US2126535A - Teletypewriter system - Google Patents

Description

Aug. 9, 1938. r. coRwlN Er AL TELETYPEWRITER SYSTEM.

Filed Sept. 28. 1935 ma x Rhoon l TLCRW/N INVENTORS B SSWEZEV EFW/1 T SON BV Wl YN A TTOR/VEV Patented Aug. 9, 1938 PATENT oFrics TELETYPEWRITER SYSTEM Thomas L. Corwin, Newark, N. J., Burdette s. Swezey, Floral Park, and Edward F. Watson, Larchmont; N. Y.: said Corwin assignor to Bell Telephone Laboratories,

Incorporated, New

York, N. Y., a corporation of New York: and said Swezey and said Watson assirnors to American Telephone and Telegraph Company, a corporation of New York I Application September 28, 1935, Serial No.. 42,560

s claims.

'I'his invention relates to teletypewrlter systems and, more particularly. to arrangements for checking the accuracy of messages perforated in tape while at the same time transmitting automatically from previously prepared tape without sacrificing any of the usual supervisory vfeatures of teletypewrlter transmission.

In certain types of teletypewrlter service, it is desirable to check the accuracy of certain messages. such as code messages or lists of order numbers, before transmitting them. 'I'his is because a mistake in a single letter of a code word or a single figure of an order number might change the entire meaning of the word or the significance of the order number.

Accordingly, it is an object of this invention to provide a convenient and practical arrangement for checking the accuracy of a message before transmitting it while also sending from other tape previously perforated.

It is also an object of this invention to enable an operator at a station, which is receiving messages from another station, to switch the teletypewrlter at the transmitting station from its local circuit to the line.

A further object of this invention is to enable an operator at a station, which is receiving messages irom another station having its teletypewriter connected into a local circuit to switch that teletypewrlter into the line circuit, during a pause in transmission, by merely transmitting ordinary message signals and without transmitting a special break signal. n

These objects are accomplished by employing a special teletypevvriter set which can rapidly perforate tape used for operating a transmitterdistributor. The accuracy of the messages perforated on the tape may be checked, before the messages are transmitted out over the line, by two methods. The first method comprises simultaneously perforating the tape and printing only a local home copy by means of the selecting mechanism of only the teletypewriter at that station. Ill'he other method consists of first perforating the tape and then sending it through the transmitter-distributor over a local circuit to only the teletypewriter at that station.

An operator at a'teletypewriter station which ls receiving messages from a second station, can transmit a break signal which will stop the second stations transmitter-distributor, operate an alarm device at the second station, and automatically switch the second stations teletype- Writer from its local circuit, should it be connected therein, into the line circuit. During a (Cl. IHS- 4) pause in transmission by a sending station, it is not necessary for an operator at a connected station to transmit a break signal in order to communicate with the first station because the teletypewrlter at the first station will be automatically switched from its local circuit, should it be connected therein, into the line upon the reception of ordinary message signals transmitted from the second station.

These and other features of the invention will now be fully described and explained with reference to the drawing in which:

Fig. 1 shows diagrammatically the general apparatus arrangement of a teletypewrlter lsystem embodying the features of this invention; and

Fig. 2 illustrates in detail the circuit diagram for the teletypewrlter system shown in Fig. 1.

According to the arrangement shown in Fig. 1, transmitter tape i is perforated in the tape perforator 2 at station A and is then fed into the transmitter 3 by means of feed holes 42 (Fig. 2) and a sprocket feeding mechanism (not shown). The perforations 4 (Fig. 2) in tape l operate the transmitting contacts 5 (Fig. 2) to condition distributor 6 for thev transmission of signals. The signal impulses originating in distributor 6 are sent through the control circuit 1 and then out over line conductor 8 to a second teletypewrlter station, such as central office B. If desired, the signals are also sent from the control circuit l to the local teletypewrlter I0 to make a home copy of the messages sent to central oiiice B. lin the drawing, central oiiice B is shown to be capable of sending messages over line conductor 9 to the teletypewrlter I0 at station A which is capable of both receiving and sending messages. It is to be understood that central olce B has been so shown for purposes of illustration but may be changed to a subscribers station according to thc requirements of a particular system.

Now that the general arrangement of the apparatus employed in this invention has been described, the operation of the invention will be described in detail with reference to Fig. 2 which shows the apparatus in its neutral condition: that is, with both stations unoperated.

To call the subscriber at station A, an operator at central oce B moves switch Il to its lower position to apply ringing current from alternator i2 to line conductor 8 and then to station A. At station A, the ringing current passes over the top armature of unoperated relay I3, through condenser it, ringer i5, and then to ground. Ringer i5 will now operate to inform the subscriber at station A that he is being called.

