Патент USA US2110910код для вставки
March 15, 1938. B. A. HENSLER Er AL, 2,110,910 TELEPHONE SYSTEM Filed Aug. 23, 1935 I 4 Sheets-Sheet l _ . Jfrr - March 15, 1938. B. A. HENSLER ET AL 2,110,910 TELEPHONE SYSTEM Filed Aug. 23, 1935 my 4 Sheets-Sheet 2 0,06 I 4T l.,! 5:: __ o Arrx - March 15, 1938. 'B_' A_ HENSLER E1- AL 2,110,910 TELEPHONE SYS TEM Filed, Aug. 25, 1935 4 Sheets-Sheet 3 I [LUJQWMHW 41 > :22 ~§ ' 5 db; -€ if March 15, 4-938. B. A. HENSLER El‘ AL 2,110,910 TELEPHONE SYSTEM Filed Aug. 25, 1935 4 Sheets-Sheet 4 m9 ?zz/wen Amman/r 5464015,? 6%; Xian/4K0 (an-519s 2,110,910 Patented Mar. 15, 1938 ‘UNITED STATES PATENT osrlcs 2,110,910 TELEPHONE SYSTEM and Charles Leonard Bernard‘ Anthony Hensler Peters, London, England, assignors to Sie mens Brothers & Company Limited, London, England Application August 23, 1935, Serial No. 37,484 In Great Britain August 29, 1934 (C1. 179-—27) '7 Claims. This invention relates to telephone systems and more particularly to an arrangement suitable for use in a toll or trunk telephone system wherein each incoming call causes a switching apparatus 5 to set itself to a position indicative of the order of arrival of the call with respect to other calls, the several switching apparatus so set being re leased in the order of arrival of the respective calls and are thereupon caused to search for a 10 free subsequent circuit as these are rendered available. The setting and release of the switch ing apparatus may ‘be controlled by a chain of relays which are operated and released respec tively to control such operations, and the system 15 may be applied to a toll or trunk system wherein calls are set up on demand by operators, i. e. a “demand system”. A system of this type has already been sug gested in which a distributor switch on being set 20 in motion by an incoming call searches for and tests into an outlet to a display panel and if other calls are awaiting’ attention the call vis added to a queue,vthe switches stepping on and so moving the call to the head of the queue as 25 earlier display positions become available. If there are no other calls waiting in a queue and a subsequent circuit is available the distributing switch nevertheless tests into the ?rst display position and is immediately released to search 30 for the subsequent circuit. In the present invention improved call queueing arrangements are provided by arranging that in moving ,a call up the queue the distributing switches do not step but a common switching 35 mechanism associated with the display effects the moving up process .byyproviding for the re lease of the switches in the display positions in ing to the order of thecall with respect to other calls which have failed to be connected to sub sequent circuits. The several switching apparatus are released from such positions in the order of .arrival of the calls as subsequent circuits are 5 rendered available to search for these circuits. According to another feature of the invention switching apparatus taken into use by‘ incoming calls and formed into a queue remains in the same position during the movement of the call to the 10 head of the queue until it is released to search for a subsequent circuit for the extension of the call. The arrangements on which the incoming calls are thus “queued” may consist of a number of relays which are operated seriatim as the calls take a position in the “queue”, and arrangements maybe provided whereby the relays are picked up in a continuous order of rotation irrespective of the actual relative position of a call in a queue. In the application of the invention to a nor mal or semi-automatic system arrangements are provided for giving relief to the demand oper ators, by signalling a further operator or oper ators when more than a certain number of calls 25 are “queued” up. The furtheroperator or oper ators may normally deal with other types of in coming calls. _ In order toeffect a certain economy modi?ca tions to- the system of the prior invention may be 30 made whereby incoming lines are connectable to the switching apparatus already referred to over a searching switch, the switching apparatus hav ing full availability ,to the subsequent connecting 35 circuits. One method of carrying out the invention is This arrangement is especially advantageous described by Way of example in the following description of the. arrangements illustrated in the accompanying drawings, wherein the inven— 40 where the distributing switches are high speed telephone system in which under normal traf?c turn as subsequent ‘circuits become available. motor driven switches as the step by step action in the queue is avoided. A furtheradvantage is gained by placing the display positions at the end of the distributing switch bank so that if a subsequent circuit is available at a time when there are no calls in the queue a searching dis tributing switch is not stopped momentarily in a display position but proceeds directly to the outlet to the subsequent circuit. It is, accordingly one feature of the present invention that switching apparatus taken into use by an incoming call is caused to‘ search for a free subsequent circuit, such as a connecting circuit on an operator’s position and if this search is unsuccessful to assume a position correspond tion is illustrated as applied to‘ a toll or trunk 40 conditions calls are dealt with in the demand basis. It is to be understood that the invention is not con?ned on its application to such systems, but is capable of utilization in any system of call 45 distribution. In Fig. l of the drawings are illustrated an in coming line circuit ILC, and a call distributor circuit DD. There is also illustrated a portion of .an operator's cordless. connecting circuit CC, 50 of which there is provided a number on each po sition, and a portion of an operator’s position circuitOPC, only those circuit elements of these latter circuits necessary to the understanding of the present invention being shown. 