US2233668A - Printing telegraph apparatus - Google Patents

Description

March 4, 1941'. H. L. KRUM 2,233,668

PRINTING TELEGRAPH APPARATUS Original Filed July 19, 1937 2 Sheets-Sheet 1 FIG. 1

FIG. 2

March 4, 1941. H. 1.. KRUM 2,233,668

PRINTING TELEGRAPH APPARATUS Ofiginal Filed July 19, 1937 2 Sheets-Sheet 2 HOWARD L.

| I I 84 i t I F164 Patented Mar. 4, 1941 UNITED STATES PATENT OFFICE PRINTING TELEGRAPH APPARATUS Howard L. Krum, Beverly Hills, Calif., assignor to Teletype Corporation, Chicago, 111., a corporation of Delaware 12 Claims.

This invention relates to printing telegraph systems and apparatus and more particularly to two channel systems of telegraphic transmission for controlling telegraphic recorders.

This application is a division of application Serial No. 154,337 filed July 19, 1937.

An object of the invention is the provision of a relatively simple telegraph system by utilizing two transmission channels for character selection and printing.

Another object of the invention resides in the provision of means for controlling transmission of impulses over two channels of transmission, comprising two groups of transmitting elements,

' one group for each channel, and means Whereby said elements are operative initially to impress character selecting impulses over each channel in staggered manner, secondly to impress printing impulses coincidentally over said channels, and finally to impress restoration impulses in staggered manner over each channel.

In accordance with the present invention, signal impulses are transmitted over a two-channel or two-wire system to a printing apparatus whereat one line wire is connected through one ratchet-controlling magnet to a winding of a printing magnet, and the other line wire is connected through a second ratchet-controlling magnet to the same winding of the printing magnet. Since the printing magnet is marginal in operation, it responds only to current applied simultaneously on both line wires, and character printing is effected only when both windings of the ratchet-controlling magnets and the winding of the printing magnet are energized. Each character signal consists of three parts; namely, a plurality of stepping impulses, a prolonged printing impulse, and a plurality of restoration impulses, all of which occur concurrently on both line Wires. For example, the stepping impulses occurring on one line wire control the stepping of a type wheel one thirty-sixth of a revolution per impulse, and the stepping impulses occurring on the second line wire control the stepping of the type Wheel one-sixth of a revolution per impulse. Although these positioning impulses exist on both line wires concurrently or exist during the same signal period but not simultaneously, the impulses on one line wire are staggered with respect to the impulses on the other line, so as not to energize the print magnet permaturely. The maximum number of impulses on either line necessary to step the type wheel from its zero or starting position to the last one of its thirty-six positions is'five.

The second part of the character signal consists of a prolonged impulse occurring on both lines simultaneously and functions to operate the printing magnet which is designed to operate in response to greater current than the selecting or ratchet-controlling magnets, hence the requirement that the current on both lines simultaneously be necessary to operate the printing magnet. The third part of the signal consists of a series of impulses, occurring on both line wires concurrently, six on each wire, and staggered similarly to the positioning impulses, so as to affect only the ratchet-controlling magnets and not the printing magnet, the function of which is to effect the restoration of the type wheel to its initial or starting position. Thus, responsive to the restoration impulses is a restoration mechanism which prevents said impulses from rotating the type wheel further than to its zero or starting position. 20

The above and other objects of the invention will be apparent from the following description When taken in conjunction with the accompanying drawings, wherein like reference characters designate similar parts throughout the several 25 views, and in which,

Fig. 1 is a front elevational View of a printer operable in connection with the transmitter according to the present invention;

Fig. 2 is a rear elevational view of the printer shown in Fig. 1;

Fig. 3 is a fragmentary sectional view taken on line 3-3 of Fig. 1;

Fig. 4 is a graphic representation of the form of signal employed by the present invention;

Fig. 5 is a partial plan View of a keyboard transmitter embodying the principles of the present invention;

Fig. 6 is a sectional view taken on line 6-6 of Fig. 5;

Fig. '7 is a view showing the series of contact cams;

Fig. 8 is a schematic electrical circuit embodying the transmitter shown in Fig. 5;

Fig. 9 is a cross-sectional view of a dial type transmitter;

Fig. 10 is a top view of the transmitter shown in Fig. 9; and

Fig. 11 is a schematic electrical circuit embodying the transmitter shown in Fig. 9.

