US1726983A - Automatic telephone system - Google Patents

Description

Sept. 3, 1929. H. M. FRIENDLY 1,726,933

AUTOMATIC TELEPHONE SYSTEM Filed July 14, 1927 5 Sheets-Sheet 1 ill Sept. 3, 1929. H. M. FRIENDLY 1,726,983

AUTOMATIC TELEPHONE SYSTEM Filed July 14, 1927 5 Sheets-Sheet 2 Elseirk- FIE]- E- I I Ii: 1. 'I. I I

Inventor- RE I A11 Sept. 3, 1929. H. M. FRIENDLY AUTOMATIC TELEPHONE SYSTEM Filed July 14, 1927 5 Sheets-Sheet 5 Sept. 3, 1929. H. M. FRIENDLY 1,726,933

AUTOMATIC TELEPHONE SYSTEM v Fil uly 14. 1927 5 Sheets-Sheet 4' =======acn==u===a=n==n Inveniur Herb efi-Pl-Frien dg Ali sept- 3, 1929- H.'M. FRIENDLY 1,726,983

AUTOMATIC TELEPHON SYSTEM Filed'J'u'ly 14, 1927' 5 Sheets-Sheet 5 Tuwdrds 152-552- 6;, Marg- Herherz-PfFriandlQ UNITED STATES PATENT OFFICE.

nnmsnn'r M. FRIENDLY, or CHICAGO, ILLINOIS.

AUTOMATIG TELEPHONE SYSTEM.

Application filed July 14,

The present invention relates to telephone systems; more particularly so-called automatic or machine switching telephone systems General objects.

The general object of the present inventionis to enable the operating concern to establish rates'for telephone service for automatic or machine switching telephone systems which will operate to discourage traflic at logical periods of densest trailic and to encourage traflic at logicalqperiods of lightest trafiic. Reference is made to my co-pending-application for U. S. Letters Patent, Serial No. 191,578, filed May 16th, 1927, with particular reference to the preamble thereofswherein the eco-' nomic phases of applying service charges in the general manner contem plated by the present invention is discussed, but with particular reference to manual telephone systems. The general advantages accruing to the invention involved in the said co'-pending-application hold for the'present invention.

.Reierence is also made to my patents 1,694,169 granted Dec. 4, 1928, and 1,694,170, granted Dec. 4, 1928. Reference is further made to my copendingapplication Ser. No..

481,259, filed J une 29, 1921, with particular reference to switches B and C therein.

However, the present invention has specific objects and structure. Among the features of the present invention are a. Means requiring the placing of a coin.

(or token) in a pre-payment collector forming a part of the callingsubscribers station so that unless the coin is first placed in prepayment device (P) the means forautomatically directing the central ofice automatic switching equipment will continue disabled. Broadly, this feature is not new in the art.

1). Means whereby the timing of the connection will start responsive to the called subscriber responding, and wherein through the agency of a timing switch auxiliary to the first numerical selector of the switch train, the

period the connectionmay be held for a specific toll charge will vary in accordance with the time of day through which the connection endures.

a. Means whereby a specific tone will be applied audible to the parties of the connection to apprise them that a'substantially definite time remains before the termination of the period allowed for the predetermined toll charge.

1927. Serial No. 205,650.

d. Means whereby a final tone will be applied audible to the parties of the connection to apprise them that the coin has been de posited in the company till and that the period.

coin is not inserted as pre-payment for the next succeeding period.

6. Means whereby the predetermined time a connection may endure for the fixed predetermmed cost will be lengthened for succeedmg periods after the first period of a maintained connection while the rate for initial penods remains the same. That is, the second and succeeding periods will'be longer for the same time of day for connections which are durating.

7. Means whereby the coin will be refunded upon the calling subscriber hanging up his telephone receiver if the party called does not respond or if the line called is that of a free subscriber so far as incoming calls are concerned. The lines extending to the information, complaint and other departments of the operating concern would come under the latter class of lines. I

g. Means whereby the coin will be refund ed upon the calling subscriber abandoning of the day, though it will be optional with himby depressing a button at his telephone to transfer the charge to the calling subscriber for any of these calls. The latter calls may be calls appertaining to, matters other than orders for his wares. The hours during which the grocer may assume charges for calls may be logical off-peak times and wherein the operating concern may make a special rate for calls of predetermined duration; perhaps of shorter duration than allowed to subscribers generally for the fixed predetermined prepayment charge in force at that time of day. The latter takes into consideration that in automatic systems the time of holding a connection is the determining factor of cost to the operating concern, almost wholly, since no manual efi'ort is applied by it in efiecting to avoid futile calls for which no revenue is derived from the calling subscriber by the operating concern. It is desired that the called subscriber desist from using the called line or provide a group of sufiicient number of lines to carry all trafiic offered during said certain hours.

j. A salient feature of the present invention is the feature for refunding the coin to the calling subscriber in the event the primary line switch or the concerned secondary line switch is not able to extend the connection due to all available outgoing trunks therefrom being busy; this responsive to the calling upon caring the specific tone denoting that the call is futile.

70. Another feature of the primary-secondary line switch arrangement of the present invention is means for barring any secondary line switch group against seizure by a primary line switch if all the trunks normally available from the group of secondary line switches are busy and also bar all thesecond? ary line switch groups against seizure by a primary line switch and indicate by specific tone to the calling subscriber when all the secondary line switches are barred because of being busy.

There are additional operative features of the present invention which will be described in descriptions to follow relating to the exemplary embodiment of the present invention chosen to explain it, having in mind that other features not specifically mentioned will be apparent from the descriptions. The invention is capable of varied modification without departing from its scope as defined by the subjoined claims.

. Drawings.

' l/Vith reference to the accompanying drawmgs Fig. 1 shows a subscribers automatic telephone A and coin controlled pre-payment device P leading to a primary line switch L.

Fig. 2 shows two secondary line switches SL and SL commonly accessible from the primary line switch L, together with sets of chain relays.

Fig. 3 shows a first selector FS and its individually companion timing switch TS and associated relays accessible from the groupof subscriber hanging up his receiver secondary line switches containing switch SL.

Fig. 4 shows a connector CON and an individually companion timing switch TS accessible from the group of first selectors containing selectors F3 It also shows the common clock controlled switch CS.

Fig. 5 shows a called subscribers line switch LS and automatic telephone A, together with a respectively designated calling meter and called meter companion there-to.

Sheets containing Fig. 1 to 5 are assembled in numerical order so that the lines extending towards the adjacent margins register.

Fig. 6 shows a preferred modification of Fig. 3.

Figs. 7 and 8 each show a preferred modification of Fig. 4.

Fig. 9 shows a preferred modification of the connector wherein armatures 901 and 902 are added on relay 472.

