1o, v1944s. -2,407,399 DUPLEX zcoNTRoL CIRCUITx Filed July 24, 1944 / .D E'. 77a IN VENTOR. » @5275@ 2,407,399 Patented Sept. 10, 1946 UNITED -s'l‘lrrts' PATENT‘Í' QFQFICEÁYI _ . 2,407,399` y ` DUPLEX CONTROL CIRCUIT l Robert vW. Carlson, VDepew, „ and -Madison G. Nicholson, Jr., Snyder, N. Y., assignors to vColonial Radio Corporation, Buiïalo, N. Y.v ' L Application July 24, l1944, Serial No. 546,404 15 Claims. (Cl. 179-15) 1 2 when the other is in.- cuits, and more particularly to such circuits as may be employed to control a transmitter which may operate with one of a number of different vAt the same time, to prevent one modulator be- i ing rendered. inoperative, it is desirable tto provide control circuits whereby these modulatorszmay be alternately operable in turn for a period ofl time which> isgsuflicient to permit them tofsend characteristics; that is to say, the transmitter . may be controlled from two different keying po-sitions I and 2 and each of the keying positions out` the may controla number of different modulators, each having its `own particular characteristicy which it impresses onthe carrier.' may be different from those of the modulators in keying position I. Similarly‘modulators F, G, n one key will operate its modulator to send out the signal characteristic of the operating modu lator, and after this action is completed, control is transf-erred to thel other modulator, which Modulator B may cause the transmitter Keying position 2 may'similarly con-_trol four ~ I and another key in keying position 2 yare closed to send three pulses of predetermined length and spacing, modulator C- four pulse-s of predeter mined length and spacing, andmodulator D five pulses of predetermined length and spacing, and 20 modulators', such as E, F, G, and I-I.,> E may'cause the transmitter to send two' pulses of predeter-`mined length’with a predetermined'spacing be# .tween them, and these pulse and space lengths " simultaneously. ' Then, under such conditions, Modulator A may, for example, cause the any yone of these may be operated from its par ticular switch or key in keying position I. f ` circuit, ’supposinglthat a key in keying position ` 10 transmitter to send two pulses of predetermined length with a predetermined spacing between them. desired> signal. For example, in the operation of `our control For instance, in keying position I there may be, for example, four «different modulators A, B, C, and D. , sary to provide arrangements for locking >one `out This invention relates to duplex Control cir causes the transmitter to send out a signal modu lated with the characteristic of the other modu lator, and the entire process of operation may be completed in lan extremely short period of time; for example, of 'the order of 1/1oo` of- a'second. Thus, while the two modulators act successively arid never simultaneously in point of time, yet their operations follow eachother so quickly that for a1l<fpractical purposesthey may be regarded as simultaneous, and this, in eil‘ect, provides for duplex opera‘tion of the transmitter. , The invention herein is an improvement on the ' invention described and claimed in the coi-pend and H may cause the transmitter to send 3, Il, and 30 ing' application of Madison G. Nicholson, Jr., 5 pulses` of predetermined length and spacing diiTering from the length and spacing of the pulses controlled b-y modulators A, B, C‘, and D. It is to be understood that the action of the modulators is not repeated; that is to say, if L the key controlling modulator A be closed in keying position I, the transmitter willr send two pulses separated by a space of predetermined entitled “Duplex control circuit,” owned by the assignee ’of the present application. It is an object of this invention to provide an improved duplex control circuit which will pre vent one modulator from controlling the trans mitter While the other is in control. It is a, further object of this invention to pro vide such a circuit in -which the operation of the length, and no further action will occur unless second modulator, although temporarily pre mission is «completed in a few milliseconds so that plex operation is provided. the key is opened and closed again, at which time 40 vented .from occurring While the first modulator is in control of the transmitter, will, nevertheless, the transmitter" will again send ltwo pulses with occur within an extremely short interval of time a predetermined space between them. after the control key is operated. ' ' » This action, as will be understood, is analogous ‘ VIt is still a further -o'oâect of our invention to to that of a'magnetically operated bell which has no interrupter in its circuit so ‘that when the .L provide an ‘improved control circuit for applying two modulators to a transmitter alternately for switch is closed, the bell will strike only once and very short periods of time whereby in effect du not ring continuously. Furthermore, the trans it is possible for a modulator in keying position 2 ïto follow very rapidly the action of a modulator in keying position I. It is desired to provide a control circuit which ' will permit operation of any modulator at will, as maybe desired, but it is also'imlportant to prevent blocking of the modulators or improper or faulty operation which might occur provided the control keys for the modulators in