55 2 2,110,910 In Fig. 2 is illustrated a lamp display circuit LDC, calling lamps DOP on a demand position and calling lamps OOP “demand” and “incom scribed in detail hereinafter. ing” on a further or omnibus position. by step switches or uniselectors AB and BA. The A fur The lamp display circuit Fig. 2 includes step ther portion of an operator’s position circuit OPC is shown in this figure. only the arc ha! of switch BA is shown, the other An incoming line circuit ICL Fig. 1 includes a step by step switch or uniselector P having arcs of the switch BA being associated with the lamp multiple extending over the arcs ab6—ab8 wipers and arcs pl to p5, driving magnet PDM, The line relay is and the method of connection of the multiple t0 10 and interrupter contacts pdm. designated LA, the test relay TA and a switch ing relay H. The incoming line, junction or trunk is designated JCT. The arcs p2 and 103 are concerned with the connection of the speak 15 tions of the relays CG, CN, and MN will be de ing wires, the arc pl with the testing circuit, the arc M for determining the type of call, i. e. whether it is an ordinary call or one from a coin box. The arc p5 is a homing arc.‘ The distributor circuit includes a motor driven switch or uniselector D with wipers and arcs I, la, . . . 4, 4a, and a latch magnet LM. The cir cuit for and the driving motor of the switch being well known per se is not shown. Each arc of contacts consists of two rows of 25 52 contacts each, a‘ double-ended wiper being adapted to traverse the rows in succession. The arcs are associated in pairs, namely, l and la, 2 and 2a, and so on, and it is arranged that dur ing search when the wipers of an arc have trav ersed the contacts in both rows of the are a switching relay WS is operated to connect the main circuit wire to the wiper of the other are of the pair. The arcs I, and la, and 2, and 2a, are for connecting through the positive and neg ative wires, and the arcs 3, and 3a, and 4, and 4a, are concerned with testing into the connecting circuits. ' The connecting circuits at the several opera tors’ positions are connected to the contacts on 40 the several arcs. To the ?nal eleven contacts in the second set of contacts of are 401. are con nected the wires 1d, and OF which lead to the lamp display circuit Fig. 2. Connections are also made from certain of the ten contacts in arcs 3a and 2a corresponding to the contacts of arc to to which the wires ld are connected, the purpose of these connections being explained fully hereinafter. The connecting circuits are commoned over‘ the arcs of the distributor switches of the several distributor circuits, the connecting circuits including those on demand positions, omnibus and other relief positions. There is provided a line relay L, a releasing relay B, a testing relay T, and switching relief relays 55 S and SS respectively. The relay TCO is pro vided for determining the origin of a call, e. g. whether it has been originated over an ordinary line or a call box line. The relay RR is a ringing relay for applying a ringing current back to a calling party. The functions of relay D8 will be best understood from the subsequent detailed description, but generally they are to modify the testing circuit for testing in to the connecting circuits after a call has been released from asso ciation with the lamp display circuit. . The portion of the connecting circuit illus trated in Fig. 1 shows contacts SPKI, SPKZ and SPKS of a speaking key and relays SK,.SL, BA, and AS this being the order in which the relays are operated. The functions of the relays Will be best understood from the following detailed description. The elements of the operator’s cir cuit CPC Figs. 1 and 2 include contacts CA! and CA2 of a call answering key, and contacts. RA 75 (Fig. l) of a release answering key. 'The func arcs abl . . . abB of switch AB are shown, but C1 the arcs will be readily understood from the con 10 sideration of the wiring of arcs ab6-ab8. The multiple wiring from the arcs ab6—ba8 extends to the display lamps l—il on the demand opera tors’ positions DOP, and it will be seen that the multiple wires over the arcs are slipped at each are so that the ?rst contact of the arc abB is connected to the wire leading to display lamp l, the ?rst contact in the arc ab‘! is connected to the wire leading to display lamp 2 whilst the multiple wire to lamp l appears at the second 20 contact in the arc and so on over the remaining arcs. sition lamps The The “demand” lamps on the omnibus po OOP are connected in parallel with the on the demand position DOP. are ab'l is concerned with the stepping and 25 homing of the switch AB, and the object of the arcs c122 and ha! is to ensure that the switches AB and BA are always in alignment, the relay SY controlling the stepping of the switch BA to bring it into alignment with switch AB. 30 The wires Zdl——ill from the arc 4a of the dis tributor switch are connected seriatim to the relays A—J, contacts of the relays A—J being connected seriatim to the wipers of arcs ab6— 12118. 