talking leads 3I4 and 320 causingrelay 504 to-..release. its top inner contact locks over lead 5I9 to ground on lead 334 previously traced. Relay 500 at its bottom inner contact opensnlead 5l3 allowing, relay 5I4 to release, thereby releasing relays 5I5,

Relay 500 at.

5I6, 5|! and 5I8 in turn. In this manner a zip tone of three zips is transmitted to the calling toll operator. Relay 500 in operating also short circuits condensers 520 and 52I leaving the toll operators induction coil 522 connected to leads 3M- and 320 ready for receiving the wanted subscribers number which is now passed by the distant calling toll operator.

Another action that follows throwing of talk key 300 has to do with insuring the connection of only one toll cord at a time to the position circuit of Fig. 3A. Inasmuch as this feature does not come within the scope of this invention no description will here be given. Description of this and other features of the toll cord of Fig. 3 may be found in Patent No. 1,608,524 to L. F. Porter.

Let it now be assumed that the called subscriber number requires that the incoming operator at ofiice Y complete the connection over another automatic toll line such as the one shown in Fig. 6. Let it further be assumed that the toll line shown in Fig. 6 is the first idle line connected with the distant toll office through which the call must be connected. In this case relay 601 will be normal and all preceding line circuits will be busy so that battery 6I5 may be traced through armature and back contact relay 601 thence through winding relay 6I4 to ground. Lamps BI!) and 62I are therefore burning dimly on induced 60 cycle current traced from ground at transformer 6I6 to front contact and armature relay 601, thence direct to lamp 6I9 and through right back contact and armature relay 6I2 to lamp 62I. The operator knowing this call will be completed by another toll operator inserts the front cord plug in outgoing jack 661 and restores her talking key to normal. Sleeve conductor 348 thus connects with sleeve conductor 635 thereby closing a circuit for cord lamp 344 and for operating relays 631 and 638 over a path traced from battery through lamp 344, contact 345 on relay 306 now in its normal position, lead 343 and normal contact 346 on ringing key 341 thence over sleeve conductors 348 and 635, left back contact relay 629, lead 636, to ground through right windings relays 631 and 638 which operate. Relay 63'! operating prevents tip conductor 633 from being grounded and relay 638 connects ground over lead 639 to winding relay 6'40, causing it to operate. Relay 640 at contact 652 closes a circuit from battery through winding of relay 655 to ground at back contact and armature relay 606 causing relay 655 to lock at its left front contact to ground at right outer make contact on relay 640 over right outer normal contact on relay 632. Relay 655 operated connects at its right make contact a ground circuit leading to left winding of relays 638 and 631 in series to the sleeve lead. 636. This being low resistance in comparisonv with the circuit through the righthand windingsv the overall resistance of the sleeve is materially lower thus causing the toll cord lamp 344 to light.

Insertion of the front plug of the cord of Fig.