Having reference to Figs. 1 to 4, the framework of the printing apparatus co-operable with the transmitting arrangement of the present invention comprises a base plate ll supporting a mounting plate l2 attached thereto through the instrumentality of a bar 63 bymeans of screws 14. A U-shaped bracket I 5 is fixed to the mounting plate 12, and together with the mounting plate l2 provides a journal bearing for a type wheel shaft 45, as seen in Fig. 3. Fixed to shaft It, to the right of mounting plate l2, as viewed in Fig. 3, is a type wheel I? which has associated therewith a star wheel 18. Between the web of bracket 15 and mounting plate I2, shaft l6 carries thereon a sleeve i5 and a pinion gear 2|, the latter pinion being fixed to the shaft l6. Inter gral with sleeve I8 is a rachet wheel 22 in which is journaled a shaft 23 which carries fixed thereon, planetary gears 24 and 25 disposed one on each side of the rachet wheel 22. The planetary gear 25 meshes with the pinion 2|, and planetary gear 24 meshes with a pinion 28 which is integral with a sleeve 2'! loosely mounted on the sleeve H]. A ratchet wheel 28 is also integral with the sleeve 2 Fixed to shaft I 5 to the left of mounting bracket I5 (as viewed in Fig. 3) is a collar 29 which carries a spring post 3! (as viewed in Fig. 2) to which is connected one end of a coiled spring 32, the other end of which is connected to a pin 33 carried on a blocking segment 34 loosely mounted on shaft l6, the function of which will hereinafter appear.

As viewed in Fig. 2, ratchet wheel 22 has asso ciated therewith a pawl 35 carried at the extremity of a pawl operating lever 36 which is associated with an armature 31 of an electromagnet 38. -.Electro magnet 38 is carried on a bracket 39 which in turn is mounted on a bracket 4| secured to the mounting plate I2. The armature 37 is pivotally supported at 42 to bracket 39 and is biased in a clockwise direction by a spring 43. Spring 43 thus normally, when magnet 38 is de-energ-ized, maintains pawl operating lever 36 against stop portion 44 of a stop bracket 45.

Ratchet wheel 28 has associated therewith a pawl 46 carried at the extremity of a pawl operating lever 4'! which is integral with the armature 48 of an electromagnet 49. Elec-tromagnet 49 is carried on a bracket 5| which is supported on a bracket 52 secured to mounting plate l2. Armature 48 is pivotally supported at 53 on bracket 5i and is biased in counterclockwise direction by a spring 54, which normally maintains pawl operating lever 41 against an adjustable stop 66.

A printing magnet 55 is supported through angle brackets 55 and 57 to a plate 58 which in turn is carried by an angle bracket 59 secured to mounting plate l2. In the present embodiment, magnet 55 is provided with two windings, one of which controls an armature 6| pivotally mounted at 62 to th plate 58. Integral with armature 8| is a printing control lever 63 near the extremity of which is secured an extension 64 which acts on a plunger 65 carried in a bracket 55 secured to mounting plate l2. Plunger 65 co-operates with a laterally disposed flange 61 integral with a print hammer 68 (Fig. 1). Flange 5! is formed with a knife-edge to co-operate with the star wheel H8, in well-known manner, to hold the type wheel in printing position during the printing operation. The print hammer 68 is biased to its downward position by a spring 69.

The printing magnet 55 is also provided with a second winding which controls an armature H pivoted at 12 to plate 58. Armatures 6| and H are biased out of engagement with their pole faces by a common spring 13. Armature H is provided, integral therewith, with an extension 14 which is so conformed as to avoid the pawl during the performance of the restoration function as will presently appear.

In Fig. 4 is shown a diagrammatic representation of the type of signals transmitted by the transmitting apparatus according to the present invention and received over the two line wires for effecting the selective control and operation of the printer. shown in Figs. 1, 2, and 3. As previously indicated, each character signal consists of three parts; namely, the selecting or stepping impulses 8'3 and 84 comprising that portion indicalted as 19, the prolonged printing impulse comprising that portion indicated BI, and the restoration impulses 85 and 86 comprising that portion indicated 82. In Fig. 4 it may be noted that the selecting impulses 83 received over one line wire are staggered with respect to impulses 84 received over the second line wire, it being understood that the number of impulses 83 or 84 vary with the character received. It will also be observed that the printing impulses 8| impressed on each line wire occur simultaneously and are prolonged in nature. I Following the printing impulses are the restoration impulses 85 and 88 which are always, according to the present invention, six in number and are staggered as indicated.