35 The functions of the various relays shown will be best understood from the subsequent detailed description. An omnibus position normally deals with in coming calls signalled on the “incoming” lamps 40 quite independently of the traffic on the demand operator’s position "unless excessive congestion exists on the latter, whereupon the “incoming” lamps on a particular omnibus position or posi tions are disconnected and the “demand” lamps connected up by the operation of relay AA. Such a condition is indicated to a supervisory operator over the lead SP. The general operations of the arrangements il lustrated are as follows: Upon a call being made over a junction or line JCT the switch P in ILC searches for and tests into a free distributor cir cuit DD. ' Normally one or more demand operators will have a position connecting circuit assigned which is brought about by throwing the speaking key SPK associated with the connecting circuit and the call answering key CA in the position circuit. On the seizing of a distributor circuit DD the switch D is caused to hunt for an assigned con necting circuit, and when such is found the call ing party is switched through to the operator who then sets up the desired connection. If the call had originated at a call box or over a line demanding special treatment, the operator would receive a tone on the origination and switching through of the call, and then cause the conversational connection to be set up by throwing a key (not shown) in the connecting cir cuit which applies earth to the negative wire. 70 The operator controls the release of the call and can release it by throwing either the key REL in the connecting circuit CC or the key RA in the position circuit OPC. In the event of a call being made whilst a. con 75 2,110,910? necting circuit is not assigned, the distributor switch hunts until afreecircuit over one- of the display leads Id is found and tests into this to cause a calling lamp to light, and busies the cir cuit against other searching distributor switches which will test into the other displaycircuit leads. The calls are thus ‘caused to be queued up in the order of origination, and when the display circuit is fu1l,‘i. e. ten calls arestored," other searching distributor switches test into an over ?ow circuit over the lead OF to which" the call meter CM is connected at this time to indicate the number of calls so» held. An operator causesthe release of the call from‘ 15 the head of the queue by simply assigning a con necting circuit, the distributor switch associated with this call then being released ‘from the dis play to search for the assigned connecting cir cuit whereupon the switches AB and BA step 20 tomove up, in effect, the remaining calls in the queue one in the order ‘of their priority of call ing. Calls held on the over?ow circuit are re leased and one of these tests into the lamp cir cuit just freed which now is so connected as to 25 place the call at the lowest position in the queue, whilst the other calls are again connected to the over?ow circuit. If a call is held in the display circuit for more the wiper pl meets a free outlet relay TA op erates from the battery ‘potential, over are pl,‘ and contacts ms‘; The driving circuit for the magnet PDM isopened and an obvious circuit is closed for the right-hand ‘coil of relay H at contacts tal. Relay H operates and at contacts hl locks itself temporarily over its left hand coil to earth over contacts lal, and at contacts hZ prepares a point in a locking and busying circuit 10 over which it locks on the release of relay LA. At contacts 71.3 a furtherpoint in the driving circuit for magnet PDMis opened. Contacts 116 prepare a circuit for the operation of relay TCO over its coil (I) and arcs p5 and p4, but however as the line calling is an ordinary line no con 15 nectionv is made to the contact in are 124. At contacts M and- n5 relay LA is disconnected, relay LA being slow to release and does not re lease immediately and the incoming loop is ex tended to relay L in DD over contacts rrl and 20 W2 and relay L operates. A circuit is closed for relay B from earth over contacts 885 and ll and relay B operates. Contacts Z2 prepare a holding . circuit for relays SS and DS, and, contacts 13 prepare a holding circuit over the arc pl for 25' holding the circuit ILC. Contacts l4 prepare a supervisory circuit for the supervision of the call. Upon the operation of relay B an earth is ap than a predetermined period a ‘timing circuit plied over contacts M and are pl to short cir 30 30 ‘i‘comes into operation to cause calling. lamps to cuit relay TA, hold relay H, and busy the outlet light on a relief position (over the lead AL Fig.‘ at the preceding selector if such has been em 2) so that a relief operator is signalled. Similar ployed. Relay LA releases shortly after relay B ly, in the example described, a relief operator is and-disconnects relay TA. Contacts 122 signalled if the number of calls in the queue ' operates connect a ‘ringing signal tone from lead RS and .areaches seven, the relief operator being held un over contacts as? to the positive wire and thence til the number falls below six; If the number to the calling party. Contacts b3 close a point of calls in the queue reaches nine then the “in in the circuit for the test relay T. coming” lamps associated with a particular 10m A circuit is closed from earth over contacts nibus operator’s'position are disconnected, and the tl, sl, i006, b4, latch magnet LM to battery and 40 “demand” lamps are connected in parallel with and the latch magnet operates closing con the lamps on the demand operator’s position earth, tacts whereby-the circuit of a driving motor is so that the omnibus operator'can assist the de closed, the motor in rotating driving the wipers mand operator. The omnibus position is dis the distributor switch in known manner. connected when the number of calls in the queue of Under normal operating conditions, i. e. when 