US2244596A - Automatic telephone system - Google Patents

Description

June s, 1941. f

e. A. ANDERSON 2.244.596

AUTOMATIC TELEPHONB SYSTEM Filed Dec. 2, 1939 2 Sheets-Sheet 2 N N By G.A.ANDERSON W @w@a TTOR/VEV Patented June 3, 1941 AUTOMATIG TELEPHONE SYSTEM Gustave Adolph Anderson, Albany, N. Y., assignor to American Telephone and Telegraph Company, a corporation f New York Application December 2, 1939, Serial N0. 307,332

6 Glaims.

Ths invezntion relates to automatic telephone systems and more particularly to systems of the type referred to as community dia1 Systems, i. e. small automatic systems for small tovvns and villages. Such Systems are usually unattended but are provided with brunking facilities to a distant larger 01fice sometimes called a master. Due, however, 150 the general service requirements of such a system simplicity and 10W co-st are very important and therefo-re various features usually found in large systems have been eliminated in -these sma11er equipments a-s, for examp1e, facilities for enabling a toll operator 110 rering a subscriber over a previously established connection, which facilities are in some cases desirable, for example When a subscriber who makes a 1arge number of toll Balls desires 120 have several ca1ls completed o-ne after the other as fast as the operabor can com-plete them,-

withouo 1:he delay incident t0 building up a counection for every -call and then perhaps, on accasi-on, finding the line busy. Ooviously, 'the most efilcient method. for providing this service would be to hold the connection between the toll openat or over the trunk to the subscribers 1ine and recall the subscriber by ringing on bis line as soon as each ca1l was ready. As previous1y mentioned, arrangements where=by a community ofilce sub-scribers line can be he1d and rerung repeatedly at the will o-f a m11 operator are not or-dinarily furnished in small systems of this type fior the reason that the cost o-f 1:he added equipment cannot in m-ost cases be justified.

An object of the present invention is therefore to provide facilities 01' a re1aively simple nature whereby an operator in a distant exchange can establ=ish and hold a connection t-o a subscribers 1ine, in an exchanse of the type described, and thereafter cause ringing current to be connected the-reto as often as desired.

Further, it is desirable in Systems cf this nature that a distant operabor be able, in case an attempt is made either by herse1f or any subscriber to complete a ca11 to a community oflice subscriber and receives a 1=ine busy indication, to verify the fact that the 1ine is actually in use by overriding the busy indicabion and estabh'shing a connection 130 the desired 1ine, either t0 mere1y verify th-e busy condition or vin a more extreme Gase 110 converse with the parties talking and ask them to make way for an emergency cal1, such as a cafl1 for police er 190 report a fire.

Busy test Veri=fication facilities are now provided in 1arge automatic exchanges and the- -srn=aller community exch-anges can be arranged t0 provide this service by employing suitable known equipment but the expense of such faci1ifies frequently cannot be justified for sma1l exchanges -of the type in question.

I1. therefore is a further object of the invention toprovide a simple and practicable arrangement for small exchanges whereby a busy ca11ed line can be seized by certain predetermined cal1- ing lines so establish a talking connection therewith and when the original busy condition is removed, to fing an said. 1ine.

A feature of the invention whereby bo-th 0f the forgoing objects are attained resides in the emp1=oyment o-f a :special no test connector switch so vvi-redand arranged that it may be controlled over certain 1ines 01 group of lines as, for examp1e, brunks from an operators position, t-o connect t0 any line available to the switch, regardless of the busy condition 0f said line, and When the 1ine is id1e, i. e. receiver 011 h00k, 1:0 ring thereon.

A fur-ther feature resides in auxiliary circuii; means as-sociated With certain predetermined subscribers 1ines -available said no test counector whereby when one '0 f these lines is being he1d by an automatic switch an a regular sonneotinn and is subsequently seized by the no test connector, the first connected switch will Joe disconnected therefr-om, except for a high impedance -connection which in pracbice may be a small condenser, during the period the 1ine is engaged by the no test switch. When the 1ine is rung by ehe no test switch on1y an audible ringing tolle will be transmicted. back through the first switch.