Impulses 83 are impressed on electromagnet 38, and as each impulse is received, magnet 38 becomes energized and causes its armature 31 to rotate in a counterclockwise direction'against the action of spring 43, thus rotating the pawl operating lever 31 counterclockwise to raise pawl 35 to engage the next preceding tooth on the periphery of ratchet 22 preparatory to effecting rotation of said ratchet. Then upon deenergizaltion of magnet 38 at the termination of said impulse, armature 3'! and lever 36 are actuated in a clockwise direction by the spring 43 so that pawl 35 rotates the ratchet 22 through one angular step. This movement of ratchet 22 causes the planetary gears 24 and 25 to be carried clockwise and since, during this movement the ratchet 28 is prevented from rotating, the gear 24 will be caused to rotate in a clockwise direction thus imparting the same movement to the companion planetary gear 25. ment of planetary gear 25 causes pinion 2|, and hence Itype wheel ll and star wheel l8, torotate in a counterclockwise direction as viewed in Fig. 2 (or a. clockwise direction as viewed in Fig. 1). By properly proportioning the gears involved in this gear chain, the type wheel I! is moved one angular step representative of a single character space on the periphery of the type wheel for each actuation of pawl 35 by magnet 38.

When a character selecting impulse 84 is received over the second line wire, it causes the energization of magnet 49, which, upon energization, attracts its armature 48 to impart clockwise rotation to the pawl operating lever 41 against the action of its spring 54 sufficiently to permit pawl 46 to engage the next preceding tooth on the ratchet wheel 28. Then, upon termination of said selecting impulse, magnet, 49 becomes de-energized and spring 54 acts to rotate armature 48 and lever 41 counterclockwise,

This movethus actuating pawl 46 upwardly to eifect the counterclockwise rotation of ratchet wheel 28 one angular step. Since ratchet wheel 22 is at this time held against rotation by its pawl 35, the counterclockwise rotation of ratchet whee1 28 effects, through gear 26 and planetary gears 24 and 2.5 counterclockwise rotation of pinion 2| and type wheel I1, as viewed in Fig. 2. However, instead of rotating the type wheel only one angular step representative of a single character space, type wheel I! is rotated six angular steps or through the span of six character spaces of the periphery of the type wheel l1.

As previously mentioned character selecting impulses are transmitted over both line wires concurrently except that the impulses on one wire are staggered with respect to the other, and the number of impulses transmitted over each line wire is determined by the character to be selected. Remembering that the type wheel is restored to an initial or starting position prior to the selection and printing of each character, it will be assumed that the fifth character on the type wheel counting from the initial or starting position is to be selected. In this event, five impulses 83 will be transmitted over the first line wire (and none over the second line wire), thus energizing magnet 38 five times and rotating ratchet 22 through the angular distance of five teeth to effect the rotation of the type wheel I! correspondingly to present the fifth character on the type wheel (counting from the initial or starting position) to the printing point. Now, in the event that it is desired to print the eleventh character on the type wheel counting from the initial or starting position, five impulses 83 will be transmitted over the first line wire to actuate magnet 38 and to rotate ratchet 22 five angular steps, and hence type Wheel I'I five character spaces; and one selecting impulse 84 will be transmitted over the second line wire to energize magnet 49 to operate lever 41 to efiect the rotation of ratchet 28 one angular step, in a manner previously described, to cause the rotation of type wheel IT, in a single movement, six character spaces which, when added to the five character space movement resulting from the operation of magnet 38, will have caused the type wheel to be moved through eleven character spaces, thus presenting the eleventh character (counting from the starting position of the type wheel) to the printing point. It is thus seen that time has been saved in selecting the eleventh character on a type wheel by operating magnet 38 only five times and magnet 49 only once, instead of operating magnet 38 eleven times. Likewise, if magnet 49 is operated twice and magnet 38 is operated five times, the seventeenth character will be presented to the printing point. The latter selection will have been achieved through the transmission of only seven impulses, instead of seventeen impulses, thus emphasizing the decided saving in line time. To select the thirtyfifth or last character on a type wheel (the thirty-sixth or zero position being the blank position of the type wheel), only five impulses 83 need be transmitted to operate magnet 38 five times, and five impulses 84 need only be transmitted to operate'the magnet 49 five times. Thus, in all ten impulses have been transmitted instead of thirty-five.