It has been deemed more simple to disclose the preferred embodiment as a modification of a simpler embodiment than in its more in volvcd, preferred form incorporating Figs. 6, 7 and 8.

E gm'pment.

The telephone A is of the well known automatic common-battery series type, having an individual pro-payment coin device or box P of well known type as used in the Bell telephone system in the Chicago, Illinois, exchange and other places, however, the said device having an additional spring 14 wired in accordance with the present invention. That is, the mechanism for actually depositing or refunding the coin is old, though the wiring arrangement and control of the magnet for operating its armature for depositing or refunding the coin belongs to the present invention.

The line switches L, SL, SL' and SL are of the well known Lamb general class as described on page 53'of the Third Edition of Hersheys Automatic Telephone Practice, however, modified in details in accordance with the present invention.

The selector FS is of the well known Strowgergeneral class (sometimes termed a Powell selector), however, modified 'in accordance with the present invention; A Powell selector is illustrated on page 60 of the said Hershey book.

The switches TS and TS have the general mechanical details of the line switch L, however, modified in accordance with the present invention.

Theconnector shown in Fig. 4 is of the well known Strowger general class as illustrated on pa e 38 of the said Hershey book, however, modi ed in accordance with the present invention.

The clock controlled device CS is like shown inFig. 4 and also described in my copending application Serial No. 191,578, filed a May 16th, 1927, and thus revolves its contive with the connector CON, the system being a three-digit system, chosen as the simplest to illustrate the present invention. However, it will be understood that the commercial embodiment of the invention would,

usually involve four or more digits, and under that condition one or more well known Powell selectors or other suitable. selectors will be introduced between the selector F3 and the connector CON; one such selector for each digit over three. Also, a well known socalled trunk repeater may be introduced between the selector FS and the connector CON at any point, without afiecting the operation of the present invention in its essentials.

Operation.

The voperationof'the system will be fully understood from exemplary descriptions of the circuit and switch operations in certain assumed calls, having in mind that while a single selector and connector is shown it is only-one of a group of similar switches, since the system contemplates a plurality oflike calls in simultaneous existence.

- Initiating a call from telephone A to telephone A.

The calling subscriber will remove the receiver of telephone A from the switch-hook.

There will be no operative efiect resulting from this until a coin is placed in the coin chute (not shown) of the device P to assume the dotted position 9 which will cause the normally free springs 12, 13 and 14 to engage together as indicated by the dotted positions thereof. This closes a series path from ground, armature 15, 'springs'14 and 13, receiver and transmitter of telephone A, armature 16 to the windin of slow-releasing line relay 17, the latter sai relay actuating. The windings of the polarized 'electro-magnet 18 of the device P will be in a path from ground to the lower line talking conductor closed by the springs 12, 13 and 14.

The line switch L will operate in the well known manner to seize the trunk its' wipers are shown resting upon or will rotate in a hunting operatlon and selze the first idle trunk line tested through the operation of. seizing (also termed brldge-cut-oflvkrelay' The line switch L has access to two groups of trunks corresponding to two groups 0 secondary line-switches of which SL and SL' are each oneswitch-of the two groups, re-

speetively. It will be first assumed that the to ground. The latter sald magnet, due toits polarized property operates to refund the trunk leading to the 'secondaryline switch SL is seized so that the winding of slow-rewhereupon the switch SL will operate in the well known-manner and seize the trunk its wipers are shown resting upon or will rotate in a: hunting operation and seize the first idle trunk line tested through the operation of seizing relay 204.

It will be first assumed that the trunk lead ing to first selector FS? is seized, so that the windingsof line relay 301 is now ina series path'including the telephone A and the upper winding of electro-polarized relay 302. The switches-L and SL are maintained operated in the well known manner due to the slow-releasing characteristic of relays 17 and 201until slow-releasing release relay 304 actuates and applies ground from its armature 305 over release trunk 306 to the winding of slow-releasing relay 307, the latter said relay actuating to apply ground from armature- 308 normal position of wiper 315 of the wiper group 312 to 316 on shaft 317 of the timing switch TS Calling subscriber abandons call.

If the calling subscriber now abandons the call by replacing his receiver on the switch-hook, the relays 301, 304 and 307 will deactuate in sequence. Before relay 307 deactuates ground is applied from retracted armature 305, armatures 319, 320, bank terminal 321, wiper 316, interrupter armature on motor magnet (designated MM) of the timing switch TS causing the wipers to be stepped to the second bank position. WVhcn' the armature 308 retracts its ground is applied through armature 322 to ,bar 323 ongaged by wiper 316 so that the motor magnet will drive the wipers on shaft 317 by interrupter action to restore. them to the drawn position.

It will be noted that wiper 315'maintains ground on bar 324 and to conductor 309 after the retraction of armature 308 to hold the switches L and SL in seizure. However,

when wiper 312 encounters bank terminal 325 it causes relay 326 to operatively energize to attract allits armatures, but for the sole object at this time of completing a path armature 327, upper winding of relay 328 armature 329, lower talking conductor through the winding of polarized magnet 18 coin to the subscriber, in the well known manner. The springs 12, 13 and 14- are now f from ground through negative battery BB,"

conductor 309, whereupon the switches L I and SL restore subject to normal use by reason of relays 20 and 204 deactuating, re-

spectively.

In this connection it will be noted that when the relay 326 actuates the armature 332 (which is adjusted to make first) will close ground derived through common retardation coil 334 to re-energize the upper winding of relay 301. However, due to the rapid movement of the wiper 312 this closure is maintained a very brief time; insufiicient for the relays 304 and 307 (which are somewhat slow in attracting their armatures due to the stated slow-releasing characteristic affecting the actuation) to both actuate to cause ground to be on bank terminal 321 when the wiper 316' returns. Otherwise (with ground on bank terminal 321), the wipers on switch T8 would be caused to thereupon make a false cycle of operation, however, to no operative confusion, since the call is completely abandoned when the wiper 315 moves off bar 324. The object of armature 332 and coil 334 will appear presently.

Calling subscriber elects to complete call in place of abandoning itSends first digit.

If the calling subscriber in place of the assumed abandoning of the call elects to complete it he will operate his calling device in accordance with the first digit 1, which will cause relay 301 to momentarily retract its armature 335, applying ground through armatures 336 and 337, winding of slow-releasing series relay 338 to the winding of the vertical magnet (designated Vert. M.). This will raise the shaft 340 carrying wipers 341 to 343 into alignment with the first level of bank terminals of which terminals 345 to 347 constitute the first set cooperative with wipers 341 to 343, respectively. If it is assumed that the connector CON (corresponding to bank terminals 345 to 347) is idle, and

having in mind the well known selective and test circuits present in the selector F8 of the present invention, the connector CON will be seized by the actuation of switching relay 350, whereupon the relay 301 will become disconnected. v

The windings of the line relay 401 of the connector are now in series with the telephone A, there being no intermediate afiecting attachments; Slow-releasing release relay 402 is now operatively energized by armature 403, which causes armature 405 to apply its ground to the release trunk 406, bank terminal 345, wiper 341, armature 351 to the lower winding of relay 350, for maintainin the selector FS in seizure and the relay 307 energized, efore a ma ure 3 5 retracts, so

that no lapse of ground on the release trunk 306 occurs.