'I'he invention will be understood from the following description when read in connection With the accompanying drawings, Figs. 1 and 2 of which, when placed together With Fig. 1 above Fig. 2, represent a so-called community d=ia1 exchange including calling and -ca11ed local stations and trunks inooming thereto from a dis- 1:ant master office, which exchange is arranged 150 provide the facilities sei; forth in the foregoing objects and features of the invention.

The arrangement whereby the present sequence cal1 service feature is obtained. Will now be described.

Referr ing the dnawings, X, A and. B are loca1 stati-ons 0f the community dfi-a1 exchange and OOI and 002 are oord circuits arranged for dialing and located in a distant master office which cord -circuits have access to the communitsr rotadzes the wipers cf ehe connec-tor 110 the de-.

sired. 1ine, which connector appears in the banks 0f 2.11 the selectors S, S! anti S2. Ab this point it may be mentioned that the seiector S, serving local subscribers such as X, has a vacant Level, for ex-ample the upper or top Level aus shown in the drawings, in which 1evel nc connector trunks are terminated.

N'IC represents a special or no test connectol also arranged for the same type of ringing 001'1- trol as the regular connector C but modified 120 the extent that it is unresponsive to a busy coudition encountered on the test terminal 016 a dialed subscfibers line andtherefore its wipers stap -on the terminais of any line to Which they are advanced irrespective cf ehe busy or id1e condition thereof.

It Will be noted that the connector C appears in the banks cf a.11 the selectors S, SH, and. S2, but the connector N'IC on1y appears in the banks of selec:tors S! anti S2, i. e., the selectors termina.ting the trunks TK! and TKZ from the master ofiice, and more specificaily appear in the upper or top 1evsl of these selectors which level, as before menoibned, is vaczmt in selector S and therefore it will be obvious that whereas an operator at the master oce 02m by means cf a cord circuit am). one cf the trunks TKI or TK2 reach a desired subscribers 1ine A B, etc. by way of either the regular ccnnector C 01' the special notest connector NTC a local subscriber such as station X can =only obain a connection With these lineg by way 0f the regular connector C, that is to say, a, loca1 subscriber can only reach anoi-her local subscribers line if that line is id1e, whereas an operator at the master ofi1ce can obtain a connection With a loca1 subscribers line either by way 0f the regular -connector C, if the desired 1ine is id1e 01 via the special no-test counector NTC regardless of whether the line is idle er busy.

Meang whereby a subscriber such as X obtains connection With another subscriber such as A o1 B, which involves standard line finders, selectors and connectcrs forma 110 =part cf the present invention and no detailed description thereo:f is necessary it being sufiicient to mention that when the caliing subscriber removes bis receiver from the hook a line finder LF seizes the line und extends it to an isi1e selector such as S following which the subscriber a=ctuates bis dial so transmit the code digits of the desired line foilowed Joy the digit designating th e ende ring cf the wanted party1ine subscriber, which dial Impulses successive1y control the movement of the wipers of the selector S, connector C and the Code switch which forms a, part of the connector.

Let us assume, however, that the subscriber B is a. very large user of iong disbauce toll facilities anti frequently desires t0 communica.te in rapid succession With a number of distant stations. As Will be understood, the ordinary rcutine in handling such ca]ls is for the subscri-ber to dial the teil operator with whom he is connected by means 0f the usual facilities (not shown) and When the operacoranswers to give her the necessary details of the desired connections after Which, unless the calls can be completed while the subscriber remains a1; bis telephone, he Will be told replace bis reoeiver on the hook anal that he Will be called as soon as the desired connections can be meide. When the operator is ready With the first call, she will connect one 0f her cord circuits, for example OCI, With a trunk, for example 'IKI, anal diai the regular ende digits 0f ehe ca11ing subscribers 1ine which, for examp1e, may be 2i2 as indicated by the drawings. 'Ihe first digit dialed Will raise the wipers of the sel'ector S to the proper leve1, for example the second leve1 as shown, und ab the conclusion of the pulses the selector will rotate its Wipers into contaci; with the first sei: 0f terminals where they will remain if we assume t'ne connector C 170 -be idle. 'Ihe operator is ncw connected to :conn'ector C anal the next two digits dia1ed Will raise und.