After the transmission and receipt of the character selecting impulses 83 and 84, the selection of the character to be printed from the type wheel has been determined, and following the receipt of these selecting impulses 83 and M a prolonged printing impulse 93 is transmitted over both line wires simultaneously, thus energizing the print magnet 55, causing armature 6| thereof to be attracted and printing arm 63 to be actuated in a counterclockwise direction against the action of spring 13 to impart, through portion 64, upward movement to plunger 65, which through lateral portion 6'! imparts counterclockwise movement (as viewed in Fig. 1) to printing hammer 69, thus throwing the pallet portion of the printing arm 68 against the type wheel l'l. At the same time the knife-edge of portion 61 co-operates with the star wheel IE to prevent movement of the type wheel l'l during the performance of the printing function.

The tape 8'! is directed in tape guide 88 through the printing area. Engaging tape 81 through a slot (not shown) in the tape guide 88 is a tape spacing roller 89 which is provided, as is common practice, with a knurled periphery and which, to effect movement of the tape, cooperates with a pressure roller 9! carried on a lever 92 which is spring biased in a counterclockwise direction (as viewed in Fig. 1) by a spring 93. Roller 89 is mounted on a shaft 94 (Fig. 2) to which is also fixed a spacing ratchet 95. Co-operating with spacing ratchet 95 is a pawl 96 which is carried at the extremity of the printing lever 63. Thus, upon each operation of lever 63 in response to the printing impulse 8|, the pawl 96 is reciprocated thereby engaging the next tooth on the ratchet 95 and upon a downward movement of pawl 96, ratchet 95 is rotated one angular step in a clockwise direction (as viewed in Fig. 2) thus causing roller 89 to be rotated one angular step in a counterclockwise direction (as viewed in Fig. 1). A detent spring 91 is provided to prevent back spacing of the ratchet wheel 95 during the performance of the spacing operation. Associated with the type wheel H, as viewed in Fig. 1, is an inking roller 98 carried on a lever 99 biased by a spring I00.

As previously indicated, the third part of each character signal comprises a plurality of impulses over each line wire, sumcient in number i to insure the stepping of the type wheel forward (in the same direction as for character selection) to its starting or zero position. Since six impulses transmitted over each line wire is sufficient to rotate the type wheel a complete revolution, this number of impulses on each line has been chosen to effect restoration. Of course, the

extent to which it is necessary to rotate the type wheel to its zero position after the selection of a character varies with the character selected. Therefore, it is necessary to provide mechanism to prevent rotation of the type wheel farther than to its zero position. To achieve this result in connection with the six-step magnet 49, the segment 34 and arm 11 are provided, and in connection with the one-step magnet 38, the pins 16 and arm M are provided.

The magnets 38, 49, and are connected in the manner shown in Fig. 8 wherein the magnet 38 is included in one line wire 3M and the magnet 49 is included in the other line wire 3l5, magnet 55 being connected to both line wires so that impulses transmitted over line wire 314 will pass through magnet 38 thence through magnet 55 to ground. In the form of the invention shown in Fig. 2, the magnet 55 is provided with two windings, one of which is margial in character (and controls armature Bl) so that the impulses transmitted over only one of the line till the path of edge 10].

wires will not energize the marginal winding of the magnet. On the otherhand, it requires the total current on the two wires to effect the energization of said marginal Winding of magnet 55- Magnet 55 is also provided with a second winding which responds to the selecting and restoration impulses over either wire to cause the operation of armature -1I.

Now, when the restoration impulses 85fare transmitted over line wire 3| 4, they will pass through magnet 38 and also the second mentioned winding of magnet 55. The effect of restoration impulses 85 on magnet 38 will be to operate arm 36 and pawl 35 to cause the clockwise rotation of ratchet wheel 22. However, since these restoration impulses also pass through the second mentioned winding of magnet 55, armature 1| is operated to rotate lever 14 clockwise to bring hook portion 15 into the path of pins 16. Thus, pawl 35 will continue to actuate ratchet wheel 22, in response to the restoration impulses 35, only until one of the pins 16 is intercepted by the hook portion 15 after which the remaining restoration impulses 85, if any, will have no eifect. During the character selecting operation, the actuation of arm 14, and hence 'hook portion 15, in response to impulses 83 and 84, will have no arresting effect on the ratchet wheel 22, for the reason that the maximum distance that ratchet 22 may be rotated during a character selecting cycle is five steps, which is less than the number of steps between successive pins 16.

