US2379221A - Communication system - Google Patents

Description

June 26, 1945- L. EsPENscHlED COMMUNICATION SYSTEM 7 Sheets-'Sheet'l Filed Oct. 9, 1942 .n /ER MIL .m u n 6 w B d 5 7 9mm Y 5mwv U ,m m m m .i 2. 4., .o

lJune 26,1945. EsPENsCHlED l l2,379,221

'COMMUNICATION SYSTEM FiledV oct. 9, '1942; v 7 sheets-sheet 2 FIG. 2

PRIMARY DEAN SIYI TCH /Nl/ENTOR ByL. ESPENSCH/El June 26, 1945. L. EsPENscHxED COMMUNICATION SYSTEM Fil-ed oct. 9, 1942A '7 Sheets-Sheet 3 SECONUR? BEAM SW! TCH i me. E SPENS CHIED A t tbe/mc June Z6, 1945. L. EsPENscHlED COMMUNICATION SYSTEM '7 Sheets-Sheet 4 Filed OCI'.. 9, '1942 START BV A Tron/MEV June 26, 1945.

| EsPENscHIED 2,379,221

COMMUNICATION SYSTEM 'Filed oct.f.9, 1942 v sheets-sheet e Patented June 26, 1945 2,379,221 COMMUNICTIQN SYSTEM Lloyd Espenschled, Kew Gardens, N. Y., assigner to Bell Telephone Laboratories, Incorporated,

New York, N. Y., a corporation of New York ApplicationOctober 9, i942, Serial No. 461,439

19 Glas.

This invention relates to electrical switching methods and switching devices and particularly to these methods and devices when applied to communication systems and to signaling systems in general.

The objects ofthe invention are to simplify the devices used yto perform the switching of communication lines and other electrical circuits; to eliminate to a large extent the moving mechanisms heretofore used for this purpose; to reduce the number. of switching stages necessary for the establishment of connections between telephone or other lines; to increase the speed with which -connectionsmay be established; and in other respects to obtain improvements in switching methcds and devices. Many varieties of automatic switching mechanisms have been proposed in the past for interconnecting the lines of telephone, telegraph, and other communication systems. In most all cases these prior mechanisms have depended largely upon the use of electromechanical devices in which moving parts serve to perform the selective and connecting operations involved in the establishment of the desired connections. While some of these types have been developed to a high degree oi reliability, it is true nevertheless that the presence of moving mechanical elements imposes limitations on the speed of operation and also introduces other problems. Also there.have been a number of suggestions heretofore for the `use of the cathode beam tube for selecting telephone lines and other'similar circuits. Furthermore, it

has been previously suggested to use cathode.

beam tubes as distributors in systems of the usual multiplex distribution type.

En accordance with the present invention improvements and advantages are obtained over these prior devices by means of a switching system in which electrical connection may be estabiished between any two lines in a group, suchas the calling and called lines in a telephone oice,

the medium of the beams once for each scanning cycle. The system is provided, however, with means for varying the relation of the two scanning beams in accordance with information receivedconcerning the connection that isvdesired. When, therefore, it is desired to establish a connection between any calling line and any called line, the relation between the two beams is varied by an amount corresponding to the identity of these lines, so that each time the rst beam engages the calling line the second beam simultaneously engages the called line. rrhus the calling and called lines are connected together once per cycle, and the scanning rate is so rapid that a substantially continuous connection is maintained.

Another and related feature of the invention is a system in which `the lines in the incoming scanning field and the lines in the outgoing scanning eld constitute two separate groups of lines or trunks. `For example, the outgoing lines may be a group of trunk circuits over which calls are extended from the incoming lines or trunks. By subdividing the outgoing-lines into subgroups it is possible to choose any one of a number of differy ent directions for routing the incoming calls.

Another feature oi the invention is a scanning system in which the elements in the scanning elds are variably energized in accordance with the current variations infthe lines produced by the speech or communication signals therein, and these variable energiaations are. communicated from one line to another by means of the intervening electron beams.

through the medium of scanning devices. More speciiically a group of lines, having an appearance in a scanning iield as calling or incoming lines, are scanned repeatedly and at high speed by an electron beam, such as that produced by a cathode beam tube, and at the same time the said group of lines, having another appearance in a second scanning eld as called jor outgoing lines, are scanned repeatedly by .a second electron beam. Normally these twobeams are in synchronism and in phase such that each line in the incoming field is electrically connected to the corresponding line in the outgoingiield through Another feature of the invention is a system in A which the designations of the lines or other circuits to be connected for conversation through the scanning beams are utilized to introduce a phase displacement between said beams, so that said beams engage the ,calling and called lines simultaneously each time they pass through a scanning cycle.

iiiuotlier feature of the invention is a system in which the scanning devices are driven synchronously from a common source of high frequency curremt and in which the designations ofany pair of lines or circuits to be interconnected are used to produce a corresponding shift in the phase of the current supplied to' drive one of said beam devices, thereby eecting a phase relation between the synchronously moving beams such that they engage simultaneously the desired pair of lines or circuits on each scanning cycle.

Another feature of the invention is a system m which the lines have an appearance 1n a primary i beam scanning device and also have appearances in each of a plurality of associated secondary beam scanning devices, the beams of all devices being driven synchronously over the lines appearing therein, together with means for introducing denite and varying phase displacements between the beams of said secondary scanning devices and the beam or said primary device. so that simultaneous communications may take place between any desired number of pairs oi' lines.

These and other features of the invention will be discussed more fully in the followingr detailed speccation. t In the drawings accompanying the specificaion:

Fig. 1 is a conventional diagram illustradns .a telephone system incorporating the features of the present invention;

Figs. 2 to '27. inclusive, when arranged in the order illustrated in me. il disclose the system of Fig. l in greater detail;

Fig. 2 discloses a primary beam switch in which the subscribers lines 'or other circuits appear and also shows two of these lines;

Fis. 3 shows two oi the secondary beam switches in which the subscribers linea also appear as well as other circuits with which it is desired to maire connection;

Figs. d and 5 show a pair of designation resisters for registering the numbers oi calling and called lines respectively;

Fiss. il and 'l' disclose a nation registers; and y Fie. ti is an enlarged fragmentary view illustrating the structure or the beam switches.