rctate the wipers of the connector inco engagement With the bank terminals corresponding 170 the line of station B which as shown is the second sei: in the first leve1. The operator then dia.1s the final or code-n'nging digit cf station B and when the subscriber answers ringing will be tripped.

When the subscriber restores his receiver 110 the switchhook at the end 01" the conversation, thesupervisory 1amp before the toll operator will be lighted. However, as other calls are 110 be completed in sequence the same subscriber, the operator Will not disconnect from the trunk at this time, but Will immediately;proceed With the next cal1.

When the cperator is ready With the nexi; aal], as the regular connector C is still in the talking condition, a.nd the ringing equipment 1 now locked out, she is unab1e 110 recall the subseriber over the original connection, i. e. cord OCI, trunk TKI, selectorl -and connector C but by means cf special connector NTC and the special equipment associated With the 1ine of subscriber B, comprising the present invention, she is a:b1e 130 accomplish this function in the following manner.

In order t0 ring the subscriber B under the above -condition the operator Will connect a second cord OC2, -for exampie, With another trunk 'I'K2 130 the community o1fice, and first dia1 the 1evel of the trunk selectors reserved for the special connector N'I'C Which from the drawings is shown as the upper or top level cf selectors S! arm S2. As selector S2 is associatecl With trunk TK2, and if We assume the selectcr to have ten Levels, the operator Will dia1 (l, i. e., transmit ten pulses by means of her dial, followed by the digit pulses i anal 2 necessary 110 advance the special connector into engagement With'the subscribers Iine terminals which as before am the sec0nd in the first ievel. In this connection, as before mentioned, special connector NTC l's on1y multipled in selector 1evels accessible to the master office trunk Which in the present case is the upper o1 tenth level of selectors S! and S2 and therefore it Will Joe evident that local subscri'bers of the community office as, for exampl-e, station X are unabie to gain access to this connector, the reason for which is obvious.

When the selector S2 raises its wiperg the tenth level and rotates them into contact with the fi1st Set; cf terminals, battery through the 1ower winding cf the so-cailed C relay 2 in the connector NTC and over the C lead 3 causes the selector 150 extend the tip and ring of the trunk through to battery and ground in series withthe upper and lower windings of the line relay I. Relays 2 and I operate, followed immediately by the so-called B relay 4. Relay 2 in operating closes its contacts thereby preparing the impulsing circuit of the vertical magnet VERT. Relay 4, at its contacts 1, grounds the C lead 3. The connector NTC with relays I, 2 and 4 operated is now in readiness 130 receive Ehe second and third digit impulses -from Ehe operators cord at the master olfice. As the line cf subscriber B terminates on the second terminals of I:he first leve1 the wipers 8, 9 and III must be ralsed one step thereby requiring a single relea.se and subsequent reoperation -of relay I. Therefore, when relay I releases, the =pulsing circuit is closed to the vertical magnet in parallel With the upper winding of relay 2 and the wipers are raised to the first level, the vertical ofI-normal contaots I2 are opened thereby opening the starting circuit through the lower winding of relay 2 and the contacts I3 are closed thcreby preparing a circuit 60 operate the release magnet I4. When relay I reoperates, relay 2 rel-eases and transfers the pulsing circuit from the vertical magnet 1:0 relay I I in parallel with the rotary magnet ROT.