45 falls below eight. calls can be answered on demand, a connecting The circuit arrangements illustrated will now a circuit, a portion of which is shown in the be described in detail. Assuming that a call is made over an ordinary rectangle CC, will be assigned on one or more oper~ ators’ positions, the assignment of a connecting line, i. e. a:line from an ordinary local subscrib circuit necessitating the throwing of a speaking 50 er or over a local selector, then a loop'will be 50 applied tolthe positive and negative wires JCT key SPK associated with the connecting circuit CC and the connect answer key CA in the oper resulting in the operation of relay LA over con ator’s circuit OPC‘. On the closing of the con tacts ~h4 and n5. At contacts lal earth isuap plied tothe P wire-to busy the line at preceding tacts SPKZ a circuit is closed from battery over selectors, if the call has been made over a selec-r a resistance in the operator’s position circuit OPC, 55 the coils of relay SK in series over the contacts tor, and at contacts Za3 the test relay TA is con nected to the wiper of the test are p1. A circuit SPKZ, contacts sZl to earth and relay SK oper is closed from earth over contacts tal, M, 1112, ates and at its contacts skl short circuits its left pdm to magnet PDM to battery and magnet PDM hand coil. A circuit is closed from earth over energizes and opens the contacts pdm whereby the left hand coil of relay MN in OPC, contacts‘ 60 60 bal, SPK3, s7c2, relay SL to battery and earth and ‘ the above circuit 'is broken and the magnet de energized and the wipers of the switch are stepped relays MN and SL operate in series. Contacts .92! hold relay SK over its‘ right hand coil independi on to the first‘ outlet in their arcs. ently of contacts SPKL ‘A battery potential is If the outlet is busy the relevant contact in arc applied to the contact in the are 4 or M of the dis 65 ~.~.pl will be marked busy‘by an earth applied from tributor D corresponding to the connecting cir the distributor circuit DD and as a consequence relay TA'will be short circuited and ‘prevented cuit, over relay BA, key contacts REL, contacts from operating and therefore when‘ the contacts s13, 8M, key contacts RA and CAl in. OPC, and pdm close 'on' the de-energization of themagnet contacts s12. Assuming that an assigned connecting circuit PDM the circuit for the magnet isxagain closed and the wipers stepped on to‘the next outlet in exists in the arcs l, 2, 3, 4 of the distributor switch D then the wipers of the switch are driven until the manner before described. A free outlet willv be marked ‘by a ‘battery po-. the wiper of are 4 meets the contact marked by’ battery over the relay BA, whereupon a circuit is tent-ial overv contacts (m2, ssG and bl in the'dis closed from earthscontact enl, (also shownin 1 . tributor. circuit DD?zandx-‘as : a,consequence when 75 4 2,110,910 ’ Fig. 2) contacts 120.3, arc and Wiper 3, contacts wsd, s34, ds3, b3, recti?er 7', both coils of relay T relay ASv in CC, the relay releasing ‘to light the supervisory lamp ASL in front of the operator in series, contacts ws5 to the marked contacts and relay T operates and at contacts tl opens the circuit for the latch magnet LM, whereby the wipers of the switch D are brought to rest, short at contacts cs2. by operating the release key RA in OPC or REL in CC and thereby release relay T which at con circuits the upper coil of relay T, and relays T and BA operate in series. The lower coil of relay tacts ti short circuits relay S. On the release of relays L and S the earth is T is of low resistance and the earth over it busies removed from the private Wire to the‘ circuit ILC, and the preceding selector, and relay H is re 10 10 the outlet to the connecting circuit against other searching distributors by preventing their T relays from operating. At contacts ba2 relay BA locks itself independently of contacts 812 and CAI, and at contacts bal disconnects the left hand coil of 15 relay MN and connects in its place the right hand coil of this relay in series with relay CG. Relays SL and MN hold and relay CG operates. At contacts 12113 a circuit is prepared for relay AS but this relay cannot operate in series with the upper coil of relay T owing to the disposition of the recti?er 1'. Contacts had close the circuit of the supervisory lamp ASL in front of the opera tor. When relay T operates and contacts tl change 25 over, a short circuit is removed from relay S, and this relay operates in series with the latch magnet LM, the latch magnet however not being energized suiliciently in this series circuit to withdraw the latch. Relay S at contacts sl locks itself independ ently of the latch magnet and at contacts s2 and s3 prepares to extend the positive and negative conductors to the connecting circuit CC. Con tacts s4 prepare a point in a circuit for relay AS in CC. Contacts 85 do not concern us at present. A circuit is closed from earth over the 0115 nor mal contacts onl, which as the switch is off nor mal are closed, contacts s5, coil (I) of relay DS, relay SS, resistance to battery and earth, and relays SS and DS operate. ' At contacts es! and over contacts Z2 a locking circuit is closed for relays SS and DS independ ently of the contacts onl and .95. Contacts ssZ and $33 prepare further points in the positive and negative wires to the connecting circuit CC. Contacts 334 connect earth over Z4 and s4, and over 10.94, ba3, relay AS to battery and relay AS operates to disconnect and extinguish the super visory lamp ASL at contacts 6052. A locking cir cuit is closed for relay AS over contacts as! and SPKl to prevent relay AS being released whilst the speak key