The invention in its broader aspects contemplates a multiplex system in which a plurality of communication channels-are established concurrently for voice communication, telegraph signaling or transmission of any other desired kind. In the present disclosure, however, a telephone system has been chosen for the purpose of illusytrating theminvention. It is also assumed that there are one hundred lines in this system, all of which may be subscriberslines if desired or a part of which may be trunks, such as those interconnectins one telephone cnice with another. ln any event it will be obvious that the invention is not limited to any particular capacitynor to any particular division 0r disposition of the circuits comprising this systern.

Referring irst to Fien l, there is illustrated diagrammatically a single primary beam switch |00 in which the incoming lines or' a group have individual appearances in a circular rowl of electrodes. Two or these lines, those having the designations 30 and "42" are shown in the drawing. The primary beam switch |00 is connected over a common transmission medium |l| to a plurality of secondary beam switches |02, III. etc., the number of these secondary switches corre-` sponding to the number of permissible simultaneous communications. The switches |02 and second pair of desis- .|03 are similar in structure to the switch H00,

and thelines appearing in the switch |00 also have the same relative spatial appearance'ln each of the switches |02, |03, etc'. T wo subscribers' lines, No. 62 and No. 20, are shown loutgoing from thev secondary switches. If it sassumed that the system comprises one hundred subscribers' lines and that the switches have a capacity for one hundred circuits, then the entire circumferential row of electrodes in each of these switches is occupied by the subscribers lines. In other words, lines numbered "0 to "99" would appear in spasame spatial sequence around the circumference mon source l l,

of each of the secondary switches |02, |03. etc; However, if it is desired to include trunks or other circuits incoming from and outgoing to distant points, a portion of the appearances around the circumference of the beam switches |00', |02, 03, would be devoted to these incoming and outgoing circuits, and the remainder of the appearances in these switches would be devoted to the subscribers lines, which would also have the corresponding spatial appearances in the beam switches, One of the incoming circuits lili and one of the outgoing circuits il@ are illustrated `in the drawing.

A plurality of designation registers 05, lllt, etc., are provided for registering the designations of any pair of lines or circuits between which it is decided to establish a communication connection by way of a pair of beam switches. M0, U02. The resister itt comprises two stepping devices itl and itt which are essentially the same in structure as the well-known two-motion step-by-step switch used in automatic telephone systems. The

subscribers lines appear according to their numerical designations in the terminal banks off the stepping device lill, which operates automatically, like a line lnder, to und the terminals oi any line on whicha calling condition is present. Having found the calling line, the vertical rotary movements perfumed by the stepping de-J vice lill are a measure or a registration of the tens and units digits ci the line. As will be explained hereinafter, these vertical and rotary' movements cause the setting of a pair of variable condensers whichy together comprise a phase shifter W0. The other step-by-step device 80d of the register itil is similar to the finder lill, except that it responds to the impulses transmitted by the calling subscriber to perform vertical and rotary movements representing the tens and units digits of the called line or circuit and in so doing imparts corresponding settings to the condensers of the phase shifter il 0.

The purpose of the phase shifters tot and titl is to impose a. phase shift in the voltage taken from the beam-driving source lll which is an exact measure of the spatial separation of the calling and called lines in the primary and secondary beam switches. Thus if the beams H2 and H3, which are' driven in synchronism over their circumferential rows of electrodes by the comare in phase with each other, they encounter simultaneously the two appearences of each,0f the successive lines over which they move. But by setting the phase Shifters itil and H0 in accordance with the designations of the calling and called lines it is possible to shift the phase of the beam H3 with respect to the phase of beam ||2 by an amount which corresponds to the spatial distance between the calling and called line appearances in the switches l0@ and M2. Therefore, as the beams rotate in synchronism they encounter thecalling and called lines simultaneously once per revolution.

1n like manner the register |06 comprises a step-by-step line nder device H6 having an associated phase shifter I|5 and a stepping device HB having an associated phase shifter il?. It will be noted that the registers |05 and |06 are commontc all of the subscribers lines and are assocated respectively withthe secondary beam switches |02 and |03. And in likeimanner for each of the remaining secondary beam switches NYclosed in a sealed vacuum tube. vare arranged on the exterior of the tube in any not disclosed in the drawing a corresponding' register is provided.

Referring now to Figs. 2 to 7, the subscribers' lines, which are assumed to be numbered from to "99, appear in the central office in individual control and transmission circuits. For

42, is connected by way of conductor 2M to the forty-second anode 200, and line 20|, the number of which is 30, is connected by Way of conductor 209 to the thirtieth anode 2I0 in the beam switch 206. The beam switch 206 includes a central electron-emitting cathode 2H, a collector grid 2| and a set of driving coils 2|3, 2M, 2lb and 2I6. The central cathode, the collector grid and the circumferential anodes are all en- The driving coils convenient manner and serve to set up a rotating magnetic field which causes the electron beam 2li (virtual or real) to rotate at a velocity depending on the frequency of the energizing source 2id. For a, more complete description of the general principles of the rotating radial beam tube reference is made to thepatent to A. M. Skellett 2,217,774 of October l5, i940.

The primary beam switch 206 is paired with each of a plurality of secondary bearnswitches 300, 30|, etc., over a common transmission conductor 302 which interconnects the collector grid `M2 of the switch 20d and the collector grids 303,

5304i, etc., of the secondary beam switches. The beam switch 300 is substantially the same as lswitch 200; it has a circular row of one hundred anodes spaced and numbered in the same order, a collector grid 303, a central' electron-emitting cathode 300 and the collector driving coils 06, 307, 000 and 303. In addition the switch 300 is provided with a control grid 3|0, the purpose of which will be explained hereinafter. Likewise the secondary .beam switch 30I comprises a central cathode 3H, a control grid 3I2, a collector grid 343, a circular row of one hundred anodes and driving coils, two of which, 3M and tlf, are illustrated in the drawings.