positionA I and position 2 were operated simultaneously. Since only one modulator can be permitted to operate at a time on the transmitter, it is nec-es AIt is still a further object `of our invention to provide such a control circuit in which more than two modulators may be employed, the first being any one> of a group of modulators which may be selectively employed and the second being any one of another group of modulators which may be selectively employed. Y Still other objects and advantages of our in vention will be apparent from the specification. The features of novelty which We believe to be vcharacteristic of our invention are set forth with partìcularíty in the appended claims. Our inven 2,407,399 3 4. tion itself, however, both as to its 4fundamental of relay 32 to fromu contact 40j of switch et, the other end of the winding of relay Sel to front con tact fs2f of switch t2, Vand the other end of the winding or” relay St to back contact ¿ith of switch principles' and as nto its., particular embodiments, will best be understoodì'by reference tothe speci fication and accompanying drawing, in which ’ The single figure is a circuit diagram of an im- . proved duplex control system in accordance with" our invention. - Referring now more particularly to the draw ing, it indicates the transmitter, which may be controlled by any one of the modulators A, B», C, 42. ‘ Like switches 3l', 3S, and 4i, switches 38, 135i, and »t2 may be biased to back contact position, and are arranged so that there is an interval of time when the circuitl is open as the switch is moved from back contact to front contact. The or D in keying position i, and by any one of the blade of switch ¿i2 is connected to the back con modulators E, E', G, and l-ï in keying position 2. The construction and operation of the modula tact of _switch til, the blade of switch lli) to the back contact of switch 35, and the blade of switch tors is not shown or described in detail since these 3B through resistance ¿it to the -I~ B source. Contacts Etc of relay 3@ close the circuit to Modulators A, B, or C may be selected and put modulator E, contacts 32e to modulator F, con into operation by means of switches 3l, 39, and 4i tacts ’32o to modulator G, and contacts `»tic to respectively in keying position I and any one of modulator H. The -I- B source is connected modulators E, F, and G may be selected and put through resistance l5 to the cathode of tube Ii into operation by switches 38, sil, and ¿i2 in keying 20 and through resistance it to the cathode of tube position 2 respectively. Modulator D in keying I2. position I and modulator H in` keying |position 2 For controlling tubes I! and I2, we provide a are not provided with a selecting switch since multivibrator comprising tubes 2i and 22, the these send clearing signals at theV completion of ~former having cathode 2SC, control electrode Zig, operation of any other modulator of the same 25 and anode i2 la, and thev latter cathode 22e, control keying position and are caused to operate by the electrode 22g, and anode 22a, circuits herein employed, as will be described y'l‘he cathodes of tubes 2l and 22 are connected Prevention of operation oía modulator oi posi together and to ground, the grids through resis tion I simultaneously with the modulator of posi tances 23 and äfi respectively to the -I- B supply, tion 2 is prevented by a pair of tubes which may 30 and resistance 23 is shunted by condenser 25 to be of the thyratron type I I and I2, tube II having resistance 2l in series, and resistance 2l! shunted cathode IIc, control grid IIg, screen grid IIeg. by condenser 26 and resistance 28 in series. and anode I Ia. Similarly tube I2 may have cath The intermediate point of resistance 2l and ode I2C, control grid 12g, screen grid I zsg, and condenser 25 is connected through a differentiat anode I2a. ' ’ l 35 ing network comprising condense-r i9 and re In the embodiment of the invention herein sistance I'I to grid llg of vtube I l, and the inter shown, the cathodes of these tubes are connected mediate point of condenser 2S and resistance 28 to ground through resistances I S and I4, and the similarly connected through a differentiating plate circuit of tube I I is connected to one end of network comprising condenser 2li and resistance the actuating winding of relays 2S, 3|, k33. and 35 40 i3 to grid lßg of tube I2. Anode 25a of tube 2I in keying position I. The other end of the wind~ is connected to the intermediate point between ing of relay 29 is connected to front contact 31j condenser 25 and resistance 2&3 and anode 22a of switch 3l', winding of relay 3.I to front contact of tube 22 to the intermediate point between` con 39j of switch 39, and the other terminal of the denser ?!5 and resistance 2l. ` winding of relay 33 to front contact 4 if of switch 45 The constants of this multivibrator circuit are fil. The other terminal of' relay winding 35 is preferably so chosen that the circuit delivers a connected to back contact Mb of switch 4I, the square wave having a frequency of the order of blade of switch 4! connected to back contact 3% 25 cycles per second. Consequently, there will be of switch 39, and the blade of switch 39 connected applied to grid Mn of tube ll through the dif to back contact 31h of switch 31 and through re 50 ferentiating network condenser I5? and resistance sistance 43 to the source of supply -I.