3 in jack 661, as just described also removes from the talking circuit the pad circuit shown in Fig. 1A.in the toll line from ofiice X and the equivalent pad in the toll line to office Z, due to the operation. of relay I 35. The manner in which relay I35 in the incoming and outgoing ends of the toll lines is made to operate follows: Relays 208. and 663 having previously been. operated on their lower windings and held operated to battery on the outer make contacts of operated relays 246 and 640 respectively, the circuit is completed for the operation of relays 246. and 646 respectively when the cord plug is inserted in jack 661. The path for. relay 246:. is traced from 5 ground through winding relay 246, windingrelay 251, retardation coil 241, top contact relay 266" 1.5.. In a similarmanner the path for operation of relay 646 may be traced from ground through winding relay 646 back over the other side of the talking. circuit to battery either through winding of marginal relay 244 of Fig. 2. or through io marginal relays 262 and. 263. Both relays 246 and 646 operate and thereafter. the circuit through winding relay 246 includes marginal relays 662 and 663 and the circuit through relay 646 includes marginal relays 262and 263. However, resistance of relays 246 and 646 is too high forthe marginal relays just mentioned to operate. Relay 246 at contact 266 closes a ground path for operating relay 244 over lead 256 and contact 242 on. relay 2I3. Relay 246 at its top 3O 'in1rer contact closes ground to lead 265 traced further over top armature and contact relay 262, top: armature and contact relay 260, top contact and armature relay 263 thence over lead I34 through winding relays I 35 and I26 in series to I 35 battery. In addition to the operation of relay I35, which removes the pad from the incoming end of the first automatic toll line, relay I20 'also operates thereby removing battery from the windings of relays I I6 and I 24 of Fig. 1B thus preventring any further incoming signals from reaching the toll line of Fig. 2 except a disconnect signal which would operate relay I I8. Relay 646; operated, at contact 662 operates relay 666 over lead 658 and right back contact on relay 6I3. Also hat its top inner contact it closes ground to lead 665 traced further through resistance 666, top armature and contact relay 663, thence over lead I34 through winding relays I35 and I20- of a circuit similar to Fig. 1 in series to battery. Relay =.t.I26 being marginal does not operate through resistance 666, thereby permitting Fig. IE to receive incoming signals but relay I35 operates and removes the pad from the talking circuit at the outgoing end of the second automatic toll line.

; For transmission reasons it is desirable to leave the pads connected in the circuit when the toll operator at office Y has her talking key 366 operated. Under this condition. relays 246 and 646,

instead of operating as noted above fail to oper- 0-ate due to tip conductor 3! in cord circuit of Fig. 3 being connected-straight through contacts 3I5 and 355 on relay 3 to tip conductor 352 and similarly ring conductor 362 is connected to ring conductor 35.! through contacts 3I6 and 356 on 5 relay 3 I I. Thus, the ground circuit through relay 246 described above meets the ground circuit through relay 646 and said relay fails to operate thereby preventing the operation of relay I35 and leaving the transmission pads connected in y-the talking circuit.

inserting the cord plug in jack 66'! sends a connect signal to the toll oifice Z by connecting groundthrough resistance 64-6=at right back contact relay 665; front contact relay; 656 which is r1 operated by relay 646; contact 65I -of relay 6I3,

tact.in the armature relay 6291to lead I33. As previously: describedthis. causes the equivalent of relay. I2'I of Fig; 1 to. operate which in turn closes a ground path traced through normal contact on relay. I26; bottomarmature and back.

contact relay I28 and bottomirontcontact relay I27; for operating relay I3I to battery. Relay I3I operating: also operates relay.I26 and thussends a connectsignalot 20' cycle1000 cycle to the tollv line circuit atterminating oflice Z.

The toll .operator at office Z receives a flashing signalin the same manner as previously described for the connect-signal received'by the toll operator-aticifice Y. Atthe 'same time the toll line circuit at ofiice Z sends'back an .acknowledgment signal of 26cyclessuperimposed on 1400cyc1es, alsopreviously described. This signal received at oiiice Y.is.transformedinto a signal to the't011 line of Fig. 6 wherein negative 43 volt battery is connected through .a high resistance to lead I23. Said "batteryis further traced through relays 666, Bill and 662 tonega'tive 24 volt battery causing relay666zto operate, which closes ground to lead 666 for operating relay 666 to battery through lower contact on operated relay 660 and top outer contact 646; Relay 669 looks from battery on its top inner contact through its own lower make contact to ground on relay 640 and thus, at its top outercontact, shunts out resistance seem the ground. path to lead I34 thereby operating the equivalent! of relay I20 for disabling incoming signals except the disconnect signal. also connects ground over lead 603 through back contact 664 on relay 605 and winding relay 666 to battery. Relay 666 operates in this circuit and releases relay 650because the operating ground for the latter relay is taken from the left-hand armature and back contact relay 666 traced further through contact 652 on the operated relay 646. Relay 650 releasing opens the ground path through ,resistance 646 to lead I33 previously traced, thereby'causing relay I26. as in Fig. 1 to release and open the connect signal being sent to the distant toll oflice Z. The opening of this 606 it remains operated on ground through the left winding of relay 605, right inner make contact relay 606 and contact 653 on relay 646 to ground. Relay 605 operates in this circuit.