Gatling subscriber sends last two digits to set the connector.

The operation of the connector, effective responsive to the calling subscriber sending the last two digits 11 of the called telephone number being well known, in view of the stat-V ed reference to Hersheys book, the detailed operation of the connector in effecting con nection to the called line leading to telephone A will be understood. It will therefore be assumed that the wipers 407 to 410 are now resting on bank terminals 411 to 414, respectively. the connector specific to the present invention will appear presently.

The armature 415 now applies its ground to operate the line-cut-ofi' relay 501 of the line switch LS and to place a guarding busyground on the private normal conductor 502 and its multipled bank terminals. Ringing current from source designated R. Gen. in Fig. 4 is now being applied effective to the signal bell of the called telephone A in the well known manner.

nector (in view of the present invention) responsive to the called subscriber removing 'hisreceiver from the switch-hook in responding to the call, reference is made to the clock operated device CS This device has a grounded contact-arm 416 which revolves making a single cycle in a twenty-four hour period, as has been referred to before. It shows twenty-four equally angular segments; one for each hour, though it will be understood that the segments may be of any convenient angular size, corresponding to any desired period of the day, to exercise the desired control. The switch-arm 416 is shown resting on the segment corresponding to 12 oclock noon to 1 oclock p. m. The segments from l oclock a. m. to 6 oclock a. m. are multipled together and connected to the switch-arm 417. The segment corresponding to 6 oclock a. 1n. to 7 oclock a. m. is connected to the switch-arm 418, and the seg- ,conductor 420 when the contact-arm .416 is resting upon the corresponding segment group 421 and segments 422 and 423. Likewise, when the switch-arms 417 to 419 are in the dotted positions it provides for ground- Other features and modifications of and lock by its upper winding and armature ing conductor 425 when the contact-arm 416 is resting upon the corresponding segment group 421 and segments 422 and 423. That is to say, during the twenty-four day conductor 420 or alternatively conductor 425 will be grounded by the contact-arm 416 in accordance with a pre-arranged schedule which may be varied at will, as for example, for the different days of the Week and for various holidays in accordance with published schedules. In view of the reference to Fig. 5 of my copfndingapplication Serial No. 191,578, filed ay 16th, 1927, it is thought more detailed discussion of the contemplated modifications of the device CS covering multiple and fractional hour segments will not be necessary in impartin a comprehensive disclosure of the device 05. i i

It will 'be noted that when conductor 420 is grounded all armatures corresponding to 427 in the connector group will be grounded, which provides for operatively energizing the reversing relay 428 and locking it to the release trunk 406, when the called subscriber responds, for an object which will appear presently. v r I And, it will be noted that when the conductor 425 is grounded all armatures corresponding to 430 inthe connector group will be 7 grounded, which provides for applying this ground through armature 431 to bank,terminal 432 on switch TS, for an will appear presently.

Subscriber on owlleii' Zine responds.

It will be assumed that the call is made switch arm 417 is in the position as drawn, and therefore the conductor'420 is grounded. When the subscriber on the called line removes his receiver from the switch-hook the ring-cut-ofi' relay 435 will operativel'yenergize to disconnect the ringing current and cut-through the talking conductors. Ground from contact-arm 416 will be applied through armature 427 to the lower winding of relay 428 causing the latter said relay to actuate 436 to the release trunk 406, reversing the direction of current applied through the calling telephone A. This will cause the current in the upper winding of relay 302 to energize cumulatively with the lower winding thereof, thereby attracting the armatures thereof. The current in the polarizing (lower) winding of relay 302 is augmented by the shortcircuiting of resistor 353 by the upper armature of said relay 302, which makes first, the

polarizing winding then being able to sustain the armatures regardless of the direction of current in the upper winding.

In this connection, it will be noted that the ground interrupter V1 revolves at a speed which varies with the time of day and may be considered similar to and operated and object which 'versation vor be prepared to insert another controlled like interrupter 16 of my said copending application. .The ground interrupter CI revolves at constant speed and is similar to and corresponds to interrupter 78 of my said co-pending application.

I .The relay 302 actuating and locking responsive to the subscriberon the. called line removing his receiver, ground impulses from interrupter VI are appliedthrough arma tures 354, 355, bar 356, wiper 314 lower Wind-= ing of relay 328, armature 327 to positivedeposit battery DB to ground, the relay 328 operating responsive to the ground impulses from the interrupter'VP. The armature 357 V will always be passed over at a constantrate occupying a substantially uniform time for alltimes of'the day. I

Advane tone or definite time before end of period.

At the time wi or 314 engages bar 358 wiper 313-engages ba terminal 359 so that-tone from source PT will -be applied through Q wiper 313, armature 360 tothe lower talking conductor, audible to the parties to the connection. This tone apprises that asuhstantially definite time remains within. the 'ensuing period before, the coinwill be deposited in the company till andthe connection thereafter broken down, and-to terminate the concoin for a succeeding period.

Deposit of the eoinz'n the company till.

When the wiper 312 engages bank terminal 325 and armature 357 thereafter attracts, the relay 326 will actuate as-before described; this time applying positive deposit battery DB from-grojund, armature 327, upper winding ofrelay 328, armature-329 lower talking conductor, winding of polarized magnet 18 to ground, the armature of the latter said.

magnet moving. in the direction to deposit the coin in the company till. This opens the circuit path through the telephone A at springs 13 1'4. Under ordinary conditions,

' this would-deenergize the line relay 401 in the connector andcause the connection to be destroyed. However, it will appear presently that under the present condition the connection will not be forthwith destroyedj At the same time that the coin is deposited in' the companytill the tone source FT is applied through bank terminal 361, wiper 313, armature 360, to the lowertalking con:

'ductor, audible to'the parties ofthe connec tion, apprising them that the period has about terminated and that a short time remains in which to deposit a coin for a continuation of the connection or it will be destroyed by selfapplied automatic means involved in the switch TS However, when the wiper 313 moves to bank terminal 362 the retardation coil 363 is bridged across the talking path to maintain the relay 401 energized in order to maintain ground on the release trunk 406 so that the connection will not be destroyed atthis time. If there is no coin in the pre-pay ment coin chute of device P at the time wiper 313 moves from bank terminal 362, and the bridge including coil 363 is thereby opened, there will be no path for energizing the relay 401 so it will deactuate and the switches will restore in an obvious manner, in View of the references to well known switches.