When the primary beam switch 206 is paired with the secondary beam switch 300 for establishing communication betweena pair of subscribers movable plate 401 of the variable condenser 403 by an amount corresponding to the vertical movement of the shaft 40|; and the pinion 406 serves to set the movable plate 409 of the variable condenser 4I0 by an amount corresponding to the rotary movement of said shaft. The shaft 40| takes a number of vertical steps varying from one to ten in accordance with the tens digit of the calling subscribers line and in so doing sets the movable condenser plate 407 in any one of ten positions with respect to the stationary plates 4H, 4|2, 4|3 and 4M. The gearing between the plate 401 and the ratchet 405 is such that the plate 40'!l makes a complete revolution -of 360 degrecs for ten steps of the shaft 60|. Therefore, each ofthe successive values of the tens digits is represented by an angular rotation of the plate 401 which is a multiple of 36 degrees.

The four stationary plates of the condenser 00 are connected to the corners of an electrical. bridge comprising resistors M5 and di@ and the` condensers di? and M8, and the bridge input circuit tis is also bridged by a resistor d20 having its mid-point connected to ground. When an alternating voltage is applied to the input circuit 4| 9, the bridge applies potentials to the four quadrant plates 0| I, SI2, 4|3 and dlt to establish adjacent these plates an electrostatic iield the intensity of which varies in synchronisrn with the f -the patent to L. A. Meacham. 2,004,613 of June l1,

In like manner the phase shifter @I0 has ten different positions representing the ten different values of the units digitl of the calling line, and

' each of these positions of the movable plate 30s is a corresponding multiple of 36 degrees. The

' stationary'plates 122, #323, Mii and S25 are conlines,`\the relative position or phase of the beams ment, step-by-step rider switch. It has a brushcarrying shaft MI which is stepped vertically to select any one of ten levels of terminals, and which is stepped in a rotary direction to select any individual set of terminals in the level. The starting, controlling and stepping mechanism 402 is illustrated conventionally and may be of the usual well-known character. In -addition to the standard vertical and rotary ratchets 403 and 404 by which the brush shaft 40| is driven vertically and in its rotary directions, the shaft 40E, carries a' driving ratchet 405 and a driving pinion 406'. The driving ratchet 405 serves to adjust the nected to the bridge comprising resistors 26 and 421 and condensers M8 and 29 which, together with the grounded resistor l$30, is connected across the input circuit tai. The effect of the variable condenser M0 and the associatedA bridge circuits is, like condenser 300, to shift the phase of 4the voltage in the input circuit @3| by ten equal steps of 36 degrees each through the entire cycle of 360 degrees.

If, therefore, the voltage from the beam-driving source 2 I 8 is applied through the phase shifters SII) and 408 in series, the voltage in the output circuit 432 will have a phase relative to that of the source 2id which has been shifted by a multiple of 36 degrees which is equal tothe numerical sum of the tens and units digits. In other words, the units phase shifter would, under this assumption, produce a shift of the same magnitude as that produced by the tens digit. It is necessary, therefore, to reduce the shift eiected by the units digit to one-tenth of the shift effected by the same tens digit. The necessity for doing this can best be understoodA by referring for the moment to the beam connectors. Since there are lines appearing in ten groups of lten around lthe 360 degrees of the beam switch, each group grees. The phase shift, therefore, of the beam SI5 over a group of ten lines corresponds to one step of the tens digit phase shifter 408, namely, a 36-degree shift. However, a shift of the beam 3|6 from one line to the next within a group of ten corresponds :to one-.tenth of the shift produced by a single step of the units phase shifter 4I0. Hence in order that the phase shifter 4l0 may produce increments of phase shift of 3.6 degrees each rather than increments of 36 degrees, a frequency multiplier 433 is inserted between the source 2|8 and .the input circuit 43i of the phase shifter 4I0. The multiplier 433 multiplies the frequency of the source 2l0 ten times. Although the shifter 4l0 shifts the frequency of the input voltage by steps of 36 degrees, each one of these steps in reality corresponds to only a 3.6-degreeshift when compared with the original frequency. In Ithe output circuit of the phase shifter 4|0 a frequency divider 434 is in- `serted for the purpose of dividing .the frequency of the output voltage by -ten and thus restoring it to the same frequency as the source 2 I8. Thus, the voltage taken from the source 2id is applied to the units shifter dit and appears in the output circuit M9 displaced in phase by a multiple of 3.6 degrees which is equal to the numerical value of the units digit of the line which causes the setting of the phase shifter M0. This voite f with the units phase shift therein is then applied to the tens phase shifter 400 as above explained and appears in the output circuit 432 with an added shift which is equal to the multiple of 36 degrees corresponding to the numerical value of the tens digit that causes the setting of the phase shifter 408. We have, therefore, in the output circuit 432 a voltage which is displaced in phase, relative to the phase of voltage 2l0, which is an exact measure of the designation of 4the calling subscribers line. An ampliiier 440 is provided if desired for increasing the energy in the output circuit 432.

The phase displacement of the beam 3|0, however, must taken into account not only the number of the calling line but also the number of the called line. To lthis end the phase shifting register 500, which responds to lthe number of the called line dialed by the calling subscriber, is provided with a tens digit phase shifter 50i and a units digit phase shifter 502. These phase shifters are identical with those shown in Fig. 4; :the shifter 50i comprises a movable plate 503 driven through ten Vsuccessive steps by the vertical movement of the shaft 504, together with the stationary plates and associated bridge circuits; and the shifter 502 comprises the movable plate 505 which is rotated through ten equal steps by the rotary movement o1' the shaft 50S, together with the four stationary plates and the' associated bridge circuits.

