US2112234A - Teletypewriter system - Google Patents

Description

March 29, 1938. l J. F. BEATTIE ET AL 2,112,234

' TELETYPEWRITER SYSTEM Filed Sept. 9, 1956 2 Sheecs-Sl'leei'l l JEBEATT/E NVENORS' um. RorcRoFr ATTORNEY J. F. BEATTIE ET A1. 2,112,234

March 2.9, 1938.

TELETYPEWRITER SYSTEM Filed Sept. 9, 1956 2 Sheets-Sheet 2 mmf.

/Nl/E/voRs: J- E BEATT/E WRROYCROFT H/'roRA/Ey Patented Mar. 29, lees ,2,l2,234

amro STATI-:s PATENT oFFlCE TELETYPEWRITER, SYSTEM James F. Beattie, Norwood, N. J., and Walter R.

Roycrcft, zone Park, N. Y., assignors to Western Electric Company, Incorporated, New York, N. Y., a corporation of New York Application September 9, 1936, Serial No. 99,940

13 Claims. (Cl. 178--23) This invention relates to teletypewriter sysbe operated by the pull bars. This pivoted plate tems and, more particularly, to systems which has an effective position and an ineffective posiinclude a teletypewriter having contacts for pertion. Biasing means normally tilt the DVOted y, forming various functions. plate in its ineffective position so that the con,-

It is an object of this invention to mount contacts are elevated beyond the reach of the pull tacts, for performing various functions, in a telebars. Control means are provided fOr tilting the. typewriter to be operated by the teletypewriter pivoted plate into its effective position for lowmechanism in response to the transmission and ering the contacts into the reach of the pull bars.

Y reception ci any or all upper case characters The plate is locked in its effective position by H lo without hindering the printing functions of these means provided for that DUYDOSe- A feW f the lo" characters. contact assemblies are mounted in other places It is also an object of this invention to open inthe teletypeWliter and are designedt0 be 0pe1`- and close, by means of a central teletypewriter, ated by certain mechanisms in the teletypewriter.

telegraph lines leading from a teletypewriter These and other features of the invention will y l oiiice to other teletypewriter stations. now be described in detail` with reference to the 15 It is a further object of this invention to prodrawings in Wheh vide a central teletypewriter office with an im- Fig. 1 represents a teletYDeWIteI Central Oflee proved switching device for switching various and shows a schematic diagram in perspective of circuits. a teletypewriter having its platen assembly in It is an additional object of this invention to the lower case position and DIOVided With Special 276'y enable a subscriber at a teletypewriter station to contacts and circuit connections leading t0 the connect his teletypewriter through a teletypeswitching relays; writer central cnice to another teletypewriter Fig. 2 shows the switching relays at the central station without the assistance of an operator at olee and the other teletypewriter stations to the central office thereby effecting a saving in which the teletypewriter central oflice shown in operating time. Fig. 1 is connected;

It is a further object of the invention to @name Fie. 3 illustrates the marmer in which the 00nsubscribers having their lines connected together tact mounting plate is locked in its eiective poat a central oiiice to disconnect the linesat the sition; central office without the assistance of an oper- Fig. 4 shows the contact mounting plate in its 30 ator at the central oiiice thereby effecting a furunlatched, or ineffective, position; and ther saving in operating time. Fig. 5 illustrates the means for enabling the These and other objects of the invention are contact asemblies to be adjustably mounted on attained by means of a plurality of contact asthe contact plate. ,Y semblies mounted in a teletypewriter at various The teletypewriter T, shown in Fig. 1, is simi- 35 predetermined positions. The contacts are lar to the teletypewriter disclosed in Patent adapted to be operated by the teletypewriter 1.745.533 granted February 4, 1930 t0 S- MOFtOn mechanism in response to certain preassigned et al. The disclosure of this Morton et al. patent teletypewriter signals which may, if desired, be is incorporated herein by reference as a part of l l0 sent from other teletypewriter stations. In the this Specication. However, the invention is not 40 preferred embodiment ofthe invention, the oplimited to this type 'of teletypewriter nor is it eration of the contacts serves to operate relays limited to the specic structure shown in the which operate and lock-up to perform any dedrawings which is a preferred embodiment of the sired functions, such as switching telegraph cirinvention and is shown and described in order to l5 cuits. Also, in the preferred embodiment of the illustrate and explain the features and Principles 45 invention, the operation of a particular contact of operation of the invention. unlocks the switching relays and causes them to For purposes of illustration, teletypewriter T is deenergize thereby restoring the system to its shown to be located at a teletypewriter central normal condition. If desired, these relays` may office although it may be located at an ordinary be designed to perform a variety of functions, teletypewriter station, if desired. Connected to such as switching on and off a teletypewriter mothis central oiiice by telegraph lines L1 to Ls, intor at an outlying teletypewriter station. elusive, are the subscribers teletypewriter sta- Most of the contact assemblies are adjustably tions S1 to Ss, inclusive, each of which is p-roattached to a pivotally mounted plate, located in vided with a teletypewrter Ti to T6, inclusive,

si.; the central teletypewriter, and are designed to and a teletypewriter motor M1 to- Ma, inclusive. 55 v ated by an individual power supply source B1 to Bs, respectively. At stations S1, Sz, S3, and S5 the energizing circuits leading from the respective local power supply sources to the motors are opened and closed by manually operable switches A1, A2, A3, and A5, respectively, controlled by the local attendant at each station.