It will be noted here that at the time relay 326 actuated to efiect the deposit of the coin in the company till the armature 329 opens the energizing circuit for relay 401, and the spring 14 of the prepayment device P also does this, so that ground applied through the common retardation coil 334 and armature 332 to the upper talking conductor serves to main-' tain the relay 401 energized by way of a new path.

Seco'nd coin deposited maintains connect-ion.

- terminal 362 there will be an energizing circuit path through the telephone A when the bridge including the coil 363 is opened, having in mind that the parties may converse past the said bridge until the connection is destroyed, the condenser 330 maintaining the talking path operative while the armature 329 is attracted for a brief time but suflicient to operate the magnet 18 of the prepayment device P.

Timing of call starts when called subscriber responds.-Oalled subscriber may assume call charge on his called meter in lieu 0 f calling subscribers meter.

The switch TS starts responsive to the relay 302 actuating when the called subscriber responds' It will be noted that this is due to the switch-arm 417 being in its drawn position, indicative that all calls at that hour are positively paid for by the calling party. However, had the switch-arm 417 been in the dotted position wherein the conductor 425 is grounded in place ofconductor 420, the charge would be assessed to the called subscriber, unless the called subscriber'by a specific manual operation, as by momentarily depressing key 505, transfers this charge to the calling line as will appear presently.

It will be noted that the battery energizing the transmitter on the called subscribers'telefunction, while armature 430 applies ground through armature 431 to bank terminal 432. The wipers 445 to 448 on shaft 449 being in the drawn position the said ground application will be applied through interrupter armature to the motor magnet MM causing the wipers 445 to 448 to move ed to first offnormal bank position wherein wiper 448 is resting on bar 450 and the motor magnet MM is thus under the control of ground interrupter VI corresponding to interrupter VI in general characteristics and variations of speed with the time of day; in fact maybe the same interrupter as VP. In the same manner the ground interrupter CI corresponds in general to interrupter C1 in fact, may be the same interrupter as C1 However, it will be understood that the operating concern may desire to grant special rates to subscribers who desire to pay for calls made to them at certain predetermined hours and moreover, to have these rates comprehend a shorter holding time than applied to general calls paid for by the calling party. Subscribers receiving orders from housewives in the early morning hours before the business or logical peak occurs and who have, as a rule, no occasionto hold the connection long would come under this class. Under this arrangement the ground interrupter VI would be operated at a speed to eflect faster ground impulses during such times when the called subscriber pays for the call and the pre-pay ment is accordingly refunded, as will appear.

Meter of called subscriber paying for incoming callvregisters a plurality of times for the period.

Itwill be noted that if the called subscriber responds under the condition of the switcharm 417 bein 'fin the dotted position the relay 428 will n'ot be caused to actuate to in turn cause the relay 302 to actuate to start the movement of the switch TS. As the wiper 445 engages bank terminals 452 to 456 successively five applications of ground will be made through wiper 445, armature 457, wiper 407, bank terminal 411 to the called meter 507, registering five points for the predetermined period. The parties to the connection will be apprised of the definite time before the termination of the period when tone source PT is applied through bank terminal 458, wiper 446, armature 459 to the lower talking conductor, and again apprised just beplied. The interrupter-s VP and C1 are constru'cted so that the ground applications therefrom are brief with respect to the time between the ground applications.

The interrupter-s P1 and FF are so timed with respect to the interrupter Cl" that they will very briefly apply tone while the wiper 446 is resting on bank terminals 458 and 460, respectively, the interrupter PI being constructed to apply the tone from source. PT even more briefly than interrupter FI admits of the tone from source FT to be applied. The interrupters VI and C1 are constructed so that the ground applications therefrom are brief with respect to the time between the ground applications.

It will be noted, in this connection, that the wiper 312 is grounded but briefly at each stepping time so that the relay 826 is only briefly energized while the wiper 312 rests on bank terminal The same holds for the wiper 4.45 so that the called meter 507 of the called subscriber's line will be only momentarily energized as the wiper engages the bank terminals 452 to 456 for a larger time, respectively.

Number of assessments against the calling subscribcfis Zinc registered on meter specific to his Zinc.

In addition to or in lieu of the pro-payment coin device P a call meter 25 is installed companion to the line switch L. It will be noted that only if the relay 302 act-uates responsive to the relay 428 actuating will ground on armature 370 be applied through armature 371, conductor 37.2 and over the obvious circuit path to the Winding of the meter 25, operating it one time. That is, the meter 25 will record the number of coins in the pro-payment device 1, or the number of periods used if the pro-payment device P is not employed. The device P may therefore be dispensed with and the subscribers line connected directly from telephone A to armatures 15 and 16 and therefore. not de pendent upon the closure of springs 13 and 14. The meter 25 may be common to a group of calling lines.

85110 to encountering his Zine busy.

Let it be assumed that when the private wiper 4-08 of the connector is set upon the bank terminals of the called subscribers line it is busy guarded by ground being on the private bank terminal 412. The busy relay 471 will lock, having in mind it may be actuated before the wiper 408 is set upon the bank terminal 412, due to passing over a grounded bank terminal. Slow-releasing rotary relay 472 will be actuated during the operation of the rotary magnet (designated Rot. M.), and for a time thereafter consistent with its slow- ,Teleasing period, after the impulses to the rotary magnet cease. Vith the relay 471 actuated. applying busy tone to the calling line andthe relay 472 deactuated, ground through switch-arm 473 is applied through armatures 474 and 4:75, wiper e107, hank terminal -l1l to the called meter 50?. thereby assessing one point thereon. The n eter 507 may be common to a group of-ca'led lines.

lV/zcf/rcr the charge for ca '11!!! be asscsscrl to busy cal/ed line as dependent upon, time of (lay cu?! is made.

The switch-arm 473 maybe variously set by the central ollice attendant in accordance with ate schedules. For example, if the switch-arm 47 3 is set upon the terminal 475, the assessment against the called line for an encountered busy condition thereof will depend upon the conductor 42:") being grounded in accordance with the time of day. And if the switch-arn'i 4.73 is set upon terminal 476 the latter said assessment against. the called line will depend upon conductor 420 being grounded in accordance with the time 01 day. And if the switch-arn'i 473 is set upon the terminal 477 no latter said assessment will be made against the called line.

Means for refunding coin subscribe-1 Zinc cannot be ca'tcncleel to first aclccfo? (Inc to busy trunk condition-11 secondary Zine switch cannot be scized 110 outgoing trunks accessible therefrom, are idle.

It will he noted that a set of chain relays 205 to 209 are companion to the group of trunks accessible from the group of secondary line switches of which switch SL is one. Also, that these are respectively energized when the corresponding private terminals are grounded, so that conductor 210 will begrounded only when all the trunks accessible from switch SL are busy. That is. relay 212 will be actuated when its corresponding group of trunks are busy.