Since the resultant phase shift for the beam of the secondary switch relative to the phase of the beam of the primary switch is the algebraic sum of the phase shifts representing the calling andqcalled lines, the calling line phase shifters of Fig. 4 are connected in series with the called line phase Shifters of Fig. 5 before the final voltage is applied to the beam-driving coils of the secondary switches. To this end the output circuit 432 from the phase shifter 408 is connected t0 the input circuit of the phase shifter 502. As in the case of the phase's'hifter 4|0, a frequency multiplier 506 is introducedto multiply thefrequency of the voltage in the circuit 432 by ten beforelapplying it to the units phase shifter 502.

` angular measure The effects of this multiplication is, as explained, to produce a voltage in the output circuit 501 whichis shifted by units of 3.6 degrees each with respect to the phase of the voltage ln the circuit 432. The voltage in the output circuit 501 is restored to the normal frequency of the source 2|0 by the frequency divider 505. This voltage is then applied to the tens phase shifter 50| and the resultant voltage in the output circuit 509 has a phase equal to :the algebraic sum of the phases representing the calling and called lines. A suitable amplifier 5I3 serves to increase the voltage in the output circuit 500.

Since it is the difference between the spatial locations of the calling and called lines in the beam switches that determines the phase diierence necessary to bring the beams onto these lines simultaneously as they sweep through their cycles, thephase Shifters of the calling and called lines are arranged to produce shifts of the opposite sense. More specifically, the phase shifters Mit and tid produce a shift of the negative sign in the voltage wave, whereas the phase Shifters bei and 502 of the called line produce a phase shift of the positive sign. This diference of sense may be obtained by arranging the driving connections of the plates 401i and 5th such that they rotate in opposite directions with respect to the stationary condenser plates and by arranging the shafts 405 and 50G to rotate the movable plates i053 and 505 in opposite directions. If the number of the calling line is numerically greater than the num ber of the called line, the negative phase shift of the secondary beam caused by the phase-shifting register 000 exceeds the positive phase shift of the beam caused by the phase-shifting register 50o by the difference between the -two numbers, and the negative sign before the resultant phase shift applied to the secondary beam indicates that this beam lags the primary switch beam by the phase angle which equals the spatial separation between the calling and called lines. However, if the number of the called line is greater than that of the calling line, the positive phase shift produced by the register' 50@ exceeds the negative phase shift produced by the register 406, and the positive sign before the resultant phase shift apn plied to the secondary beam indicates that the secondary beam leads the primary beam by the shift produced in accordance with the number of a calling line and the positive phase shift produced in accordance with the number of a called line gives a resultant phase shift between the primary and secondary beams which is an exact of the spatial separation of the lines.

f It will be noted that one of the advantages of multiplying the frequency by ten before and dividing it by ten after applying the voltage to the units phase Shifters is the uniformity obtained in the degree of motion and accuracy required for both the tens and units Shifters. Ii' desirable, however, it would be possible to obtain the necessary shift intervals of 3.6 degrees for the units digits without changing the frequency by arranging the movable plates of the units Shifters to move through distances which areV one tenth of the distances traversed by the tens Shifters for the same digital values. Also it will be understood that "where the frequency multipliers and dividers are used they are arranged to preserve the proper relation between phases of the voltage Tucker and H. J. Merchant, Post Omce Electrical Engineers' Journal, July 1942, volume 35, Part 2, page 62. However, it will be understood the frequency controlling devices used herein may be of any suitable and desirable type.

When the primary beam switch 205 is paired with the secondary beam switch 3M for establishing communication between a pair of subscribers numbers.

lines, the relative position or phase of the beams 2li and Sil is controlled by the pair of phaseshifting registers 600 and 700. The calling line register 600, like the register v300, is a line-iinding mechanism having access to all of the subscribers lines and includes a tens phase shifter ddl and a units phase shifter 602. Likewise, the called line register 100 corresponds to register 500 and coniprises a tens phase shifter Tdi and a units phase shifter lill. Voltage from the alternating source 2id is applied to shifter W2 through a multiplier B03 which multiplies the frequency by ten and the output voltage from the shifter Z, after having its frequency divided by ten by the divider 801i, is applied to the phase shifter 50i. The output voltage from the shifter 60H is amplified by amplier E05, following which its frequency is again multiplied by ten by the multiplier 'm3 and applied to the shifter m2, The output voltage from the shifter 'Q02 is restored to its original y frequency by the frequency divider ldd and is then applied to the phase shifter ldl. The voltage output from the shifter mi is amplified by amplifier i053 and is then applied over circuit 'ldd to the quadrature coils sid, dit, etc. of the secondary beam tube 30E.

In like manner other pairs of phase-shifting registers and secondary beam switches (not shown) are provided, the total number being selected in accordance with the maximum num ber of conversations to be permitted.

From the foregoing it will be seen that any pair of lines may be connectedv for communica- I tion through the primary and secondary switch beams by utilizing a single source of alternating voltage 2id to drive the primary beam in phase with the voltage from said source and to drive the secondary beam with the necessary phase displacement introduced. Accordingly, the source 'dit is connected directly to the quadraturecoils .2l3, 2M, 2|5 and 2H; of the primary Switch 26E and is connected by Way of circuit il@ and the several pairs of phase-shifting registers in parallel to the quadrature coils of the corresponding secondary beam switches. For examplel the circuit 2l@ is connected through the phase Shifters did, 08, 502 and 50i in series, thence over circuit dd to the quadrature coils of the beam switch 3mi.' Also the circuit 2id is connected. through the phase Shifters 602, 6M, 102 and '110| and thence over circuit '506 to the quadrature coils of the beam switch 30|. And in like manner 'the supply circuit 2 l 9 is connected through the phase Shifters of succeeding pairs of phase-shifting registers to the quadrature coils of the correspondpaired with the beam 2H for a particular conversation, is driven in synchronisni with the voltage of the source ZIB and with the beam 2li' but with a phase displacement which measures the difference between the calling and called line And the same is true of the beam dll and of the beams of other secondary switches not shown in the drawings.