The energizing circuit of the motor M4 is normally open at the armature and contact A4 of the normally unoperated relay 43. This energizing circuit is adapted to be opened and closed by any control method that may be desired, such as the method described in Patent 1,913,431 granted June 13, 1933 to W. Daum. The disclosure of this Daum patent is incorporated herein by reference as a part of this specification. The energizing circuit of motor M6 is normally open at contact A5 of relay Re located at the central office. It is to be understood that these different motor control circuits may be varied as desired to meet the particular requirements of a given system and that they are shown here for the purpose of illustrating the wide extent to which the invention may be applied. It should also be understood that the invention is capable of use with any other type of line circuits, such as duplex circuits.

The teletypewriter T at the central office has a motor M which is operated by a power supply source B over an energizing circuit closed by a manually operable switch lever A. Motor M operates teletypewriter T by means of gears G1 and G2 which alternately raise and lower the reciprocating printing bail I9 to actuate the pull bars selected by the code bars operated by the selecting mechanism I8, as is described in the Morton et al. patent.

Just above the code bars 80 is a base plate 8l which is attached to the frame 95 of the teletypewriter T by any convenient means, such as screws 82. Pivotally mounted on base plate 8| by pivot is a contact plate 83. This pivotal connection provides contact plate 83 with two positions, one an ineffective position and the other an effective position. Contact plate 83 is normally held in its ineffective position by means of a retractile spring 85 asis shown in Fig. 4.

Contact plate 83 is placed in its effective position in response to the reception by relay R of a preassigned teletypewriter code signal. In the preferred embodiment of the invention this signal is a so-called bell signal; that is, it is a signal which is designed to effect the ringing of a bell (not shown) in the teletypewriter T. With the type of teletypewriter shown in Fig. l, a bell signal is what is known as an upper case signal and, accordingly, requires that it be preceded by a figures shift signal. Furthermore, if a code signal corresponding to a bell signal should be sent while the platen 21 is in its lower case position, the bell pull bar 81 would not be selected but, instead, another pull bar (not shown) would be selected. This other pull bar is not selected by any upper case signal so its associated type bar (not shown) is blank in the upper case. Y

The reception of a figures code signal by relay R actuates the selecting mechanism. I8 which operates the code bars 8D to select the figures pull bar 41 for enabling its shoulder to be engaged by the printing bail I9. Bail I9 then elevates pull bar '4l and causes the extension 48 to elevate the left end of bell crank'49. This causes: the right end of bell crank 49 to dip down and 2,112,234 vEach of the motors M1 to Me, inclusive, is operlower catch 19 thereby releasing latch 58. The release of latch 55 allows spring 5I to pull the platen assembly 52 forward. In moving forward, the platen assembly 52 pulls lever 28 forward sufliciently to remove slot 'l5 from the path of travel of extension 29 of the so-called blank pull bar I4 and, at the same time, closes a contact C7 for a purpose to be explained hereinafter.

Now, when a bell code signal is received by relay R, selecting mechanism. I8 will operate code bars 8D to select the bell pull bar 81. Ball I9 then engages with the shoulder of the bell pull bar 81 and elevates bar 81 with the result that the upper end of bar 8'! pushes the left end of lever 88 upward. Lever 88 is pivotally mounted at 89 (Fig. 4) so that, when its right end goes up, its left end comes down and carries with it link 90 thereby overcoming the tension of spring 86 by pulling down the right edge of the contact plate 83. This enables latch 9| to engage with catch 92 on contact plate 83. Retractile spring 94 pulls latch SI to the left for holding contact plate 83 in its effective position.

Contact plate 83 remains in its effective position until a particular preassigned teletypewriter code signal is received by relay R. In a preferred embodiment of the invention, this particular code signal is what is known as the letters shift signal. When this letters shift signal is received by relay R, it effects the selection of the letters pull bar 53 by the code bars 88. Bail I9 then elevates the letters pull bar 53 so that the top end of bar 53 hits against lever 93 and causes it to turn counterclockwise around its pivot thereby overcoming the pull exerted by spring 94 and tripping latch 9i. The release of latch 9I allows retractile spring 83 to pull the contact plate 83 back to its normal, or ineffective, position.

Adjustably mounted along the contact plate 83 in the manner shown in Fig. 5 are the assemblies for contacts C, C2, C3, C5, and C5. Although these Contact assemblies have been shown to be adjustably mounted, it is to be understood that this is merely one form of the invention and that the Contact assemblies may be xedly located by being drilled and tapped onto the contact plate 83. All of these contacts are normally open except contact C which is normally closed. Contacts C, C2, C3, C5, and C6 are each designed to be momentarily operated in response to only upper case selections of pull bars I7, I2, I3, I5 and I6, respectively, and are then effective to perform their intended functions only when their operating signals are preceded by a preassigned code signal which, in the preferred embodiment of the invention, is a so-called bell signal. Thus, the pull bars II, l2, I3, I5 and I6 may be used for performing their normal lower and upper case printing functions as well as for operating contacts C, C2, C3, C5, and C5 to perform various functions, such as switching telegraph lines, as will be described hereinafter.

In addition to these switching contacts, the switching mechanism also includes the normally open contact C7 which is operated by the platen assembly in the manner described above. The switching mechanism further includes the normally open contacts C1 and C4 which are designed to be operated by portions of the teletypewriter mechanism only in response to the reception by the receiving relay R of certain upper case teletypewriter code signals. The manner of operating contacts C1 and C4 will be described hereinafter in connection with the description of the operation of the system as a whole.