is operated. At contacts ss5 an obvious circuit is closed for relay TCO and the circuit for relay B is opened. Contacts $85 per form no function at this stage. Relay TCO oper ates. When relay B releases after its slow releasing period the circuit ILC, and the preceding selector if such has been used, are held over contacts bl, $86, and s6 and Z3 in parallel. On the operation of relay TCO contacts i002 and i003 complete the connection of the positive and negative wires to the connecting circuit. The other contacts of relay TCO will be referred to ' hereinafter. The operator may now converse with the call ing party and completes the connection to the wanted party. The speak key SPK in CC and the key CA in OPC are restored and relays CG, 70 MN, and SL are released at SPK3. Relay SK is released at contacts sZI, and relays BA and T are held over the contacts ba2 and s13. When the calling party clears the line, or flashes the operator to call her attention, relay L 75 releases and at contacts 14 opens the circuit for The operator may release the distributor circuit leased which at contacts 716 closes an obvious homing circuit for the switch P. At contacts 35 the original circuit for relays SS and DS(I) is opened, but these relays remain held over onl, Z2, and ssl, and a homing circuit for the switch D is closed over onl, 85, b4, LM to battery and the switch commences to home and when the home position is reached contacts on! open dis connecting the circuits for the magnet LM and relays SS and DS. Relays SS and DS release, 20 and relay SS releases relay TCO. The testing cir cuit for the switch P is held open at contacts 0212 until the switch reaches home. The circuits are now at normal in preparation for dealing with further calls. 25 If the circuit ILC terminates a call box line the connection from the arc M to the coil (I) of re lay TCO over contacts tool! will be completed, and it will be seen that on the operation of relay SS relay TCO will be prevented from operating 30 over this coil as it is short circuited. As a conse quence: a tone will be given to the operator over contacts i002 and the positive conductor and the operator on observing such tone throws a key (not shown) in the connecting circuit whereby an 35 earth is applied to the negative wire and relay TCO is operated over its coil (II) and contacts tcol3, ss3, and s3. Relay TCO operates and performs the func tions before described. In the event of the assigned connecting cir cuit being connected to the arcs la, 2a, 3a and 4a of the switch D, then when the wipers meet the last contacts in their arcs a circuit is completed from earth last contact in arc 3, contacts ws4, ssll, 45 (183, 123, recti?er r, relay T, ws5, last contact in arc 4, (coil (1) of relay WS to battery and relays T and WS operate. At contacts wsl relay WS locks itself over its coil (II) to contacts on]. At contacts 1082-1085 the arcs I, 2, 3, and 4 are dis 50 connected and'arcs I 11, 2a, 3a, and 4a are connect ed up. Contacts ws6 prepare to lock relay TCO over its coil (I). The circuit of relayT is opened when contacts ws5 change. over and relay T re leases. Relay T is operated only for a very short 55 time which may be insu?icient to allow relay S to operate. Even so, if relay S does operate relay SS and DS cannot operate as they are short cir cuited at‘ this time by the connection of earth over contacts 882, $2, ws2 and are I a, the earth to 60 the other side of the relays being derived over contacts on! and .95. The switch now searches over the second half of its arcs for the assigned connecting circuit and when this is found the operations as before 65 described take place. If it is required to ring a calling subscriber who has left the line the operator throws a ringing key (not shown) in the connecting circuit where by a battery potential is applied to the positive 70 wire which operates relay RR. At contacts rrl and 7‘7‘2 ringing current over the leads R and RRS is applied to the calling line. In the event of a connecting circuit not being assigned such as will happen at busy periods the 75 ‘2,110,910 distributor switch D drives‘until the wiper of arc ' 4a meets the wires ld leading to the lamp display circuit Fig. 2. Assuming‘ that the display is en tirely free then when the wipe-rs of arc 4a. meets the contact connected to the lead Zdl a circuit is closed from earth over~contacts'tco1, arci3a,'con tacts wsd, s34, (Z33, b3, recti?er 1*,relayT, contacts It will-‘be seen that providing the‘ switches AB and BA‘ are- standing in correspondingpositions a circuit is closed over arcs ab2 :and bal for relay SY which at contacts syl opens the self drive circuit for the magnet BADM. , Upon an operator assigning a connecting cir » cuit by throwing the speaking key SPK associ ated with the connecting circuit and by throw ws5, arc M, leadv Zdl, relay A (Fig. 2),‘arc a193, ring the connect answer key CA.v in the position contacts col, st3, arc 11b4, resistance to battery ~ circuit OPC, a circuit is completed from earth, Relay T on opera contacts CA2, relay CN, contacts cgl, mnl,‘ tion allowsS- to'operate at contacts tl and locks over (relay MN being operated at this time in series itself in series with relay A independently of con relay SL Fig. 1), e112, ac?, stl, lower coil tacts tco'l. Relay SS and coil (I) of relay D‘Sare “with of relay ST to battery and relay ST operates and short circuited over contacts s32, 82, we! and are locks itself over its upper coil and contacts st2,; L15 15 la. so that they cannot operate. and ac5. When contacts stl are in the mid posi A circuit is closed from earth over contacts ss3, tion relay CN which is a very fast operating relay