W'henthe toll operator at oifice Z answers, order tone is returned to the originating toll operator ofoflice X who again passes the called number and the connection is completed to the subscribor line by the toll operator in the oflice Z. This portion of the connection wherein ringing current is automatically connected to the called line may be in accordance withthe usual practices in completing inward connections through the local 13 or cordless 13 board and therefore need not be described here. As soon as the called subscriber answers, a receiver-off-hook signal of 20 cycles superimposed on 1000 cycles is sent back over the built up connection through the toll cord conductors of Fig. 3 in ofiice Y to the outgoing automatic toll line in the originating ofiice X.

This signal resuts from the subscriber remov ing-his receiver from the switchhook thereby re} leasing relay 244- in: the toll line circuit at office Relay 666" contact .62I on relay 628 and right back con-.

from contact-on relay 238 through winding relay 264 to continue to hold relay 288 operated and thereby also to cause relay 264 to operate. Relay 264 at its left contact supplements ground to right armature and back contact relay 244 for operating relay 226 traced through right contact relay 288, right armature and contact relay 219, left armature and contact relay 280 to battery through winding of relay 225. Relay 226 looks to lead 283 traced further over left outer armature and contact relay 232 to ground at left outer contact relay 240. Relay 226 in turn operates relay 280 which locks over the right back contact and. armature on relay 219, right front contact relay 288 to ground at back contact relay 244 for holding the operating circuit of relay 226 open. Relay 226 at its left front contact closes ground through resistance 282 to contact 223 on relay 2I3 and thence over a previously traced circuit through relays 228 and 229 to lead I33. This results in the operation of relays I21, I29 and I3I and the sending of the receiver-off-hook signal of 20 cycles superimposed on 1000 cycles back over the built up toll line through toll office Y.

At the originating ofiice X this signal is transformed into negative 48 volt battery connected through high resistance I22 to a lead which is the equivalent of lead I23 of Fig. 1B. Theoutgoing toll line at office X may be considered as being identical with Fig. 6, previously described, except that signal control relay 630 is normal. Thus when battery through resistance I22 is connected to lead I23 it operates relay 600 which in turn operates relay 632 in a circuit traced over lead 603, operated right inner. contact relay 685, and lead 654. The operation of relay 532 at its right outer break contact opens the holding circuit for relay 655 which in turn releases and opens a path through the left-hand windings of sleeve relays 638 and 531 thereby increasing resistance of said sleeve and causing relay 340 in the associated toll cord sleeve to release and put out supervisory lamp equivalent to lamp 344. The operation of relay 632 also sends an acknowledgment signal of 20 cycles superimposed on 1400 cycles back over the built up connection to the ofiice Z by connecting negative 48 volt battery through high resistance 624 to lead I33. This path is traced further through contact 558 on relay 640, left outside contact on relay 5I3, left armature and front contact relay 532, back contact and armature relay 650, contact 65I on relay 6I3, contact 621 on relay 628, right outer back contact and armature relay 528 to lead I33. This signal at office Z terminates the receiver-off-hook signal releasing relays 600 and 532 at office Z. Release of relay 532 then terminates the acknowledgment signal and the completed connection is ready for conversation.

If the originating toll operator at office X, whose toll cord is identical with Fig. 3 and toll line is identical with Fig. 6, wishes to recall the toll operator at the terminating office Z she operates ringing key 341 which thereupon releases relay 631 due to breaking ringing key contact 346, thus introducing high resistance 358 in sleeve lead 348. At its top contact key 341 connects ground through tip conductor 354 which is further traced over what would be lead 610, back contact relay 631, right inner armature relay 640, and first make contact to battery through winding relay 650. The front contact of the latter relay prepares a path for sending out a recall signal of 30 cycles superimposed on 1000 cycles, traced from 48 volts through low resistance 618 front, contact and armature relay 605,