Similarly, the restoration impulses 86 transmitted over line wire 3l5 will pass through magnet 49 and said second winding of magnet 55. The effect of staggering impulses 85 and 86 is to maintain lever 14 steadily in its clockwise position, thus giving the effect of a continuous current on the second winding of magnet 55. The reception of the restoration impulses 86 by magnet 49 will cause lever 41 and pawl 46 to rotate ratchet wheel 28 step by step in a counterclockwise direction. As previously described, lever 41 is provided with a vertically extending arm 11 having a laterally extending portion 18. Thus, as lever 41 is oscillated, the portion 18 is reciprocated vertically. Portion 18 is thus free to reciprocate vertically until the segment 34 is presented in its path, whereupon oscillation of lever 41 is prevented. In this manner, type wheel [1, during the restoration operation, can be moved in six-step or six-character-space intervals until segment 34 is presented beneath the portion 18, after which the remaining restoration impulses, if any, will have no effect upon lever 41. The mechanism is so designed that when a pin 16 is intercepted by hook portion 15, and the portion 18 is intercepted simultaneously therewith by segment 34, the type wheel l1 will have reached its zero or starting position with the blank portion onthe periphery of the type wheel presented to the printing point.

Segment 34, as previously described, is yieldably connected to shaft l6 by means of coil spring 32. The purpose of this is to prevent segment 34 during the character selection operation, from binding against the lateral portion 18; that is, assuming that segment 34 during character selection is presented with its forward edge l0! just to the right of the vertical path of portion 18, the lever 41 in response to a selecting impulse will be actuated in a clockwise manner,'thus bringing portion 18 downwardly into Then on its upward move- ,latches 306. initiated substantially simultaneously with the menrt, lever 41 will actuate'ratchet wheel 28 to cause its counterclockwise rotation. However, before ratchet wheel 28 has advanced very far, edge l0l will impinge against portion 18 which has not yet escaped the segment 34. Without the yieldable spring connection between segment 34 and shaft I6, the pressure of pawl 46 against ratchet wheel 28 by means of spring 54 would cause segment 34 to'bind against portion 18, thus possibly injuring the mechanism. To compensate for this, segment 34 is permitted to yield and pawl 46 is permitted to complete its action upon ratchet wheel 28, whereafter when portion 18 clears the segment 34, segment 34' will be biasedby spring 32 to its normal counterclockwise position. v

I Transmitting mechanism In Figs. 5 to 11, inclusive, are shown various forms of transmitters and circuits therefor which may be employed in connection with the receiving printer shown in Figs. Ito 3. In Figs. 5 to 7, inclusive, is illustrated a. keyboard transmitter of the type shown and disclosed in United States Patent No. 1,595,472. As shown in Figs. 5 and 6 the keyboard portion, indicated generally as 30!, is provided with a set of keys 302 arranged similarly to the well-known typewriter keyboard, and, as illustrated in Fig. 5, key levers 303 associated with the keys 302 are pivotally mounted on a common shaft 304 and are spring held in normal horizontal position by individual springs (not shown). Arranged transversely below the key levers 303 (Fig. 6), in operative relation thereto, are a series of 'V-notched selector bars 305 which are adapted to be operated permutably, in well-known manner, in accordance with the key depressecL' The selector bars 305 are pivotally articulated to a corresponding series of locking latches 306 which are adapted to be rocked to either of two positions thereby. Associated with latches 306 is a corresponding series of contact levers 301 for making and breaking. contacts 308. Contact levers 301 co-operate with individual contact cams 309 mounted on shaft 3| I. The shaft 3 is provided with a single revolution clutch mechanism (not shown) which is controlled by a universal bar member as set forth in Patent No. 1,595,472. 1

The operation of the transmitting unit 'con- 'sists essentially in the depression of a key lever 303 which effects the arrangement of the set of selector bars 305 periodically in accordance with a predetermined code combination, thesetting of which determines the position of the locking The rotation of the cams 309 is setting of the locking latches 306, and a locking loop 3|2 controlled by a cam 3I3 is permitted to rotate in a counterclockwise direction (Fig; 6) to effect the locking of latches 306. The setting of the locking latches 306 determines whether the contact levers 301 shall or shall not be affected by their associated cams 309 to cause the opening or closing of. their associated contacts 308 to transmit over a signal line (as will appear presently from a description of Fig.8) to the receiving station apredetermin'ed combination of signaling impulses. The respective notches in the cams 309 are arranged in a spiral progression so that upon the rotation of the cam assembly, the contacts 308 will be controlled suecessively.