Also, it will be noted that a set of chain relays 215 to 215) are companion to the group of trunks accessible from the group of secondary line switches of which switch SL is one. Also, that these are respectively energized when the corresponding private terminals are grounded, so that conductor 220 will be actuated each release trunk conductor as 231 is busy-grounded to bar it from seizure by a line switch as L, there being a direct connection from conductor 220 to the resting contacts of all armatures corresponding to 235. This ground is removed from the release trunk conductor 231 by the attraction of either armature 235 or 236. Thus, normally all idle release trunk conductors 231 will be tied to conductor 220 and each untied as the corresponding switches are seized. However, a switch of the group containing switch SL cannot be seized if the conductor 220 is grounded by the closure of the chain ground by relays 215 to 219.

The release trunk conductors as 230 are not normally tied together since the conductors as 238 are individual to each armature as 240 and an armature as 241 on relay 212.

,That is to say, if all trunks of a group accessible from line switch SL or SL are busy, the switches SL or SL, as the case may he, cannot be seized. This is in order to prevent a secondary line switch being seized in a group wherein there is no idle outgoing trunk as denoted by the conductor 210 or 220 being grounded. The conductor 220 may be falsely busy-grounded at the instant of seizure of an idle secondaryline switch as SL', but only for a very brief, almost inappreciable time so far as any affecting operative function is concerned. This would only endure after the idle trunk is seized until the armature corresponding to 235 thereofattracts to free it from conductor 220.

It will be noted that bank terminals 245 and 246 accessible from switch SL lead to the tone source 8T to minus (refunding) battery RB and through retardation coil 250 to the latter said battery. This also applies for bank terminals 247 and v 248, respectively. The private bank terminal 251 is normally connected through armatures 252 and 253 to ground to guard the bank terminals 245 and 246 against seizure. The private bank terminal 255 is normally connected through armatures 256 and 253 to ground to guard the bank terminals 247 and 248 against seizure, it being noted that armature 253 is common to the grounding of both private bank terminals 251 and 255. g

It will be noted that when all trunks accessible from switch 'SL are busy theterminals 245-and 246 are unguarded, and that when all trunks accessible from switch SL' are busy the terminals 247 and 248 are unguarded. This is so in the event there is a sole idle trunk accessible from either switch SL or SL and two line switches as Ls ize a switch as SL or S L wherein but one of the switches will be enabled to seize the sole idle trunk the other switch involving the futile extension will then be caused to seize the bank terminals corresponding to tone source ST The calling subscriber of the futile call will thus be apprised by the distinctive tone from th latter said source. Also, the refunding bat- I tery RB applied through the retardation coii 250 will operate the magnet 18 in the device P to refund the coin to the calling subscriber. In this connection, it Will be noted, that the subscribers line will become opened at spring 14. No ground being applied back over the private terminal 251, or 255 as the case may be, the switch as SL, or switch SL as the case may be, would not in any event remain in seizure beyond-the sustaining period of the relay 201, or 260, as the case may be.

Calling subscriber notified by specific tone if initiated call is futile because of all trunks outgoing from his primary Zine switch or the secondary Zine switches are busy, respectively.

In the event, when all trunks normally accessible from the secondary line switches SL and SL'- are busy, the relays 212 and 222 to 224 will be actuated and ground chained to actuate relay 265. This Willremove the ground applied from the resting contact of armature 253, so that not only will the ground he removed from the bank terminals 245 and 255, but ground will also be removed from bank terminals as 31 of the primary line switch L to unguard bank terminals as 32 and 33, so that any subscriber now initiating a call wherein no extension can be made due to all outgoing trunk paths being busy, the terminals corresponding to 32 and 33 will be seized and distinctive tone from source PT applied audible to the calling subscriber. The minus (refunding) battery RB" applied through retardation coil 275 will cause the refunding of the coin in the same manner as when a refund is made by battery RB applied through coil 250.

It will be understood in this connection that all terminals corresponding to 251, 245 and 246 of the group containing switch SL will be in multiple, respectively. The same holds for-all terminals corresponding to 255, I

247 and 248 of the group containing switch SL'. And the same holds for the primary line switches as L wherein all the terminals correspondin to.31, 32 and 33 are tied together, respectlvely.

It will thus. be clear that not only are the primary line switches as L barred from seizing a secondary line switch wherein there is at the time no idle outgoing trunk available from the secondary line switch, but in the event of an all busy trunk condition outgoing from the secondary line switch seized occurring after the seizure of a secondary line switch the calling subscriber concerned will cific tone and will have his pre-deposited coin refunded forthwith.

Also, in the event there are no idle trunks outgoing from the primary line switch as L the calling subscriber concerned will be apprised of the fact that the call is futile by a specific tone and have his pre-deposited coin refunded.

It will be noted that the present invention comprehends armatures 240, 271 and make contact 272 of switch SL, and armatures 235, 236 and make contact 275 of switch SL',

together with interlinked circuits, having in mind that the line switch L-is not new in the art and in itself without consideration of its cooperative circuits is not a part of the present invention. What is shown in switches SL and SL' .beyond what is shown in the switch L belongs to the present invention.

Preferred modificatiom.

Fig. 6 shows a preferred modification of Fig. 3 wherein an added armature 601 on relay 326 causes added relay 602 to actuate and lock by armature 605 to the release trunk 309 so that the ground interrupter VI is disconnected and the-ground interrupter VI is connected in-its place b armature 604. The latter interrupter whi e variable with the time of day, as is interrupter V1 runs slower so that the time required for the wipers 312 to 316 to pass over the space embraced by bar 356 will be longer under the influence of the interrupter VI than under the influence of the interrupter VI That is, for the same time of day the periods after the first for a maintained connection will be longer for the same assessment. The interrupters VI andVI may have speeds which are correspondingly variable during the day. Thus, the percentage increase in the allowable time for succeedin periods over the initial period may be uni orm, but of course,

this is not necessarily so. I

Fig. 7 shows a preferred modification of Fig. 4 wherein when wiper 445 applies ground to bank terminal 470 relay 701 is caused to lock by armature 702 to the release trunk 406. Armature 703 disconnects interrupter- VI and substitutes interrupter VI therefor. The latter. interrupters may bear the same relation to each other as interrupters-VI and VI in Figs. '3 and 6, for a similar object, but-with respect to assessments on the called meter as 507 'of the line called.

Fig. 8 shows the retardation coil 440 in Fig. 4 changed to a relay 801 havin an armature 802 and the relay 441 change to, relay 803 having cumulative windings in place of differential, and the armature 804 of relay 803 provided witha grounded resting contact 1 n place of a make contact. The relay 803 1s marginally adjusted. In the event the called amaees subscriber at telephone A wishes to cause the relay 428 to lock he will momentarily depress button 508 to remove the short-circuit from the resistor 509 to attentuate the strength of current traversing the cumulative windings of marginally adjusted relay 803 so that it will retract its armature 804, while armature 802 remains attracted, thus causing a ground impulse to be applied to energize the upper winding of the relay 428 to cause the reversal effective to actuating relay 302. That is, in place ofapplying ground by means of button 505 the inclusion of resistance involved in the resistor 509 is employed. One or theother button 505 or 508 will not be employed.

