US2454809A - Telephone system utilizing register controlled final selector switches - Google Patents

Description

Nov. so, 1948,

J. KRUITHQE ETAL 2,454,80 9 TELEPHONE SYSTEM UTILIZING REGISTER CONTROLLED FINAL SELECTOR SWITCHES Filed Jan. 16, 1943 6 Sheets-Sheet 1 INVENTOR5 JACOB KRU/THUF mn/sms kozMn MflRT/NUS 051v HERTOIi ATTORNEY Nov. 30, 1948. J. KRUITHOF ETAL I 2,454,809-

. TELEPHONE SYSTEM UTILIZING REGISTER CONTROLLED FINAL SELECTOR SWITCHES Filed Jan. 16, 1-943 6 Sheets-Sheet 2 m NM um S ATTORNEY Nov. 30, 1948. J. KRUITHOF ETAL 2,454,809

TELEPHONE SYSTEM UTILIZING REGISTER CONTROLLED FINAL SELECTOR SWITCHES Filed Jan. 16, 1943 e'sheet-sneet 3 E s k i q (i E %R 60! 7? f? I INVENTORS \IHCOB KPU/ THOF L flD/SLHS KOZMH MEET/NUS DEN HERTOG Nov. 30, 1948..

Filed Jan. 16, 1943 J. KRUITHOF ETAL TELEPHONE SYSTEM UTILIZING REGISTER CONTROLLED FINAL SELECTOR SWITCHES 6 Sheets-Sheet 4 l N V ENTOR 6 .mcoe KRU/THOF LIFO/SL195 [(OZMH A'ITORN EY I Nov. 30, 1948. I J. KRUlTHbF ET AL 2,454,809

TELEPHONE SYSTEM UTILIZING REGISTER CONTROLLED FINAL SELECTOR SWITCHES Filed Jan." '16, 1943' s sheets-sheet 5 in I M w sfl 1 1 i fi i? QI v -o I "I" T & k k 61*- N w v 'L fi-OH'|U 5 S m H a La lib BY 1 4 v l A ORNEY 6 Sheets-Sheet 6 STER J. KRUITHOF my.

TELEPHONE SYSTEM UTILIZING REGI CONTROLLED FINAL SELECTOR SWITCHES Nov. 30,

Filed Jan. 16. 1943 ATTORNEY 5 m M H m n w W H N Patented Nov. 30, 1948 TELEPHONE SYSTEM UTILIZING REGIS- TER- CONTROLLED FINAL. SELECTOR SWITCHES Jacob.-Kruithof,. Ladislas. Kozma, and Martinus den H'ertog, Antwerp, Belgium, assignors to International Standard Electric Corporation, New York,gN. Y1, a corporation of Delaware ApplicationuJa-nuar-y 16, 1943-, Serial No. 472,624 In the Netherlands June 10, 1941.

Section 1, Public Law 690, August 8, 1946- Patent expires June 10, 1961 22 Claims; 1.

The invention relates to-new and useful improvements in automatic or semi automatic: telephone systems or similar systems in which: final selectors are used.

In the copending applications, Serial No. 472,- 623, filedJanuary 16; 1943; by Simon; Kruithof, and den Hertog, now Patent No. 2,424.585dated July 29', 1947 and Serial No. 473,278, filedJanuary 22, 1943, now Patent No. 2,452,578; granted November 2, 1948, by Kruithof, Kozmav and den Hertog, inventions are describedwhich are applicable to telephone system and more particularly to group selectors used in such systems.

As is the case with the types of group selectors discussed in the last-mentioned application, various types of final selectors also have characteristic disadvantages which it is the objectof'the present invention to overcome. The-- embodiment of the present invention inautomatic telephone systems insures the following advantages in the final selectors thereof:

(a) Simple, one-motion construction;

(1)) Possibility of forming-P; B. X groups witha number of outlets larger-than the number existing in one group or level of the'terminalbank, without introducing any extra complications;

(0) No marker switch-needbe provided-inassociation with or individually to eaclr final" selector;

(01) Absence of common controlcircuits;

(e) Absence of a marking multiplecommonto a plurality of-final selectors per group, on'which' only one selection could be made at a time, whereby splitting of this multipleamong different final selectors of each group isavoided;

Absence of artificial load on final selectors when a common control circuit is occupied by one of them;

(9) Absence of impulsing during any part of the selecting operation, doing away with the customary means for counting impulses at the register controller or at the selector stage;

(h) High speed operation insuredby the kind of signaling system used.

According to the present invention, discriminating signals are employed for setting the final selector on the first terminal of a group or level,- or alternatively, on the last terminal preceding such a group or level,. whereby the first or last of'these terminalsisselectedunder. the control of a register controllen This is. accomplished.

lector.

0nd selection is made to selecta predetermined terminal in a group. or level, durin which all the signals sent from the terminals exercise an influence. on the register.