In the present form of transmitter,-the' contact cams 309 are eight'in number and are divided in, groups of four each, each group of four beingconnected to a separate line wire over a two-wire telegraph-system. In Fig. 7 is shown the series of eight contact cams 303 with their. respective contact levers and contacts. In this illustration, contact cams 32!, 322, 323, and 32 comprise one group, the contacts 358 of which are connected Over line wire 3! 4 of Fig, 8, and contact earns 33!, 332, 333, and 334 comprise a second group, the contacts 308 of which are connected over a second line wire 3!5 of Fig. 8. It will be noted that contact cams 32! and 33! are provided with a single depression in response to which a single impulse is transmitted through a contact 308 for each revolution of the cam. It will be noted further that cams 322 and 323 and cams 332 and 333 are each provided with two adjacent notches so that for each revolution of these-cams, two impulses will be transmitted. Then to enablethe sending of one to five character impulses over each wire 3! and 315, the cams in each group may be selected in proper combinations; for example, to send a single impulse over line 3I4, cam 32! only would be perated. To transmit two impulses over line 3M, cam 322 or cam 323 will be operated. To send three impulses over line 3M, cam 32! would be operated simultaneously with cam 322 or 323. To send'four impulses over line 3|4, cams 322 and 323 would be operated simultaneously, and to transmit five signals over the line all of the earns 32!, 322, and 323 would be operated simultaneously. The same permutable operation of the second group of cams 33!, 332, and 333' is effected to transmit signals over line 3!.5. It will be observed that the notches of each group of cams arearranged in a progressive manner.

Cams 324' and 334 are not controlled by. lock latches 336 and are permitted to rotate invariably for every operation of transmitting shaft 31!. Each of the cams 324 and 334 isso cut as to transmit (following the character selecting impulses) first the prolonged printing impulse and thereafter-six restoration impulses.

Having reference to Fig. 8 there is shown a circuit diagram for a two wire telegraph system employing the transmitter shown in Figs. 5 to 7 and printers according to Figs. 1 to 3; for example, herein described. According to this system, impulses in accordance with the diagram shown in Fig. 4 are transmitted, from battery 335, through contacts 338, over line wires 3M and M5, through their respective stepping magnets 38 and 49, thencethrough printing magnet 55 to ground.

In Figs. 9 to 11 is shown a dial type of transmitter. In accordance with this form of transmitter, a series of dialing keys 35! are disposed above a casing 352, and integral with each dialing key is a key lever 353 loosely carried upon a shaft 354. Each of the key levers 353 is provided with oppositely directed arcuately shaped arms 355 and 356, the upper arcuate edges of which are notched in code manner. Associated with the arm 355 of each of the key levers 353 is a pin351 carried on a common rod 353 suitably journaled in the casing 352. There is also carried on the rod 358 a contact operating pin 359 which co-operates with the upper blade 35! of contact 332. The assembly comprising rod 353 and pins 35'! and 359 are biased in their clockwise direction (as viewed in Fig. 9) by a spring 363. When a key lever 353 is rotated in a counterclockwise direction, the code projections on the arm 355 rock the rod 358 repeatedly in a clockwise direction and rotate arm 353 away from the contact 33!. Then, upon the return of key lever 353 to its rightward or clockwise position (as shown in Fig. 9), the code projections on arm 355 will again rock rod 353 repeatedly in a counterclockwise direction against the action of spring 353 to close the contact 352 intermittently to transmit impulses over the line wire, as will be hereinafter explained.

Similarly there is associated with the arm 353 of eachof the key levers 353 a pin 354 which is carried upon a common rod 365. There is also fixed to rod 335 a contact operating pin 355 which operates a contact 361. As a key lever is rotated counterclockwise, the code projections upon arm 353 act, through pins 355, to rock rod 335 repeatedly in a clockwise direction and rotate arm 363 away from contact 331. Then, upon return of the key lever 363 to its clockwise position, the code notches on arm 355 act to rock rod 355 repeatedly in a counterclockwise direction against the action of its spring 358 to close contact 36'! intermittently to transmit signal impulses over a second line wire.