s3; ws3, arc 2a, coil (II) of relay‘TCO to battery :operates vin series with the resistance and closes .4 and relay 'I‘CO operates and looks over contacts a circuit in series’with itself for-coil (II) of relay 'wsl and tool. At contacts i005 a circuit is closed CG over contacts c'nl but this coil is shunted for, 20 for relay DS over its coil (II) andicontacts ss5 the moment. Relay CG operates when contacts and relay DS operates Relay B is‘held inde pendently-of contacts ll. at contacts (152 so that stl change over and at contacts cgl‘ opens a relay B cannot be released in the-event of the point in the operating circuit for the lower coil of 10 and relays T and A operate. calling party leaving the line. .25 ¢ , 'When relay A, Fig. 2, operates it closes a locking circuit for itself at contacts al independently of " the arcs'ab3 and M24, and at contacts a2 prepares a circuit for relay B. Contacts 413 prepare a point in the circuit to'the overflowv lead‘ OF, ‘but this relay ST; > - A further point in the operating circuit for the; 25 lower coil of relay ST’ is opened at contacts stl and this coil, beingjshunted, gives the relayslow releasing characteristics. ~ ' r 7 Thus the signal transmitted from the operator’s circuit OPC‘ to the relay ST is of very short dura-.: ber of calls are‘storedlon the display. Contacts tion and occupies only‘ a part of the movement a4 and all close in parallel and'completea cir v’ of the contacts stl, this minimizing the chances of the simultaneous connection of two» operators’ cuit over arc abt for the calling lamp I on the de 30 circuit is not completed until a» maximum num mand operator’s position DOP. Relay AC oper 35 ates in parallel with lamp I and over contacts 3% and looks over contacts-ac! independently ofthe positions to“ the'display circuit. A circuit is closed’ from earth over-contacts lsyl, ac3, std, magnet 'BADM' to negativeiand'the former contacts. Contacts (102. prepare to con - magnet energizes. 'A circuit is‘also closed from nect an earth to the wire ld leading to the dis ,earth ' over- contacts (104, stE, arc abl, magnet tributor circuit DDeto release the relay T thereof . ABDM to battery'and this magnet energizes. I At ‘40 when the call is released from theidisplay. C‘on ‘contacts stB a point in the original operating cir 40 tacts a.c3 prepare anjenergizing- circuit for the cuit for relay AC is opened, but thisgrelay holds Ymagnet BADM,»and contacts (104 prepare an en > over contacts acl. Anearth is extended over contacts (102, $153, col, ergizing circuit for the magnet ABDM. Contacts ' ac5 prepare a circuit for the upper coil of‘relay arc ab3, to relay A short circuiting this relay and 45 ST and. contacts act prepare a circuit-for the also relay T in the distributor-circuit both of . which relays release. lower coil of this relay. 'Relay EN also operates Upon the relapse of relay T in the distributor over its left hand coil in parallel with lamp I. At circuit relay S is short circuited at contacts ti contacts e112 a further point is prepared in the and relay S releases.‘ A circuit is ‘thereupon ' circuit for relay ST. At contacts enl (see CC Fig. 1) the earth for the normal testing operations of closed from earth over contacts onl, s5; toot, b4, all connecting’ circuits associated with the dis tributor switches‘ so that distributors searching to close the circuit of the driving motor and the wipers of the switch are advanced to the home 50 .50 the relays .T in' the distributors is removed from ‘ magnet LM to battery and the magnet energizes position where the contacts onl open releasing are prevented from testing in~whilst callsare 'relay WS which in turn releases relay TCO at: 55 contacts 1086. Upon the relapse of relay TCO the ‘waiting on the display lamps. The distributor switches D and their associated circuit for the magnet LM is completed over circuits over which succeeding calls are made contacts tl, sl, tco? and b4 and the wipers are driven in search of the ‘assigned connecting are caused. to test into and associate themselves circuit, and when this is found relay T'operates' with the relays B—J which operate in succession 60 as calls arrive and at their respective contacts-4 from earth over contacts tco'l, ds3, b3, recti?er for a connecting circuit ‘in response to fresh calls R, relay T, contacts ws5 and over arc 4 or 4a. Relay T on operation allows relay S to operate switch BA, that is, provided meanwhile no calls [and the operations as before ‘described take .65 have been answered. When the maximum num place. When relay A in the lamp display circuit Fig. 2 ber of calls are queued up on the display lamps, releases the circuit for the lamp DOPI and for . and therefore relay J operated, further search ing switches test into the lead OF which extends :relay AC is opened at contacts at and a5, and to the callmeter CM over contacts 9'3 and arcv (1125, relay AC releases. At contacts act and act! the . and 5 close the circuits for the lamps DOP2--O over the arcs ab'l—~ab8 and similar arcs of the the call meter indicating the number of calls so connected. The resistance in the connection from each distributor circuit to the lead OF is individual to the distributor circuit so that the relays T of other searching distributors are not affected and can freely test into the lead OF. circuits for the magnets vBADM and. ABDM are - opened and the wipers of the switches BA and AB are stepped. The short circuit is removed from relay A at contacts ac2. The holding cir cuit for the upper coil of relay ST is opened at contacts ac5 but relay ST does not release -im—,; 6 2,110,910 mediately as it is rendered slow to release by virtue of its shunted lower