The final selector switchmay be caused to-hunt over a group of lines commonly knownasP. B; X group of' lines if the first of swine group of lines is-found to be busy. Arrangements are disclosed for terminating the .P. B. X hunting. when the last. lineof the P. B, X group is reached.

Certain lines in a P B. X group could, accord.- ing to thepresent invention, be individually: selected without starting the final selector to hunt if the line isbusy'. This. is'particularly usefulfor througheswitching at nighttime, when certainof.

the P. B. X lines are connected through to' par..- ticular subscriber. stations at the P. B. Xand it is not desired-to call other stations.

The invention will now be described with the aid ofthe drawings in which one embodimentis diagrammatically shown.

Figs. 1 and 2 represent apart of the register controller circuit, which comprises the equipment required to perform the selection in the final se- Fig. 2 should be placed below Fig, 1.

Fig. 3 illustrates the finalselector circuit.

Fig. 4 illustrates how one hundred subscribers line circuits connected to the banks of one group of final selectors are identified or characterized.

' by alternating current sources of different phasesand potentials. This drawing shows also the manner in which P. B. X groups of subscriber lines are identified. Fig. 4 is to be placed to the right of Fig. 1.

The register circuit is connected over a suitable, link andover. one or more group selectors. having circuits like the final selector of Fig. 3'. The operationof the register, as far as the group. selectorsare concerned, is described in full detail. in said application ,(Kruithof, Kozma, den Hertog,.

SerialflNo. 473278). The following descriptionis therefore limited to the final selector. I I

Fig. 5' is adiagram illustrating the.controLofl tens, selection by employing a counting method;.

Figs. 6 and .'7' (to. be. placedside-by-side.) illus-- trate. an..alter.native. P. B- X selectingarrangement; and

Fig. 8 illustrates-an arrangement for simulta-w neously. con-trolling'the tons and units selections. 50

I. OPERATION OF THE SYSTEM.

The' wanted subscriber is-indicated tothe-regrist'er-by'th'e"1ast'=two digits of the called number: sent bytha-calling partyv Thesetwodigits; the? 3 tens and units, are stored on two step-by-step switches SMT and SMU, respectively, (Fig, 2').

The drawings do not show how these two digits are received and stored on the two switches, because that is well-known. It is assumed, for the sake of simplicity, that the selection in'the'final selector starts when both the tens and units digits have been received, although the selecting operation could be started while the tensdigit is being sent. As soon as the units digit is received, relay Urr (Fig. l) is energized, indicating that the selection may start.

The selection in the different group selectors is carried out in successive positions of the step-bystep switch OM as described in the above-mentioned application of Kruithof, Kozma and den Hertog. Fig. 1 shows the positions N, l and 2 of OM reserved for such selections. The tens selection will, therefore, start as soon as OM has been advanced to position 3 when the last digits have been received.

(a) TENS SELECTION Relay Ar (Fig. 3) of the final selector operates as soon as the final selector is seized by a preceding group selector. The operating circuit is described in the last-mentioned application as applied to group selector circuits. Relay Ar locks itself to the d brush of the last, e. .g. third group selector. The power magnet of the final selector operates in the following circuit: Ground, Urr front, Vtr back, (Fig. 2) Vrr back, a-Wire over all the group selectors, Br back in final, A1 front, magnet P, battery. The brush carriage of the final selector starts to rotate in order to reach the first terminal of that group of subscribers lines which have the indicated tens digit. These so-called. subnormal positions are characterized by the presence of ten different phases of alternating potential having a certain voltage (3 v.) as shown in the following table:

Tens selection Phase (po- Terminals in final selector arcs; tenfial 3 v The selected one of these alternating current signals is compared with an alternating current signal applied to are I) of SMT. These two currents are received in the register controller circuit, which has the necessary equipment for comparison. This equipment is shown in Figs. 1 and 2 within the dotted lines and includes transformers, tubes, coils, resistances, and the relay Vtr. The operation of this equipment has been described in the above-mentioned applications. The signaling current, to which reference is made in said applications, corresponds here to the alternating current received from the subscribers line circuits in the final selector, and the reference current is the alternating current connected over brush b of SMT- The circuit for the signaling current can be traced as follows: Source of alternating current in the line circuit, brush d of final selector, Br back, Ar front, c-wire, group selectors, Vhr back, windings of transformer HC1, ground. The circuit of the reference current is as follows: alternating current source, terminal and brush b of SMT, terminal 3 and brush d of OM, winding of transformer H02, ground. The brush d of the final selector wipes over the terminals until the signal receiver detects that the signaling and reference currents are in phase. The tube T2 be comes then ionized, relay Vtr operates and the brush carriage of th final selector stops on the subnormal terminal corresponding to the wanted tens group.

The alternating current sources connected to arc b of SMT are the same as those connected to the subnormal terminals on the final selector.

Relay Vtr operates relay Sar in the circuit: Ground, Urr front, Vtr front, brush 6 and terminal 3 of OM, winding of relay Sar, battery.