When the operator transmits the next o1 third series of impulses, two in this case, relay I releases and reoperates twice. On alle first release o! relay I, relay II operates in parallel With the rotary magnet ROT in the following circuit: Ground, back contact of relay I,contacts I5 cf relay 4, back contacts 0f relay 2, and from this point one brauch extends through the winding of relay II to battery and the other brauch can be further traced over contacts I6 of relay I1, contacts I8 of relay I9, conductor 20, contacts 2I of relay 22 and Winding cf rotary magnet ROT, also 120 battery. Relay I I in operating closes the following circuit so opera.te relay 23: Ground, contacts 24 0f relay 4, contacts 26 of relay 22, contacts 21 of relay II, contacts 28 of relay I1 and c0nductor 34 120 battery through the upper winding of relay 23. Relay 23 operates and locks over its contacts 30 in series with the lower winding of relay I1 to ground at. contacts 24 cf relay 4 in the followlng circuit: Ground, contacts 24 of relay 4, concluctors 25 and 3I, contacts 30 of relay 23, contactg 32 cf relay 33, contact 34 of relay 22, lower winding cf relay I1, conductor 34 and upper Windlng cf relay 23 110 battery. Relay 23 ab its contacts 35 also connecIs-s ios lower winding in parallel with the upper Winding of relay I1. Relay I1 does not operate at this time, however, as its lower winding is short circuited at contacts 21 0f relay II.

In response to the transmission of owo dial pulses the rotary magnet ROT moves the wipers 8, 9 and I0 two steps into contact with the second terminal cf the first level of the connector switch during which interval relayg 4 and I I re main opera'bed.

When relay I reoperates foll0wing the sec0nd impulse, relay II after a short interval releases thereby opening its contact 21 and removing the short circuit from the lower winding of relay I1 which relay thereupon operates in the followlng circuit: Ground, contacts 24 of relay 4, conduct0rs 25 and 3I, contacts 30 of relay 23, contacts 32 of relay 33, contacts 34 of relay 22, lower wlnding of relay I1 and the upper winding cf relay 23 120 battery.

Relay I1 in operating opens its contacts I6 thereby interruptlng the clrcult of rotary magnet ROT and closes its contacts 36 thereby extending the impulse circuit to the rotary magnet 31 of the minor cr ringing code selector switch and ab its contacts 38 completes an energizing circuit for relay 39 which can be traced from grond, contacts 24 of relay 4, contacts 26 of relay 22, conductor 40, contacts 38 0f relay I1 and winding of relay 39 to battery. Relay 39 operates in turn operating relay I9 over ii;s cantacts 41 to ground at contacts 24 of relay4. Relay I 9 locks so ground at c0ntacts 24 of relay 4 over its contacts 4I and ab its contacts I8 introduces another break in the previous circuit for the rotary magnet ROT. Relay I9 also closes its contacts 42 thereby operating relay 43, the circuit for which can be traced from ground at contacts 24 0f relay 4, contacts 26 cf relay 22, conductor 40, contacts 42 of relay I9 and winding of relay 43 1:0 battery. Further, relay I9 closeg its contacts 44 and 45 thereby shunting the normally opened contacts 46 and 41 of relay 33 by fing-back condensers 48 and. 49, respectively.

Relay 43 in operating closes a listening circuit between i;he tip =and ring cf the line and the wiper 6 and 9 including condensers 50 and 5I. 'I'he connector is now in the verification position, the operator at the master 0ffice is connected 1:0 the called subscribers llne and is able .to determine if ehe line is in use by li-stening for conversation.

If the line is idle the operator ca.n ring the subscriber5 station B by dialing the final or code digit which Operation 1Sas follows: Relay I fol- 10Ws the impulses of the last series dialed by the operator and when 113 releases for I;he first impulse, lt recloses the circuit for relay II which reoperates in parallel with the rotary magnet 31 of the code switch. Relay II in operating opens its upper contacts thereby opening the listening circuit previously mentloned and closes its contacts 21 thereby connecting ground to the upper winding of relay I1 and the lower winding of relay 23. Relay 23 releases at this time due to the fact that the flux generated in the lower winding opposes and neutralizes the flux in the upper Winzling.

