US2658943A - Printing telegraph system - Google Patents

Description

o '10, 1 5 1. .DURKEE 2,658,943

' Pamzm TELEGRAPH SYSTEM I Original Filed Jan. 23, 1950 s Sheets-Sheet 1 I INVENTOR. Ame/a 3) Dwqfiew, BY

A TI'ORIVFY Nov. 10, 1953 J. D. DURKEE 2,658,943

PRINTING TELEGRAPH SYSTEM Original Filed Jan. 23, 1950 3 Sheets-Sheet 2 I //4g //5.9 "'6 i H /4/ 496 I .51 E. 5 d? F mmvron.

BY 6. DA/.140

TE. 1 U

Nov. 10, 1953 J. D. DURKEE PRINTING TELEGRAPH SYSTEM 3 Sheets-Sheet I5 Original Filed Jan. 23 1950 Patented Nov. 10, 1953 UNITED STATES PATENT OFFICE PRINTING TELEGRAPH SYSTEM James D. Durkee, Fairlington, Va., assignor, by

direct and mesne assignments, to Dualex Corporation, a corporation of Delaware 14 Claims. 1

My invention relates broadly to printing telegraph systems and more particularly to a high speed polarized system of printing telegraphy utilizing printing telegraph apparatus of compact size and light weight.

This application is a division of my application Serial Number 139,977, filed January 23, 1950, now U. S. Patent No. 2,613,267, dated October 7, 1952, for Printing Telegraph System.

One of the objects of my invention is to provide a printing telegraph system constituting an improvement upon conventional sequentially operated systems, overcoming inherent difiiculties in these systems and to supplement the purpose for which the system described in my co-pending application No. 109,648, filed August 11, 1949, for Printing Telegraph System was developed.

My co-pending application is directed to a printing telegraph system, which when applied to space radio systems, overcomes conditions of fading, interference, and static, and is particularly adaptable to mobile radio printer operations where compactness and portability and a minimum of mechanical equipment with incidental maintenance are major requirements.

The system of my invention employs a polarized electrical matrix which requires the transmission of only five polarized pulses, without the necessity of transmitting start-stop or synchronizing pulses, to accomplish the thirty-two different permutations and combinations of signal impulses presently used in printing telegraph systems.

Since in my application a smaller number of permutations and combinations of signal pulses are required to produce the same number of permutations and combinations as used in currently existing systems, a greater number of permutations and combinations can be sent in less time with fewer impulses thereby requiring a smaller number of transmission bands and less frequency band-width.

In addition, since the system of my invention requires only a reversal of current direction or polarity, the transition from one polarity or phase to the opposite polarity or phase may be accomplished by sinusoidal wave form; thus, the impact excitation resulting from a rapid make or break keying operation 01' from a rapid frequency shift is eliminated, thereby further decreasing the keying band-width required at any speed of transcission.

A further object of my invention is to provide a self-synchronizing receiving system which may be made operable over a fairly wide range of transmission speeds and which requires a minimum of equipment or adjustment.

Another object of my invention is to provide means for supplying a pulse or pulses which may have been lost in transmission or obliterated by interference and means for indicating on the receiving copy a mark or symbol which visually indicates that the character received is incorrect.

The apparatus described in this application is intended for use with the printing mechanism of my co-pending application No. 109,648 supra but may be used with an electric typewriter or with slight modification of the present printing telegraph systems may be used interchangeably with conventional equipment.

My invention will be more fully understood from the specifications hereinafter following by reference to the accompanying drawings in which Figure 1 diagrammatically shows the transmission system of my invention; Fig. 2 is a schematic plan view of a fragmentary portion of the transmission keyboard Fig. 3 is a schematic end elevational view of the transmission keyboard, the view being taken on sectional line 3-3 of Fig. 2 and showing the frame structure in vertical section; Fig. 4 shows the receiving circuit of the printing telegraph system of my invention; Figs. 5 and 6 are detail views illustrating the operation of the control mechanism in the receiving apparatus; Figs. 7 and 8 are detailed views of the operating solenoids controlled by the printing telegraph receiving system; Figs. 9 and 10 are enlarged schematic views showing the operation of the error indicating means employed in the receiving system of my invention, the views being shown in front elevation and wherein Fig. 9 shows the error indicating means in printing position whereas Fig. 10 shows the error indicating means released and free of printing position; and Fig. 11 is an end view of the error indicating means shown in Fig. 9.