Relay Sar operates relay Vrr, whereupon relay Chr releases. Relay Chr is normally kept 0pcrated by relay Urr and it connects positive battery of v. to the anode of the cold cathode tube T2. As soon as relay Chr releases, the tube T2 extinguishes and relay Vtr releases.

Relay San once operated, locks itself to the interrupter contact of OM, in order to ensure the full operation of the magnet of the step-by-step switch. When the magnet OM opens its back contact and if at that time relay Vtr is released, then the relays Sar and Vrr also release. The brushes of switch OM make one step and change on are d the reference current. Relay Chr operates again and the circuit is ready for the units selection.

(12) UNITS SnLsc'rioN The subnormal positions of the final selector correspond to the units digit 1. If, therefore, this digit was sent by the subscriber, then the step-bystep switch SMc will be in position I and via brush b of SMc and brush 1) of SMT the reference current characteristic for this subnormal position will be connected. As soon as relay Chr operates, relay Vtr prevents the selector switch from leaving the subnormal position occupied and the units selection is thereby terminated.

If the units digit is not 1, then the final selectors brush carriage is started again, since relay Vtr does not operate. The ten groups of nine terminals, each group lying between two subnormal positions, are multiplied and also con nected to the alternating current sources of nine different phases, which have diiferent potentials (2 volts) from those used to characterize the subnormal positions. Complete information concerning these connections is shown in the table below:

Units selection Phase Terminals in final selector arcs (potential 2 v) When the final selector encounters the signaling current identical with the reference current, then relay Vtr operates and the final selector stops on the circuit of the wanted line.

(0) WANTED LINE Is FREE In this case relay Vtr energizes relay Vhr via terminal 4- or the brush e cf OM. The o-wire of the subscribers line circuit is tested in the following circuit: Ground, Vhr front, resistance of 3000' chins, winding of relay Pb r, b-wire, group selectors, Br back in final selector, Ar front, winding I of relay Br, brush 0, winding of relay Cor (Fig. 4), battery.-

In this circuit only relay Pbr operates; the winding of relay Br, due to the high resistance of the circuit, does not get suflicient current. Relay Pbr energizes relay Sir 'andthis relay connects the low resistance Windingrelay Sor in parallel to relay Pbr. Relay S07 operates and replaces the function of the contact of relay P111- which, being shunted, releas'e'a's'. The grounding of the terminal, indicated at F (Fig. 1) via a front contact of relay Sfr, indicates that the subscriber line is free. 7 The control of the four wires a, b, c and d, is then taken over by the cord or link circuit, and the register is released in the well-known manner. V

Relay B1- in the final selector operates as soon as relay S01 is introduced in shunt to relay Pbr. Relay Br removes the short circuit from its windiiig II, and closes a locking circuit to the battery ever the too chm resistance. It short circuits its operating Winding via a front, which closes later in order to connect through the c-wire. The busying ground of the subscribers line cireuit will be provided over a suitable resistance in b the cord circuit.

Asecond winding on relay Sor is connected via front contacts of the relays S and Wu to the c-wire, from which the winding of transformer I-IC has been disconnected. Low resist- If the wanted line is busy, then the potential on the c-wire is reduced by the busyling ground, preventing the relay P297 to operate. The operation of relay Vhr is followed by that of relay Grbr, which is slow operating in order to cover the operation times of relays Pbr and Sfr in case the line is free. Relay Gbr energizes relay PCT and the latter energizes relay Sbr via back of relay Psr. The grounding of the terminal B (Fig. l) indicates to the cord circuit or other circuit used in the connection, that the wanted subscriber is busy. The final selector is not connectedthrough in this case and the cord circuit will release all group and final selectors behind it and will give the busy tone to the calling party.

'(e) HUNTING IN P. B. X GROUPS In P. B. X groups the first and last lines have a resistance R connected in parallel to the relay C'or.

If the first line of a P. B. X is busy, th-en relay Pbr of the register connected in series with a resistance of 3000 ohms, cannot operate in spite of the reduced resistance of the subscribers c'-wire. Relay Vhr energizes relay Gbr and this closes the circuit for relay Per. The above-mentioned resistance of 3000 ohms is now short circuited, and relay Pbr will operate since the resistance R is in parallel to relay cor. The relay Pbr does not operate in the above circuit when a single line or an intermediate line of a P. B. :X groupis contac'te'dby the final selector. P. B. X hunting can, therefore, start cmy if the first line 6 of the group is selected. All other lines of the group, except the last, can be called individually.

Relay Pb? operates relay Pgr in the circuit: ground, Pbr front, Pcr' front, P'Zr back, winding of relay Psr, battery.

Relay Psr prepares a locking circuit for itself over relay P11, and relay Vrr is energized in the circuit: ground, relay Per front, relay Psr front, winding of relay V'rr, battery.