- B. I‘I 25 positive pulses per second and te grid 12g Switches 31, 39. and ¿Il are preferably spring of tube 4I2 through differentiating network con biased to back contact position, and they are of denser 12!) and resistance I8 25 positive pulses per the type in which there is no wipe-over; that is second, and these will be delivered alternately, to say, when they are moved from back contact 55 ñrst to tube I l, then to tube I2, so that these to front contact position, there is an intermediate grids electrically may be regarded as the opposite position in which the switch is open, relay 29 ends of a see-saw, never going positive at the controls its contacts 29e, relay 3! its contacts 3 Ic, same time. relay 33 its contacts ttc, and relay 35 its Contacts Of course, negative 'pulses are also applied to 35e, these contacts beinor normally biased to open 60 said grids once per cycle. ‘but since these negative position and closed by the flow of current through pulses »play no part in the operation of the circuit, their respective windings. they need not be considered. Contacts 29e close the circuit controlling modu The operation will now be described with ref lator A. contacts 3io modulator Bi, contacts 33C erence to keying position l, and it will be under modulator C, and contacts 35e modulator D, in 65 stood that the description as applied to keying form per se no part of this invention. such a manner that when any one of these relays position I applies equally to keying position 2. operates, its respective modulator is put in con trol of the transmitter and causes the transmis sion of the signal characteristic of such modula tor, Keying position 2 is entirely similar to key~ 70 Under normal conditions; that is, when no signal is being transmitted, the relays and switches are in the position shown. Tube I! is ionized and will remainY ionized, the negative pulse which is Anode I2a of tube 2&2 is connected to onerend of ing position I. the actuating windings of relays 3Q, 32, 34, and 36, periodically impressed upon this tube by the mul tivibrator being insufficient to deionize. Plate current flows only through the winding the other end of which may be connected to front of relay 35, and contacts 35e are closed. contact 38j cfgswitch 38, the other end of winding contacts of the other relays, 29, 3i, and 33, are The 2,407,399 g5 position I and a switch in keying positionV 2v are open, and the plate circuit of tube II is com simultaneously closed for about 1/25 second or longer, four signals will be sent; ñrst', the oper ating signal from either keying position I or 2, pleted through back contact Mb, blade of switch 4I, back contact 39h, bladev of switch 39, back7 contact 3‘Ib, and blade of switch 3l. If now switch 4| be moved from back to front depending upon which of tubes II and I2 is ñrst ionized; second, the operating signal from the other-keying position; third, the clearing signal contact, the plate circuit of tube-II is open during the interval when'the blade of switch 4I moves from the one keying position; and finally, theoff back contact 4Ib until it reaches front con clearing signal from the other keying position; tact 4If. By opening the plate circuit, tube 3l is caused to deionize, this interrupting plate cur 10 and the entire sequence of operation will be com pleted in not more than a tenth of a second rent through relay 35 and allowing relay con tacts 35o to open. . longer than theV time during which the keys were , held down. While we have shown and describedvcertain When the blade of switchVlII reaches front contact, the plate circuit of’tube II is completed through the winding of relay 33. The operating preferred embodiments of our invention, it will be understood that modiñcations and changes may be made without departing from the spirit .and voltages on tube II are so chosen that the tube will not ionize until a positive pulse is impressed upon grid' I Ig from the multivibrator. There fore, tube II will remain in deionized condition until a positive pulse reaches grid IIg. When this occurs, tube I I ionizes and plate current be ginsv to flow through winding of relay 33, there by energizing the relay and causing closure of contacts33c, and the closure of these contacts Vcauses operation of modulator C, causingrthe transmitter to send the characteristic signal pro duced by modulator C. Once the signal has been sent, no further ac ment, or combination Which we claim'as our in vention or discovery,l and we have explained the tion will occur so long as switch III is held on front contact 4If. When this switch is released, ‘ l. The combination with a transmitter, of a plurality of banks'of modulators, each bank com scope thereof, as will be clear to those skilled in the art. ed out andhdistinctly claimed the part, improve principles thereof and the best mode in which we have contemplated applying those principles so as tc distinguish our invention from other in ventions. We claim: it is carried back to bac-k contact, and in passing off front contact 4U opens the plate circuit of tube II, which causes deionization of the tube. 'Iïl'n's interrupts the plate current flowing through the actuating winding of relay 33 and contacts 33o open. quential operation of the modulators when two switches controlling molulators in different banks are closed simultaneously. 