According to the presently described form of the invention, means is provided for preventing the operation of more than one key lever 353 at a time; that is, whenone key lever 353 is operated, all of the remaining key levers are locked against operation. To achieve this result, an arm 339 is associated with each key lever whicharms 339 are fixed to the shaft 354. Pivotally carried on key lever 353 adjacent the outer extremity of arm 359 is a bell crank lever 31!. There is also carried on key lever 353 a bell crank lever 312, and bell cranks 31! and 312 are biased attrahently by a common spring 313. Extending longitudinally through the casing 352- and supported therein is a rod 31 which cooperates with bell cranks 31! and 312. Also fixed to the shaft 354 is an arm' 315 to the extremity of which is connected one end of a spring 315, the other of which is anchored to the casing 352. Thus, in this manner, all of the arms 3% are biased to their clockwise position against a stop 311 carried on each of the key levers 353.

When the arms 359 assume their clockwise position against stops 311, their ends 318 thereof also bear against bell cranks 312 to rotate the latter sufiiciently to remain disengaged from bar 313 as indicated in Fig. 9. Also, when key lever 333 is held in its clockwise position, bell crank lever 31! bears against bar 314 in such a manner as to maintain its horizontal arm disengaged from end 318 of arm 3%.

Now, when a key lever 353 is operated by means of its associated dial ng key 35!, and is thereupon actuated in a counterclockwise direction, its pin 31'! engages arm 353 and carries said arm forwardly therewith. This action is rendered possible because arm 339 is still bearing against bell crank 312 to hold said bell crank disengaged from bar 314, and as lever 353 is moved counterclockwise, bell crank 312 passes under the bar 315. Since all of the arms 363 are fixed to shaft 354, the remaining arms 359 will be moved independently of their associated key levers 353. Then, because of this operation of arm 333 independently of key levers 353, bell cranks 312 of all but the operated key lever 353 will be free to be actuated by their respective springs 3'13, so as to bring the horizontal arms of hell cranks 312 into latching engagement with bar 314. Therefore, so long as arms 339 of all but the operated key lever 353 remainout of contact with their respective bell cranks 312, all of the remaining key levers 353 are locked against operation. In Fig. 10 is shown a plan view of the dial transmitter with a part broken away to show the contact 362.

In Fig. 11 is shown a circuit diagram of a two wire telegraph system employing the dial transmitter shown in Figs. 9 and 10. In this system the contact 362 is operated intermittently in accordance with the code notches on the arm 355 of a key lever 353 to transmit impulses over the first line wire 319 through a stepping magnet 38! and print magnet 382 to ground. Similarly, contact 361 is operated intermittently in response to the code notches on the arm 356 of a key lever 353 to transmit over a second line wire 383 signal impulses to a stepping magnet 384 thence through the print magnet 382 to ground. Since print magnet 382 is of marginal operation, it will not respond to impulses received over either line wire singly but only when a printing impulse is received over both line wires 379 and 383 simultaneously. It is understood that the code notches on arms 355 and 356 may comprise the character signaling impulses, the printing impulse, and restoration impulses in accordance with the signal indicated in Fig. 4.

Although the present invention has been disclosed in connection with certain specific embodiments thereof, it is understood that such embodiments are merely illustrative and not restrictive, and that all forms coming within the scope of equivalency of the appended claims are intended to be covered by the invention.

What is claimed is:

1. In a telegraph transmitter, means for controlling transmission of impulses over two channels of transmission, comprising two groups of transmitting elements, one group for each channel, and means whereby said elements are operative initially to impress character selecting impulses over each channel in staggered manner, secondly to impress printing impulses coincidentally over said channels, and finally to impress restoration impulses in staggered manner over each channel.

2. In a dial transmitter for transmitting signals over two transmission channels, a plurality of dialing keys, a pair of coded arms carried on each key, a pair of contacts, one included in each channel, and contact controlling means for each contact co-o'peratively associated with corresponding arms of said pairs of arms.

3. In a dial transmitter for transmitting signals over two transmission channels, a plurality of dialing keys, a pair of coded arms carried on each key, a pair of contacts, one included in each channel, contact controlling means for each contact co-operatively associated with corresponding arms of said pairs of arms, and

means controlled by each key for locking, during each actuation thereof, the remaining keys against operation.