Relay Vrr disconnects relay Chr, which releases and extinguishes the tube T2. Relays Vtr, Vhr, Gbr, P01 and Pbr release in sequence. The short circuiting ground on relay P11 is removed, so that this relay can now operate in series with relay Psr. Relay For releases relay Vrr, so .that relay Chr may now again be operated, whereby the receiving circuit is again in testing condition. Relay Vhr energizes the magnet of the step-by-step switch SMU so that for each test the brushes take one step. Byadvancing to the next terminal, switch SMU changes the reference current to the phase of the next subscribers line circuit.

.As soonas relay Vrr releases, the power magnet of the final selector is again energized and the brushes start to rotate again. Due to the correspondence of the phases, the final selector stops on the next terminal and relay Vtr starts the same operation as above described. If the second line of the group is free, then rela Pbr operates before relay Gbr can close its front contact, whereupon relay Sfr energizes in the same way as on a single line. If the line is found busy, then. relay Pcr energizes as soon as relay Gbr closes its front contact. Relay Pcr energizes relay Vrr, the tube T2 is extinguished, the brushes of switch SlVIc take one step and the B. P. X hunting continues. If the last line of the P. B. X is also busy. then relay Pbr operates due to the increase of current flowing through its winding as soon as relay Per operates. Relay Pfr operates in the following circuit: Ground, Pbr front, Pcr front, Plr front, Winding of relay Pfr, battery.

By grounding terminal B relay Pfr indicates that the called lines, i. e. all lines of the called P. B. X group are busy.

The brushes of switch SMU advance one step I for each testing and thus advance the reference current in synchronism with the signaling current. The P. B. X group may contain any number of subscribers lines. When during the P. B. X hunting the final selector reaches the next subnormal position, the reference current has to be changed in accordance with the signaling current used for the tens selection. This change is effected by relays Skr and Msr. The former is energized in position 2 of switch SMU and remains locked to the interrupter contacts of both magnets SMT and SMU. The arrival of SMU in it's normal position is an indication that the final selector will meet a subnormal position on the next test. Relay M'sr operates and both magnets SMT and SMU are energized. When the terminals on both interrupters are opened, relays S701" and Msr release and both switches move their brushes one step. The winding of transformer I-ICz is connected via position 1 of the are I) of 'SMc and via are I) of SMT to the reference current correspondin to the next subnormal position.

II. CIRCUIT VARIATIONS The "above disclosed circuits and operations have been described by way of example only.

This invention is in no way limited to the arrangements described and several alternative methods are possible. By way of example, the following three alternative applications of the principle involved in the new invention will be described:

(a) Alternative method of making tens selection, employing counting principle.

(b) Alternative method of controlling P. B. X

hunting.

() Alternative method of controlling tens and units selections simultaneously.

(a) COUNTING OPERATION FOR THE TENS SELECTION The scheme of final selection described in the previous chapter 1 required the use of two series of alternating current sources: one to designate the ten subnormal positions and the other one to designate the terminals between subnormal positions. As was shown, the dilference between the two series was in the value of the potential, one having currents of 2 volts and the other currents of 3 volts.

Fig. 5 shows the modifications that must be made in order to perform the final selection with a single series of alternating current sources. Two relays Ctr and Cir and one step-by-step switch SMC are added to the arrangement shown in the previous figures. The 100 terminals of the final selector have to be connected to the alternating current sources as follows:

The circuit operation as far as the tens selection is concerned, changes in the following respects:

As above, switch SM'r records the tens digit sent by the subscriber. The connection in arc I) must however be changed as shown in Fig. 5. The brushes of the final selector start to rotate, whereby the power magnet of the selector is operated over the back contacts of relays Vtr and Ctr in parallel. The primary winding of transformer I-ICz is during this selection permanently connected to phase I.

When the final selector encounters the first terminal d, to which the phase I is connected, i. e. terminal I, the receiving equipment responds and relay Vtr operates. Relay Vtr energizes Cir and this in turn operates relay Vrr, with the result that the tube T2 is extinguished and relay Vtr releases, whilst the final selector, driven over the back of relay Ctr, continues its rotation.

Relay Cir operates magnet SMc and when relay Cir releases, the brushes of SMc take one step. The above operation is repeated for each terminal to which the phase 1 is connected (terminals 11, 21 until relay Ctr operates via are 22 of SMc and are b of SMT Relay Ctr operates after the brushes of SMC have stepped. over to the next terminal, thus at a moment when relay Vtr has already released;

The final selector continues to rotate until relay Vtr operates on the next subnormal terminal, but now the circuit of the power magnet is opened.

Over the front of relay Vtr relay Sar is energized at present and the tens selection is terminated.

The arcs of terminals 22 of SMT and SMc are interconnected in such a way that relay Ctr operates one subnormal position earlier than it otherwise would according to the tens digit, in order to stop the final selector under the control of relay Vtr in the usual test circuit.