Almost from the beginning of the art of printing telegraph systems efiorts have been made to accomplish the selection of characters by electrical resolution of the units of the Baudot code. Each solution required the use of a large number of electrical contacts and electro-magnetic relays in simultaneous operation with the resulting presence of a multiplicity of potential error producing elements. Practical experience indicated that greater reliability could be placed on mechanical resolution and the present state of the art reflects this experience. Mechanical operations, however, have the inherent characteristic of requiring a longer time to perform the same functions than does electrical energy.

However, operational communication require ments for increased speeds of operation have now exceeded the capabilities of the mechanical equipment except under strained and abnormal conditions which require excessive maintenance and mechanical tolerances and precision of ap paratus which are difiicult to achieve.

The application of printing telegraph systems to radio communication also introduced additional dificulties which do not readily lend themselves to solution by mechanical methods due to the speed limitations of mechanical operations.

Two of the major difficulties introduced by radio communication are various forms of fading and interference in addition to the,- basic limitation in the number of cycles available in the total radio frequency spectrum.

Heretofore, various approaches to the radio applications of printer systems have been by increasing power of transmission and improving receiving conditions in an effort to duplicate the operating reliability of a land line to overcome fading and increasing the dot cycles of operation by additional fail safe impulses or increasing the units of the basic five unit code to provide error detection resulting from interference and certain forms of fading.

The approach of my invention to the solution of the requirement for increased speeds has been to eliminate the basic mechanical limitation of the mechanism used to resolve the units of the five unit code into characters by use of a polarized electrical matrix; to decrease the electrical contacts required to a minimum by use of rectifying apparatus and the application of new and novel electrical circuitsand to decrease the operational functions to a minimum by simplification of equipment and electrical circuits.

The fading and interference problems introduced by radio communication have been accepted as natural characteristics of the medium. Circuits and operations are provided. by my invention which take these natural characteristics into account and provide substitute characteristics in the form of locally produced impulses to replace those lost in transmission due to fading or to counter balance impulses introduced in transmission as av result of interference and to indicate on the receiving equipment when these functions have been. required to complete the formation of a character.

In endeavoring to achieve greater economy of bandwidth, the start-stop or synchronizing impulses heretofore usedin both, radio and wire methods have been eliminated in. my invention by self-synchronizing apparatus resulting in an approximate saving of twenty per cent of bandwith required to perform the functions necessary to the formation of a character as compared to systems which transmit start-stop impulses or synchronizing impulses.

My invention employs. apparatus and methods which are compatible with existing methods and apparatus, allowing in almost every instance, the use, with slight modification, of existing equipment and methods to accomplish its purpose.

Transmitting apparatus Figs. 1', 2 and 3 show the transmission system of my invention, the transmitting keyboard being shown in plan view in Fig. 2 and inend view in Fi 3.

When the key I, pivotally mounted at la, is depressed, bars 2, 3, 4, 5 and: It which extend therefrom depress levers I, 8, 9-, I0 and II in a downward direction to form. contact with. the contacts 12 to 2 I. The levers 'I-I,lv are supported at opposite ends in frame N6 of the transmitting keyboard as shown at la and w; 811 and 8b; 9a and 9b; Illa and 19b; and Ha and [lb through resilient self restoring flexing strip members la'l'b; 8a'-8b; 3a'-5b'; iila--i0b; and l ia'l ib'. Contacts l22i are insulatingly supported in relation to frame M6 in alignment with thepivoted levers 'I-i i as shown. The levers 7-4 I are normally biased by the resilient self restoring flexing strip members Yer-lb; 8a'--8b'; 9a-'-9b; leer-46b; and Ha'iib, to a position in horizontal planes and flex under the pressurev ofthe bars 2-5 in either a clockwise or a counterclockwise direction depending on the relative positions of the bars 26 with respect to the centers of levers l-l I, for effecting momentary contact at l2--2I. When pressure of bars 26 on the levers 'i-H is removed the levers l-H are restored to horizontal position breaking the contacts l2-2i by the self restoring action of the flexing supports at each end of the levers !'-i l. The contacts which are formed depend uponwhich side of the center of levers 'lto I l, the bars- 2 to, 6 are positioned. In the position illustrated in Fig. 1 lever 7 will contact l2, lever B will contact l5, lever 9 will contact 16, lever [0 will contact l9, and lever II will contact 20, placing alternatively positive and negative currents from source of battery 29 on stepping relay contacts 22, 23, 24, and 26 arranged in the path of switch arm 2! of continuously cycling driven steppingrelay 28.