In the operation of the system, let it iirstbe assumed that the subscriber at station S1 wishes to connect himself through the central ofce to the subscriber at station S3. The subscriber at station S1 normally has his switch A1 closed during business hours so that his motor M1 is energized by his local power supply source B1. Accordingly, the subscriber, by means of his teletypewriter T1, rst transmits a figures shift signal o-ut over line L1, conductor 2li, line L2, through station S2, line L2, conductor 2 I, through the normally closed contacts of relay R2, conductor 22, through the normally closed contacts of relay R1, conductor 23, sending contacts 26, conductor I0, receiving relay R, conductor 8, outer left armature of the normally unoperated relay R4, and then to grounded battery 24.

The figures shift signal transmitted over this p-ath energizes the receiving relay R which operates the selecting mechanism I6 to select the gures pull bar 41 which is then elevated by the printing bail I9. In rising, pull bar 4'! causes its extension 48 to elevate the left end of bell crank 49. This causes the right end of bell crank 4S to dip down and lower catch I9 thereby releasing latch 50. 'I'he release of latch 50 allows spring 5I toI pull the platen assembly 52 forward. As was stated above, the forward movement of the platen assembly 52 pulls lever 28 forward suiiciently to remove slot I5 from the path of travel of extension 29 of the so-called blank pull bar I4. At the same time, the forward movement of the platen assembly 52 closes contact Cv for a purpose to be explained hereinafter.

The subscriber at station S1 now transmits a preassigned code combination of significant current variations which, in this preferred embodiment of the invention, is known as a blank signal, Upon being received at the central o-illce, this particular upper case code signal causes the selecting mechanism i8 to select the blank pull bar I4. Accordingly, the printing bail I9 elevates the blank pull bar I4 with the result that extension 29 of pull bar I4 engages with the left end of lever 28 and raises it up. This elevates the left end of lever 30 and, consequently, lowers the right end of lever 3i) thereby allowing spring 3| to pull down the left end of lever 32. As a result, the right end of lever 32 is raised and allows the spring contact C4 to close. This closing is only momentary because pull bar I4 is soon lowered by bail IS, and spring 'Il then pulls lever 28 back into the position shown in the drawing.

It should bey noted that contact C4 can only be closed by this upper case blank signal because, when the platen assembly 52 is in its lower case position (as is shown in Fig. l), slot 'I5 in lever 28 is then positioned over extension 29 of the blank pull bar I4. Elevation of pull bar I4 would then be futile to cause the closing of contact C4 because extension 29 would pass through slot I5 and would thus be unable to tilt lever 28.

The closing of contact C4 momentarily closes. the energizing circuit of relay R4 from grounded battery 33, through the winding of relay R4, conductor Il, contact C4, conductor 9, conductor 3E, and then to ground 3?. As a result, relay R4 becomes energized and operates both its armatures. Before contact C4 opens, relay R4 locks-up over a path leading from grounded battery 33, through the winding of relay R4, inner left armature, conductor Sti, conductor l, through the normally closed contact C, conductor 35, conductor 36, and then to ground 3l. At the same time, the communication circuit is switched from grounded battery 24 to the joining conductor 33 and then to conductor 3Q, out over line La to station Se, over line Le, conductor 4i?, line L3, and then to station S3.

Since the subscriber at station Ss normally has his switch A3 closed during business hours, his motor M3 will be energized at this time by his local power supply source B3. Accordingly, the system is now in condition for communication to take place between the subscriber at station S1 and the subscriber at station S3. Signicant current variations transmitted by the teletypewriter T1 will travel over line L1, conductor 2&3, line L2, through station S2, line L2, conducto-r 2l, conductor 22, conductor 23, sending contacts 25, conductor It, receiving relay R, conductor 8, conductor 38, conductor 39, line Ls, through station Se, line Lc, conductor III?, line La, and then to station S3.

When, during the course of communication., the subscriber at station S1 wishes to effect a lower case selection, he transmits the so-called letters shift code signal for causing the selecting mechanism i3 of teletypewriter T to operate the code bars a@ to select pull bar Upon being elevated by the printing bail I9, pull bar 53 elevates its extension 5ft which correspondingly elevates the left end oi lever 55 thereby depressing the right end of lever 55. When the right end of lever 55 is depressed, it causes the left end of bell crank 5t to be correspondingly depressed, thereby causing the top end of bell crank 51E to move backward to the rear of the teletypewriter "i". This acts as a lever to pull hack the platen assembly 52. In traveling to the rear of the teletyp-ewriter T, the platen assembly 52 causes latch 5h to also move to the rear of the teletypewriter T with the result that latch 553 will engage with the catch i9 in the right end oi bell crank lever 523. This serves to hold the platen assembly 52 in its rearward position and prevents spring 5i from pulling it forward. Thus, the platen assembly 52 is latched in its lower case position, as is shown in Fig. l, where it remains until a gures shift signal is received by relay R.

Since both stations S4 and S5 are disconnected from the communication circuit at the armatures of relays R1 and R2, respectively, neither teletypewriter T4 nor teletypewriter T5 will record the signals sent from teletypewriter T1 at this time. Teletypewriter Ts will also not record these signals due to the fact that the energizing circuit for its motor M6 is open at contact Ae of relay Rs. However, with the system in the condition shown in the drawings, teletypewriter T2 will follow the signals transmitted by teletypewriter T1 because the energizing circuit for its motor M2 is closed at switch A2. If the subscriber at station S2 nds that the message being transmitted from station S1 to station S3 is of no interest to him, he can open switch A2 thereby shutting clown his motor M2 with the result that his teletypewriter T2 will not now record the signals being transmitted.