(1)) P. B. X GROUP DESIGNATIONS BY ALTERNATING CURRENT Figs. 6 and '7 show an alternative P. B. X group selection. The designations are derived from thirty different alternating current sources. The first series of ten alternating current sources, which have different phase angles but are of the same frequency F1, are assigned to characterize the individual subscribers line circuits as shown in connection with Fig. 5. The second series of ten alternating current sources have also ten different phase angles, but another frequency F2. This second series serves to designate the first line of each P. B. X group in such a way that the alternating current source of the first series connected to the d terminal of the line circuit concerned is replaced by that alternating current source of the second series which "has the same phase angle. The third series of ten alternating current sources, which have again a different frequency F3, are used to designate the lastline of each P. B. X group, in such a Way that the alternating current source of the first series connected to the d-terminal is replaced by the corresponding alternating current source of the third series.

The circuit operation is briefly as follows:

The register controller has three receiving units, I, II and III, instead of one. The transformers H02 are connected over three separate arcs of SM to the reference current sources of different phases and frequencies. SMu is, as in Fig. 2, the step-by-step switch recording the units digit sent by the calling subscriber.

The circuit of the power magnet of the final selector is controlled over the back contacts of all three Vtr relays associated with the three receiving units. The final selector can, therefore, be stopped by any of the three receiving units depending on the frequency of the signaling current connected to the d-terminal of the called subscriber. Thus, the receiving unit I responds if the called line is a single line or an intermediate line of a P. B. X group. The unit II energizes on the first line of a P. B. X group and unit III on the last line of a similar group.

In case of a single line relay Rori is operated. Relay Tr is connected to the c-wire of the line circuit and, if the wanted line is free, the relays Tr and Dir will operate as previously described. The grounding of the terminal-F indicates that the subscribers line is free. If the line is busy, relay Tr fails to operate and therefore relay Gbr will be energized. Relay Gbr grounds terminal-B via the front contact of relay Ron and back con tact of relay Psr, to indicate that the called subscriber is busy.

In case the first line of a P. B. X group is tested, relay Rorz energizes. If the line is free, relays Tr and Dtr energize, as for single lines. However, if the line is busy, relay Gbr operates and relays Sar and Psr are energized over front contacts of Rorz. Relay Sar locks itself to the interrupter contact of SM, which magnet is energized at the same moment. Furthermore, relay Sar operates relay Vrr which, in a manner similar to that essence shown in Figs. 1 and-2, releases thereceivingunit. The release of relay Vtr is followed by;thatof. 17.6- lays .RO72, Gbr, Sar, Vrr, etc. The brushes of switch SMu take one step in order tochangethe reference currents of all three frequencies to the next phase. RelayPsr. once operated, l;ocks itself independently of relay Rorz to some swunucontrolled in the register circuit.

The final selector is now stopped on the second line of the P. B. X group to which the alternating current source of the first frequency F1 is connected. Relay Ron operatesand if the lineis free, the relays Tr and. Dtr are energized. If the line is busy,relay Gbr operates and relay flai is energized via fronts of .relayBon' and,,,re l' ay Bsr. The receiving. unit I is released and.P.. -B-. X hunting continues until a free lineis found.

The receiving unit 111 responds to the last line of the P. B. X group. RelayRora operates and connects relay Tr inthcknown ,Way to theitest wire. If the line is bl.lSy,.the;fl'.Q11t ofrelay G112" connects ground to. terminal-B .via a front of relay Roirs and thus indicates the busy condition.

The advantages of this arrangement are, that no individual P. B. X, resistances are required and that, the c-wire of the subscriber line-having .a constant resistance, regular double test (byrelays Tr and Dir) can be carried out. ,F urthermore, since different signals are se t ior ,-th efirst and for the last BB. K line, the-last line may be called as an individual line. This isnot possible with the arrangement described inchapter I, because the increased c -wire current of the last line would start P. ,B. X hunting. In. the

present case, however, the operation. of relay Rom is followed by the regular test,.b.ut no ,P.. B. X hunting can start.

The tensselection can be carried out. in different ways. The register can, e. g., count thenumber of subnormal positions over which the brushes of the final selector pass, in the same way as .de-- scribed in chapter IIv (a). The difierencewill be that all three receiving units have to be connected and that the phase I will be detected by one ,of these three units, depending on the subscriber line, i. e. depending on the frequency of. the. alternating current connected to the, d;-terr ninal.

Another method of performing the tens selection is that described in the introduction. This method necessitates thirty more sourcesofalternating current, whichdiiier from the firstthirty only in their potential. Thirty alternating current sources of the frequencies. Fl', F2 and. F3 of 3 volts potential may, for instance; be'used to designate the first position of each group of ten subscribers lines corresponding to the same tens digit. Depending whether the subscribers line belonging to this terminal is a single line, or the first or the last line of a P. B. X group,the alternating current sources of frequencies Fl, F2 .or F3 will have to be connected. Similarly, thethirty alternating. current sources of the. frequencies Fi, F2 and F3 of 2 volts potential are usedto mark the positions between the subnormali positions (in fact only 3x9 sources arereqiiired), and these sources must be connected as required by the subscribers lines concerned.

