US2241258A - Teletypewriter switching system - Google Patents

Description

` May 6,1941.

L A. GARDNER Erm.A 2,241,258 TELETYPEWRITER SWITCHING- SYSTEMA Filed Sept. 15, 1938 4 Sheets-Sheet 1 Lkk GDN Maly 6,' l941--` l. A. GARDNER Erm. 2,241,258

TELETYPEWRITER SWITCHING SYSTEM Filed Sept. 15; 1958 4 Sheets-Sheet 2 CORD CC 7'. REPEAT/NG RELAYS l F/G. 3

LAGARDNER NVENTORS E SINGER EJ'. WATSON ATTORNEY May 6, 1941. L. A. GARDNER E-rm. 2,241,258

.TELETYPEWRITER SWITCHING SYSTEM Filed sept. 1.5, 1958 4 sheets-sheet s SR N. www@ Toen R MMT m VGW @or WAJkWA Lr... No.

May 6, 1941. l., A. GARDNER E'rAn. 2,241,258

' TELErYPEwRITER S'wITcHING SYSTEM l Filed sept. 15. 1958 4 sheets-sheet 4 WLAN/Z50 AHORA/5r Patented May 6, 1941 TELETYPEWRITER SVVITCHING SYSTEM Leland A. Gardner, Maplewood, N. J., and Fred J.

Singer, Rockville Centre, and Edward F. Watson, Larchmont, N. Y., assignors to Bell Telephone Laboratories, Incorporated, New York, N. Y., a corporation of New York Application September 15, 1938, Serial No. 229,984

9 Claims.

This invention relates to manual telegraph switching systems and more specically provides an inexpensive manual teletypewriter switching -system in which the necessary operators functionsin handling a call at-the manual switching office are reduced to a minimum. In this system the only service required of an operator is to connect and disconnect the calling and called parties. In this system the called station teletypewriter moto-r is automatically started without the necessity of any operation by the central station operator other than inserting the plug of a cord in the called station jack. It is not necessary to perform any additional operation such as operating a key. A called station identifying signal is transmitted to the callin-g party, to assure the calling party that the connection is properly established. Further, the duration of the call is automatically timed.

It is generally understood by those familiar with telephone and teletypewriter switching systems operation, that in deciding whether manual or mechanical switching oices should be used to handle traiiic, the load which a single operator can handle satisfactorily in the operation of a manual board is a vital factor. This load may be increased as the operations required in handling a call are reduced. But as the operators functions are reduced, automatic means for performing the operators eliminated functions must be incorporated in the circuits, if the service is to be reliable andV the'subscriber is to be properly charged. Further, these automatic facilities should be simple and inexpensive, for as they become elaborate and costly, their initial cost and the cost of their maintenance approaches that of a full automatic switching system.

In this inventio-n by providing called station identification signals to 'the calling subscriber, the necessity of monitoring a call by the central stat-ion operator, to insure that the calling party is connected to the desired party, is eliminated. By providing for automatic starting of called station apparatus, another operator function is eliminated. By pnoviding automatic call-duration timing, yet another of the operators functions is eliminated. In eliminating all three of the functions there remains only the necessity of connecting and disconnecting the subscribers. The invention herein resi-des in devising circuits in which all three of the eliminated functions are performed automatically and by means of simple, inexpensive apparatus.

It is an object of this invention to reduce the operations required by a central office operator in establishing a connection in a manual tele-l typewriter switching system to a minimum;

It is a further object of this invention to eliminate an operation now performed by the central station operator in starting all known teletypewriter remote control circuits in manual teletypewriter switching systems. v

It is a further object of this inventionto provide automatic call-duration timing in amanual teletypewriter switching system. Y,

It is a further object of this invention to provide an automatic called station identification signal to a calling subscriber in a manual teletypewriter switching system in which call duration is automatically timed.

It is a further object of this invention to provide automatic called station teletypewriter motor starting, automatic .called station identification to the calling subscriber, and automatic call-duration timing al1 in a single manual teletypewriter switching system.

bIt is a further object of this invention to provide simple, inexpensive apparatus to perform,

the three functions enumerated in the preceding paragraph.

A feature of this invention is a novel, inexpensive automatic call-duration timing -device for a manual teletypewriter switching system.

A further feature of this invention is an inexpensive automatic called station identifyingdevice, or answer-back device, as it is otherwise known in the art, for a manual teletypewriter switching system.

A further feature of this invention is an inexpensive relay controlled transmitting distributor common to a plurality of subscribers lines at a particular business office, which may be used in sending back an identifying signal to a calling station.

A further feature of this invention is a device for controlling the connection of incoming calls to subscribers oilices wherein there are a plurality of teletypewriter receivers so that the incoming circuits are connected individually to a transmitting distributor which transmits station identifying signals to the calling subscriber in an ordered sequence.