front contact and armature relay 650, to lead I33 over a path previously traced. Relays I26 and I21 operating close a ground path for operating relay I32 and thus sends out a 30 cycle- 1000 cycle signal which passes through the toll line and toll cord talking conductors and is received at the terminating toll ofiice Z by the toll line which is the equivalent of Fig. 1. Said signal operates the equivalent of relays H1 and I24 in Fig. 1B causing ground through a resistance I25 to be connected over lead I23 through relays 200, EDI and 202 in series to battery. Relay 200 being polarized does not operate and relay 282 being marginal operates only on direct ground. Relay 2PM although marginal operates on this resistance ground and closes direct ground from back contact relay 202 to lead Z'II armature and front contact 212 of relay 2E3, winding relay 213, contact 214 on relay 215 to right winding of sleeve relay 238 thence over the sleeve to battery through toll cord lamp 384 as previously traced. Relay 213 operates in this circuit and locks to the toll cord sleeve and to relay 215. Relay 213 at its left contact closes ground through interrupter 216 to winding relay 215 and to left winding relay 211 in parallel to battery causing both of said relays to operate. Relay 215 thus follows the interrupter 216 thereby opening and closing the lead to right winding relay 236 and causing the toll cord supervisory lamp 304 to flash indicating a recall signal. The toll operator at oflice Z upon throwing her talking key 380 causes the sleeve resistance to be increased thereby releasing relay 213 which in turn releases relays 215 and 211 and retiring the flashing lamp. The re-ring signal continues only as long as the originating operator holds the ringing key open.

When the called subscriber in office Z disconnects, a receiver-on-hook signal is sent back over the toll line which is received at office X as ground through a resistance over lead I23. This operates relay Bill and in turn relay 855 which looks to relay 632 over a path traced from ground at right contact relay 540, right back contact and armature relay 532 through left armature and contact and winding relay 655. Relay 555 at its right armature and contact closes ground to left winding of sleeve relay I538 which lowers the resistance of sleeve lead 636 and lights operators toll cord lamp 344 as previously described. Relay SUI also sends an acknowledgment signal of 20 cycles superimposed on 1400 cycles by closing the circuit traced from 48 volts battery through high resistance 624, contact 656, relay 648, left outer contact and armature relay BI3, left armature and contact relay 68L back contact and armature relay 650, thence over previously traced path to lead I33 which results in the operation of relay I29 and therefore the sending of the acknowledgment signal. This signal when received at office Z by the toll line terminates the receiver-on-hook signal which thus releases relay 20I. Relay 20I released terminates the acknowledgment signal.

If in building up the connection the toll line at oflice Z encounters an all-trunks-busy or subscribers-line-busy or if later on during conversation the call subscriber wishes to attract the original operators attention by flashing his receiver on and off the hook the receiver-off-hook and receiver-on-hook signals will be sent back over the toll line in the same manner as is done in the case of the subscriber answering and disconnecting described above. If the called subscriber should flash very rapidly, a receiver-onhook signal will be transmitted and until the acknowledgment of the signal is received, further motion of the switchhook will be ineffective. If the receiver is off the hook when the acknowledgment signal is received at office Z relay 244 releasing opens the holding circuit for relay 219. Relay 219 at its right back contact thus closes the circuit for operating relay 226 and traced from ground at left front contact relay 264, armature and back contact relay 244, right contact and armature relay 263, right armature and back contact relay 210, left armature and back contact relay 280 to battery through winding relay 226. Relay 226at its contact 28I connects ground to winding relay 280 which in turn locks to ground over the circuit thus traced to the right back contact relay 244. Relay 226 at its left make contact also connects ground signal will be transmitted. From the above it.

has been made clear that no matter how rapidly the subscriber flashes flashing signals will be transmitted to the calling operator and a correct indication of the position of the subscribers switchhook will be given when the flashing ceases. These voice-frequency signals of 20 cycles-1000 cycles and 30 cycles-1000 cycles, respectively, being connected directly to the talking circuit pass through the toll cord and associated automatic toll line circuits at the through toll oflice Y.