2.l The combination with a transmitter, of a contact, the plate circuit of the tube is again completed, `but the tube does not reionize until the next positive pulse from the multivibrator is yplurality of banks of modulators, each bank comprisingV a plurality of modulators, each ar ranged to impress its characteristic modulation f When this occurs, the tube fires and the plate on the transmitter, a switch for controlling each current flowing through the winding of relay ‘35 closes contacts 35o, and molulator D isestab lished as the controlling molulator, causing the transmitter to send the clearing signal. This completes the cycle of'operation, and the appara tus is now ready for another closure of switches 31, 3S, or 4I to front contact. y . it will be understood that operation of the prising a plurality of modulators, each arranged to impress its characteristic modulation on the transmitter, a switch for controlling each modu lator respectively, and means for causing se As soon as switch 4I closes on back impressed upon its grid. ` In this application we have particularly point- ' modulator respectively, means ,for causing se quential operation of a modulatorY in each bank » kwhen their control switches are closed simulta neously, said last mentioned means includingv a pair of gas discharge tubes, and means for pre venting simultaneous ionization of said tubes. 3. The combination with a transmitter, of a modulator in keying position` 2 is the same as that 50 plurality' of banks of modulators, each bank comprising a plurality of modulators, each ar already described except't‘oat they are controlled ranged to impress its characteristic modulation by tube I2 instead -of tube II and that, as on the transmitter, a switch for controlling each already stated, no modulator of keying position I modulator respectively, means for causing se can operate while any modulator of keying posi quential operation of a modulator in each of tion 2 is operating, and vice versa. said banks when their controlling switches are Suppose, now, that switch 4| in keying position closed simultaneously, said last mentioned means I and switch 42 in keying' position 2 happen to be includinga pair of gas discharge tubes, means closed simultaneously. It cannot be predicted for preventing simultaneous ionization of said which tube, II or I2, will ionize ñrst, this being dependent upon which ñrst receives the positive 60 tubes, and a relay for each modulator respec tively operated by the space current of said gase pulse from the multivibrator. If it happens that tube I2 receives the positive pulse before tube II, then tube I2 will first ionize and modulator G will be put in control, sending out its characteristic group of pulses. If switch 4I is still closed after the signal is sent by modulator G, fthen the contacts of relay 33 will be closed, modulator C of position I will beI placed in control, and its characteristic signal will be sent. Upon release of keys 4I and 42 modulators D and I-I will be successively estab lished in control and both clearing signals sent, depending on which of tubes II and I2 first re ceives a positive pulse. Thus, it will be seen'that if a switch in keying ous discharge tubes. _ » 4. The combination with a transmitter, of a plurality of banks of modulators, each bank co-m prising a plurality of modulators, each arranged tc impress its characteristic modulation on the transmitter, aswitch for controlling each of said modulators respectively, means for causing'se quential operation of one modulator in each bank when their control switches are closed simul taneously, said last mentioned means including a pair of ‘gas discharge tubes each having a control electrode, a substantially square wave generator, 75/ >means forV impressing alternately upon said con 2,407,399 7 trol electrodes positive pulses derived from the the transmitted signal,V means for selectively output of said square Wave generator. 5. 'Ehe combination with a transmitter, of a plurality of banks of modulators, each bank com causing operation of any one ,of said working signal modulators, and means for energizing the clearing signal modulator at the completion of the prising a plurality 0l modulators, each arranged working modulator signal. to impress its characteristic modulation on .the 11. In a signaling system, in combination, a transmitter, a plurality of working signal modu transmitter, a switch for controlling each modu lator respectively, means for causing sequential operation ci one modulator in each bank when said their last control mentioned switchesmeans are closed including simultaneous a pair of gas discharge tubes each having a control elec trode, a generator of substantially square waves, and a pair of diiîerentiating net works connected to said electrodes respectively and to points oi 160 degrees phase opposition in said square wave generator. The combination with a transmitter, of a plurality of banks or modulators, each bank com» prising a plurality of modulators, each arranged to impress its characteristic modulation on the transmitter, switches for controlling said modi;n laters respectively, means for causing sequential operation of one modulator in each bank when their controlling switches are closed simultane ously, said last mentioned means including a pair ci gas discharge tubes each having a pair of con~ trol electrodes, a generator of substantial square waves, means for applying alternately positive pulses _from said square wave generator to one or” .» said >control electrodes in each tube, the other of said control electrodes being normally biased with respect to the cathode of its respective tube so as to prei/‘ent ionization thereof, said switches lators, and a clearing signal modulator, means for selectively energizing any one of said working signal modulators, said means operating to inter rupt the control circuit of said clearing signal modulator whenever the control circuit of any working modulator is established. 