Fig. 1 is a block diagram representing the interconnection of two subscribers stations. This connection involves two lines, two stations. and one cor-d circuit. The station circuits are Figs. 2A and 4A which are identical electrically. The line circuits are 2B and 4B which are also identical electrically. The circuits are interconnected cord circuits.

by the cord circuit per Fig. 3. Figs. 2A and 4A include individual called station identifying signal apparatus or answer-back apparatus as it is otherwise generally known.

Fig. 1A is a block diagram also representing the interconnection of subscribers by means of The line circuits and cord circuits are the same as in Fig. 1.

The called station identifying apparatus connected to the station A signals will care for a number of station circuits on the premises. The station circuit and the common identifying apparatus for this condition are shown in Fig. 5. As represented therein and in Fig. 1A, the identifying apparatus is' con'- nected to three station circuits at eachend of three telegraph paths, each comprising a cord circuit per Fig. 3 interconnecting a line circuit per Fig. 2B and a line circuit per Fig. 4B and two station circuits. The number of station circuits which may be served by a common identifying signal supply circuit per Fig. 5 is not limited to three, as the number may be increased to care for any .number which may be used at a particular subscribers location.

Fig. 2A -shows a teletypewriter subscribers station circuit.V This station circuit, in addition to the usual receiving magnet, sending contacts and break key 20|, 202 and 233, respectively, includes a relay 208, operated -by remote control, to start the operation of teletypewriter motor 206 by operating relay 229, which closes the power circuit to the motor. It also includes relay 201 which operates to close the telegraph loop. The circuit includes also a manually operatedswitch 2|| for starting and stopping the station motor locally. In addition to thisV apparatus, the station circuit includes a slow-tooperate relay 2|0, which operates when the station circuit responds to remote control and in turn operates solenoid 205 which `actuated a key in the station transmitter to send an identifying signal to the calling subscriber. Lamp 2|3 when lighted is a signal to the attendant at the subscribers station that a call is incoming to the station.

Fig. 2B is a well-known'line circuitwhich has been improved in accordance with this invention to include the call-duration timing apparatus and means to start a station circuit remotely, automatically. That is to say, on establishing a connection, through a cord to such a line circuit, it is not necessary to operate a key to start the apparatus at the station, as is the case with other presently known line and cord circuits.V

YThe timing apparatus comprises relay 226, selector switch 221 and its associated rotary and release magnets 228 and 230 and switch offnormal contacts 23| The message register magnet and indicator 233 and 23d, respectively, are also `parts of the timing apparatus.

Relay 2|6 in Fig. 2B operates, upon the Vestablishing of a connection `to the line circuit, to reverse the battery through polarized relayv 2% to closevthe loop circuit.

Fig. 3 is a well-known cord circuit used in inter-connecting two subscribers through their line and stat-ion circuits. This circuit contains relays and resistances/which have been added in accordance with this invention to cooperate with .the call-duration timing feature included in` this invention.

Figs. 4A and 4B- show a teletypewriter subscribers station and line circuit. They are identical in every res ect with Figs. 2A and 2B, except that they are drawn in reverse to facilitate visualization of a connection with another subscribers line and station circuit per Figs. 2A and 2B.

Fig. 5 shows a called station identifying ap- ,.paratus common to a plurality of station circuits. Three of these station circuits designated A, B and C, are considered as being located on one subscribers premises, and three others, D, E and F,Yare considered as being located at another subscribers premises as indicated in Fig. 1A. The stations are identical. The station circuit connects toy a line circuit per Fig. 2B or 4B as is also shown in Fig. 1A.

We are concerned herein with improved and added means of reducing the operators functions so that an operators work in handling a connection may be reduced.

These features have been incorporated into circuits well known in the art which otherwise remain unchanged. It is not thought necessary to an understanding of this invention to describe' in detail the unchanged circuit functions and they will not therefore be described herein.

The detailed operation of the circuits involved in a connection per Fig. l will now be described in so far as it `is necessary to an understanding of this invention.

Refer now to Figs. 2A and 2B. When the circuit is inthe normal condition current flows, from battery, through the winding of relay 220, the top, outer, back contact and armature of relay 22|, which is released, resistance 221i and relay winding 222 to ground. This current is insufcient to operate either relay.

When an attendant at the subscribers station wishes to call another subscriber, the power switch 2|| is operated so that its top armature engages its fro-nt contact. At the same time the circuit throughv the bottom armature and its back contact, which forms part of the remote control circuit to be explained in detail hereinafter, is broken. When the top armature of switch 2|| engages its front contact, a circuit is closed, from oneside of the power source 2|2, through the top armature and front contact of switch V2H, through motor 206 to the opposite side of power source 2|2, starting the motor.