They also, of course, are received in the associated receiving circuit equivalent to Fig. 1B but are made ineffective due to the operation of relay I20 in the Pad circuit equivalent to Fig. 1A previously described. Thus, in building up connections over automatic toll lines it makes no difference how many intermediate ofiices the call is routed through because at all through-points the Pad circuits are removed and the incoming signalling circuit is disabled except for the disconnect signal which Will later be described. At the originating and terminating toll ofiices', however, the Pad circuits are not removed and the apparatus for receiving and sending signals is operable at all times.

When the calling toll operator at office X disconnects, a disconnect signal consisting of 45 cycles superimposed on 1000 cycles is caused to be transmitted to the built up toll line. The circuit arrangement for doing this may best be described by referring to Figs. 3 and 6 which may be assumed to represent the outgoing toll line at ofiice X. The toll operator upon removing the cord from the equivalent of jack 661 releases sleeve relays 631, 638 and relay 660 connected to the ring side of the talking conductors. Relay 638 removes ground from winding relay 640 causing it to release. Relay 628 then operates in a path traced from battery at left back contact relay 640, winding relay 628, front contact and armature relay 6 to ground at contact 6I0 on relay 606, which still remains operated from ground at right inner armature relay 632 over operated connects ground directly to lead I33 through right outer break contact on relay 629, thereupon operating both relays I21 and I28 in a circuit the equivalent of Fig. 1. Relay I26 being normal connects ground through bottom armature and front contact relay I28 to battery through winding relay I30 which operates and prepares a path for the 45 cycle-1000 cycle disconnect signal. Relay I30 in turn operates relay i20 which thus completes said signal path to the toll line.

The disconnect signal is received both at office Y and ofilce Z in a circuit the equivalent of Figs. 1 and 2 and results in operating relay II8 which thus connects direct ground to lead I23 through the back contacts of relays I24 and H0. This ground path is further traced through windings of relays 200, 26I and 202 in series to battery. With direct ground so connected, both relays 20I and i202 operate. Relay 202 operates relay 229 through contact 284 on relay 2l3. Relay 229 thus transfers the sleeve of the associated toll cord from ground through relays 23'! and 238 to 48 volt battery through its own right Winding. Relays 23? and 238 thereupon release, in turn releasing relay 240. The operation of relay 229 connects 43 volt negative battery through high resistance 224 to lead I33 as an acknowledgment signal all in a manner previously traced; operates relay 232 from ground at its left inner make contact; and holds relays 205 and 2I3 operated. The operation of relay 232 removes ground at its left inner contact for releasing relays 205 and 206 and in turn relay 2I I. When relay 229 operated,

the 48 volt through its own right winding, being .1

connected to sleeve lead 235 and the associated toll cord sleeve 302 and lamp 304, causes lamp 304 to light as a disconnect signal the same as if direct ground were so connected. Since the disconnect signal is received at both offices Y and Z it follows that the cord lamp 304 at these oflices both light as a signal to the operator to disconnect which they proceed to do. When relay 229 operated and caused an acknowledgment signal to be sent back on the line this signal at oflice X causes the disconnect signal to terminate as explained below. The termination of the disconnect signal at office Y thus releases relays 20I and 202 and in turnrelay 229. The release of relay 229 releases relays 205, 2I3 and 232 restoring the circuit to normal. The automatic toll line between ofiice Y and office Z likewise restores to normal in a similar manner.

As mentioned in a previous paragraph, an

-acknowledgment signal was returned over the toll line to the toll oflice X which causes relay II6 to operate and in turn operates relay II9. The latter relay connects 48 volt negative battery I2I through high resistance I22 to lead I 23 and operating the equivalent of relay 600 which in turn operates relay 632. The latter relay at its right inner contact removes the ground that has continued to hold relays 606, SH, 628 and 655 operated. These release and in turn release relay 608. The release of relay 628 terminates the disconnect signal which at offices Y and Z results in terminating the acknowledgment signal being received over the toll line. Upon termination of the acknowledgment signal at office X relays 600, 605 and 632 release thus restoring the circuit to normal.