When relay 23 releases, it opens the previously mentioned circuit through its lower winding ab its contactg 35 and opens the circuit through its upper winding and the lower windlng of relay I1 a.t its contacts 30. Relay I1 holds operated, during the pulses, over its contacts 55, contacts 21 of relay II, contacts 26 of relay 22 and contacts 24 of relay 4 to ground.

The code switch MS is moved forward under control cf the rotary magnet and on the fi.rst step actuates the elf-normal switch 56 to close its contactg thereby preparing circuits to operate the release magnet 51 and relay 22.

Relayg 4 and II remain operated during the pulsing.

AI; the and of the last impulse, relay I I releases and recloses at its upper contacts the listening circuit previously referred to. Relay II also opens its contacts 21 thereby deenergizing the upper winding of relay I1 which thereupon releases open at its contacts 38 the circuit for relay 39 which releases. Relay I1 also opens its contacts 36 to disconnect the rotary magnet 31 and, by closing its contacts 53, connects the lower Winding of relay 22 to the third wiper I0 of the connector switch. When relay 39 releases lt opens, at its contacts 4I, the operating circuit for relay I9, but relay I9 remains operated through its contacts 4I to ground a1: contacts Relay39 in releasing also closes its lowermost back contacts thereby connecting ground a.t 0011- tacts 24 of relay 4 through the lower winding of' relay 22 t.o the wiper I0. The test; terminal of the line of subscriber B, which line is special, is noi: multipled to the corresponding terminal in the bank of connector C and therefore it is always at battery potential and relay 22 Will operate Which locks through its upper Winding and contacts 57 and contacts 58 of re1ay 4 t ground. Rela5 22 in closing its contacts 54 nonnects direct ground over conductor 52 m the wiper I5. Further, relay 22 closes its contacts 59 thereby connecting ground over contacts 60 of relay 33 to the ringing machine starb Iead S! which extends to the ringing machine, not shown. Relay 22 further connects relay 62 across: the tip am! ring of the line, opens ab contacts 26 the ground connection .for relay 43 anti ab contacts 63 and 65 connect.s the upper winding of relay 23 to the soca.l1ed pick-up ]ead 66 from the ringing machine which can be traced from battery, upper winding of re1ay 23, contacts 63 of rela.y 22, contacts 32 of rela.y 33, contacts 64 of relay 23 and contacts 65 of re1ay 22 to the pick-up lead 55 which will be grounded ab the ringing machine at the proper point in the ringing cyc1e. Relay 43 releases and reopens the listening circuit. It Will be noted at this time that the line of subscriber B is specia.l in that an auxilia.ry line circuit is connected between the subscriber and the regular subscribers line circuit which auxiliary circuit comprises a relay and sma1l capacity condensers 68 and 69 for the purpose of providing the specia1 sequence call feature which is a characteristic cf the present invention and therefore when relay 39 re1eases a.nd closes its lowermost back contacts 120 complete a. circuit from ground thr0ugh the lower winding of relay 22, 130 the conductor 52 anal. the third wiper of the conneetor relay 61 operates thereby introducing condensers 68 and 69 in the connection between the 1ine of subscriber B and the bank terminals of regular connector C which terminals vve have assumed a.re engaged by the wipers o1 that connector and he1d in fuhat position from the master office. V

'Ihe capa.city of condensers 63 and 59 is very small (of the oraler of .04 microfarad 0r sma.ller, depending on the characteristic of t.he ringing current employed) and therefore they introduce ahigh impedance between the tip and ring bank terminals 0f the two connectors through Which when ringing current is a.pplied to the 1ine of subscriner B by connector NTC only a small portion will be transmitted back to the master oifice through connector C which sma11 current is on1y suflicient to serve a.s an indication to the operator that the cal'led subscriber B is being rung.