coil so that the circuit to the operator’s circuit is maintained open at contacts stl for a short period to enable the ap paratus in the display circuit to function cor rectly. As the call of the ?rst order of priority has been answered it is necessary that the other calls that are queued up on the display lamps should all 10 be moved up one in their order of priority. This is accomplished over the arcs ab?, ab‘! etc. It will be seen that when the switch AB steps a circuit is closed over contacts bl! and b5, second contact of arc ab‘! to lamp DOPI and to relay 15 AC in parallel therewith when relay ST releases. Thus the call of the second order of priority is moved into the ?rst place, whilst the third call lighting the lamp DOP3 is moved into second place and associated with the lamp DOP2 and so 20 on. When the switch AB steps the circuit to the lead OF is broken at arc ab5 and the wipers are stepped on to the contacts connected to the con tacts a3. Thus all of the T relays in the dis 25 tributors held over the lead OF are released and connected at contacts call to aa20. Thus an omnibus operator is called to assist the demand operators and may answer the calls in an eX actly similar (manner to that previously described, the omnibus operator having connecting circuits associated with the demand distributor circuits. At contacts aaZl a circuit is closed over the wire SP for a supervisory device to indicate the state of congestion to a supervisory operator. When the number of queued calls fall below eight relay OM is released releasing relay AA, and the demand calling lamps on the omnibus position are disconnected and the incoming lamps re connected. If however nine or more incoming calls are queued up on the incoming calling lamp display on the omnibus position a relay, say OOM sim ilar to relay OM in LDC associated with that display will be operated and contacts oomZ will be open. Thus it will not be possible to inter 20 rupt the incoming 'tra?ic to the omnibus oper ator’s position until somerof the incoming traffic has been dealt with. 7 In order that calls are'not held beyond a cer tain period during the time that insu?icient calls' 25 the vassociated switches search for the free dis are in the queue to signal the omnibus position play lamp circuits, one of the distributors seiz ‘there is associated with each of the relays A—J ing the circuit of the freed relay A whilst the ofvthe lamp display circuit LDC two relays, such unsuccessful switches continue in operation un til they again test into the lead OF over contacts 113, arc'ab5, and the’ call meter CM. When the operator has dealt with the call the key CA is restored releasing relays CN and CG and that portion of the position circuit shown in 35 Fig. 2 is restored to normal. It will be seen that under normal operating conditions when no calls exist on the calling lamps, and relay EN is normal, relay CO is oper ated on the operation of the key CA and at con 40 tacts col opens a point in the test circuit into the display circuit. 7 ' When seven calls exist on the calling lamps DOP a circuit is closed for relay ON over its right hand coil in parallel with the lamp 1 and relay ON operates and locks over itsileft hand coil in parallel with- lamp 6. An earth is con nected over contacts 001122, 0712, to the lead AL leading to the lamp display circuits on one or more relief or omnibus positions whereby the 50 operators‘ on these positions are signalled to assist in the answering of the calls. Relay ON is released when the number of calls falls below six. In the event of nine calls becoming queued up 55 a circuit is closed for the right hand coil of relay OM in parallel with the calling lamp 9 and relay OM operates and closes at contact cm! a circuit for its left hand coil' in parallel with lamp 8. 60 ' At contacts omZ a circuit is closed for relay AA at one_ or more further relief or omnibus positions, the operating earth being derived over contacts oomZ which are contacts of a relay sim ilar to relay OM but which is associated with the 65 display lamps on an omnibus position, so that if more than a certain number of incoming calls are signalled in this position the omnibus posi tions cannot be called to assist in handling the traffic on the demand position. ' Relay AA operates and at contacts cal to aal? connects the demand display lamps on the omni bus position OOP in parallel with the display ‘lamps on the demand position so that the, corre sponding lamps‘ light. The circuits for the in 75 coming lamps on the omnibus position are dis as relays SA and?ZA, only those relays asso ciated with the relay A however being shown, the 30 other pairs being connected and operated in an ' identical manner. ' Two contacts a6 and a1 control the operation of the relays SA and ZA, and as all of the other relays B—J are provided with similar contacts, which however are not shown, the relays are designated as having seven contacts. ' ‘ Earthed impulses are periodically and alter~ nately delivered over the leads S and Z. Assuming that a call is held on relay A over a period during which the impulses, are delivered 40 to the leads S and Z,’then, when the impulse is given over the lead S a circuit is closed for the right hand coil of relay SA over contacts 2112 and a6, and relay SA operates, and looks over its left hand coil, contacts a'!, left hand coil of relay ZA, and contacts sal. Relay ZA will not operate in this circuit. When the impulse occurs over lead Z relay ZA operates over its right hand and contacts 8112. At contacts zal a locking cuit is closed for relay ZA over its left hand and the left’ hand coil of relay SA is short the coil cir coil 50 