If it be assumed that the toll operator at office Y pulls down her toll cord connecting the two toll lines before the calling operator at office X disconnects, a pulled down signal of 45 cycles- 1000 cycles is caused to be sent back over the toll line to oflice X as described above, due to the release of relays 231, 238, 240, 244, 263, 264, 219, 280 and the operation of relay 228. When this signal is registered and acknowledged by the toll line equivalent to Fig. 6 at office X sending back the 20 cycle-1400 cycle signal as will further be described, said signal operates relay H6 in a circuit at office Y equivalent of Fig. 1B. Relay II6 operates relay II9 thus connecting negative 48 volt battery through high resistance I22 to lead I23 for operating relays 290 and 232. The operation of relay 232 releases relays 206, 2| I, 228 and 208. The release of relay 228 terminates the disconnect signal which at office X causes the acknowledgment signal to terminate which in turn at office Y causes relays 200, 205, 2I3 and 232 to release, restoring the incoming end of the toll line at oflice Y to normal.

Under the assumption that the toll operator at oflice Y pulled down as above described and caused a disconnect signal to be sent to the toll line at office X, which for the purpose of this description may be assumed to be the same as shown in Figs. 6 and 1, this signal causes relay H8 to operate and connect direct ground to lead I23. Relays 60! and 602 operate in said circuit. Relay 602 connects ground over lead 61I, armature and back contact relay 6I3, winding relay 613, contact 614 on relay 615 to left winding sleeve relay 638, thence over sleeve lead to battery through cord lamp 304. Relay 613 at its right contact locks up to the sleeve lead when relay 215 is normal or to battery through resistance 685 when relay 215 is operated. Relay 613 at its left contact operates relays 615 and 611 from ground through interrupter 616. Relay 611 locks to ground at contact 6I0 on relay 606 traced through armature and front contact on operated relay 6II, thence through contact 686 on relay 6I3 to battery through armature, contact, and left winding relay 511. Thus when relay 215 operates on the first ground period of interrupter 616, it opens the lead to left winding of sleeve relay 638, thereby allowing the sleeve relays 638 and 631 to be held over a high resistance path which extinguishes the operators toll cord lamp 304. When interrupter 616 opens the ground path to release relay 615, a low resistance ground path to left winding of relay 638 is again connected which causes toll cord lamp 304 to light. Thus the operators cord lamp flashes in accordance with the period of the interrupter and informs her that the connection has been pulled down.

Relay 60I being previously operated as described above closes a path for sending back an acknowledgment signal to the toll line in office Y, said path being traced from 48 volts through high resistance 624, contact 656 on relay 640, left outer contact relay 6I3, right armature and contact relay 60I, back contact and armature relay 650, thence through previously traced path, through contacts on relays 6I3, 628 and 629 to lead I33. This closure of 48 Volts to lead I33 results in sending an acknowldgment signal back to office Y which, when it is received, terminates the pulled down signal in a manner as previously described. The termination of the pulled down signal thus releases relays 60! and 602. Relay 60I released in turn terminates the acknowledgment signal. The toll operator then disconnects and if necessary reorders the called number as on a new call. When the toll operator disconnects, relays 631, 638, 640 and 660 release and relay 628 operates, in turn releasing relay 632. The operation of relay 632 releases relay 606 which in turn releases relays 6II, 608, 628 and 611. Relays 628 and 611 released, cause relays 605 and 632 to release, thus restoring the circuit to normal all in a manner as previously described.

Connection between automatic and ring-down toll lines It is now assumed the called number was such that it required the connection to be completed over the ring-down trunk of Fig. '1 instead of over the second automatic toll line of Fig. 6.