In answering the call tromicentral ofiice B. the subscriber at station A moves switch Il to its call-answer position at the left and also closes power switch |`|l for operating motor-generator Il and motor from power supply source Il. when the motor-generator il is started, current enses, or man le. over conductor is. through relay il. and then to the negative terminal of motor -lenerator Il. Relay i8 is now energized' operates its armatures to disconnect ringer connecting the printer equipment lat station A 'ro muuu s can, the mmr'ibern maan a followsthesameprocedureasinansweringacall and operates switch II to its call-answer" posil porforator switch 22. This closes a path from the positive terminal of motor-generator Il through perforator switch 22 to Junction 2l. vll'rom junc tion 2! there are two paths: one leads through relay 2l to the negative terminal of motor-generator Il, the other path goes through the dis` tributor start magnet 2l and upper top armature of imoperated break relay 2l to the negative terminal of motor-generator Il. Current from motor-generator I0 now energises relays 24 and 2l. Upon being energiled, relay 2l operates its amature 2'I- thereby releasing distributor brush 2l for rotation to transmit signal impulses.

Relayuinbeingoperatedatthistimewould close a path for positive current from motorgenerator il to pass along conductor 42 over the ar'mature of operated relay 24, through relay 2l, armature of relay Il, right set of contacts oi' break key Il, break contacts l2, and then to the negative terminal of motor-generator Il but for the fact that the break contacts 82 are normally open, due to the rotation of cam 8| mounted on shaft 4l, when the contact of relay Slisclosedand are normally closedonlydurlng a part of the sixth pulse of a signal combination at which time the contact of relay il is opened. eneeptwhen abreakaisnalistnnsmittedaswill be explained hereinafter.

communication may now take place with perforations I in tape controlling transmitting contacts i for causing distributor 0 to transmit signal impulses, corresponding to the signals perforated in tape I, out over the line circuit to central oiiice B. At the 'same time, these signal impulses pass through the subscribers receiving magnet 8l for making a home copy of the outgoing message.

In the event that it is desired tosend from the tape i without making a home copy of the messages transmitted, the operator moves switch Il to its middle position. This opens the ener- Iiromthelineandtoprepareacircuitfor4 gising path for relay 2|. As a result, the subscribers teletypewriter III is disconnected from the line circuit and is connected into a local circuit leading from the positive terminal of motorgenerator It. over conductor Il, lower top contact -oi operated relay I3, upper top armature of non-operated relay 2|, receiving magnet Il. sending contacts Il, break key Il, bottom armature of non-operated relay 2l, and then to the negative terminal of motor-generator Il. Transmitter distributor 0 can now send messages over the line to central oi'iice B without causing a home copy to be made by teletypewriter Il.

While teletypewriter I0 is connected into this local circuit it may be used for further perforation of tape I with or without a home copy according to whether the perforator transmitter switch 22 is closed or open.

During transmission by the subscriber at station A, relay 2l. which is connected directly into the line circuit, will follow all the signals transmitted, opening its contact when energized by the line current from battery I1 at central oiilce B. Also, during this time, cam Il mounted on distributorshaft Il, will be constantly rotating because shaft is continuously driven by motor 4| through the usual friction clutch (not shown) during the period of communication. Cam Il is so mounted on shaft lil as to close the break contacts I2 during a portion of the -sixth pulse, or stop impulse, of each code combination transmitted. This is to test for a "bx-esk during each revolution because, if the line is open when contacts I2 close, a break" will be recorded through the contacts of relay Il. However, during normal transmission of signals, either the breali contacts 'I2 or the contact of relay 2l will be open at all times.

If an operator at central oillce B, or any other connected station, sends a break signal while the subscriber at station A is transmitting from perforated tape with his switchv it in its middle position, the break signal will open the line circuit for the duration of one or two characters. During this opening of the line, relay Il will become deenergized and will close its amature contact. When break contacts I2 close now due to the rotation of cam Il, a circuit will be closed for current from the positive terminal of motorgenerator Il to pass over conductor 48, upper right set of contacts (now closed) of switch Il, upperleft set of contacts of switch Il, through relay 20,' contact and armature of relay Il. right set of contacts of break key 2|, break contacts I2, and then to the negative terminal of motor-l generator Il.