Thus, the subscriber at station S1, which may be located at a remote point, has connected himself through the central crice to the distant subscribers station S3 without any assistance from an operator at the central office. In other words,

the subscriber at station S1 has switched both his and the other subscribers lines 8 and 39 from their terminations at batteries 24 and 25, respectively, to the joining conductor 38 thereby switching the line conductors 3 and 39 together. Consequently, a considerable saving in operating time is effected since the subscriber at station S1 simply transmits the upper case code combination assigned to select pull bar I4 which closes contact C4 to operate relay R4 which immediately switches the two lines 8 and 39 together without any act by an operator at the central oce. This saving in operating time is of importance in certain types of business where time is of the essence and promptness in putting calls through is essential.

When the subscribers at stations S1 and S3 have finished communicating with each other, either one of them may effect a disconnection of their lines 8 and 39 at the central oflice by transmitting, from either station S1 or station S3, a figures shift signal followed by a preassigned telegraphic signal, which in this preferred embodiment of the invention, is a bell signal. This bell signal is received by the receiving relay R at the central office which accordingly actuates the selecting mechanism |8 to operate the code bars 83 to select the bell pull bar 81. The resulting elevation of bar 3l by the reciprocating bail I9 causes lever 88 to be tilted thereby pulling down the contact plate 83 which is then latched in its effective position by latch 9| as was described above.

Then, either of the subscribers transmits another preassigned code signal which causes code b-ars 86 to Select pull bar Bail I9 then elevates pull bar which momentarily opens the normally closed contact C thereby opening the locking-up circuit of relay R4. Consequently, relay R4 releases its armatures and switches the line conductors 8 and 39 from the joining conductor 38 to batteries 24 and 25, respectively, thereby disconnecting stations S1 and S3 from each other and restoring the circuits to their normal condition. If desired, the subscriber at station S2 may also eiect this disconnection. Since this disconnection is accomplished by any of the connected subscribers without the assistance of an operator at the central ofce, a further saving in operating time is eiTected.

The nature of the business of the subscriber at station S1 may be such that it woul-d be desirable for him to send a message to both the subscriber at station S3 and the subscriber at station Se (which may, for example, be an outlying station near the central oliice) and have the message recorded practically simultaneously by the teletypewriters T3 and Ts. To accomplish this conference connection, it is first necessary to start the teletypewriter motor Me at station Se by energizing relay Re. Accordingly, the subscriber at station S1 transmits a figures shift signal for selecting the figures pull bar 4l to effect the release o1" latch 53 which then allows the platen assembly 52 to be pulled forward by spring 5|. In moving forward, the platen assembly 52 carries latch 58 forward along the top edge of bell crank lever 49 thereby forcing down the right end of bell crank lever 9 to close contact C7. Since latch 50 now engages with the catch 19 in the right end of bell crank lever 49, contact C7 will remain closed during the time that the platen assembly 52 remains in its upper case position.

The subscriber at station S1 next transmits a bell signal over line L1, conductor 20, line L2,

through station S2, line L2, conductor 2|, conductor 22, conductor 23, sending contacts 26, conductor l0, receiving relay R, conductor 8, and then to grounded battery 24. This elects the selection of the bell pull bar 87 which causes the contact plate 83 to be latched in its effective position in the manner described above. The subscriber at station S1 now transmits a preassigned combination of code impulses over the circuit traced above. This code combination causes the selecting mechanism 8 of teletypewriter T to select pull bar |6 which is then operated by the printing bail I9 to close contact Cs momentarily. A path for energizing relay Re is now closed from grounded battery 4|, through the winding of relay Re, conductor 6, through contact C6, conductor '|6, conductor 9, con-ductor 36, and then to ground 31.

As a result, relay Re operates its armatures and locks-up through a path from battery 4|, through the winding of relay Re, operated left armature, conductor 34, conductor through the normally closed contact C, conductor 35, conductor 36, and then to ground 31. At the same time, the right armature of relay Re is operated and closes a path from power supply source Bs at station Se, over line conductor 45, operated armature and contact Ae of relay Re, line conductor 46, motor Ms, and then back to power supply source Bs thereby energizing motor Me and starting it into operation. The subscriber at station S1 then transmits the code signal for selecting pull bar i4 in the teletypewriter T at the central office. When bail I9 elevates pull bar I4, contact C4 will be momentarily closed and relay R4 will operate its armatures and lockup in the manner described above.

Messages now sent from station S1 will pass through station S2, through the central office, and then through stations Se and S3. 'Ihe messages will thus be recorded practically simultaneously on both the teletypewriters T3 and Ts. They will also be recorded on the teletypewriter T2 at station S2 provided the subscriber at this station has his switch A2 closed. The subscriber at station S3 can transmit messages to any of the connected stations and these messages will be practically simultaneously recorded by the teletypewriters T1, T2, and Ts. Likewise, the subscriber at station Se can also send messages which will be recorded on all of the connected teletypewriters.