4. In a. dial transmitter for transmitting signals over two transmission channels, a plurality of dialing keys, a pair of coded arms carried on each key, a pair of contacts, one included in each channel, and contact controlling means for each contact co-operatively associated with corresponding arms of said pairs of arms and effective to transmit over said channels concurrently signals in accordance with the codes on said arms.

5. In a dial transmitter for transmitting signals over two transmission channels, a plurality of dialing keys carried loosely on a common shaft, a pair of coded projections carried on each key, a pair of contacts, one included in each channel, contact controlling means for each contact co-operatively associated with corresponding projections of said pair of projections, an-

terlocked therewith to actuate thereby all said' arms simultaneously to render the locking means of the remaining keys effective to lock said remaining keys against operation.

6. In an apparatus for transmitting signals over two transmission channels, a series of contacts, a permutation code selector mechanism, two groups of contact controlling mechanisms, one group for each channel, and means whereby said mechanisms are controlled permutably by said selectormechanism and are operative in a single cycle to impress concurrently signal impulses over each channel in staggered manner, followed invariably by a printing impulse occurring coincidentally on each channel and a definite series of restoration impulses occurring on each channel in staggered manner.

'7. In a keying device, a shaft, a plurality of keys carried loosely on said shaft, an arm asso ciated with each key and fixed to said shaft, locking means carried by each key and controlled by saidarms, and means effective upon each actuation of a key whereby the arm associated with the actuated key is interlocked therewith to actuate therebyall said arms simultaneously,

to render the locking means of the remaining keys effective to lock said remaining keys against operation.

8. In a keying device, a shaft, a plurality of keys carried loosely on said shaft, an arm associated with each key and fixed to said shaft, a lock bar, dual bell crank locking means carried by each key and co-operable with said lock bar and controlled by said arms. andmeans eifective upon each actuation of a key whereby the arm,

associated with the actuated key is interlocked therewith to insure control of said shaft by said key lever and simultaneously'to render the locking means of the remaining keys effective to lock said remaining keys against operation.

9. In a keying device, a shaft, a plurality of keys carried loosely on said shaft, an arm associated with each key and fixed to said shaft, a

lock bar,.dual bell crank locking means carried by each key and co-operable with said lock bar and controlled by said arms, and means effective upon each actuation of a key whereby the arm associated with the actuated key is interlocked therewith through the instrumentality of one of said bell cranks to insure control of said shaft by said key lever and simultaneously to render the locking means of the remaining keys elfective, through the other of said bell cranks, to lock said remaining keys against operation.

10. In a dial transmitter for transmitting signals over two channels, a shaft, a plurality of dialing keys loosely mounted on said shaft, a pair of coded arms on each key, an arm associated with each key and fixed to said shaft, a pair of contacts, one included in each channel, contact controlling means for each contact cooperatively associated with corresponding arms of said pairs of arms, locking means carried by each key and controlled by said arms, and means effective upon each actuation of a key whereby the arm associated with the actuated key is interlocked therewith to actuate thereby all said arms simultaneously to render the locking means of the remaining keys effective to lock said remaining keys against operation.

11. In a dial transmitter for transmitting signals over two channels, a shaft, a plurality of dialing keys loosely mounted on said shaft, a pair of coded arms on each key, an arm associated with each key and fixed to said shaft, a pair of contacts, one included in each channel, contact controlling means for each contact cooperatively associated with corresponding arms of said pairs of arms, a lock bar, dual bell crank locking means carried by each key and cooperable with said lock bar and controlled by said arms, and means effective upon each actuation of a key whereby the arm associated with the actuated key is interlocked therewith to insure control of said shaft by said key lever and simultaneously to render the locking means of the remaining keys effective to lock said remaining keys against operation.

12. In a dial transmitter for transmitting signals over two channels, a shaft, a plurality of dialing keys loosely mounted on said shaft, a pair of coded arms on each key, an arm associated with each key and fixed to said shaft, a pair of contacts, one included in each channel, contact controlling means for each contact cooperatively associated with corresponding arms of said pairs of arms, a lock bar, dual bell crank locking means carried by each key and cooperable with said lock bar and controlled by said arms, and means effective upon each actuation of a key whereby the arm associated with the actuated key is interlocked therewith through the instrumentality of one of said bell cranks to insure control of said shaft by said key lever and simultaneously to render the locking means of the remaining keys efiective, through the other of said bell cranks, to lock said remaining keys against operation.

HOWARD L. KRUM.

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