. This serves to operate relay 20 which locks-up through its bottom armature subject to the release of relay 2l. The operation of relay 2i closes a path for positive current from motorgenerator Il to pass along conductor u, through the lower right set of contacts (now closed) of switch il, over the top armature of operated relay 2l, through break relay 2,.and then to the negative terminal of motor-generator Il. Break relay 2l now operates its three armatures and closes a path for positive current from motorgenerator il to pass along conductor Il, through the lower right set of contacts (now closed) of switch il. operated lower top armature of relay 2|. through relay 2|, and then tothe negative terminal of motor-generator Il thereby energising relay 2|. Relay 2|, in operating its bottom and upper top armatures. switches the local teletypewriter Il from its local circuit to the line 2,190,535 circuit for receiving signals transmitted from station B.

In operating its upper top armature, break relay 28 opens the circuit through the transmitterdistributor st'art magnet 28 and causes it to release its armature 21 which catches the distributor brush arm 28 to prevent it from rotating and transmitting signals. Relay 28 also closes a path for positive current from motorfgenerator I8 to pass along conductor 35, through break lamp 38, upper top amature of relay 28, and then to the negative terminal of motor-generator I8 thereby lighting break lamp 38-as a visible signal to the subscriber at station A that the operator at station B desires to communicate. At the same time the bottom armature oi relay 28 shortcircuits the sending contacts 33 and break key 34 of the local teletypewriter I0.

The break signal can be locally discontinued by moving switch I8 to its "call-answer position at the leit and by opening the perforator switch 22. This opens the energizing circuit of relay 24 which releases its armature thereby opening the locking-up circuit of relay 29 which releases and `opens the energizing circuit for relay 28. Although relay 28 releases, relay 2| remains energized over a path through the contacts of switch I6. Relay 29 cannot be operated again until both the contacts of relay 30 and the break contacts 32 are closed.

In the event that the operator at station A has transmitted a series of messages, he might wish to pause for a short interval of time while gathering information for other messages. To eiect such a pause in transmission, the operator at station A merely opens the perforator switch 22, leaving the power switch I1 closed and the switch I6 in its middle position. This opens the energizing circuit of the distributor start magnet 25 while leaving relay I3 operated. Magnet 25 now releases its armature 21 which catches the distributor brush 28 and stops it from rotating. Since the distributor brush 28 is attached to the shaft 40, stoppage of brush 28 by armature 21 will stop shaft 4U and cam 39 from rotating further by disengaging the usual friction clutch (not shown) employed with such transmitterdistributors. This leaves the distributor brush 28 in engagement with lever 21, as is shown ln the drawing, and also leaves cam 39 in a position `where it will close the break contacts 32, as is also shown in the drawing. With the circuit in this condition. all that the operator at station B need dn to effect a break signal is to transmit ordinary message signals. Relay 30 will follow these message signals and, since with the usual permutation code employed the rst, or start, impulse of a signal is always an open impulse, relay 30 will move its armature to close its contact. This serves to operate relay 29 which, as is described above, eiects the operation of break relay 26 and relay 2|. Relay 2l, in operating its bottom and upper top armatures, switches the teletypewriter In into the line circuit for receiving the message signals transmitted from station B. Thus, the operator at station B can break station A Aand can convert the teletypewriter at station A from a sending condition to a receiving condition without transmitting the usual break signal thereby obtaining a saving in transmission time.

If the subscriber at station A should be transmitting from perforated tape with switch I6 in its call-answer" position at the left and with switch 22 closed at the time when an operator at station B transmits a break signal. the circuit operation is much the same as that `lust described above except that relay 29 is now maintained locked-up over a circuit traced from the positive terminal oi' motor-generator Il, over conductor 42, operated armature of relay 24, through relay 2l. over the operated bottom armature of relay 29, and then to the negative' terminal of motor-generator I8. As a result. lamp 98 and relays 2l and 28 will operate. Since switch I8 is already in its call-answer position, all that need be done to discontinue the break signal is to open the periorator switch 22 which opens the locking-up circuit for relay 29 as was described above.

It the operator at station A has switch I8 in its left ptsition and is transmitting from the keyboard with the perforator switch 22 opened,

a break signal transmitted from central office B will not now operate relay 29. However, since the teletypewriter I is now connected into the line circuit, the opening of the line by the break' signal will cause the teletypewriter I0 to run open and no printing will take place for the duration of the break signal. 'I'his will serve to indicate to the subscriber at station A that the operator at the distant central office B wishes to use the line.

When the subscriber at station A wishes to disconnect the station equipment, he opens his power switch I1 thereby stopping motor 4I and motor-generator I8 thereby effecting the release of the relays. vRelay I3 in releasing its armatures connects ringer I5 to line conductor 8 and grounds line conductor 9. If the subscribers printing apparatus is to be used for another call shortly, switch I8 may be left in its call-answer position at the left.