Fig. 9 shows a preferred modification of the connector wherein armatures 901 and 902 are added on relay 472. -Armature 901 energizes added slow-releasing relay 903, so that relay 903 will sustain a short time after relay 472 deactuates. During the time relay 903 is actuated while relay 47 2 is deactuated, tone from source T is applied to the called line, whether it is idle or busy, so that if it is busy the party thereon will be apprised that a calling party is seeking connection with his line and will perhaps hasten the termination of the ensuing call so his line may be available if a subsequent attempt to connect with it is made. i

The conductor from the switch-arm 47 3 is run to the armature 905 so that the path from switch-arm 473 to the make contact of armature 474 is only closed while relay 903 is actuated. This obviates energizing the called meter 507 for the entire time the con nector is left into selective relation to the busy called line.

In this connection, it is to be understood that the said preferred embodiments, excepting that disclosed by Fig. 8, are to be assumed as part of the exemplary embodiment, shown as modifications in order to make the descriptions as simple as possible. That is, the preferred embodiments, so termed, are not intended as merely possible alternative embodiments, though obviously they may be omitted without departing from the spirit of the invention defined by certain subjoined claims which may not require all disclosed structure to support-them.

I claim 1. In an automatic telephone system, a connective switch, a called line, a test terininal of the called line, means for automatically operating the connective switch to effect selection of and seizure of the called line, means responsive to a specific electrical potential existing on sa1d test termiml for barring the seizure of the selected called line, means for applying and removing said specific electrical potential from sa1d test terminal, a call meter device for the called line, and means for operating said device to record a barred call to the called line only if said switch is operated into selective relation with the called line and said switch is prevented from seizing the called line-due to the said specific potential existing on said test terminal thereof.

2.' In an automatic telephone system, a connective switch, a called line, a test terminal of the called line, means for automatically operating the connective switch to effect selection of and seizure of the called line, means responsive to a specific electrical potential existing on said test terminal for barring the seizure of the selected called line, means for applying and removing said specific electrical potential from said test terminal,.a call meter device for the called line, and means for operating said device to record a barred call to the called line only if said switch is operated into selective relation with the called line and said switch is prevented from seizing the called line due to the said specific potential existing on said test terminal thereof, and automatic 'means for causing the operation of last said means onlyguring certain predetermined periods of the ay. 7

3. In an automatic telephone system, lines, a primary line switch for each said line, a group of secondary line switches accessible from said primary line switches, specifically distinctive tone sources for the primary line switches and for the group of secondary line switches, another switch accessible from said secondary line switches, means responsive to initiating a call on a random one of said lines for causing the corresponding primary line switch to seize a said secondary line switch and for the seized secondary line switch to thereupon seize said other switch, means for barring a seized said'switch from being fur ther seized by another said switch while the first seizure endures, and means for applying the corresponding said tone source audible on the concerned said line responsive to the initiation of a call on a random said line if the concerned primary line switch is barred from seizing all secondary line switches or ii the secondary line switch seized by the primary line swi ch is barred from seizing the said other switch. y

4. In an automatic telephone system, lines, a primary line switch for each said line, a

'group of secondary line switches accessible from said primary line switches, sources of direct current specific to the primary line switches and to the group of secondary line switches, another switch accessible from said secondary line switches, means responsive to initiating a call on a randomvone of said lines for causing the primary line switch to seize a said secondary line switch and for the seized secondary line switch to thereupon seize said other switch, means for barring a seized said switch from being further seized by another said switch while the first seizure endures, and means for applying the corresponding said current source to a talking conductor of the concerned said line responsive to the initiation of a call on a random said line if the concerned primary line switch is barred from seizing all secondary line switches or if the secondary line switch seized by the latter said primary line switch is barred from seizing the said other switch.

5. In an automatic telephone system, lines, a primary line switch for each said line, a group of secondary line switches accessible from said primary line switches, another switch accessible from said secondary line switches, means responsive to initiating a call on a random one of said lines for causing the corresponding primary line switch to seize a said secondary line switch and for the seized secondary line switch to thereupon seize said other switch, means for barring a seized said switch from being further seized by another said switch while the first seizure endures,

and means for applying a tone audible on the;

said line responsive to the initiation of a call on 'a random said line if the concerned primary line switch is barred from seizin all secondary line switches or if the secondary line switch seized by the latter said primary line switch is barred from seizing-the said other switch. Y

6. In an automatic telephone system, lines,

a primary line switch for each said line, a

group of secondary line switches accessible from said primary line switches, another switch accessible from said secondary line switches, means responsive to initiating a call on a random one of said lines for causing the primary line switch to seize a said secondary line switch and the seized secondary line switch to thereupon seize said other switch,

means for barring a seized said switch from being further seized by another said switch while the first seizure endures, and means for applying a' source of direct current to a talking conductor of the concerned said line rcsponsive to the initiation of a call on a random said line if the concerned primary line switch is barred from seizing all secondary line switches or if the secondary line switch seized by the latter said primary line switch is barred from seizing said other switch.

7 In an automatic telephone system, lines;

a line switch, other switches, a source of direct current, another switch accessible from said line switch and said other switches, means responsive to initiating a call on one of said lines for causing said line switch to seize said another switch, means for barring said another switch from beingfurthe'r seized by one of said other switches responsive to said seizure only while said seizure endures, and means for applying said source of current to a talking conductor of any said other switches seeking to seize said another switch when it is barred against seizure.

8. In an automatic telephone system, a group of line switches, a group of lines accessible from said switches, a common conductor, a chain ground closed from said common conductor, an antecedent switch having common access to the switches of said group, a private busy conductor individual to each switch of said group for barring the corresponding switch against seizure by said antecedent switch, means for conductively connecting the private conductors of all switches of said group when idle to the common conductor, means for closing said'chain ground to apply busy ground bar to all switches of said group to prevent the antecedent switch from seizing an idle switch of said group only if all the said group of lines accessible from said group of switches are busy, and means for disconnecting the private conductor of any switch responsive to the seizure of the corresponding switch by the antecedent switch, the said seizure being possible only when the switch seized is idle and there is an idle said line accessible from the switch seized.