cir cuited making the relay slightly slow to release. The circuit for the right hand coil of relay SA is opened at contacts zaZ and after a short period relay SA releases. A circuit is closed for relay DL at contacts 203, and relay DL operates. At contacts all! a circuit is closed for relay AA, and at contacts (H2 an earth is applied to the lead AL to operate similar relays such as AA on the relief positions. The switches AB and BA are stepped in the manner described to alter the position of the calls in the queue until the switch AB is stepped to the twenty ?rst contact whereupon a circuit is closed from earth over contacts abdm, arc and wiper ab‘! magnet ABDM to battery and the switch AB is stepped to its normal position under theccontrol of its interrupter contacts. Imme diately the wiper of are (1112 steps out of align ment with the wiper of arc bal relay SY releases and at contacts syl closes the circuit for magnet BADM and the switch BA homes whereupon re lay SY operates and opens the homing circuit for magnet BADM at contacts syl. 75 2,110,910 The common relays NA in the lamp display cir~ cuits are night alarm relays adapted to operate when any lamp is alight to operate an alarm. We claim: 1. In a telephone system, a group of connec tive circuits, a group of hunting switches of the homing type having access to said circuits as ?rst choice, a group of over?ow circuits accessi ble to said switches as second choice, whereby 10 switches operated at times when no connective circuits are available will connect with successive over?ow circuits, and controlling means operat ing on switches connected with over?ow circuits in the order in which the connections are estab lished for releasing a connected switch and for causing it to rehunt over said connective circuits each time a connective circuit becomes idle. 2. In a telephone system, a group of individual over?ow circuits, automatic switches having ac cess to said circuits if no regular outlets are available, means for making each individual over ?ow circuit busy when seized, a common over?ow circuit which is not made busy when seized and which may therefore be occupied by a number of iv 111 switches when the individual over?ow circuits are all busy, means for successively releasing the switches connected to individual over?ow cir cuits, and means effective whenever an individual over?ow circuit is freed for causing the switches connected to the common over?ow circuit to hunt for the free individual over?ow circuit. 3. In a telephone system, a group of automatic switches, a group of connective circuits accessible to said switches,v a group of individual over?ow circuits accessible to said switches only if none of said connective circuits are available, a com mon over?ow circuit accessible to said switches only if all said individual over?ow circuits are busy, means operative at a time when one or more 40 switches are connected to the common over?ow circuit and responsive to a connective circuit be coming available for releasing one switch con nected to an individual over?ow circuit and for causing it to hunt for the available connective cir r cult, and means for releasing all switches con nected to said common over?ow circuit and for causing them to hunt for the free individual over ?ow circuit. 4. In a telephone system, a group of over?ow 50 circuits, at corresponding group of lamps, switches 7 having access to said circuits, means for busying each circuit when seized and for lighting the cor responding lamp, means for releasing switches from over?ow circuits one at a time, and means intervening between the said circuits and lamps and operative every time a switch is released for changing the relation between said circuits and said lamps to associate each circuit with a dif ferent lamp. 5. In a telephone system, a group of relays numbered consecutively, a group of lamps cor respondingly numbered, means for energizing said relays in the order of their numbering to light the corresponding lamps, means for releas ing said'relays in the same order, and means op- ;; erative each time a relay is released for shifting each relay into association with the next lower numbered lamp. 6. In a telephone system, a plurality of con nective circuits common to a plurality of opera it) tors, automatic switches having access to said cir~ cuits, circuit arrangements such that the con nective circuits are normally unselectable by said switches and are individually made available for selection when the operator handling the calls * is ready to take a call, over?ow circuits accessible to said switches at times when no connective cir cuits are available for selection, and means re sponsive to a predetermined number of over?ow circuits becoming occupied for automatically sig nalling another one of said operators to assist in handling the calls. '7. In a telephone system, a plurality of connec tive circuits common to a plurality of operators, automatic switches having access to said cir- .2.) cuits, circuit arrangements such that the con nective circuits are normally unselectable by said switches and are individually made available for selection when the operator handling the calls is ready to take a call, over?ow circuits accessible to said switches at times when no connective cir cuits are available for selection, means for suc cessively releasing switches from over?ow cir cuits to permit them to hunt for connective cir cuits as the latter are made available by the op erator, and means for automatically signalling another operator if a switch remains connected to an over?ow circuit for a predetermined time. BERNARD ANTHONY HENSLER. CHARLES LEONARD PETERS.