At the close of communication, if the platen assembly 52 happens to be in its upper case position, any of the subscribers at stations S1, Sz, S3, or Se may disconnect the conference connection by transmitting a bell signal to place plate 83 in its efrective position and by then transmitting the preassigned code signal for selecting pull bar which will momentarily open the normally closed contact C as was described above. However, if the platen assembly 52 happens to be in its lower case position, then the bell signal must be preceded by a gures signal before contact plate 83 can be placed in its effective position. The opening of contact C will open the lockingup circuits of both relays R4 and Rs and will cause them to release their armatures. This switches the communication circuit from conductors 8 and 39 to grounded batteries 24 and as was described above. At the same time, the energizing circuit of motor Me is opened at contact As of relay Re and, consequently, motor M6 stops running. The circuits are thus restored to their normal condition.

In the event that the subscriber at station S1 wishes to communicate with the subscriber at station S4 (which may, for example, be an outlying station near the central cnice), he will transmit the gures shift signal to cause the platen 2l to be shifted to its upper case position. The subscriber will then transmit a preassigned upper case code signal which, upon being received by the receiving relay R, will effect the selection of pull bar II b-y the selecting mechanism I8 and the code bars 80. The elevation of pull bar I I by bail I9 will, by means of ratchet l and gear 58, drive the top of type bar 59 downward in an arcuate path. The projection 84 on bar 59 will then hit lever 60 thereby tilting downward the right end of lever 6I. This drives the top end of lever 6I to the right and allows spring 62 to pull down the right end oi lever 63 into latching engagement with the top end of lever 6I. Consequently, the left end of lever 63, which is normally located immediately beneath the printing bail I9, as shown in the drawings, is driven upward to close contact C1 momentarily. It should be noted that contact C1 can only be closed by an upper case selection of pull bar I I because, when the platen assembly 52 is in its lower case position, lever 66 is carried to the rear of teletypewriter T a short distance which is sufiicient to remove it from the path of travel of projection 84.

The closure of contact C1 closes a path from grounded battery 64, through the winding of relay R1, along conductor I, through contact C1, conductor 65, conductor 36, and then to ground 3l. Consequently, relay R1 operates both its armatures and locks-up through its right armature over a path from grounded battery 64, winding of relay R1, operated right armature and contact of relay R1, conductor 34, conductor I, normally closed contact C, conductor 35, conductor 36, and then to ground 31. It is necessary that relay R1 be designed to lock-up quickly because, when the reciprocating bail I9 cornes down, it strikes the left end of lever 63 thereby knocking the right end of lever 63 up out of latching engagement with the top end of lever 6l. This permits contact C1 to resume its normally open position.

The operation of the two left armatures o'f relay R1 opens the normally closed make-beforebreak left contacts of relay R1 and closes a path from conductor 22, over the inner left armature of relay R1, conductor 56, line L4, through station S4, back over line L4, conductor 61, outer left armature of relay R1, conductor 23, sending contacts 26, conductor Il), relay R, conductor 8, and then to grounded battery 24. The subscriber at station S1 now transmits motor start signals, such as those described in the Daum patent mentioned above, which eect the energization of a relay 43 at station S4 similar to the motor control relay disclosed in the Daum patent. Upon being energized, motor control relay 43 operates its armature to close the contact A4 thereby closing the energizing circuit oi motor M4 and starting motor M4 into operation.

Communication may now take place between stations S1, S2, and S4, the signals passing out over line L1, conductor 2B, line L2, through station S2, line L2, conductor 2l, conductor 22, conductor 66, line L4, through` station S4, line L4, conductor 6I, conductor 23, and then to grounded battery 24 as was described above. These signals will also pass through the receiving relay R. It might be mentioned here that this is the case with all connections between the various subscribers stations; that is, receiving relay R follows all the signals sent between these stations thereby making a complete record of all the communication which takes place throughout the system.

At the close oi communication, any of the subscribers at the three connected stations S1, Sz, and S4 may, after rst putting the platen assembly 52 into its upper case position in the manner described above, send a bell signal followed by the code signal for selecting pull bar I'I which momentarily opens contact C with the consequent opening of the locking-up circuit of relay R1. Relay R1 now releases its armatures and its make-before-break contacts now open the circuit leading to station S4 and connect conductor 22 directly to conductor 23. Incidentally, the motor at station S4 may be stopped by any of the subscribers in the manner described in the Daum patent. It might be stated here that, in this ernbodiment of the invention, they central oice operator can effect any of the connections and disconnections between any oi the subscribers stations because her sending contacts 26 are always connected in series with the communication circuits. This circuit construction can be modied in accordance with the requirements of dierent systems.

If the subscriber at station S1 wishes to send a message to be recorded by the teletypewriters Ta and T4 at stations S3 and S4 (leaving station S2 out of consideration for the sake of simplicity) he will, after rst causing contact plate 83 to be put in its effective position in the manner described above, send the code signals to select pull bars II and I4 for closing contacts C1 and C4. This will operate relays R1 and R4 which will lock-up as described above to close the lines leading to stations S3 and S4. nected subscribers may disconnect this confer'- ence connection, after placing contact plate 83 in its effective position, by sending the code signal to select pull bar I'I for opening contact C. This opens the locking-up circuits of both relays R1 and R4 thereby restoring the system to its normal condition.

Also, if the subscriber at station S1 wishes to send a message to be recorded by the teletypewriters at each of the stations S3, S4, and Se (again leaving station Sz out of consideration for the sake of simplication), he will follow the same procedure as that outlined in the preceding paragraph except that he will, in addition, send the code signal to select pull bar I6. The operation of pull bar I6 will close contact Cf; and will operate relay Re which will lock-up and close the energizing circuit of motor Ms at station Ss thereby conditioning station Ss for the reception and transmission of messages. Any of the connected subscribers, or the central oiiice operator, may disconnect this conference connection in the manner described above.