It is, of course, desirable in a communication system, such as the one here illustrated, that the parties be able to carry on a two-way conversation.` This facility'is made possible in the present system, notwithstanding the unilateral character of the usual cathode-beam tube, by taking advantage of the well-known phenomenon of secondary electron emission. The space between the collector grid and the ring of anodes of the rotary beam tube disclosed herein is capable of conductingA signals in both directions if the proper relative voltages are selected. -The central cathodes are connected to the negative pole of the battery which produces the electron beam, the positive pole of this battery being grounded, the anodes are connected respectively through their individual transmission circuits to ground, and the common collector grid is connected to the positive pole of a battery of relatively low voltage, which also has its negative pole grounded. For exemple, the rotary beam switch 206 has its central cathode 2li connected to the negative pole of battery 220 and the positive pole of this battery is connected directly to ground. The individual anodes 200, 2id, etc., are connected through their transmission circuits 20d, 205, etc., to ground;

is connected over the common transmission conductor 302 through impedance coil Sid to the positive pole of battery dit. The battery 22d sets up a voltage, say 15G-volts, between the cathode 2M and each anode, which is suicent to cause a beam of electrons to ow from the cathode to the anode through slits or openings in the collector grid 2&2 notwithstanding the positive potential impressed upon the collector grid by the relatively small battery tlg. say l0 volts. lf, while the electron beam 2li is passing through the collector. grid 2li? to an individual anode, the potential of the anode is varied in accordance with the speech signals originated in the line connected to said anode, the intensity of the secondary emission set up by the impingement of the beam on the anode varies correspondingly and in turn imparts a corresponding variation to the potential'of the collector grid, to which the electrons of secondary emission are directed. The variations of grid 2li are impressed over the common medium 302 to the collector grid of the associated secondary switch, sayA the grid 30e of to impinge upon aparticular anode, and these variations in the beam are reflected by corresponding potential variations on the anode, which lin turn are impressed as speech signals upon the called line connected to said anode. On the other hand, if speech signals are originated in the called line wl'iichis connected to a particular anode in the beam switch 300, the potential varia- And the collector grid 2&2

cathode 000.

' the associated anode 8c3.

collector grid 303 to which the secondary emission is directed. 'Ihe potential variations of the grid 303 are transmitted over the medium 302 to the collector grid 2l2, and the grid 2l2 varies the intensity of the beam 2li as it passes from the cathode 2li through the grid to the particular anode with which the calling line is associated. Accordingly the potential of the anode is varied in accordance with speech signals and results in the transmission of these signals over the calling subscribers line. Thus the calling and called subscribers may tall: to each other in either direction over the established connection, making use of the primary and secondary emissions of the beam switches.

A clearer understanding may be had of the physical structure of the beam switches by reference to Fig. 8. This iigure shows the central cathode 80o, the collector grid 80H and the annular series of anodes Bilt, tot, 804, etc. As shown a in the Skellett Patent 2,217,774 referred to herein, the cathode llt@ may comprise a filamentary element located along the central axis of the cylindrical envelope of the tube, and the anodes may comprise a series of vertically disposed cylindrical strips arranged concentrically with respect to the cathode. The collector grid 80E consists of a cylinder having a series of vertical slots miti, 006, 807?, located in line with the central cathode and the respective anodes. The collector grid E is also provided with integral i'lns 00d, 809, 8 l 0 which act as partitions to form spaces individual to the respective anodes. The purpose of these spaces between adjacent fins is to conne the secondary electron emission from the associated anodes to prevent interference between circuits connected to adjacent anodes. In the figure the primary emission from the central cathode 80() is illustrated by the electron beam 8| l, which in the construction described is in fact in the form of a sheet of electrons emerging from the illamentary through the slots in the collector grid, one after kthe other, as the beam rotates, and, as illustrated,

after passing through the slot 306 implnges upon The impingement of the beam on the anode 803 causes the secondary emission of electrons which are attracted back to the collector grid 80G by. reason of the potential diiference between the anode and the collector grid. As above noted and as illustrated in the figure, this secondary emission is confined to the space formed by the fins 809 and. 8|0 and the anode 003. The beam switch shown in Fig. 8 is also provided with a control grid 8|2 the purpose of which will be explained presently.

Inasmuch as the primary beam switch B may be paired with a plurality of secondary beam switches for concurrent conversations between a number of pairs of lines, it is desirable. that the rotating beam of each of the secondary switches shall remainvirtual in all of its angular positions around the cycle, except the position corresponding to the called line. In this position the virtual beam is transformed into a real beam in order lill liti

This beam of electrons passes Y that conversation may take place between the lines of the conversational pair. To ellect this transformation of the secondary switch beams these switches are provided with control grids 3i 0, 3l2, etc. The control grid 3|0, for example,

is biased negatively with respect to the cathode 305 by means of a biasing battery 320 which is connected to the grid through the coil of high frequency transformer 32|. The normal bias on the grid 3l@ is suiiicient to prevent the iiow of electrons from the cathode 305 to the anodes in response to the voltage of battery 322. Therefore, as t1 ye magnetic held rotates about the switch 3mi, a virtual beam rotates therewith until the position is reached occupied by the anode to which the called line is connected. At this same instant the rotating meam il of the primary switch, which exists always as a real beam, is connecmd to the anode to which the calling line is connected. As the beam 2li rotates through its successive cycles it generates in the transmission circuits 201i, 205, etc., connected to the respective anodes, momentary impulses of high frequency, namely, a frequency which is one hundred times the frequency of the source Zit. When, therefore, the beam Eil engages the anode of one of the lines of a pair engaged in conversation the high. frequency impulse developed in the associated transmission circuit (20d, for example) is passed by the high frequency transformer 22l and is transmitted through the associated register fifi@ through the high frequency transformer @2i the control grid 3io. The polarity of this high frequency impulse is such. that it overcomes ino mentarily the negative bias on the control grid 3l@ whereupon the beam 3l@ assumes a real character and electrons flow from the cathode 305i to the anode of the other line of said pair. An instant later, as the primary beam 2l?! moves on the Aanode of the first-mentioned line and passes to the next successive anode, the high frequency impulse ceases, the negative bias of the grid @I0 is restored, and the beam 3io resumes its virtual character until it has completed another cycle.

