US2658941A - Printing telegraph system - Google Patents

Description

Nov. 10, 1953 ,1. D. DURKEE PRINTING TELEGRAPH SYSTEM Original Filed Jan. 23, 1950 3 Sheets-Sheet l m UH Nov. 10, 1953 J. D. DURKEE PRINTING TELEGRAPH SYSTEM Original Filed Jan. 23, 1950 3 Sheets-Sheet 2 a? ax I INVENTOR.

, By J m 90%,

J.- D. DURKEE 2,658,941

3 Sheets-Sheet 3 Nov. 10, 1953 PRINTING TELEGRAPH SYSTEM 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 9 Claims. (01. 178-47) 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. I

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 difficulties in these systems and to supplement the purpose for which the system described in my co-pending application Ser. 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 systerns.

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 or from a rapid frequency shift is eliminated, thereby further decreasing the keying band-width required at any speed of transmission.

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.

The apparatus described in this application is intended for use with the printing mechanism of my co-pending application Ser. 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 33 of Fig. 2.

and showing the frame structure in verticalsection; 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 efforts have been madev to accomplish the selection of charactersby 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. tions', however, have the inherent characteristic of requiring a longer time to perform the same functions than does electrical energy.

However, operational communication requirements 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 operaitation 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 circuits and 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 a 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 used in 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 bandwidth 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, or 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 in end view in Fig. 3.

When the key I, pivotally mounted at la, is depressed, bars 2, 3, 4, 5 and B which extend therefrom depress levers I, 8, 9, i0 and II in a downward direction to form contact with the contacts I2 to 2|. The levers '!-i l are supported at opposite ends in frame N6 of the transmitting keyboard as shown at 1c and 1b; 8a and 8b; 9a and 917; 10a and "3b; and Ha and Nb through resilient self-restoring flexing strip members Ia-'Ib'; 8a8b'; 9a--9b; i0a-lllb; and Hal lb. Contacts l2-2i are insulatingly supported in relation to frame 146 in alignment with the pivoted levers 'l-ll as shown. The levers 1-H are normally biased by the resilient self restoring flexing strip members la'lb'; 8a8b'; 9a9b; IBM-Nb; and llalib, to a position in horizontal planes and flex under the pressure of the bars 2-6 in either a clockwise or a counter-clockwise direction depending on the relative positions of the bars 2-6 with respect to the centers of levers 1-4 I, for effecting momentary contact at I22l. When pressure of bars 2-6 on the levers 7-! I is removed the levers IH are restored to horizontal position breaking the contacts i2-2l by the self restoring action of the flexing supports at each end of the levers 1I I. The contacts which are formed depend upon which side of the center of levers I to H, the bars 2 to 6 are positioned. In the position illustrated in Fig. 1 lever T will contact i2, lever B will contact I 5, lever 9 will contact 16, lever It will contact I9, and lever H will contact 2t, placing alternatively positive and negative currents from source of battery 29 on stepping relay contacts 22, 23, 24, 25 and 26 arranged in the path of switch arm 21 of continuously cycling driven stepping relay 28.

When this contact was made a positive current flow took place from battery 29 (Fig. 1) contact through 82, and the contact carried by lever i 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 3! 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 of 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 21 was in contact with contact 22, a positive voltage was applied to line 36 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 resulting in movement of arm 39 of relay 49 to make contact at 43 which in turn keyed the marking frequency of a frequency shift radio printer keying circuit.

As soon as arm 21 left contact 22 the current in relay coil 36 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, sufliciently long at each contact 22 to 26 to permit the full cycle of operation previously described to be completed.

When arm 21 arrived at contact 23 the same cycle of operation was set in motion as when the arm 2'! 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 37a 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 27 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 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 cousing five pulses divided beagocaecr i tween two. difierenti alternating currents: to be. transmitted Since the pulse caused to. be. transmitted. when arm 21 is in contact with contact: 22", isthe startingpulse;.rt. does not have. to beespecially spaced in relation to any'previous'pulse. The pulsacreated by contact arm 21' with contact 26 is: the end of. th character forming combination.

2' and; 3' show the arrangement of. the transmission keyboard more. clearly from which the coactionv of the pivoted keylevers- 4'5; withthe contact control means will be: understood; The key-levers are: arranged abovethe angularly shiftable levers Lit, 9,. I13 and. LI andrthroughbarsv 2,. 3,. 4, 5 and 6' selectively control: the. angular movement of; the. levers about their pivots a, lb-Ha, I1Ib,.that in turn control" the contact I2; It, I4, I5, I6, IT, I'8, Ira, 2!] audit. for. controlling the circuitsheretofore described.