On the other hand, if the subscrbers printer y set is to be used on local circuits, such as for locally testing the equipment or perforating tape for future calls, switch I6 may be put in its disconnect position at the right. The subscriber then closes his power switch I1 which starts up his motor-generator I8 and motor 4I. However current from motor-generator I8 will not energize relay I3 at this time because the lower right set of contacts of switch I6 are now open. Therefore, the subscribers teletypewriter IIJ and distributor 6 will now be connected in a local circuit extending from the positive terminal of motorgenerator I8, over conductor 35, middle top armature of unenergized relay I3, distributor 8,- relay 3i), left contacts of the break key 3l, conductor 44, lower top armature of relay I3, upper top armature of unenergized relay 2i, receiving magnet 38, sending contacts 33, break key 34, bottom armature of relay 2i, and then to the negative terminal of motor-generator Ill. The subscriber can now perforate tape while making a home copy or local transmission from the teletypewriter keyboard or transmitter-distributor may now take place.

lin case the subscriber at station A wishes to send a break signal while he is receiving messages from central oce B, he uses the break key 3i of the subscriber set and not the break key :it in the teletypewriter Ill. When the subscriber set break key 3i is operated, the line circuit is opened at the left contacts of break key 3i. In addition, the energizing circuit for relay 28 is opened at the riglnt` contacts of break key 3i. This prevents operation of break relay 28 and also prevents the lighting of break lamp 36 and operation of relay 2l thereby obviating extra manipuolswitohssllandllbetoretransmission abov'especiilc embodimenthas been debedinordertoillustratetheinventionandit istobeiinderstoodthatvariousmoditicationsan-- ployingthepl'inciplesandfeaturescttheinvenrent variations: and instrlnnentalities at the nrst switching the teletype- 'l'lki' t "llt muon from itl local circuit inw tion a iirst teletypewriter station having a teletypevriter convertible from a sending condition to a receiving condition and vice versa. a tape perforator-trannnitter. a transmitter-distributor. and a localcircuit leading from the pertoratortransmitter and through the transmitter-distributor to the teletypewriter at that station: a second teletypewriter station having a teletypewriter capable of both receiving and lending message signals to the ilrst teletypewriter station; a ccmmunication line connecting the tvo stations for the tranlnission oi' llshicant current variations: means for enabling the transmitter-distributorl to transmit over the line while the periorator-transmitterandtheteletrpevriterattheilrststation are available for peri'orating and checking tape in the local circuit, and means operating in response tothereceptionofabreaksignaltransmitted trunthesecondstationiorautcmatically convesting the teletypewriter at the iirst station from itssending condition toits receiving condition and ios'switchingtheteletypewriteriromitslocalcircuit into the line.

3. A teletypevvritcr system having in combination a iirst teletypewriter station having a teletype'riter, a tape pertorator-transmitter, a transmitter-distributor. and a local circuit leading from the periorator-transmitter through the transmitter-distributor to the teletypewritsr at that station: a second teletypevritsr station having a teletypewriter capable oi both receiving and sending message signals to the first teletypewriter station; a communication line connecting the two stations ior the transmission of signincant current variations and instrumentalities ior enabling the perrorator-transmitter and transmitterdistributor at the ilrst stationto transmit mss sages from perforated tape to the teletypewriter at the second station while having the teletypewriter attbeiirststatio'n idle andinstantiyavailableforbeingswitchedintothelineinrespcmeto a break signal sent from the second station.

4. A teletypevn-iter system having in combination a iirst teletypewriter station having a teletypevvriter convertible from a sending condition toareceivingconditionandviceversa.saidtele typewriter' having sending contacts. a second teletypewriter station having a teletypewriter. a communication line connecting the two stations for the transmission ot permutation code signals. a normally open circuit for short-circuiting the sending contacts o! the teletypewriter at the rst station. a normally unoperated instrumentality tor closing said normally open circuit. and means for operating said normally unoperated instrumentality in response to the transmission over the communication line by the teletypewriter at the second station of an ordinary permutation codesignalduringapauseintransmissionbythe teletypewriter'at the ilrst station.

5. A teletypewriter system having in combination a nrst teletypewriter station having a teletypewriter, a tape pertorator-transmitter, a transmitter-distributor, a local circuit leading from the perforator-transmitter and through the transmitter-distributor to the teletypewriter at that station. a second teletypewriter station having a teletypewrlter capable of both receiving and sending message signals to the ilrst teletypevriter station; a communication line connecting the two stations for the transmission oi signiilcant current variations; a circuit for converting the teletypewriter at the ilrst station from a sending condition to a receiving condition; nrst control means for preparing said circuit during a pause intransmisaionbytheteletypewriterattheilrst station: and second control means operating in response to ordinary message signals transmitted from the teletypewriter at the second station for completing said circuit.

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