The above scheme is given only as an example,

and it is evident that-the electrical characteristics can be varied in any other convenientway. An-

other scheme is, for instance, to: assign .theljdifferent potentials P1, P2, Pa for indicating single lines,.first and last .P. B; Xlines and to use two different frequencies F! and -.F2, one serving, for the tens andthe .otherfor theunitsseleotion.

is e

. EL HQ W Fig. 8 shows a circuit arrangement which per- H neo'us' ontrast the tensand unitsfselectio s."The receiving "equipment is shown split totwo parts. One'pafrt' is the signal r andth'eother the responding part. o'rs nds overtwo'separate paths, g 'currents, one"representi ng other the units digits of the h e ected' to the terminals engaged bfy-tlrebr1ishes ii and e. Th'rgi'ster controller is prone, d "with two signal discriminating units, H t to [the brush d of'tlihnal selector; joverhicn thesigna-1ing' current of the tens'is' s'ent', arid II connected to blfush 'e 'of the final selector, over which the signaling current ciffthe units 'd-i gitis 'rfeceived. Thisbrush e is an additional brush inalt final and group selectors andis fonly requi a in connection with this reference A, current of the first discriminating" received 'viaarcb of SM'r, which recprcs'tne tens digitjsehtfby tr e'flcalling party. The 'referenc'e currentbflthe second unit is apli foversilnf ich re 0 d t n 7 139 units :tl i 'i signaling andrefer phase. The' 'power n'ragnet isdrivenvia thebac ssietf i J the reaches the terminals ofthe wanted subscriber. This: arrangement j has the; advantage that the selfl ie i th fg a 9 5 r r e bymeans ofonejs'et'ofaltern gcurrent sources, wiihqu witnes ecstat an the final s'elector ca'n beset direct qr; the wantedjte'rm w th??? T 535 Sh p af'su r'm l' post i c u i W r flai calle the; sa het sai s ek r h vi 'e se tank, b itec 'h ne a e n i brushes'codpe'ratin bntat mea r lsf or me ines i liwsh d 'sa h he "c'a'lli telephone system according to claim 1,

d t sa d. l's'e vctlor' menses tw e a ha ,pptatspntrolling alloperatiqngtwcrgf. p.

t phqs sr tses sy em 12 M3 1 e t nesssel ilid iiii Xersmps ,swi ehi amean including fi electors fo ...c9m; 2t n a sel n wi it called 1a each. of.., a d.- se e or a in se pf b n ontacts to ic lines. r icenne tedr h he cooper t n Mause -nest .me ns orm rine said brushes over said contacts in succession, a register controller, an impulse device associated with the Calling line for operating said register controller in accordance with the designation of the called'line, switches for associating said register controller with a final selector, means directly controlled by the register controller for operating said brushes to select a line in accordance with the tens and units designations thereof and to hunt for an idle P. B. X line, and signals characteristic for the lines sentthrough the moving brushes of the final selector to the register controller controlling the operation thereof.

4. The telephone system according to claim 3, characterized in thatsaid final selector comprises two relays having contacts controlling all operations thereof. 7

5. In a telephone exchange system, a plurality of numerically designated lines, some divided into P. B. X groups, switching means including final selectors for connecting a calling with a called line, each of said selectors having consecutive sets of bank contacts to which lines are connected, each set including a test contact, brushes cooperating with said contacts, means for moving said brushes over said contacts in succession, a register controller, an impulse device associated with the calling line for operating said register controller in accordance with the designation of the called line, switches for associating said register controller with a final selector, means directly controlled by the register controller for operating said brushes to select a line in accordance with the tens and units designations thereof and to hunt for an idle P. B. X line, a source of electric potentials .difiering in at least one of their electric properties, means for applying one of said potentials to the test terminals between which a P. B. X group is located, a counting device in the register controller, a signal receiver in the register controller, means for operating the signal receiver in accordance with signaling current having electric properties corresponding to those of the potentials applied to one of said test terminals, means for operating the counting device to count the number of P. B. X line terminals passed over by the brushes of the final selector switch, and means under the joint control of the signal receiver and counting de-,

vice for controlling the operations of the register controller and the selector.

6. In a telephone exchange system, a plurality of numerically designated lines, switching means including selectors for connecting a calling with 9. called line, each of said selectors being operable in accordance with twodesignations of the called line and having sets of bank contacts to which lines are connected, each set including a test contact, the sets of contacts from which one is selected during the selection in accordance with the first designation beinglocated at intervals in the contact bank, and the ones from which one is selected in accordance with the second designation being between. contacts selectable in the first selection, brushes cooperating with said sets of contacts, means for moving said brushes over said sets of contacts in succession, a register controller, an impulse device associated with the calling line for operating said register controller in accordance with the designation of the called line, switches for temporarily associating said register controller with a selector, means directly controlled by the register controller for operating said brushes to select a line in accordance with the two designations thereof, a source of potential, means for applying to the test contacts of the lines from which the first selection is made, potentials of which at least one of the electrical properties is dififerent for each line, means for applying to the intermediate test contacts of the lines, potentials of which at least one of the electric properties is different for the diiTerent intermediate lines and of which at least one other electric property is difierent from that applied to the test contacts of the lines from which the first selection is made, and signals characteristic for said potentials sent through the brushes of the selector to the register controller controlling the operation thereof.