When arm 2T arrives at. contact 25,. current from negative battery 29 flows. through coil. E6, arm 2i? and coil: 30 to the center tap 25a of: battery 2.9. This causes armature; cl to be attracted by the electro-magnetic core of coil making contact at 4.8 permitting current to. flow through;

coil 4E from positive battery 29 to negative battery 29. When coil 49* shown more clearly in Fig. 3 was; energized-1 armature 5a was. drawn. towards the electro-magnetic core or the coil 49 pushing: osciil ating bar 50:" against armature 5i releasing pressure. of point 514: 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 keybarse 2.", 3, 4, 5- and 6- from bars 1, 8,. 9;. I50 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. it under selective control 01 the keyboard as described.

Had it been desired. to utilize the keying mechanism in the manner described in my co-pending application Ser. No.. 109,648 supra for simultaneous transmission of a coded character, the oscillators 40a, 46b, 46c, 40d and 49a of the circuit of Fig. 1 of that application would be connected. to contacts f3, I5, H, I9 and H", and levers 1,. 8,. 9, I0' and H would be connected together and returned to contactwith Ml Contacts I3, I5 I-I, I9 and 21 would have been disconnected and levers I; it, 9, to and II, when in normal position, wouldv have been making contact with contacts I2, l4 Hi, I8 and 28 causing oscillators 40a, 407),. 40c. 4nd and AIIe'to continuously generate. alternating'current tones into the line 35 or an amplifier as described in my aforesaid co-pending application.

When key I is depressed contact is broken at contacts I, it, at 9, I4 and at II, 2-0, causing oscillators 56a, 40c and Me to be removed from the line and the character which is made upof signals from oscillators 40b and 433d in. simultaneous combination would be formed.

Receiving apparatus The permuta-- mitted by the apparatus described in Figs. 1-3.

larity with respect to 55, which the: center tap.

29a of battery 29 from. which the. voltage on. line I4! is derived, through rectifier 64 to line 55-.

The current also flows through coil 65' from line 1 I41 to line. 55.

When current. passed through coil 65, armature 65 made connection with contact 61 completing the circuit between positive battery 29 and" coil 68 and ground 55. This moved armature 69 to the left causing ratchet arm 'H) to turn ratchet wheel H, which caused arm 6I to move from contact 56. to. contact. 51, and through shaft I45 caused arm 12 to move from open. contact I3 to contact 1'4- When armature 66 made connection withcontact '61, extension rod. 5 6a connected with operating spring $611 the continuity of the. circuit I41 to arm SI was broken between spring. 66b and contact. 56c, 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 anon condition during the. interim between the formation of signal characters.

When current was passed through relay 53.

Upon arrival of arm 6|. at contact; 5'! the oil.- 7

cuit from line I41 through rectifier 6:1 to line 55 is completed. If the voltage on line I4! is now negative, rectifier 64. will not pass current through relay coil 91- to ground 5.5 and thus. armature 98- remains in position shown and contacts to I62 are not broken.

The current through coil 65 again caused the arm: 5!, as a, result of the action similar to that previously described, to move to contact 58. If the voltage in line I4! is now positive with respect to ground.- or center tap 29a of battery 29 and the circuit is completed from line I41 through arm SI, contact 58, coil I03, to rectifier 64, and line 55, the current flow through coil I03, caused armature I 04 to move bar I05 causing .;leaf spring contacts I05 and Ill-I to connect with contacts I08. and I09.

When arm 6I- arrived at contact 58- the action resulting from current action, in coil 65 was again repeated causing 6I to move to. contact 59 and arm 32 of the stepping switch52 to move to contact I6.

Thev arrival of arm 6| at contact 59 completed the circuit from line I41 through coil IIO, arm

' 61 contact 59-, to. rectifiers 64. If the voltage is .now negative, rectifier 64 will not pass current through coil III) to ground 55. and armature III and bar I.I-2 remain in the position shown.

The current in coil 65 present when contact 62 of arm 61; is in contact with contact '59 caused arm BI. to moveto contact Eli and arm 12 to move to contact 11'.

Line I41 is now connected thru arm 61, con tact'BIl and contacts H3; till, Hit, II! I, and 9.4. to the printer magnets N and SP, to rectifiers H54 and I I5 to line: 55through lead 55a.

tive current Will now pass through the printer magnet N (Fig. 4) and rectifier II5 to and by the process described above. This will cause the letter N of the printer to print.

When the letter N function'was activated by the action of arm 6| contacting contact 60, current also passed through relay coil H6 in the lead 55a which caused armature In to unlatch I03 and H9 preparing the system to receive a new cycle of character forming impulses.