A detailed description will now be given of the operation of the system, assuming that a plurality oi conversations are taking place concurrently. For this purpose it will be assumed that the subscriber of. line 20o (line No. 42) wishes to converse with the subscriber of line 323 .(line No. 20) and that the subscriber of line 20! (line No. 30) wishes to converse with the subscriber of line 32d (line No. 62). When the line ad@ calls, a starting condition is applied to conductor 222, and, if the registers 300, 50o are the set next allotted for use, the controlling mechanism 402 of the finder register 400 starts the register in operation to hunt for and seize the calling line 2te. The number of the calling line being 42, the brush shaft 40E takes four vertical steps and two rotary steps to bring the brush sets into engagement with the terminals representing the calling line. Accordingly, the movable lcondenser plate 401 is rotated to its fourth position relative to the stationary plates, and the movable plate 409 is rotated to its second position relative to the stationary plates. When the register 400 reaches the terminals of the calling line, a test circuit is closed over conductor 435, brush 43S, terminal 437 to conductor 438 on which a hunting condition exists. Closure of this circuitl causes the cessation of the hunting operation, and ground is thereupon applied over conductor 435 to render the line 200 busy to other registers. The loop of the subscribers line 200 is now extended over conductors 439 and 440 through brushes 44| and 442, conductors 443 and 444 to the operating mechanism Ell of the associated called line register 500. Ilhe calling subscriber manipulates his dial 223 to transmit the tens and units digits 2 and "0 of the called line 323. These impulses operate the register 500, which takes two vertical steps and ten rotary steps to position the movable plates 503 and 505 correspondingly. The shift of phase, which is negative in sense, imposed by the register 400 upon the voltage in the circuit 32 is equal to 4x36 degrees +2 3.6 degrees or` -151.2 degrees; and the shift, which is positive in sense, imposed by the register 500. upon the voltage in circuit 509 is equal to 2x36 degrees or +72 degrees. Therefore, the resultant shift, of phase of the voltage appearing in the circuit 509 is 151.2 degrees +72 degrees or 79.2 degrees. Thus, as the beams 2H and 3io rotate in synchronism, each time the beam 2H reaches the anode 208,

which occupiesA a radial position 151.2 degrees' from the zero position the beam 3HE engages the anode 325 which occupies a radial position 72 degrees from the zero position. In other words, the beam Si@ is lagging the beam 2 il by the fixed angle 79.2 degrees, which is the phase displacement introduced by the phase-shifting registers 200 and 500 in accordance with the numbers of the calling and called lines.

When the calling condition appears on the other calling line 201, the start circuit is closed and the next available set of registers 600 and H00 is taken for use. The operating mechanism dit@ of the finder register responds to the starting condition and operates the shaft 501 three steps in a vertical direction and ten steps in the rotary direction to drive the movable plate 600 to its third position relative to the stationary plates and the movable plate E09 to its tenth position (a full cycle) relative to the stationary condenser plates. The setting of the register 200 on the terminals of the calling line 200 extends the calling line loop over the conductors 225 and 22o and brushes dit and tit to the operating mechanism 707 of the called line register 200. The calling subscriber manipulates his dial 221 to transmit the tens and units digits "6 and 2 of the called line 32d, and the register F00 positions the movable plates E28 and '09 correspondingly. The negative phasel shift introduced by the setting oi the register dit@ is equal to 3x36 degrees or -108 degrees, and the positive phase shift introduced by the register lo@ is equal to 6x36 degrees +2 3.6 degrees or +2232 degrees. Thus the resultant phase shift appearing in the circuit 'F05 is 108 degrees +2232 degrees or 115.2 degrees. Thus, as the beams 232 and 3W rotate in synchronism, each time the beam 2H reaches the anode 210, which occupies a radial position 108 degrees from the zero position, the beam 3H engages the anode 32d, which occupies a radial position 223.2 degrees from the zero position. In other words, the beam` 3 i l is leading the beam 2 i 'l by 115.2 degrees which is the phase displacement introduced by the phase-shifting registers 600 and 180 in accordance with the numbers of the calling and called lines.

The transmission circuits for conversation be`` tween the subscribers of the two pairs of lines will now be described. As above explained, the real beam 2li of the primary switch is rotating in phase with and in synchronism with the voltage of the source 2id, the virtual beam 316 of the switch 300 is rotating Ain synchronism with but 79.2 degrees behind the beam 2H, and the virtual beam of switch 30| is rotating in synchronism with but 115.2 degrees ahead of beam 2li. This relation continues as long as the subscribers remain in conversation. Assume that at a given instant the primary beam 2l1 has reachedthe angular position correspondingto the calling line 200 and is dwelling briefly on the anode 208. At this same instant the secondary beam 316 is dwelling on the anode 325 individual to the called line 20. If at this instant the calling subscriber' is speaking, the voice currents in the line `Zilli the common transmission medium 202. Also at this same instant the beam 2W, upon striking the anode 202, has produced an impulse of high frequency which is transmitted over conductor 202 through the transmission circuit 20d and the high frequency transformer 22! thence over conductors 230, brushes dit, conductors M6 to the primary winding of high frequency transformer 32E. This impulse is induced in the secondary Winding ci the transformer 32i, and as above explained, opposes the normal bias on the control grid 3io, causing the beam 36S to strike or to change trom its virtual to its real character.

Since at the instant assumed the common medium 322 has assumed a certain potential, in accordance with the instantaneous value oi the calling subscribers speech, the collector grid @uit likewise takes up a corresponding potential. Therefore, the real beam 3io is controlled in its intensity in a manner to produce a proportional potential on the anode 325 on whichit impinges. Theanode 325 being connected by Way of conductor 32? to the transmission circuit 328 of the called line 20, the successive potential values thus assumed by it in accordance with the rotarI tion of the beam reproduce the audio-frequency Wave and cause talking current to now inthe subscribers line 323 representing the speech of the calling subscriber.