The call having originated at office X and come in over Figs. 1 and 2 at office Y is assumed to have been answered by the toll operator inserting the rear plug of the toll cord of Fig. 3 in jack 248 of the automatic toll line of Fig. 2 as previously described. The operator at this point received the wanted subscriber number from the originating toll operator, requiring that a connection be established over a ring-down trunk such as the one shown in Fig. '7. The insertion of the front plug of the toll cord in jack in addition to extending the talking conductor 353 to 103 and conductor 354 to conductor 104 closes the sleeve circuit. Assuming the talking key of the cord operated at this time, said sleeve circuit is traced from battery at contact 404 of key 405 in operators dial circuit of Fig. 4, through battery contact key 40I, lead 406, contact 336 on relay 331, through winding of relays 339 and 340 in series, contact 342 on relay 306, lead 343, contact 346 on key 341, lead 348, thence over sleeve lead 105 and upper winding relays 106 and 101 in series to ground at contact 103 on relay 109. Relay 106 operated, connects ground to winding relay 109 to battery at contact 1I0 on relay 1| I. Relay 109 operated, connects ground at its right contact to winding relay 1 to battery. Relay 101 performs no useful function at this time and releases as soon as relay 109 operates and connects ground through resistance 1I2. Relay 109 at its right inner contact opens the circuit through winding relay 1I3 to prevent false operation of the latter relay. Relay III in operating at its left outer contact removes the termination 1I4 from across. the tip and ring and at contact 1I0 removes battery supply for relay 109. Relay 109 releases, reducing the sleeve resistance to normal and permitting relay 101 to reopcrate. Relay 1II at its left inner contact connects battery to winding relay 124 to ground. Thus relay 124 in operating releases relay 129 and extinguishes idle indicating lamps. 125, 126 and 121 which may be assumed to have been dimly lighted from ground through transformer 128 as described for the automatic toll line circuit of Fig. 2.

The operator then throws ringing key 341 for calling in the distant operator. Said key, in addition to placing the termination 359 across the calling end of the toll cord, connects ground to the tip conductor 354 and its bottom contact346, opens the shunt around resistance 358. The sleeve circuit previously traced is thus now traced through resistance 358, top inner contact relay 3II to sleeve lead 343. This increase in sleeve resistance releases relay 101 which in turn closes a path for operating relay H3. Relay 1I3 operated closes a path at contact 1I5 for operating ringing relay 1I6 traced from ground at top contact ringing key 341, leads 354 and 104, contact 1I5 on relay 1I3, lead 1I1, armature and front 2,119,269 contact of normally operated relay IIB, through winding relay H6 to battery. The latter relay operating closes a circuit at its front contact from ground and ringing generator H9 over leads I20 and HI to toll line conductors I22 and I23, respectively. In this manner, ringing current will continue to be sent out over the toll line as long as the ringing key is held operated.

The distant operator upon receiving a flashing line signal in the manner similar to that described for Fig. 2 answers by inserting the rear plug of an idle cord in what would be the equivalent of jack I02 of this circuit. The ringing key 341 of the toll cord having now been restored to normal, relay H6 is released, thus preparing a circuit for the ring-down relay I so that when a distant toll operator rings at any subsequent time, relay I30 will operate and at its back contact open the circuit for relay H8 to release and connect ground to lead H1. Ground on the latter lead operates relay I3I through contact H5 ings of relays I11 and I06 to sleeve 105 to battery in toll operators cord circuit. Said path being of low resistance causes the operator toll cord lamp 344 to light. 'Ihe operation of relay I32 looks through its left contact to the sleeve circuit and at its right contact connects ground through a flashing interrupter I34 to winding relay 133 to battery. The latter relay, following the intermittent interrupter ground, opens and closes the low resistance sleeve ground causing the toll cord lamp 344 to flash on and off in accordance with the interrupter I34.

The toll operator, upon throwing her talk key 32! increases the resistance of the sleeve suiliciently to release relay I32 the next time relay I33 is released. In this way the toll cord lamp is extinguished.