Likewise, the subscriber at station S1 may connect himself through the central oflice to station S5 by first transmitting the gures shift signal for shifting platen 2l in teletypewrter T to its upper case position. The subscriber at station S1 then transmits a bell signal (thereby placing contact plate 83 in its eiective position) followed by the preassigned code combination for selecting pull bar I2. The elevation of pull bar I2 by bail I9 momentarily closes contact C2 thereby closing the energizing path for relay R2 from grounded battery 68, through the winding of relay R2, con- Any of the conductor 2, contact C2, conductor 99, conductor 9, conductor 36, and then to ground 31 thereby energizing relay R2.

Upon being energized relay R2 operates its armatures and locks-ups from battery 68, through the winding of relay R2, operated left armature, con-ductor 34, conductor 1, through the normally closed contact C, conductor 35, conductor 36, and then to ground 31. In operating its two right armatures relay R2 switches the line circuit from along conductor 2 I, over the outer right operated armature and make-before-break contact of relay R2, conductor 69, line L5, teletypewriter T at station S5, back over line L5, conductor 10, inner operated right armature and make-before-break contact of relay R2, conductor 22, conductor 23, and then through the receiving relay R to grounded battery 24.

If a conference connection is desired, other stations may be connected into the communication circuit in the manner described above. At the close of communication, any of the connected subscribers may disconnect the connection by effecting the operation, or opening, of the normally closed Contact C at the central ofce in the manner described above.

In the event that it is desired to connect some other station into the communication circuit, or to perform any other switching function, the platen 21 is first shifted to its upper case position in the manner described above. After a bell signal has been sent to place the contact plate 83 in its effective position, the preassigned upper case code combination is transmitted for selecting pull bar I3.

The operation of pull bar I3 by bail I9 momentarily closes the switching contact C3 for enabling relay R2 to operate over a path traced from grounded battery 1I through the winding y of relay R3, conductor 3, contact C3, conductor armature, conductor 34, conductor 1, through the normally closed contact C, conductor 35, conductor 39, and then to ground 31. In operating its right armatures, relay R3 will perform the desired switching function.

When it is desired to ldiscontinue the switching operation, the contact plate 83 is placed in its eective position in the manner described above, the upper case code signal is sent for causing pull bar I1 to open the normally closed contact C which opens the locking-up circuit of relay R3 thereby causing relay R3 to release its armatures thus restoring the system to its normal condition.

If it is desired to perform still other switching functions, they may be effected by rst shifting the platen 21 to its upper case position. After sending a bell signal to place contact plate 83 in its effective position, the preassigned upper case code combination for selecting pull bar I 5 is then transmitted. The elevation of pull bar I5 momentarily operates the switching contact C5 for closing a path from grounded battery 13, through the winding of relay R5, conductorY 5, contact C5, conductor 14, conductor 9, conducto-r 36, and then to ground 31 thereby energizing relay Rs. Upon operating its armatures, relay R5 will lock-up over a path leading from grounded battery 13, through the winding of relay R5, operated left armature, conductor 34, conductor 1,

through the normally closed contact C, conductor 35, conductor 36, and then to ground 31. In operating its right armatures, relay R5 will perform the desired switching functions.

When Iit is desired to terminate this switching operation, the contact 'plate 83 is placed in its effective position in the manner described above and the upper case signal for effecting the opening of the normally closed contact C is transmitted thereby opening the locking-up circuit of relay R5 which now releases its armatures and restores the system to its normally unoperated condition.

Another switching function may be accomplished by means of contact C7 which is operated by movement of the platen assembly 52 as was described above. That is, contact C7 is closed when platen assembly 52 is moved forward to its upper case position and is opened when platen assembly 52 moves back to its lower case position. This opening and closing of contact C7 opens and closes the path along conductors 42 and 44 and may be utilized for accomplishing any desired function analogous to those described above.

If additional operations, or functions, are desired, more contacts can be mounted upon the contact plate 83 and can be connected into the system in a manner similar to that in which the other contacts are connected.

Whereas the operation of the system has been described principally with reference to connections originating from the dominant station S1, it is to be understood that the connections described above may be effected and disconnected. in a similar manner by the subscriber at the other dominant station S2. It is to be further understood that other dominant stations may be added according to the particular requirements of an individual system.

For the purpose of illustration, contact C1 has been shown to be operable by an individual arrangement of the teletypewriter apparatus. If it is desired to have levers 69, 8l, and 63 perform some other function, contact C1 may be mounted on the contact plate 83 above a pull bar the same as contacts C2, C3, C5, and Ca.

The same applies to contact C4 which has also been shown to be operable by an individual arrangement of the teletypewriter apparatus. If it is desired to have levers 28, 30, and 32 perform some other function, this may readily be accom plished by placing contact C4 on the contact plate 83 above a pull bar the same as contacts C2, C3, C5 and C5.