Conversely, if the called subscriber is speaking 'at the instant the beams 2i? and 3l@ are engaging the anodes representing the calling and called lines 2b@ and 323 respectively, the current variations in the line 323 cause potential variations to be applied by way of conductor 32'i to the anode 325 on which the real beam @It is now impinging. 'floevariations of potential on the anode 325 cause through the secondary electron emission corresponding variations on the collector grid 303 at the successive instances marked by the striking of the beam, and this succession of diiiering potentials are applied over the common medium 202 to the collector grid 292 of the beam switch 205. The appropriate succession of potentials of the collector grid 2&2 vary at thecorresponding instances the intensity of the beam 2li, resulting in` a succession of diiering potentials on the anode 208 which reconstruct the audio-frequency wave shape. The resulting voice variations are imparted over conductor 2011 to the transmission circuit 20d and are induced through thetransformer 228, causing the flow of talking current in the calling subscribers line 2o0.

dit, a fragment of the speech is transferred in this manner between the calling and called lines For each of the rapidly recurring cycles of the beams 2H and 200 and 328, the fragments following so rapidly upon each other as to give the impression of continuity to the speakers in accordance with the principles of the time division form of multiplex telephone system.

In a similar manner the synchronous beams '2H and 3H engage the anodes 2|0 and 3 26 simultaneously and repeatedly; at each such engagement a high frequency impulse is transmitted by way of transmission circuit 205, high frequency transformer 23|, circuit 232, brushes 6i2, circuit SIB, causing the beam 3H to strike; and transmission takes place in either direction between the calling line 20| and the called line 324.

When the subscribers have ilnished their conversation they replace their receivers on the switchhooks, and the calling condition is removed from the line circuits 202 and 203, permitting the release in any well-known manner of the register sets 400, 500 and 600, lull. These registers may now be selected in response to new calls on any oi the subscribers' lines.

Thus it will be appreciated that the speech of each individual conversation is transmitted through this system, over the common connecting medium of it, as a rapid succession of sharp impulses, the successive peak values of any one set of which trace out 'the voice-frequency wave oi. that particular connection. It is this feature which enables the single rotating beam switch i@ (Fig. l) to accommodate simultaneously calls over all of the lines associated with it. This it does by transmitting for each such line over the common medium for but a brief interval in accordance with the superposition principle of the time-division multiplex type of system. In that type of system two such rotating switches are employed, one at each end, which are operated in synchronism and in iixed phase relation, whereby a given line at one end is always connected with a given line at the other, and generally in the samerelative position. The departure from this prior art in the present system, in respect to this time-division multiplex phase of it, is that the present system provides for connecting any one line at one end of the system with any other line at the other end.

It has already been explained thatI the invention contemplates the use of virtual as well as real beams of electrons. The controlling eld which rotates the radial beam may be electrostatic instead of electromagnetic as illustrated. The inventionalso contemplates the use of beams of other forms of energy, and it should be understood that whenever the specication or claims speak of these beams either in motion or in their instantaneous positions these descriptions are intended to apply to the beams in their virtual nature as well as in their real form.

It Awill be understood that other types of phase shifters may be used if desired. For example the rotating condenser plate may be replaced by a succession of xed networksccmprising tapped condenser units which are connected to sets of contacts selected by the settings of the register switches.

What is claimed is:

l. The combination in a communication system of a group of lines, means for causing a beam of energy to scan said group of lines repeatedly and to establish communicative engagement with any desired line in said group, means for causing a second beam of energy to scan said group and to establish communicative engagement with any transformer 329 to the control grid SI2,

desired line in said group, and means for controlling the relation between said beams to establish communicative engagement simultaneously between any desired pair of lines in said group.

2. The combination of a communication system of a group of elements, means for producing two separate beams of energy, means for driving said beams synchronously to traverse the elements of said group repeatedly, circuit means including said beams in serial relation for establishing communication channels between elements of said group, and means for varying the phase relation between said beams for causing them to traverse any desired pair of elements simultaneously and repeatedly to establish a connection between said pair of elements.

3. The combination in a signaling system of a group of lines, each line having a different designation, means for producing two separate beams of energy, means for driving said beams synchronously to traverse the lines of said group repeatedly, circuit means including said beams for establishing signaling channels between pairs or lines of said group, and means controlled in accordance with the designation of one of the lines of any desired pair to determine the phase relation of said beams for causing them to engage the lines of said pair simultaneously and repeatedly to es tablish a connection between said pair of lines.

4. The combination in a signaling system of a group of lines, each line having a different designation, means for producing two' separate beams of energy, means for driving said beams synchronously to traverse the lines of said group repeatedly, circuit means including said beams for establishing signaling channels between pairs of lines of said group, and means dependent on the designations of both lines of any desired pair for adjusting the space relation of said beams to cause them to engage the lines of said pair simultaneously and repeatedly to establish a connection between said pair of lines.

5. The combination in a signaling system of a group of lines having appearances arranged in a fixed spatial relation, each of said lines having a definite designation, means for producing two movable beams and for driving them synchronously and cyclically over said fixed line appearances, circuit means including said beams for establishing signaling channels between the lines of said group, and means for effecting a time displacement between said beams corresponding to the spatial displacement between any desired pair of lines in said group.

6. The combination in a signaling system of e group of lines having individual appearances arranged in a xed spatial relation, each of said lines having a diierent designation, means for producing two movable beams and for driving them synchronously and cyclically over said xed line appearances, means including said beams for establishing signaling channels betweenI the lines of said group, and means dependent on the designations of the lines of any desired pair for ei'- fecting a time displacement between said beams corresponding to the spatial displacement between said pair of lines.