When this contact was made a positive current flow took place from battery 29 (Fig. 1) contact through I2, and the contact carried by lever l to stepping relay contact 22 through arm 21 through relay coil 38 to the center tap 29a of battery 29. The current in coil 30 caused armature 31 to move down, making contact with contact 32 which in turn caused the armature 33 of stepping relay '28- to be moved down because of the current in relay coil 34 produced by closing or" contact 32. The movement of armature 33 caused ratchet arm 35 to pull arm 21 away from contact 22 counterclockwise towards stepping relay contact 23. During the time the arm 2'! was in contact with contact 22, a positive voltage was applied to line 35 with respect to ground or center tap 29a of battery 29, or was caused to flow through rectifier '38 through relay coil 38a in a positive direction re sulting in movement of arm 39 of relay 40 to make contact at 43 which in turn keyed the marking frequency of a frequency shift radio printer keying circuit.

As soon as arm 27 left contact 22' the current in relay coil 3%] was released and contacts 3! and 32 were opened de-energizing coil 34 of the continuously cycling spring driven stepping relay 28 which in turn repositioned ratchet arm 35 preparatory for another ratcheting operation.

The capacity 4| and adjustable resistor 42 across coil 34 acts to retard the arm 21, suiiiciently long at each contact 22 to 25 to permit the full cycle of operation previously described to be completed.

When arm 2? arrived at contact 23' the same cycle of operation was set in motion as when the arm 21 was at contact 22, except that the charge of voltage on contact 23 is now derived from the negative source of battery 29, thru the contact on lever 8 and contact [-5- and a negative charge was placed, thru rectifier 3"! and relay coil 31a to ground or center tap 29a of battery 29, causing armature 39 to close contacts 44 keying the spacing frequency of the frequency shift keying system or causing a negative charge to be placed on line 36.

The same cycle of operation is repeated at stepping relay contacts 24, 25 and 26 resulting in moving arm 21 back to the original position in contact with contact 22 having thus completed a transmission cycle of four self-cycling operations from contact 22 to contact 28 which v resulted in sending four equally spaced pulses and one starting pulse of alternate positive and negative charges to a line or causing the two frequencies of a frequency shift keying system to be alternatively operated causing five pulses divided between two diiferent alternating currents to be transmitted.

Since the pulse caused to be transmitted when arm 21 is in contact with contact 22, is the starting pulse, it does not have to be especially spaced in relation to any previous pulse. The pulse created by contact of arm 21 with contact 28 is the end of the character forming combination.

Figs. 2 and 3 show the arrangement of the transmission keyboard more clearly from which the coaction of the pivoted keylevers 45 with the contact control means will be understood. The key-levers are arranged above the angularly shiftable levers 1, 8, 9, I8 and II and through bars 2, 3, 4, 5 and 6 selectively control the angular movement of the levers about their pivots 1a, 1b||a, III), that in turn control the contacts I2, I3, I4, I5, I6, I1, I8, I9, 28 and 2|, for controlling the circuits heretofore described.

When arm 21 arrives at contact 28, current from negative battery 29 flows through coil 46, arm 21 and coil 38 to the center tap 29a of battery 29. This causes armature 41 to be attracted by the electro-magnetic core of coil 46 making contact at 48, permitting current to flow through coil 49 from positive battery 29 to negative battery 29. When coil 49 shown more clearly in Fig. 3 was energized armature 58 was drawn towards the electro-magnetic core of the coil 49 pushing oscillating bar 58 against armature 5| releasing pressure of point 5Ia of pivoted member 5| on roller 52 carried by the end of keylever 45 permitting spring 53 to pull keylever 45 up against stop 54 which action lifted key bars 2, 3, 4, 5 and 6 from bars 1, 8, 9, I8 and II, allowing the latter to resume normal position. Thus permutations and combinations of signal pulses can be formed and transmitted by contacts 43 and 44 under selective control of the keyboard as described.