All of the contact assemblies on plate 83 have been shown to be adjustably mounted in order that their positions may be readily varied to meet the requirements of different systems. It is to be understood that this has been done for the purpose of illustration and that they may be fixedly mounted on plate 83 by being drilled and tapped thereto. The preferred method of adjustably mounting the contact assemblies is shown in Fig. 5 in which the contact assembly 95 is shown to be provided with a spring contact CX and a clamp 91 having a screw 98. To install this contact assembly 9S, it is slid onto the contact plate 83 in such a manner that the clamp 91 embraces the contact plate 83 as shown in Fig. 5. The contact assembly 96 is then slid along the contact plate 83 until it is over the top of the proper pull bar. The screw 98 is then tightened so that the Contact assembly 96 is held firmly in place on the contact plate 83.

This position ofthe contact assembly 93 may be changed by rst loosening screw 98, then sliding assembly 9B along contact plate 83 to its new location, and then tightening screw 98. Contact assembly St can also be readily removed by simply loosening screw 98 and then sliding assembly 96 off the contact plate 83. Thus, it can be seen that the use of this adjustably mounted contact assembly 96 renders the apparatus more flexible and adaptable to meet different and changing requirements of the system.

It may be stated here that, after contact plate 83 has been latched in its effective position and after the desired switching relays have been operated and have locked-up, then the desired message, or messages, are sent to the connected stations. As soon as a letters code signal appears in the message, pull bar 53 will be selected by code bars 80 and will be operated by the reciprocating bail IS. The elevation of pull bar 53 operates lever 93 which trips latch 9|. As was described above, the release of latch 9i permits spring 86 to pull contact plate 83 into its ineffective position. However, this has no effect on the status of the switching relays at this time because all the operated switching relays remain locked-up. This is because the movement of contact plate 83 from its effective `position to its ineffective position does not open the normally closed contact C. Contact C remains closed until contact plate 83 is again placed in its effective position and pull bar I1 operated as was described above.

Thus, by means of this invention, the Various pull bars of the teletypewriter T at the central office may be used for performing their regular printing functions in response to both upper and lower case selections. The restriction of the switching functions of the pull bars to only those upper case selections which have been preceded by a bell signal facilitates regular communication between the stations during the period that the contact plate 83 is in its ineffective position. This is due to the fact that, if contact plate 83 were not in its ineffective position, every time the pull bars should be operated they would close their contacts to operate the particular switching relays associated therewith.

It is to be understood that this specific application of the invention has been shown and described for purposes of explaining the principles and features of operation of the invention. Many changes may be made in the construction shown without exceeding the scope of the invention. More switching contacts to be operated by the pull bars of the teletypewriter at the central cnice may be added whenever desired to perform any functions that may be required. Likewise, the circuit connections of the various subscribers stations may be varied as desired to meet the requirements of any particular communication system.

For example, the teletypewriter at each subscribers station could be provided with these switching contacts and circuit connections. This would enable a subscriber to perform the various switching operations desired without sacrificing the ordinary upper and lower case printing functions associated With the pull bars of his teletype- Writer. Thus, after connecting himself to the desired stations, the subscriber could avail himself completely of the ordinary printing functions of his teletypewriter.

What is claimed is:

l. A teletypewriter having pull bars, selecting mechanism for selecting certain of the pull bars, a bail for elevating those pull bars selected by the selecting mechanism, a plate pivotally mountedv near the pull bars, contacts mounted upon the plate and positioned above the pull bars, said contacts being adapted to be operated by the pull bars when the pull bars are elevated, said pivoted plate having an ineffective position for elevating the contacts beyond the reach of the pull bars and an effective position for lowering the contacts into the reach of the pull bars, biasing means for tilting the pivoted plate into its ineffective position, and control means for tilting the plate into its effective position.

2. A teletypewriter having a plurality of pull bars, selecting mechanism for selecting certain of the pull bars, a bail for elevating those pull bars selected by the selecting mechanism, a plate pivotally mounted near the pull bars, contacts mounted upon the plate and positioned immediately above the pull bars, said contacts being adapted to be operated by the pull bars when the pull bars are elevated, circuits adapted to be opened and closed by the contacts, said pivoted plate having an ineffective position for elevating the contacts beyond the reach of the pull bars and an eiective position for lowering the contacts into the reach of the pull bars, biasing means for tilting the pivoted plate into its ineffective position, control means for tilting the plate into its effective position, and locking means for locking the plate in its elective position.

3. A teletypewriter having a plurality of pull bars, selecting mechanism for selecting certain of the pull bars, a bail for elevating those pull bars selected by the selecting mechanism, a plate pivotally mounted in the teletypewriter just above the pull bars, and a plurality of contacts adjustably mounted upon the plate in operative relationship with the pull bars, said contacts being adapted to be operated by the pull bars.

4. A teletypewriter having a plurality of pull bars, a reciprocating'bail for elevating the pull bars, a base plate located near the tops of the pull bars, a contact plate pivotally mounted upon the base plate, a plurality of contact assemblies mounted upon the contact plate, each of said con--` tact assemblies having a contact projecting over the edge of the contact plate and adapted to be operated by the pull bars when elevated by the bail, said Contact plate having an ineffective position for maintaining the contacts above the upper limit of the path of travel of the pull bars and an ellective position for lowering the contacts into the path of travel of the pull bars, and a spring for holding the contact plate in its ineffective position.

5. A teletypewriter having a plurality of pull bars, a reciprocating bail for elevating the pull bars, a base plate located near the tops of the pull bars, a contact plate pivotally mounted upon the base plate, a plurality of contact assemblies mounted upon the contact plate, each of said contact assemblies having a contact projecting over the edge of the contact plate and adapted to be operated by the pull bars when elevated by the bail, said contact plate having an ineffective position for maintaining the contacts above the upper limit of the path of travel of the pull bars and an effective position for lowering the contacts into the path of travel of the pull bars, a spring for holding the contact plate in its ineifective position, a latch for latching the contact plate in its effective position, and a lever for bringing the contact plate into latching engagement with the latch.