7. The combination in a communication system of a group of lines having appearances arranged in a xed spatial relation, each of said lines having a different designation number. means' for producing two beams of energy and in synchronism over the xed appearances of said lines, registers for registering the ,designations of any desired pair o:

lines, and means controlled by said registers for effecting a time'displacement between said beams oi energy corresponding to the spatial displacement between the lines of said pair to cause said beams to engagethe lines of said pair simultaneously.

8. The me'thod of establishing a signaling connection between any pair of lines of a group of lines which comprises arranging said lines in a xed spatial order, causing beams of energy to traverse said lines synchronously and cyclically, and eilecting a phase displacement between said beams of energy corresponding to the spatial displacement of the lines oi the desired pair.

9. The method of establishing a signaling connection between any pair of lines cfa group of lines which comprises arranging said lines in a nxed spatial order, causing beams of energy to traverse said lines synchronously and cyclically, and utilizing the designations of said lines for eifecting a phase displacement between said beams of energy corresponding to the spatial displacenient of the lines of the desired pair.

10. The combination in a Signaling system of a group of elements arranged in xed spatial relation, means for producing a plurality of beams .of energy and for driving them synchronously and cyclically over said xed elements, means including said beams for establishing signaling connections between said elements, means for introducing phase displacements between said beams for causing them to engage the elementsof a plurality of pairs, each pair comprising any element and any desired other element, the engagement o! the' several 'pairs occurring cyclically and sequentially and the engagement of the element of cach pair .occurring simultaneously., v

i1. The combination in a communication sus tem of a group of lines, a primary beam switch in which said lines appear in a xed spatial relation, a secondary beam switch in which said lines appear in the same iixed spatial relation, means tor driving the beams of said switches in synchronism to scan said lines successiveh' and cyclically, means including said beams for establishing communication connections with said lines, and'means for introducing phase displace# ments between said beams forcausing them to engage the lines of any desired pair simultane ously. y

12. The combination in avcommunication sys= tem of a group oi lines, two beam-producing de-a vices, said lines appearing in a lined spatial rela@ tion in both of said devices, a source of voltage of a given frequency. circuit means for applying voltage from said source to said devices to drive both beams at synchronous speed over said tem of a group of lines having designationsbased on the decimal system., means for producing` beams of energy, a source of voltage for driving said beams synchronously tov scan the lines o! said group, a pair oi phase-shitting registers for registering the digital values of the vdigits in two successive digital places of the designation of any particular one of saidv lines, means for setting said registers in accordance with the values of the, correspondingc digits of said particular line, cir-A cuit means for applying voltage from, said source to said registers in series to eiect a shiit'ot phase which is the sum oi the shifts produced by said registers. each register serving to shift'the phase yby an amount proportional to the numerical value of the digit registered thereon. and means for changing the frequency-oi the voltage applied to one of said registers with respect to the irequency applied to the othe yregister by an amount which corresponds 4to the dierence in decimal value between the successive decimal places to which said registers correspond.

l5. The combination in a communication system of a group oi lines having designations based on the decimal system, meam -for producing beams of energy, asource of voltage for driving said. beams synchronously to scan the lines' of said group, a pair of phase-shifting registers for registering the digital values of the digits in two successive digiizi places of the designation oi any particular one of said lines, means for setting said registers in accordance with the `values of the corresponding' digits of said particular line, circuit means for applying voltage from said source tosaid registersinseriestoeiiect a shift ofphuow isthesum ofthe ahiftsproduced by am s ri-rie: servingto shift the phase b w propomonai to the numerical value oi the digit theln.

lines in succession and cyclically, and phaseshifting means for shifting the phase of the voltage applied to one of said devices to'introduce a desired phase displacement between said beamse 13. The combination in a communication sys= tem of a group of lines arranged in ilxedspatial relation, means for producing two separate beams oi energy,l means for driving said beams synchro-= nously to traverse the lines of said group repeatedly. circuit means including said beams for establishing communication connections between said lines, and phase Shifters for shifting theA phase of one of said beams in opposite senses to introduce a. resultant shift in the phase ot said beam relative to the phase of the other beam which corresponds to the spatial displacement of any desired pair of lines in said group.

i4. The combination in a communication sysmeansfor multiplying` the frequency of the volt-I age applied to a particular one'oi said registers by a factor representing the dinerence in decimal value between the digital place to which said reg ister corresponds and the digital place to which. the other oi said registers corresponds, and means for dividing by the same factor the frequency ot the voltage after it has experienced the shift of phase imposed by said Aparticular register and before it is applied to said other phase-shifting register.l

16. The combination in a communication system of a. plurality of lines. a common medium having communication channels,F one between each line oi' said plurality of lines and each other line oi' said plurality. beam switches in which the channels or said common medimn appear, means for driving the beams of said switches synchronously over said channel appearances, and means y controlled by any particular one of said lines for shifting-the phase relation between said beams to select the communication channel of said cnmon medium which interconnects said particular line and any other desired one of said lines.

1'1. The combination in a communication system of a plurality o! lines, a common medium having communication channels, one between each line o! said plurality voi lines and each other line ot said plurality. beam switches in which the channels ot said common medium appear, means for driving the beams of said switches synchronously over said channel appearances, and means controlled by any number or said lines as calling lines' for varying the phaserelation between said synchronousbeams to select the communication channels which interconnect said calling lines respectively with e. corresponding number of said lines chosen at will as called lines for concurrent communication. r

18. The method of interconnecting any pair of lines of. a plurality of lines over a. common transmission medium which consists in establishing in said medium recurrently and in rapid succession time-separated transmission channels individual respectively to said lines and shifting the position of any one of said channels in time to coincide withthe time position of any other one of said channels.

osmosi 19. The method of interconnectingany pair of stations of a plurality of stations over a common transmission medium which consists in establishing in said medium recurrently and in rapid succession time-spaced transmission channels individual respectively to said stations, and shift;

ing the position of any one of said channels in time to coincide with the time position of. any other one of said channels.

LLGYD ESPENSCHIED.

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