Had it been desired to utilize the keying mechanism in the manner described in my co-pende ing application No: 109,648 supra for simultaneous transmission of a coded character, the oscillators 48a, 48b, 40c, 48d and 48c of the circuit of Fig. 1 of that application would be connected to contacts I3, I5, I1, I9 and 2|, and levers 1, 8, 9, I8 and II would be connected together and returned to contact with 48 Contacts I3, I5, I1, I9 and 2| would have been disconnected and levers 1, 8, 9, I8 and II, when in normal position, would have been making contact with contacts I2, I4, I6, I8 and 28 causing oscillators 48a, 48b, 48c, 48d and 486 to continuously generate alternating current tones into the line 36 or an amplifier as described in my aforesaid co-pending application. When key is depressed contact is broken at contacts 1, I2, at 9, I4 and at |I,28, causing oscillators 48a, 48c and 48e to be removed, from 6 the line and the character which is made up of signals from oscillators 48b and 48d in simultaneous combination would be formed.

Receiving apparatus Fig. 4 shows the receiving circuit for the receiving printer of my invention. I provide a pyramid or Christmas tree arrangement of relays 63, 91, I83, and H8, in series with a rectifier circuit, and having associated armatures 18, 98, I84, and III, respectively, arranged to control permutations and combinations of signal pulses through associated contacts and circuits connected therewith. An unlatching or fifth relay H8 is used for controlling an armature II1 for unlatching armatures 18, 98, I84 and III for enabling the system to receive the next succeeding signal impulse group. The permutation and combination incoming signal pulses, whether received by line or as a result of rectification of a radio or audio frequency current, appears on line I41 of Fig. 4 as a positive or negative voltage with respect to ground.

55 in accordance with the manner in which it was transmitted by the apparatus described in Figs. 1-3. The current flows through the stepping arm 8| of cycling switch 82 to contact 56 and the winding of relay 63 and, if the voltage is orpositive polarity with respect to 55, which is the center tap 29a of battery 29 from which the voltage on line I41 is derived, through rectifier 84 to line 55. The current also flows through coil 95 from line I41 to line 55.

When current passed through coil 85, armature 88 made connection with contact 81 completing the circuit between positive battery 29 and coil 88 and ground 55. This moved armature 89 to the left causing ratchet arm 18 to turn ratchet wheel 1|, which caused arm 8| to move from contact 58 to contact 51, and through shaft I45 caused arm 12 to move from open contact 13 to contact 14.

When armature 88 moves to the left under control of coil 65, armature 98 makes connection with contact 61. An extension rod 96a interconnects armature 88 with the operating spring 691) and draws operating spring 981) to the left whereby the continuity of the circuit I41 to arm 8| is broken between spring 882) and spring 880, insuring against the possibility of a prolonged pulse causing a false operation prior to the completion of the pulse duty cycle. This also permits the carrier or signal current to be maintained in an on condition during the interim between the formation of signal characters.

When current is passed through relay 69, armature 18 causes extension bar 19 to pull contacts 88 to 81 into connection with contacts 89, 98, 9|, 92, 93, 94, 95 and 96.

Upon arrival of arm 9| at contact 51 the circuit from line I41 through rectifier 84 to line 55 is completed. If the voltage on line I41 is now negative, rectifier 84 will not pass current through relay coil 91 to ground 55 and thus armature 98 remains in position shown and contacts to I82 are not broken.