9. In an automatic telephone system, a rotary line switch, a set of movable wipers of the switch, sets of fixed terminals of'thc switch swept by said wipers moving in a single direction, the wipers constantly engaging a random set of said fixed terminals, a line relay of the switch, a wiper switching relay of the switch, a group of lines corresponding to said fixed terminals, means for making random ones of said lines busy, means for preventing the wiper switching relay from operating when the wipers are resting upon the terminals of a busy said line, an antecedent switch having access to said switch, directively controlled means including said antecedent switch for causing the said relays to operate only when the wipers are resting upon the terminals of an idle said line, means for guarding the said line switch against seizure y the antecedent switch it one of said relays is actuated, and means for guarding said line switch against seizure by the antecedent switch if all said lines are busy although neither one of said relays is actuated, the

last said means involving a circuit path including a normally closed contact on each said relay.

10. In an automatic telephone system, a calling line, a pre-payment device on the call ing line, a called line, a train of automatic switches for linking a connection from the calling line to the called line, means responsive to initiating a call on the calling line only if the pre-payment device is operated by inserting a pre-payment therein for operating a first one of said automatic switches to link a preliminary call' extension towards the called line, means thereafter directively controlled over the calling line for operating other of said automatic switches to complete said extension to the called line, means responsive to abandoning the initiated call for causing the pre-payment device to refund the inserted pre-payment, and means operated responsive to said initiation only if the first said switch is barred from making said preliminary extension due to all call extension paths therefrom being barred as busy for 7 causing the pre-payment device to refund the inserted pre-payment.

11. In an automatic telephone system, a calling line, a pre-payment device on the calling line, a called line, a train of automatic switches for linking a connection from the calling line to the called line, means responsive to initiating a call on the calling line only if the pre-payment device is operated by inserting a pre-payment therein for operating a plurality of said switches to link a preliminary call extension train towards the called line, means thereafter directively controlled over the calling line for operating other of said automatic switches to complete said extension to the calledline, means responsive to abandoning the initiated call for causing the pre-payment device to refund the inserted pre-payment, and means operated responsive to said initiation only if one of said plurality of switches is barred from making said preliminary extension due to all call extension paths therefrom being barred as busy for causing the pre-payment device to refundthe inserted pre-payment. I

12. In a telephone system, a calling line, a called line, automatic switch mechanism for extending a'connection from the calling line to the called line a pre-payment device, means dependingupon first operating said pre-payment device by a pre-payment for capacitating the operation of the said switch mechanism, a collecting receptacle and a refunding receptacle for the pre-payment device, tmeans manually controlled over the called line only after the calling line has been extended to the called line for establishing a talking relation between the calling line and the called line, means for thereafter at willdestroyingthe extended connection and for depositingsaid pre-payment in. the refunding receptacle, and means controlled over thecalled line at will after establishing said talking relation and before destroying said extended connection for preventing said pre-payment from being deposited in the refunding receptacle.

III

13. In a telephone system, a calling line, a

- manually controlled over the called line only responsive to destroying the extendedconnection for depositing said pre-payment in the collecting receptacle.

14. Ina telephone system, a calling line, a called line, automatic switch mechanism for extending a connection from the calling line to the called line, a pro-payment device, means depending upon first operating said pro-payment device by a pre-payment for capacitating the operation of the said switch mechanism, a collecting receptacle and a refunding receptacle for the pre-payment device, means after the calling line has been extended to the calledline for establishing a talking relation between the calling line and the called line, means for thereafter at will destroying the extended connection and for depositing said pre-payment in the refunding receptacle, means controlled over the called line at will after establishing said talking relation and before destroying said extended connection for preventing said pre-payment from being deposited in the refunding receptacle, and means thereafter operated at the termination of a predetermined period of time for conversation following the said control of last said means for depositing said prepayment in the collecting receptacle.

e 15. In a telephone system, a calling line, a called lin'e leading from a central exchange to a gsubscribers station, automatic switch mechanism for extending a call connection from the calling line to the called line, a toll assessing device for the called line at the central exchange. and means controlled over the 4 called line for operating the toll assessing device after said extension to the called line has been made to 'record a toll assessment for the call connection from the calling line to the called line against the called line Without refording a toll assessment against the calling 16. In a telephone system, a calling line, a called 'linc, automatic switch mechanism for extending a call connection from the calling line-to the called line, a toll assessing device for the calling line, a toll assessing device for the called line, means responsive to a manual operation on thecalled line for operating the toll assessing device only of the called line, and other means operated responsive to a manual operation on the calledline applied at will while said connection exists for operating the toll assessing device for the calling line and for disabling the operation of the toll assessing device on the called line.

7 17. In a telephone system, a calling line, a called line, automatic switch mechanism for extending a call connection from the calling line to the called line, a toll assessing device for the calling line, a toll assessing device for the called line, and means controlled over the called line by a manual operation for defining what portions of the total toll charge for the call shall be respectively assessed against the calling line and the called line on the corresponding said devices.

18. In a telephone system, a calling line, a called line, automatic switch mechanism for extending a call connection from the calling line to the called line, a toll assessing device for the calling line, a toll assessing device for the called line, means on the called line manually operated for completing a talking connection between the connected calling and called lines and means depending upon the time of day the last said means is operated for determining Whether the toll charge for the talking connection will be recorded against the calling line or the called line by its corresponding toll assessing device.

19. In telephone system, a calling line, a called line, automatic switch mechanism for extending a connection from the calling line to the called line, a pre-payment device, means depending upon first operating said pre-payment device by a prepayment for capacitating the operation of the said switch mechanism, a collecting receptacle and a refunding receptacle for the pre-payment device, means for causing the pre-payment device to deposit the pro-payment in the collectin receptacle in a substantially predetermined time variable in length depending upon the time of day the said time durates through, a first. and a second specifically distinctive tone source, means for applying one said tone source audible on the call-' ing line at a substantially predetermined time before the termination of said period, and means for applying the other of said tone sources audible on the calling line at a substantially predetermined time before the termination of said period, the elapsed time between the said applications of the tone sources beingsubstantially constant for a plurality of callsregardless of the fact that the length of thesaid eriod may Vary among said plurality' of cal s, so that a listener on the calling line will have substantially definite notice of the times remaining of a said period regardless of the length of the period.

'20. In an automatic telephone system, a called line, an automatic connective switch for effecting connection to said called line,

a private terminal of the called line, means for applying a specific electrical potential to the private terminal indicative of the busy condition of the called line, means responsive to efl'ecting connection to the called line when it is busy for preventing the switch from effecting seizure of the connected called line so that a talking relation between the switch and the busy called line is barred, a tone source, and means operated for applying the tone source to a talking-con ductor of the called line responsive to the switch eiiecting connection to the called line whether busy or idle.

21. In a telephone system, a called line, switch mechanism for extending connection to said line, a toll assessing device for the called line, means controlled over the called line for operating the toll assessing device, and means dependent upon the time of day the connection is made to the called line for determining the extent of said assessment.