6. A teletypewriter having a plurality of pull bars, a reciprocating bail for elevating the pull bars, a base plate located near the tops of the pull bars, a Contact plate pivotally mounted upon the base plate, a plurality of contact assemblies mounted upon the contact plate, each of said contact assemblies having a contact projecting over the edge of the contact plate and adapted to be operated by the pull bars when elevated by the bail, said contact plate having an ineffective position for maintaining the contacts above the upper limit of the path of travel of the pull bars and an eliective position for lowering the contacts into the path of travel of the pull bars, a spring for holding the contact plate in its ineffective position, a latch for latching the contact plate in its effective position, and a lever for bringing the contact plate into latching engagement with the latch, said lever being adapted t0 be operated by a preassigned pull bar of the teletypewriter.

7. A teletypewriter having a plurality of pull bars, a reciprocating bail for elevating the pull bars, a base plate located near the tops of the pull bars, a contact plate pivotally mounted upon the base plate, a plurality of contact assemblies mounted upon the contact plate, each of said contact assemblies having a contact projecting over the edge of the contact plate and adapted to be operated by the pull bars when elevated by the bail, said contact plate having an ineffective position for maintaining the contacts above the upper limit of the path of travel of the pull bars and an effective position for lowering the contacts into the path of travel of the pull bars, a spring for holding the contact plate in its ineffective position, a latch for latching the contact plate in its eiective position, a rst lever for bringing the contact plate into latching engagement with the latch, and a second lever for releasing the latch from its latching engagement with the contact plate.

8. A teletypewriter having a plurality of pull bars, a reciprocating bail for elevating the pull bars, a base plate located near the tops of the pull bars, a contact plate pivotally mounted upon the base plate, a plurality of contact assemblies mounted upon the contact plate, each of said contact assemblies having a contact projecting over the edge of the contact plate and adapted to be operated by the pull bars when elevated by the bail, said contact plate having an ineffective position for maintaining the contacts above the upper limit of the path of travel of the pull bars and an effective position for lowering the contacts into the path of travel of the pull bars, a spring for holding the contact plate in its ineiective position, a latch for latching the contact plate in its eiective position, a rst lever for bringing the contact plate into latching engagement with the latch, and a second lever for releasing the latch from its latching engagement with the contact plate, said second lever being adapted to be operated by a preassigned pull bar of the teletypewriter.

9. A teletypewriter system having a teletypewriter central oiilce having a teletypewriter with a platen, a plurality of subscribers teletypewriter stations connected to the central office by a plurality of telegraph lines, switching apparatus at the central office for enabling a subscriber at one of the teletypewriter stations to establish a con- `ference connection through the central office with a plurality of the other subscribers stations, said switching apparatus including a pivotally mounted contact plate, a plurality of switching contacts mounted upon the contact plate, and control means for operating the switching contacts in response to the reception by the teletypewriter atthe central office of preassigned teletypewriter signals transmitted over one of the lines by one of the stations.

1G. A teletypewriter system having in combination a teletypewriter central office having a teletypewriter with a platen, a plurality of telegraph lines, a plurality of subscribers teletypewriter stations connectable to the central office by the telegraph lines and normally disconnected from each other, and switching apparatus for enabling a subscriber at one of the teletypewriter stations to connect himself through the central oflice to one of the other teletypewriter stations, said switching apparatus including a pivotally mounted contact plate mounted in the teletypewriter at the central cnice and a plurality of switching contacts mounted upon the contact plate.

1l. A teletypewriter system having in combination a teletypewriter central ofce having a teletypewriter with a platen having an upper case position and a lower case position, shift mechanism for shifting the platen from one of said positions to the other, a plurality of telegraph lines, a plurality of subscribers` teletypewriter stations connectable to the central oflice by the telegraph lines and normally disconnected from each other,V and switching apparatus for enabling a subscriber at one of the teletypewriter stations to connect himself through the central office to one of the other teletypewriter stations, said switching apparatus including a pivotally mounted contact plate mounted in the teletypewriter at the central oflice and a plurality of switching contacts mounted upon the contact plate, said switching contacts being operable only when the platen is shifted to a preassigned case position.

l2. A teletypewriter having pull bars, selecting mechanism for selecting certain of the pull bars, a reciprocating bail for elevating those pull bars selected by the selecting mechanism, a contact plate pivotally mounted near the pull bars, a plurality of contacts mounted upon the contact plate and adapted to be operated by the pull bars when the pull bars are elevated, circuits adapted to be opened and closed by the contacts, and an instrumentality for moving the contact plate about its pivot to render the contacts inoperable.

13. A teletypewriter having shift mechanism, a plurality of pull bars, selecting mechanism for selecting certain of the pull bars, a bail for elevating those pull bars selected by the selecting mechanism, a contact plate pivotally mounted in the teletypewriter near the pull bars, a plurality of contacts mounted upon the contact plate and adapted to be operated by the pull bars when the pull bars are elevated, a plurality of circuits adapted to be opened and closed by the operation of the contacts, said contacts being normally inoperable, and an instrumentality operable by a preassigned teletypewriter code signal for rendering said contacts operable.

JAMES F. BEATTIE. WALTER R. ROYCROFT.

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