Examination of Fig. 4 will show that, predicated upon the polarity of the currents in line I 41 with respect to line 55 as presented to the matrix shown in the lower right hand portion of Fig. 4 in sequential combination and with the use of pressure roller springs H8, H9, I20 and I2I to latch armature I8, 88, I04 and III in a fixed position for a period covering the cycle of operation, it is possible to individually select any one of the multiplicity of magnets in various permutations and combinations represented by reference Let designating Letters to Elk designating Blank of Fig. I. In Figs. 5 and 6 I have shown the two limiting positions of armature II I on an enlarged scale to illustrate the two extreme latched positions thereof under control of pressure roller spring IIS. All of the armatures I8, 98, I64 are arranged in a manner similar to armature III, that is the armatures I8, 98 and I M are controlled in their limiting positions by pressure roller springs IZI, I29 and H9 respectively.

Figs. 7 and 8 are enlarged views of the solenoids in the polarized matrix circuit wherein Fig. 7 represents the juxtapositions of the operating solenoids for letters W and A and letters Z and E while Fig. 8 shows the electrical equivalent of the same juxtapositioned solenoids.

The capacitor-resistor combination I22 and I23, are used to control the dissipation of current in condenser I22 through coil 58 after opening of the circuit to battery 29 by the operation of relay B5 and which in turn controls the length of time in which arm 5| moves from one contact to the other of the group of contacts 55 to 60.

Under certain conditions of operation particularly in radio circuits the possibility of loss of one or more impulses due to fading or obliteration of signals by interference is always present.

To overcome this condition, provision has been made in the selector system for the supplying of lost impulses and recording this circumstance on the printed copy. The effect of interference is made to appear as a lost impulse in this system.

Each time that the armature BS is in contact with contact I 24 in addition to holding armature I25 in contact with contact I25, battery 29 charges the condenser resistor delay network I21 and I28 across coil I29. Each time the armature 66 is opened by removal of energy from coil 65, contacts 66 and I24 are broken which opens the circuit from positive battery 29 to negative battery 29 through coil I29. When this occurs the energy stored in capacitor I21 starts discharging through resistors I28 and I 28a into'coil I29 holding armature I25 that is in circuit with condenser I 39 through contact I26 to battery 29.

If no voltage appears on line I41 for a fixed period of time after contact has been established by arm 6| with any one of the contacts 51, 58, 5s and 6!? before the dissipation of energy in condenser I21 is complete, armature I25 will be released from contact I26 and contact will be established with contact I3I allowing condenser |3II to discharge through resistor I30a, coil I32, arm I2 and contact M, I5, IE or II of a duplicate bank of contacts on the same shaft as contact arm BI to line Ill through which ever circuit arm El provides through its contact with contacts 58 to 60, thus producing the same action which would have resulted from an incoming signal on line I41.

When this current passed through coil I32 the armature I 33 was moved and closed the circuit through contact I33a connecting battery 29 to a relay I 34 associated with the printing mechanism.

When the relay I34 was energized, the armature I35 was attracted to the pole of coil I34, latching itself to latching armature I35 and bringing the extension wire I31 of armature I35 across the surface of the character A for example on the type pallet I38 which may strike the ink ribbon I39 of Fig. 11 and be printed on the paper web I40 being advanced on platen MI of the printer as shown more clearly in Figs. 9 and 10, and 11. Fig. 9 shows the condition for indicating error while Fig. 10 shows an all clear condition with the error indicator removed.

When relay I It was energized contact was made between M4 and III, placing battery on coil I42 which caused armature I36 to release armature I35 allowing spring I43 to draw armature I35 to its normal position with the extension I3! clear of the printing surface of the next character placed in a printing position.

When the letter key is operated to print the character formed, partly by the self-imposed impulses of condenser I30, the character which is printed will be marked by a vertical bar stroke by the extension bar I3! of armature I35 plainly indicating to the operator that the character was not properly received.

The rotary selecting printing mechanism described in my co-pending application Ser. 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 of a printing mechanism. This may be accomplished by connecting the contacts of the rotary switch and the Letters, Figures and Space relays to the contacts represented by the solenoids for Letters K, W, etc. of Fig. 4.

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 matrix in the lower left corner of Fig. 2.

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 the selection 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 certain of its preferred embodiments I realize that modifications may be made and I desire that it. be understood that no limitations upon my invention are intended 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. A printing telegraph system comprising a transmission system for selectively establishing permutations and combinations of positive and negative current pulses, a keyboard selectively op- I erative to establish permutations and combinations of positive and negative current pulses representative of different signal characters, a stepping relay including an actuating winding, a switch arm and a multiplicity of contactors controlled by said switch arm, an armature controlled by said winding, said switch arm being angularly shiftable step-by-step under control of said armature over said multiplicity of contactors associated therewith, and a polarized relay circuit responsive to said positive and negative current pulses selectively controllable through the circuits established by the movement of said angularly shiftable arm for controlling the selective transmission of signal impulses.