22. In a telephone system, a called line, switch mechanism for extending connection to said line, a toll assessing devicf for the called line, means controlled over the called line for operating the toll assessing device,

and means dependent upon the duration of the connection for determining the extent of said assessment.

23. In a telephone system, avcalled line, switch mechanism for extending connection to said line, a toll assessin device for the called line, means controlled over the called line for operating the toll assessing device, and means dependent upon the time of day the connection is made to the called line for determining whether or not the assessment will be made.

24. In a telephone system, a called line, switch mechanism for extending connection to said line, a toll assessing device for the called line, means controlled for initiating the operation of the toll assessing device for causin a plurality of assessments to be successive ly made against the called line, and means controlled over a series path of a talking conductor of the called line at will for preventing further said assessments being thereafter made while maintaining the connection. 25. In a telephone system, a calling line;- 2. called line, automatic switch mechanism for extending connection from the'calling line to the called line, a toll assessing device for the calling line, a timing device for measuring elapsed time, means controlled over the called line for initiating the operation of said timing device, means responsive to the operation of said timing device for assessing a toll charge on said toll assessing device, means for periodically reoperating said timing device for assessing accruing toll charge on said toll assessing device, and means the operation of which is. dependent upon whether the assessment is the initial assessment for a call or a succeeding assessment for said call for determining the length of time the toll assessment covers.

26. In a telephone system, a calling line, a called line, automatic switch mechanism for extending connection from the calling line to the called line, a toll assessing device for the cally reoperating said timing device for assessmg accrumg toll chargeon said tell as-' sessmg device, and means governed by the time of day the call transpires for determining the length of time the respective said assessments cover.

27. In a telephone system, a calling line, a called line, automatic switch mechanism for extending connection from the calling line to the called line," a toll assessing device for the called line, a timing device for measurin elapsed time, means controlled over the called line for initiating the operation of said timing device, means responsive to the operation of said timing device for assessing a toll charge on said toll assessing device, means for periodically reoperating said timing device for assessing accruing toll charge on said toll assessing device, and means the operation of which is dependent upon whether the assessment is the initial assessment for a call or a succeeding assessment for said call for determining the length of time the toll assessment 4 covers.

28. In a telephone system, a calling line, a called line, automatic switch mechanism for extending connection from the calling line to the called line, a toll assessing device for the called line, a timing device for measuring elapsed time, means controlled over the called line for initiating the operation of said timing device, means responsive to the operation of said timing device for assessing a toll charge on said toll assessing device, means for periodically reoperating said timing device for assessing accruing toll charge on said-- toll assessing 'device, and means governed by the time of day the call transpires for determining the length of time the respectivesaid assessments cover.

29. In a telephone system, a calling line, a

ing line to the called line, a toll-assessing device for defining a predetermined toll charge against the calling line for the connection to the called line and for a predetermined duration period of said connection, a progressively movable wiper switch for measurin elapsed time of said connection for 'sai charge, means for thereafter defining an additionalperiod of continued connection by a further movement of said movable wiper switch, and automatic means for varying the length of individual successive said periods for a single said connection depending upon the duration of said connection.

30. In a telephone system, a calling line, a primary line switch for the calling line, primary lines accessible from the primary line switch, a secondary line switch for the respective said primary lines, secondary lines accessible from said secondary line switches, means operated'responsive to initiating a call on the calling line for causing the primary line switch to hunt for and connect to a said primary line and for thereupon causing the corresponding secondary line switch to huntfor and connect to a said secondary line, means for making said primary lines and said sec ondary lines busy,meansforbarringbusysaid lines against connection to by the cooperative said switches, means responsive to an all busy condition of said secondary lines for preventing the primary line switch from connecting to the primary line, and means whereby r'esponsive to an all busy condition of said sec ondary lines occurring after a primaryline has been connected to by a primary line switch and before its corresponding secondary line switch has connected to a secondary line, a busy indication will be applied discernible on the calling line to indicate that the calling line has been barred from extension to a said secondary line.

31. In a telephone system, a callingline, a primary line switch for the calling line, primary lines accessible from the primary line switch, a secondary line switch for the respective said primary. lines, secondary lines acces sible from said secondary line switches, means operated responsive to initiating a call on the calling line for causing the primary line switch to hunt for and connect to a said primary line and for thereupon causing the corresponding secondary line switch to hunt for and connect to a said secondary line, means for making said primary'lines and said secondary lines busy, means for barring busy said lines against connection to by the cooperative said switches, means responsive to an all busy condition of said secondary lines for preventing the primary line switch from connecting to a primaryline, means whereby responsive to an all busy condition of said secondary lines occurring after a primary line has been connected to by a primary line switch and before its corresponding secondary line switch has connected to a secondary line, a busy indication will be applied discernible on the calling line to indicate that the calling line has been barred from extension to a said secondary line, and means responsive to the all busy condition of the secondary lines terminating for stopping the application of the busy indication and for causing the secondary line switch to operate and complete the connection from the calling line to an idle said secondary line.

32. In a telephone system, a calling line, a primary line switch for the calling line, primary lines accessible from the primary line switch, a secondary line switch for the respective said primary lines, secondary lines accessible from said secondary line switches, means operated responsive to initiating a call on the calling line for causing the primary line switch to hunt for and connect to a said primary line and for thereupon causing the corresponding secondary line switch to hunt for and connect to a said secondary line, means for making said primary lines and said secondary lines busy, means for barring busy said lines against connection to by the cooperative said switches, and means including a circuit path from ground individual to each said secondary line switch and a contact of a relay of latter said switch responsive to all said secondary lines becoming busy for preventing the primary line switch from connecting to a primary line.

33. In a telephone system, a calling line, a primary line switch for the calling line, primary lines accessible from the primary line switch, a secondary line switch for the respective said primary lines, secondary lines accessible from said secondary line switches, means operated responsive to initiating a call on the walling line for causing the primary line switch to hunt for and connect to a said primary line and -for thereupon causing the corresponding secondary line switch to hunt for and connect to a said secondary line, means for making said primary lines and said secondary lines busy, means for barring busy said lines against connection to by the cooperative said switches, means including a circuit path from ground individualto each said secondary line switch and a contact of a relay of latter said switchresponsive to all said sec ondary lines becoming busy for preventing the primary line switch from connecting to a primary line, and means for disabling said circuit path at said contact when the secondary line switch is in its connected condition with respect to a secondary line. a

34:. In a telephone system, a calling line, a primary line switch for the calling line, primary lines accessible from the primary line switch, a secondary line switch for the respective said primary lines, secondary lines accessible from said secondary line switches,

means operated responsive to initiating a call on the calling line for causing the primary line switch to hunt for and connect to a said primary line and for thereupon causing the corresponding secondary line switch to hunt for and connect to a said secondary line, means for making said primary linesandsaid secondary lines busy, means for barring busy said lines against connection to by the co-

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