12. In a signaling system, in combination, a transmitter, a plurality of working signal modu lators, and a clearing signal modulator, and means for selectively operating any one of said working signal modulators, said means operating, when actuated, to interrupt the control circuit oi‘ said clearing signal modulator and establishing the control circuit of said clearing signal modu lator when returned to initial position. 13. The combination with a transmitter, of a plurality oi banks of modulators, each bank com prising a plurality of working signal modulators and a clearing signal modulator, each arranged to impress its characteristic modulation on the transmitter, a switch for controlling each Working signal modulator respectively, means for causing sequential operation of one f-.rorking signal modu lator of each bank when two working modulator signal switches in diii‘erent banks are closed simultaneously, the switches in each bank being so interconnected that the closure of a working being arranged to alter the bias on said last mem . signal modulator contro-l switch in either bank tioned control electrode in the respective tubes to a valve such that the tube will ionize when a posi tive pulse applied to the other control electrode of said tube. interrupts the controlv circuit to the clearing 7. In a signaling system, in combination, a pressing transmitter, a predetermined a plurality ofcharacteristic modulators, each upon the transmitted signal, and a switch for selectively modulator of said bank. 14. The combination .with a transmitter, of a plurality of ba ci modulators, each bank com* prising a plurality of worlÍ g signal modulators and a clearing signal modulator, each arranged to impress its c' ai yoteristic modulation on the transmitter, a switch for controlling each work operating each of said modulators, said switches ing signal modulator respectively, means for having front and back contact positions, and 45 causing sequential operation of a working signal being interconnected in a manner such that when all of said switches are on back Contact position a control circuit is established. 3. In a. signaling system, in combination, a modulator in each bank when their control switches are closed simultaneously, said last men tioned means including a pair of gas discharge tubes, and means for preventing simultaneous transmitter, a plurality of working signal modu ionization of said tubes, the switches oí each bank being interconnected so that when all of the switches oi either bank are in bank contact posi tion the control circuit to the clearing modulator of said bank is established. lators and a clearing signal modulator and `a switch for controlling each of said working modu lators, said switches having front and back con tact positions and being so connected that when all of said switches are on back contact position l5. The combination with Va transmitter, of a the control circuit is closed for operating said clearing modulator. 9. In a signaling system, in combination, a transmitter, a plurality of working signal modu lators, and a clearing signal modulator, a thyra tron, a relay ior each modulator having one ter minal of its energizing winding connected in the anode circuit of said thyratron, and a switch for plurality of banks of modulators, each bank oom prising a plurality of working signal modulators and a clearing signal modulator, each arranged to impress its characteristic modulation on the transmitter, a switch for controlling each work ing signal modulator respectively, means for causing sequential operation of a modulator in each of said banks when their respective con each of said working signal modulators for com pleting the circuit through the respective ener gizing winding, said switches having front and back contacts and being so interconnected that when the said switches are on back contact posi tion the circuit through the energizing winding of the clearing signal modulator relay is com pleted. trolling circuits are closed simultaneously, said last mentioned means including a pair of gas discharge tubes, means for preventing simultane» ous ionization of said tubes, and a relay for each modulator respectively, operated b-y the space cur rent of said gaseous discharge tubes, the switches of each bank being interconnected in a manner to establish the control circuit t0 the clearing signal modulator of said bank when all of the l0. In a signaling system, in combination, a transmitter, a plurality of working signal modu~ switches in said bank are on back contact. lators, and a clearing signal modulator, each ROBERT W. CARLSON. impressing a predetermined characteristic upon 75 Y MADISON G. NICHOLSON, JR.