'7. In a telephone exchange system, a plurality of numerically designated lines, some divided into P. B. X groups, switching means including final selectors for connecting a calling with a called line, each of said selectors having sets of bank contacts to which the called lines are connected, each set including a test contact, brushes cooper ating with said sets of contacts, means for moving said brushes over said sets of contacts in succession, a register controller, an impulse device associated with the calling line for operating said register controller in accordance with the designation of the called line, switches for temporarily associating said register controller with a final selector, means directly controlled by the register controller for operating said brushes to select a line in accordance with the tens and units designations thereof and to hunt for an idle P. B. X line, characteristic potentials applied to the test contacts of individual lines and differing in at least one characteristic depending on the busy or idle condition of the line, characteristic potentials applied to the test contacts of P. B; X lines difiering in at least two electrical characteristics depending on the busy or idle condition of the P. B. X lines, test means in the controller selectively responsive to said potentials, and signals characteristic for the numerical designations of the lines sent through the moving brushes of the final selector to the register controller controlling the operation thereof.

8. In atelephone exchange system, a plurality of numerically designated lines, some divided into P. B. X groups, switching means including final selectors for connecting a calling with a called line, each of said selectors having sets of bank contacts to which the called lines are connected, each setincluding a test contact, brushes cooperating with said sets of contacts, means for moving said brushes over said sets of contacts in succession, a register controller, an impulse device associated with the calling line for operating said register controller in accordance with the designation of. the called line, switches for temporarily associating said register controller with a final selector, means directly controlled by the register controller for operating said brushes to select a line in accordance with the tens and units designations thereof and to hunt for an idle P. B. X

line, characteristic potentials applied to the test contacts of individual lines and differing in at least one characteristic depending on the busy or idle condition and the designation of the line, characteristic potentials applied to the test contacts of P. B. X lines differing in at least two electrical characteristics depending on the busy or idle condition of the P. B. X lines, test means in the controller selectively responsive to said test potentials, a discriminator in the controller for controlling the operation of the final selector, means -for applying to the discriminator. potena r-taste tialscharacteristic for the numerical designation of the called line, means for applying to-said discriminator the potentials applied to'test terminals of the final selector, and means for operating the discriminator when'the potentials applied thereto bear a predetermined relationship to one-another.

9. Ina telephone exchange system, a plurality of numerically designated lines, switching means including final selectors for connecting a calling with a called line, each of said selectors having sets of bank contacts to which lines are connected, brushes cooperating with said contacts, means for moving said brushes over said contacts in succession, a register controller, an impulse device associated with tne calling line for operating said register controller in accordance with the designation of the called line, switches for associating said register controller with a final selector, means directly controlled by the register controller for operating said brushes to select a line in accordance with the tens and units designations thereof, and signals characteristic for the numerical designations of the lines sent through the moving brushes of the final selector to the register controller controlling the operation thereof.

10. In a telephone exchange system, a plurality of numerically designated lines, switching means including final selectors for connecting a calling with a called line, each of said selectors having sets of bank contacts to which lines are connected, each set including two special contacts, brushes cooperating with said contacts, means for moving said brushes over said contacts in succession, a register controller, an impulse device associated with the calling line for operating said register controller in accordance with the designation of the called line, switches for associating said register controller with a final selector, means directly controlled by the register controller for operating said brushes to select a line in accordance with the tens and units designations thereof, potentials characteristic for the tens digit of the lines applied to one special contact thereof, potentials characteristic for the units digit applied to the other special contact thereof, and circuits for controlling the register controller including said special contacts.

11. In a telephone exchange system, a plurality of numerically designated lines, some divided into P. B. X groups, switching means including final selectors for connecting a calling with a called line, each of said selectors having sets of bank contacts to which lines are connected, brushes cooperating with said contacts, a magnet for moving said brushes over said contacts in succession, a register controller, an impulse device associated with the calling line for operating said register controller in accordance with the designation of the called line, switches for associating said register controller with a final selector, a circuit for said magnet, a relay in the register controller for closing said circuit to move said brushes to select a line in accordance with the tens and units designations thereof and to hunt for an idle P. B. X line, a source of potential, means in said register controller for applying potentials of certain characteristic to said relay depending on the setting of said controller by the impulse device, means in said selector for applying potentials of certain characteristic to said relay depending on the setting of the brushes on certain contacts, and means for operating said relay only if the two potentials applied thereto bear a predetermined relationship to one-another.