2. A printing telegraph system as set forth in claim 1 in which said keyboard for controlling the establishment of permutations and combinations of positive and negative pulses which are applied to said polarized relay includes finger actuable levers extending over a plurality of lever members disposed in directions normal to the direction of said finger actuable levers said lever members each being centrally pivoted and biased to open circuit position, contacts carried by the peripheries of said members and coacting with aligned fixed contacts and selector means carried by said finger actuable levers and movable into the path of said lever members for selectively moving said lever members either in clockwise or counterclockwise directions for selectively closing predetermined combinations and permutations of said contacts.

3. A printing telegraph system as set forth in claim 1 in which said keyboard includes key levers pivoted at one end and having a finger actuating means at the other end and selectively movable to an actuated position from an unactuated position for establishing permutations and combinations of positive and negative current impulses for application to said polarized relay, and means engageable with the end of the lever that carries said finger actuating means for selectively maintaining said key levers in actuated position.

4. A printing telegraph system as set forth in claim 1 in which said keyboard includes key levers pivotally mounted adjacent the rear ends thereof in a frame and selectively operative in either lever members extending in directions normal to the direction of said key levers and pivoted at their opposite ends in said frame in a plane beneath said key levers, depending members carried by said key levers selectively engageable with the peripheral edges of said lever members, said lever members carrying contacts adjacent their peripheral edges and coacting with aligned fixed contacts, said lever members being biased to positions normally maintaining said contacts and fixed contacts in open circuit position and said depending members operating upon actuation of selected key levers to move said lever members selectively clockwise or counterclockwise for closing said contacts for effecting the transmission of positive and negative current pulses to said polarized relay, and means located adjacent the front of said key levers for selectively maintaining said key levers in either actuated or unactuated positions.

5. A printing telegraph system as set forth in claim 1 in which said actuating winding has an adjustable retarding circuit associated therewith for adjustably prolonging the cycle of operation of the circuits established by the movement of the angularly shiftable arm step-by-step over said contactors.

6. A printing telegraph system as set forth in claim 1 in which said actuating winding has a condenser and an adjustable resistor connected in shunt therewith and controllable to electrically retard the cycle of operation of said angularly shiftable arm with respect to the associated contactors for completing a full cycle of operation for each position of the angularly shiftable arm with respect to an associated contactor.

'7. A printing telegraph system as set forth in claim 1, in which said keyboard includes a frame, depressible levers pivoted at one side of said frame, bars associated with each of said levers, horizontally extending lever members disposed substantially normal to the direction of said depressible levers and pivotally mounted at their opposite ends in said frame, contacts positioned on said pivotally mounted lever members on opposite sides of the paths of movement thereof whereby said lever members are selectively moved in either clockwise or counterclockwise directions for-closing electrical circuits for the establishment of said positive and negative current pulses, by contacting abutment of said bars with the upper surfaces of said lever members.

8. A printing telegraph transmitter comprising a frame, a set of fixed contacts mounted in prearranged positions adjacent the base of said frame, a plurality of lever members extending substantially the lengthof said frame in a plane above said fixed contacts, means for mounting said lever members in opposite ends of said frame in positions wherein said lever members may flex sideways about longitudinal centers from a horizontal position and be restored to the normally horizontal position thereof, contacts carried by the peripheral edges of said lever members in alignment with the aforesaid fixed contacts, key levers pivotally mounted at one side of said frame and extending in directions normal to the longitudinal centers of said lever members to a position adjacent the other side of said frame and selector bars depending from said key levers in prearranged positions for engaging the tops of said lever members in positions displaced from the longitudinal centers thereof and applying pressure thereto for flexing said lever members about said longitudinal centers through a sufficient displacement for moving the contacts carried thereby into contacting relation with said aligned fixed contacts for establishing permutations and combinations of signal pulses in a transmission circuit connected With said contacts.

9. A printing telegraph transmitter as set forth in claim 8 in which the bars depending from said key levers are variably spaced along the length of said key levers in positions for striking said lever members on opposite sides of the longitudinal centers thereof whereby to selectively orient the respective lever members clockwise or counterclockwise about the longitudinal centers thereof for moving the contacts carried by said lever members into contacting relation with said fixed contacts for establishing the permutations and combinations of pulses comprising the telegraph signals.

JAMES D. DURKEE.

Name Date Gundlfinger Nov. 11, 1941 Number

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