The current, through coil again causes the arm 6|, as a result of the action similar to that previously described, to move to contact 58. If the voltage in line I41 is now positive with respect to ground or center tap 29a of battery 29 and the circuit is completed from line 41 through arm 8|, contact 58, coil I83, to rectifier 84, and. line 55, the current flow through coil I83, causes armature I84 to move bar I 85 causing leaf spring contacts we and. lit! to conn ct with con acts 508."

the circuit from line; I412 through coil 1.10,. arm: 62I1: contact 59,. to rectifier 64; the, noltage: is.

nownegative, rectifier M will. not pass current; through coil. i ifltoground fiiaand armature: MI.- and bar 1 i2 remainin the. position shown The. current. in. coil. 6 5 present. when. contact. 62 of arm ti is. in contact-:with. contact 5.9; causes arm BI tomove tQcOntact-EIIandarmH to more. to. contact TI:

I41 is now-connected thrir arm.6.I contact. 60? and contacts: H3; I Eil- IaGEh. "It, 85 and. 9%,-

to. the printer magnets N. and SE; to. rectifiersv Hat and :5 to line 55 through: lea-($5511.

If: the voltage. in. line 11th was positive: when contact: was made by. arm 51: atcontactrfifi; aposie tive. current. will. now pass through the printer. magnets N? (Fig. 4) and rectifier I115; to. and by. the process described above.. the letter N of the printer tQprint.

When the letter N functionwas; activated by the action of arm GI; contacting contact 6.51; cur.- rent also passed through relay; coil: 161111117116? lead' 55a which caused armature H112 to. unlatch armatures 18', 94",. I184: and: MI of? relays: 9?, I03 and H preparing: the systemmo: receive a. new cycle oficharacter forming. impulses.

Examination of Fig. 4.Wi1llSh0Wrth8;-l7,. predicatedupon the polarity of currents. in line: Mi'with; respect to line55: aspresented to the: pyramid? or Christmas. tree shown; in. the lower right hand portion of Fig. 4- insequentiali. combination and with the use of pressure roller springs H181, I19; I26 and IN to latch armature; 1.8;. 9%, Iiii and III in a fixed position for a periodcoverin the cycle of operation; it is-possible toindividually select any one of the multiplicity of magnets. in various permutations. and. combinations repre sented by reference Let? designating: letters? to -B1k designating blankf of. Fig; 4; In: Figs. Sand 6 I 'haveshown the twolimiting positions of armature I H. on an, enlarged scale toillustrate the two extreme latched positionsthereof:under. control of pressure roller spring: H82. All; of: the. armatures: T8 98, I84- are. arranged in a. manner; similar to armature. i:I.:I;, thatisthe armature 1.8; $181 and Hit are controlledjin. their limiting posi'e tions by pressure rollersprings: 1.21; lid and; Iii respectively.

Figs. 7 and 8 are enlarged: views. of: the: sole;- noids in the polarized pyramid or Christmas: tree" circuit wherein Fig. 'lz'represents the juxtae positions of the differentially: polarized; operating solenoids for letters W'and'Av and letters-Z and E'- while Fig. 8 shows: the. electricaliequivalem oi the same juxtapositioned soienoidsl The capacitor-resistor combination. I12: and I23, are used tocontrol: the dissipationofi'current in condenser I22 through-coil fidzaiter opening of the circuit to battery 29. (1+). by'the operation of'relay: 65 and which in turn controls;the length of time which arm 61* moves" from one contact to the other of'the-group of" contacts 5.6 to Bil Under certain conditions of operation: particularly in radio circuits the possibility of lossof one or more impulses due to fading or-obliterae tion of signals by interference is' always present.

will cause.

8. Tc overcome this condition provision has been. made in the selector system for. the. supplying. of lost impu ses; andz recording this circumstance. on; the-printed copy; The effect of interference isimadeto appear asza lost impulse in this system.

. energy storedin capacitor 21 starts-discharging through resistors I28 and lite-into coil I-29-hold.- ing; armature. m5.- that; is in, circuit with condenser I30 through: contact I26. to battery 29.

If. no roltagerappears. on; line I417!- for a: fixed:

miod ofitimeafter contact-has been established. bwarmti with anyone of the contacts. 5?, 58-, 5B and; id-"before the dissipation ofenergy in CD11:'- denser I2! is complete, armature I will be released from contact. [26. and contact will be establishemwith; contact I31 allowing condenser liflzto; dischargethrou hresistor I-a-, coil. 132, am I2. and;c0ntact:l4,.15; It or. ll: of: a duplicate bank; of: contactsonthe: same; shaft as contact arm: Eli to: line.- H.453 through: whichever; circuit arm 6.1% provides through its contact withrcontacts;v 55 to 611:, thus; producing; the same; action. which; would; have resulted. from; an. incoming Si nal, on, line:- I451.