1' 2. In a"tele ohoife exchange system, a plurality of numerically designated-line's, s'ome "divided into P. -B. X groups, switching means including final selectors for connecting a calling with a called line, each of said selectors hating sets of bank contacts to which lines are connected, brushes cooperating withs'aid contacts, a magnet 'formoving said brushes over said contacts to select a line in accordance with *the tens and units designations thereof and tohurit ior an idleP. B. X line, a register controller, an impulse device associated with the calling line for operating said register controller in accordance with the design'aticn of the called line, switches for temporarily associating said register controller with 'a final selector, a source of potentials, means for applying to contacts of 'a line various classes of characteristic potentials identifying the line, a plurality of means'in said register controller, each responsive to a different class of characteristic potentials, a switch in said register controller and controlled by the impulse device for selecting a particular characteristic potential, and a -"c uit for said magnet jointly controlled by the lastm'entionedswitch and said plurality of means.

13. In a telephone exchange system, a plurality of numerical-1y designated line's, switching means including final selectors for connecting a calling with a called line, each of said selectors having sets of bank contacts to which individual lines and a group of P. B. X lines are connected, brushes cooperating with said contacts, a magnet for moving said brushes over said contacts in succession, means for making busy lines with whose contacts the brushes of a selector are connected, and for preventing the selection of a busy line by a selector, a register "controller, an impulse device associated with the calling line for operating said register controller in accordance with the designation of the called line, switches for associatingsaid register "controller with a selec tor, two relays associated with each selector, circuits controlled by the register controller for op-- erating said relays to control all operations of said selector, to select a line in accordance with the tens and unitsdesig-n'ations thereof, and to select an idle P. B. X line.

14. The telephone system according to claim 13, characterized in that talking conductors terminate in two brushes, and in contacts of one of said relays, and a circuit for said one of said relays closed by said register controller upon the selection of a free line to switch through said talking conductors.

15. The telephone system according to claim 13, characterized in that a source of direct current potential is provided at the called line to prevent simultaneous selection of the line by more than one selector, and that one of said relays has a winding connected in series with said source of potential, and a test relay at the register controller in said circuit.

16. The telephone system according to claim 13, characterized in that a source of D. C. potential is provided at the called line to prevent simultaneous selection of the line by more than one selector, and that one of said relays has two windings, a circuit for one of said windings extending from said source to said register controller, and a circuit for the other winding independent of the register controller and the direct current potential at the engaged line, providing a metallic connection to a brush of the final selector.

17. In a telephone exchange system, a plurality of numerically designated individual lines and a group of RB. X lines, switching means including final selectors for connecting a calling with a called line, each of said selectors having sets of bank contacts to which lines are connected, each set including a test contact, brushes cooperating with said contacts, means for moving said brushes over said contacts in succession, a register controller, an impulse device associated with the calling line for operating said register controller in accordance with the designation of the called line, switches for associating said register controller with a final selector, means directly controlled by the register controller for operating said brushes to selecta line in accordance with the tens and units designations thereof and to hunt for an idle P. B. X line, a source of direct current potential, means for applying busy potentials to the test contacts of busy first and last P. B. X lines and different busy potentials to the test contacts of other P. B. X lines, a second source of potential, means for applying from said second source a characteristic potential to certain contacts in said bank characteristic for the numerical designation of the line connected therewith, and means in the register controller responsive to both potentials applied to the bank contacts of the selector for controlling the operation of the latter.

18. The telephone system according to claim 17, characterized in that the register controller comprisesa marginal relay, means controlled by the marginal relay to initiate the hunting action of the final selector from a selected busy first line of a P. B. X group, a circuit for said marginal relay including said source of direct current potential, said marginal relay being adjusted to operate only when the brushes engage contacts of idle lines, but to operate when the brushes engage contacts of busy first or last lines of a P. B. X group; and means for operating said brushes to select any of the other contacts in accordance with the numerical designation thereof without initiating the hunting action if the selected line is foundbusy.

19. The telephone system according to claim 17, characterized in that the register controller Number comprises a marginal relay, means controlled by the marginal relay to initiate the hunting action of the final selector from a busy first line of a P. B. X group, and a circuit for said marginal relay including said source of direct current potentialto operate only when the brushes engage the contacts of a busy'first line of a P. B. X group.

20. The telephone system according to claim 1, characterized in that the register controller starts the selecting operation of the selector While impulses representing said selecting operation are received by the register controller.

21. The telephone system according to claim 1, and in which the register controller controls the operation of said selector in accordance with two digits of the called number, characterized in-that said register controls the operation of the selector in accordance with one digit While impulses representing said digit are being received by the controller.

22. The telephone system according to claim 1, an electrical discharge device in the register, sources of different electrical potentials, means for applying a potential to the discharge device responsive to the operation of the register controller under the control of the impulse device, means for applying a second potential to the discharge device over a bank contact and a brush of the operated final selector and said switches, and means operated by the discharge device when the two potentials applied thereto bear a predetermined relationship to one-another for stopping the movement of the final selector brushes.

JACOB KRUITHOF. LADISLAS KOZMA. MARTINUS DEN HERTOG.

REFERENCES CITED Ihe following references are of record in the file of this patent:

FOREIGN PATENTS Country Date 58,220 Netherlands Aug. 16, 1946

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