When the ringing equipment (not shown) Starts a new cycle of code rings, the pick-up lead 66 is grounded in a well-known manner thereby reoperating relay 23 in a circuit which can be traced from ground on the pick-up lead 66, sontacts 55 of relay 22, contact 54 cf re1ay 23, Contacts 32 of relay 33, contacts 63 of relay 22, :and upper winding of relay 23 of battery. Relay 23 thereupon locks over its contacts 30 to ground at eontacts 24 of relay 4 and closes its contacts 70 and H thereby connecting the segments 12 and 13 of the switch MS 130 the ring am]. tip wipers 8 anti 9. Depending on the position of the switch MS the selected ringing code will be transmitted 130 the called 1ine in series wioh the upper winding of relay 33 which relay will operate when the called subscriber answers. If the last digit dialed is between 1 and 5, the top wiper 14 of switch MS will connect the selected generator lead 170 the top 01 ring wiper 8 and the tip wiper 9 will be connected through the lower Wiper 19-0f switch MS and the upper winding of 1e1ay 33 to battery. If the digit dialed is between 6 and G, the above connection Will be reversed with respect t-0 the wipers.

As before mentioned, a small portion of this ringing current Will flow through t.he condensers 68 and 69 and the connector C to the trunk 'IKl anal thence 130 the operator ab the master ofifice as an audible ringing tone.

When the ca11ed subscriber B answers by removing bis receiver from the switchhook, the rela.y 33 operates in series With the subscribers set in the following circuit: ground on the selected generator 1eaol, segment 72 and Wiper 'a'4, of the switch MS, resistance lamp 75, contacts HI 0f relay 23, conta.cts 76 of relay 33, ring comductor of the connector, wiper 8 and the se lected ba.nk terminals, over the subscribers Iine, through the subscribers set and back to the connector anal wiper 9, 'c0ntacts T. cf relay 33, contacts H 015 relay 23, resistanc e lamp I8, wiper 19 and segment 73 of the switch MS, conductor 84 and upper Winzling of relay 33 to battery. Rela.y 33 operates and. locks over its lower winding to ground at contacts 580f relay 4. Relay 33 also opens its contacts 76 and 17 thereby disconnecting ringing through the code switch MS, by opening its contacts 32, relea.ses relay 23, and at its contacts 46 and 41 closes the 1ine through, and by opening its contacts 60 removes ground from the ringing machine.start lead 6I.

Relay 62 which is bridged across the tip and ring conductors operates and reverses battery and ground back through the selector S2 and trunk TK2 to the operator thereby extinguishing the cord supervisory lamp (not shown) .as an indication that the subscriber has answered. At this time the vertical oif-normal contacts I2 are open and contacts 13 are closed, the contacts of the code switch ofl-normal springs 56 are c1osed and relays l, 4, 33, I9, 62 and22 a.re operated.

When the operator notes from her supervisory la.mp on cord OC2, that the subscriber B has answered, she discomiects the cord from the trunk TK2 whereupon -ohe circuit of relay l is opened which re1ay thereupon releases thereby releasing re1ay 4 which in releasing removes ground ab its contact5 24 from the c0nductor 52 Which is connected to the third wiper I0 of the connector thereby releasing re1ay 61 in the subscribers line and removing the high impedance condensers 68 and 69 between this 1ine and the bank terminals of connector C. The release of re1ay 4 also initiates the release of connector NTC which restores 1:0 normal in readiness f 0r another ca1l. Conversation now proceeds in the usua1 manner ab the end of which, if there are still other calls to be completed, thesubscriber Will restore his receiver but the Operator will not disconnect her cord circuit OCI from the trunk 'IKl thereby still holding the subscribers line in readiness for completion of the next call.