When. this. cnrrentrpassedi through coil I32: the.

armature. I%33;- was. moved; and. closed. the; circuit through contact tfimconnecting battery- 29; to a relay 1:31; associated; with the printing mecha- Wheir the; relay I34; was. energized; the armature I35 wasattracted. to;the. ole of coil I34-, latching itself to; latching. armature. I36 and. bringingthezextension wire I31 of armature. I35.- acrossthesurface of the character Afor; example. on the type pallet. Ifitwhich may strikethe. ink.

is ribbon- Hit of Figil; andbeprintedonthe; paper.

web I40 being advanced. on. platen. MI 01: the: printer as shown more: clearlyirr Rigs. 9. and; 10', and: 1 1. Fig; 9 showsthecondition.for-indicating. error'whileFig; lO-showsanaall clear condition with the errorindicatorremoved.

When relay I I'G- was energized contact was: made between I44 and Ifill; placing: battery. on. coil: M2 which caused armature: I36 to release armature I 35 allowing spring I53 to draw'armacture I35- to-itsnormal position-.with the. extensi'om I'3liclear of the printingsuriace of theenext character placed in. a. printing; position.

When the letter key is operatech tozprint the; character'f-ormed; partly by. the self-imposed. impulses of condenser M9,. the character; which; is printed willbo marked by a: verticalbar stroke bythe extension bar I31 of armature-I35 plainly: indicating to: the: operator that the.'cha1:acter wasnotiproperlyreceived;

The rotary selecting printing mechanism: dc..- scribedin my-co-pending application No;.109.;648 supra may be used in connection with the apparatus described in this application to select and print the characters and perform the other Operations required ofa printing mechanism; This may; be accomplished by connecting the contacts. of: the. rotary switchand the; letters, figures-""and space. relays to. the contacts. rep.- resented by. thezsolenoids for-letters K,. etc. of?" Fig. 4r

It will be fully understood that these same contacts of Fig. 4 can be connected to a series of solenoids or magnets and be used to operate an electric typewriter or initiate the Printing mechanism of other types of presently used printing telegraph equipment.

Conventional printer mechanism is operated by the solenoids letters through blank shown in the polarized pyramid or Christmas tree in the lower left corner of Fig. 4.

Due to the fact that the necessity for a mechanical selector is eliminated in the printer system of my invention and yet very accurate and quick movement of theseleotion system of my invention obtained by use of positive and negative electrical impulses, I am able to reduce the size and weight of the equipment, as compared to conventional equipment, very materially.

While I have described my invention in cer-,

tain of its preferred embodiments I realize that modifications may be made and I desire that it be understood that no limitations upon my invention areintended other than may be imposed by the scope of the appended claims.

What I claim as new and desire to secure by Letters Patent of the United States is as follows:

1. In a printing telegraph system, a plurality of pairs of printer operating solenoids each including differentially polarized individual solenoids, a polarized pyramid circuit, selective conditioning means for controlling said polarized pyramid circuit for selectively exciting the individual printer solenoids of said pairs of printer operating solenoids by positive or negative current pulses, a signal input circuit, a stepping switch including an arm operative over a multiplicity of contactors, control relays individual to the said contactors, and means in said signal input circuit for selectively operating said stepping switch relative to signal pulses for selectively exciting certain of said relays, and means operated by said relays for controlling said polarized pyramid circuit.

2. In a printing telegraph system, a circuit for receiving positive and negative signal current pulses, a step-by-step switch controlled by said pulses, contactors individual to the step-by-step positions of said switch, relays selectively excited by currents from circuits extending from said contactors, a polarized pyramid circuit including sets of make and break movable contactors with associated contacts, means operated by said relays for controlling the displacement of said make and break movable contactors with respect to the associated contacts, and differentially polarized printer solenoids arranged in pairs and connected with the contacts in said polarized pyramid circuit and selectively operative by positive and negative current pulses for selectively operating printer mechanism.

3. A printing telegraph system as set forth in claim 2 including means for latching said movable contactors in selectively displaced positions.