The pad control arrangement shown in Fig. 7A

. is normally in the line leading to toll line re- ;peater I35 and is cut out only when the two circuits arranged for pad control are connected j a toll cord with the talking key in normal position. This transmission pad is cut out due to relay 136 being operated from ground in series with the upper winding of retard coil I3? to line conductors I48 and I04, thence over cord conductors 354, 352,302A, 302 and 234 to lower contact on operated relay 208 in the toll line of Fig. 2, lower winding of retard coil 24?, contact 26I on relay 246, thence through winding of relays 262 and 263 to battery. Battery through winding relay I38 may likewise be traced back to ground on winding of relay 246 but relay I38 being marginal does not operate. Thus a path is established for operating relay I30 traced through its winding, contact on operated relay I31, through armature and contact on relay I38 to ground. Relay I39 being operated is arranged to disconnect the pad by short-circuiting resistances I40 and MI at contact I42, short-circuiting resistances I43 and "I44 at contact I45 and opening bridge circuit M6 at its top break contact. The pad associated with the calling automatic toll line is likewise cut out due to ground being connected by relay 24B throughresistance 206 and normal contact on relay 263 to lead I34, thence through relays I35 I20, however, being marginal, does not operate. Thus all supervisory signals are terminated on the incoming automatic toll line and the toll operator receives supervision from the calling subscriber. 515 If the connection is completed to a tributary ring-down toll line, the operation of the automatic toll line circuit is the same as described above for a regular ring-downtoll line except that relay 263 of Fig. 2 also operates and opens io the circuit to lead I34 so that the associated pad circuit cannot function to cut out the transmission pad. l

Connection between automatic toll line and talkswitching trunk 5 Assuming now that the incoming call over the automatic toll line at ofiice Y from the originating toll office X previously described requires that the connection be completed to a subscriber in a go manual office. In this case, the toll operator of ofiice Y inserts the front plug of the toll cord of Fig. 3 in jack 800 of a trunk to a manual oflice shown in Fig. 8. Trunks of this type are provided with a single lamp which serves as a com-" 25 bined answering and idle indicating lamp. It serves as an answering lamp on incoming recording completing calls and as an idle indicating lamp for outgoing tollswitchingtrunk calls. Thus in completing the call here described, the toll 30 operator will observe one of the lamps 80I burning dimly in a circuit traced from ground on transformer 802, front contact on operated relay 803, right back contact relay 804, through lamp 80! to ground. This lamp indicates an idle trunk h5 because ground at 805 must be connected to lead 806 through contacts 807 on relays in the preceding trunks. To do this, each relay equivalent to relay 808 in each preceding trunk must be operated that is, be in a busy condition. Also, relay 40 808 in this particular trunk must be normal because the trunk is not in use. In this manner, ground at 805 operates relay 803 individual to this trunk, thereby causing lamp 30! to light over the path described above.

When the toll operator plugs into jack 800 and the operator is not connected at the local office, sleeve relays B09 and M0 operate in a path traced from battery through lamp 344, contact 345 on relay 306, lead 343, contact 346 on key 341, sleeve lead 348, thence over sleeve 8I I of the toll switching trunk and through left winding relay 809 and right winding relay M0 to ground. Relay 809 opens battery from lead 8I2 and relay 8I0 operates relay 8| 3 over a path traced from ground at its own front contact through winding relay 8I3 to battery. Relay 8I3 at its left inner contact connects battery to lead 8I4, traced further over lead 8I5 through winding relay 8I8 to ground at bottom break contact on relay 8 I I, thus operating relay 8I6. The latter relay through its continuity contacts connects an obvious battery and ground circuit through windings of relay 8I8 and contacts on relay 8I9 to the trunk conductors 820 and 82I connecting with the distant manual office. The closing of said circuit causes a suitable signal to be given to the B operator at the local manual office in accordance with wellknown practices for this trafiic. Relay 8I8, however, does not operate at this time.

Plugging a toll cord in jack 800 also closes a path for operating relay 822 traced from positive battery 243 through relay 244, contact 242 on relay 2I3, contact 245 on relay 246, through lower winding of retard coil 241, lower contact 'relay- '16

Images