When the operator is ready to establish the next connection, she Will again connect the cord OC2 to the trunk 'I'K2 and transrnit dig*it im-' pulses as befo-re to seize anal ring on the subscribers 1ine. 'I'his process will be repeated as long as the operator has ca1ls to be completed. When the series of calls are completed, the operator will disconnect from trunk TKI whereupon connecdsor C releases in the usual manner and the subscribers 1ine is free for other ca1ls.

If connector N'IC is used merely to verify the busy or idle condition of a regular subscribers 1ine, such as the line at subscriber A, for example, ground will not be connected to couductor 52 and wiper I and. the 1ine will not be made busy 130 other connectors, unless a1- ready busy 01' the final digit is dialed. In this case, however, the operator will not (in most cases) dial the final or code ringing digit and after verification will immediately re1ease the special conneetor.

In case it is desired to make connector NTC inaccessible to the selectors such as S! and S2, busy key 8I can be operated, thereby removing battery from conductor 3 leading back frem re- 1ay 2 so the selector.

What is claimed ist 1. In an automatic telephone exchange, a subscribers line, a first connector switch having access thereto, ancl for making said line busy when connected thereto, a no test connector having access to and adapted 120 seize said line regardless of its busy condition, means in said no test connector for applying ringing current to said 1ine, and meang in said. line responsive t seizure by said no test connector to connect a high impedance between the line and t'he first connector, 120 exclude from the first calling line all but a small amount of the ringing current appliecl to the ca1led 1ine by the no-test connector.

2. In an automatic telephone exchange, a subscribers 1ine, a first connector switch having access thereto, and for making said line busy when connected l;herozzto a 110 test connector having access t0 and adapted to seize said line regardless of its busy condition, means in said no test connector for applying ringing current 130 said line, and means in said 1ine responsive toseizure by said no test connector to connect a sma1l capacity condenser between the 1ine and. the firs1; connector.

3. In an automatic telephone exchange, a subscribers line, a first connector adapted to seize said line only if id1e, and to thereafter make said line busy, a second connector adapted 1:0 seize said 1ine regardless of its busy or idle condition, means for transmitting impu1ses to move said second connector into connection with said line, means in said second connector responsive to the transmission thereto of a predetermined number of impulses after said line has been seized so apply ringing current to said line, and meang associated with said 1ine responsive 170 its seizure by said second connector to interpose a condenser betvveen said 1ine and said first connector.

4. In an automatic telephone system, a subscribers 1ine, a first connector am]. a test counector, each having access 130 said line said test connector being adapted seize said line regardless of its prior seizure by said first connector, means in said test connector responsive to dia1 pulses transmitted thereto subsequent to its seizure of said 1ine 170 cause ringing current to be connected to the line, and means associated with the 1ine responsive to its seizure by said test connector introduce a relatively high impedance between said first connector and ehe 1ine.

5. In an automatic telephone system, first and second connecoors, a telephone 1ine terminating in contact of both connectors said first connector being arranged seize said 1ine only when idle and said second connector being arranged to seize said 1ine regardless 015 its busy or id1e condition, am! means in said line responsive 120 seizure 'thereof by said second connector to interpose a high impedance between said 1ine and the coutacts of 1;he first connector on which said line terminates.

6. In an automatic telephone exchange, a first calling line, a cal1ed 1ine, a firsr, connector switch having access to said called 1ine and controlled over said first calling 1ine, said first connector switch being adapted 120 make said. callecl 1ine busy when connected there*to, a second ca1ling 1ine, a no-test connector controlled over said second calling line and having access to and adapted to seize said called. line regardless cf its busy condition, means in said no-test connector controlled over said second calling line for applying ringing current to said. called. line, and means in said called line responsive to seizure of the line by the no-tesd; connector 130 introduce a high impedance in the connection between said first 001'1- nector and the called line to exclude from the first calling line all but a. small amount 01 the ringing current app1ied to the called 1ine by the no-test connector.

USTAVE A. AI TIDER SONv

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