4. A printing telegraph system as set forth in claim 2, including means for simultaneously restoring said movable contactors in said polarized pyramid circuit to the original positions thereof from their displaced positions.

5. A printing telegraph system as set forth in claim 2 in which said differentially polarized printer solenoids are selectively connected through unidirectional current feed circuits whereby the individual solenoids of each pair are 10 selectively excitable by current pulses according to the polarity thereof.

6. A printing telegraph system as set forth in claim 2 which also includes an auxiliary circuit selectively excitable under conditions of failure of receipt of all of the current pulses constituting a signal permutation or combination.

'7. A printing telegraph system as set forth in claim 2 which also includes an auxiliary circuit operative upon failure of any one of the signal permutations or combinations and means for restoring said auxiliary circuit to normal condition after correction of the failed permutation or combination.

-8. A printing telegraph system as set forth in claim 2 which includes a circuit containing an electrostatic capacity wherein said electrostatic capacity accumulates an electrical charge upon the incomplete receipt of a code signal permutation or combination, an electrical circuit controlled by said electrostatic capacity, a relay controlled by said electrical circuit, and means for restoring said relay to normal condition after dissipation of the electrostatic charge in said electrostatic capacity.

9. A printing telegraph system as set forth in claim 2 in which said differentially polarized printer solenoids are arranged in pairs by a connection bonding adjacent ends of the windings of said solenoids and wherein the opposite ends of each winding are connected in series with separate rectifiers which are polarized to pass current through one of said solenoids in one direction and to pass current through the other solenoid in the opposite direction.

10. A printing telegraph system as set forth in claim 1 in which unidirectionally current conducting devices are electrically connected in series with the individual solenoids of each of said pairs of printer operating solenoids for selectively supplying operating current to said printer operating solenoids unilaterally according to the operation of said polarized pyramid circuit. v

11. A printing telegraph system as set forth in claim 1 in which there are at least four of said control relays each having an operating armature for controlling the operation of said polarized pyramid circuit and wherein a fifth relay is connected in series with said polarized pyramid circuit and is provided with an armature onerative after each printing operation to restore the armatures of the aforesaid control relays to positions preparatory for receiving signal impulses representing a succeeding character.

12. A printing telegraph system as set forth in claim 1 in which there are at least four of said control relays each having an operating armature for controlling the operation of said polarized pyramid circuit, the windings of said control relays all being connected with said signal input circuit through a rectifier for sup-plying unidirectional operating pulses to said windings and wherein a fifth relay is connected in series with said polarized pyramid circuit and is provided with an armature aligned with respect to all of the armatures of said control relays and operative after each printing operation to restore all of the aforesaid armatures to positions preparatory for receiving signal impulses representing a succeeding character.

13. A printing telegraph system as set forth in claim 1 in which the means in said signal input circuit for selectively operating said stepping 11 7 switch comprise a pair of relays, due a! said relays having its winding 'Veenneeted in said si nal input eircuit and operating an armature-101' controlling a multiplicity'of leaf sprin s and assooiated contacts; the other pf said relays having its winding conneetedin series with one of the aforesaid leaf springs and associated contacts and having an armature ,ratchetmg the arm of said stepping switch, certain of the leaf springs and contacts of said aforementioned relay forming a circuit path ior signal impulses through said stepping switch and one of the leaf springs and associated contacts Roi the aforementioned relay forming a circuit path through said last mentioned relay ior ,efiecting a stepping Qperation of said steppingswitch according to the .re- .ception of the vsignal pulses and a rectifier disposed in circuit with saiderm for restricting the current flow therethrough to unidirectional pulses.

.14. A printing telegraph system as setiorthoin claim ,1 in which three independent reetifiers are 12 disposed in the cireiiit of said telegraph system (one of said rectifiers being connected .in series hetweenlsaidisignail input veinmit and said control relays and the ether '01 said rectifiers being connected in series with said solenoids .in said pyramid circuit, said last mentioned rectifiers being electrically reversed with respect to each ether whereby current flows .unidirectionally in 1 said pyramid \circuit in opposite directions aecording to the permutations and combinations of the signal pulses.

JAMES TD. DURKEE.

References Cited in "the me of this "patent

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