VThe closing of switch 2|| also establishes a circuit through the winding of relay 201 in parallel with the path through motor 2%. Relay 261 is operated, which closes the subscribers loopL by breaking the tip conductor of the loop from ground through the left-hand, inner, back contact and armature of relay 201 and connecting the tip and ring loop conductors together through the same armature and its front Contact. The operation of relay 201 further opens a path short-circuiting the station printer equipment through the left-hand, outer armature and back contact of relay 201. This short circuit protects the station equipment, while it is in the idle condition, andlinsures the operation of relay 208 under adverse conditions when the station is called. t A

When Vthe tip and ring conductors of the loop 'are connected, a circuit may be traced from the left-hand, inner armature and front contact of relay 201, resistances 235 and 2|5, the bottom winding of relay 2 I9, the bottom, inner, back and front contacts of the make-before-break combination of relay 22| to positive battery.y Relay 2I0 is operated. The operation of relay 2| 9 in turn operates relay 2|8 over an obvious circuit.

Relay 2|8 closes a circuit, from ground, through its top, outerarmature and front contact, the top, outer armature and back contact of relay 22 I, the winding of relay 220 to battery, operating relay 220. The operation of relay 2I8 also established a circuit from ground, through its top, inner armature and front contact, the top armature and back contact of relay 2| 1 and the winding of relay 2|6 to battery, operating relay 2I6. Relay 2|6 operated performs no useful function at this time. Relay 220 operated closes a circuit from battery, through its bottom, inner armature and front contact and the lament of lamp 223 to ground, lighting the lamp. Relay 220 operated also closes a circuit, through its bottom, outer armature and front contact and night alarm 225 to battery, operating the night alarm. A switch, not shown, is ordinarily Vconnected in series with the night alarm so that it may be disconnected when not required. The operation of relay 220 further transfers the termination of the loop tip conductor, from ground to negative battery, through resistance 236 and the top armature and front contact of the make-beforebreak combination of relay 220. Relay 22| remains unoperated when relay 220 operates. We therefore have positive battery connected to one end of the loop in series with negative battery at the other end through the bottom winding of relay 2I9, holding relay 2 I9 operated.

The operator, in response to the calling signal, inserts plug 30| of her cord circuit per Fig. 3 into jack 222.

The cord circuit per Fig. 3 is a modification of a cord circuit well known in the art. It is shown in more detail and its operation is more fully described in Patent 2,073,468 to K. E. Fitch issued March 9, 1937 and in the copending application of J. M. Desmond, Serial No. 200,542 led April 6, 1938. It is not thought necessary to show it in full, or describe its operation completely in detail herein, and only so much of it is shown and so much of its operation is described as is necessary to an understanding of the present invention.

When plug 30| is inserted in jack 222 the tip, ring and sleeve connections of the jack are extended through the tip, ring and sleeve connections of the plug. The ring connection extends through various relay windings andcontacts, ineluding the operators position equipment, all of which are not shown, to the single line repeater equipment 3|2 which functions in a Well-known manner. The sleeve connection likewise extends, through various windings and contacts not shown, with the operation of which we are not concerned, to terminate in negative battery. Of the apparatus shown in the cord circuit, relays 302, 304, 301, 338, 309, 3I0 and 3|4 are relays presently used in the cord and readily identifiable by one skilled in the art from the description in the above-listed patent and application. They correspond respectively with relays 435, 433, 421, 536, 520, 5|| and SI2 of the above-mentioned application per Serial No. 209,542. Relays 306 and 3|| and resistances 3|1, 3|8, 3I0 and 320 are added per thisrinvention and the cord circuit is modified as indicated in Fig. 3.

Relay 22| of Fig. 2B is operated over a circuit, from battery on the sleeve of plug 30|, through the sleeve of jack 222 and the top winding of relay 22| to ground. The operation of relay 22| breaks the circuit through the winding of relay 220 at the top, outer, back contact and armature of relay 22|, releasing relay 220 and extinguishing lamp 223. The operation of relay 22| also connects ground through its bottom, outer armature and front contact, the bottom, front contact and armature of relay 2|6, through the winding of relay 2|1 to battery, operating relay 2 I1. Relay 2|1 operated locks to this same ground, through its bottom armature and front contact. .Relay 2|1 operated breaks the circuit through the winding of relay 2 I 6, which releases. The operation of relay 22| further transfers the termination of the tip of the subscribers loop, from negative battery, from the top armature and front contact of relay 220, through its top, inner 4armature and back contact, to a circuit extending from the same armature and its associated front contact, through the top Winding of relay 2 I9, and the armature and back contact of relay 2|6 to negative battery. The operation of relay 22| also breaks the termination of the ring side of the subscribers loop from positive battery, through the front and back contacts of the makebefore-break combination associated With its bottom, inner armature and extends the ring eircuit through said armature, the rings of jack 222 and plug 30| to positive battery, not shown, in the cord repeating relays. The effect oi the current flowing through both windings of relay 2I9 is such that the relay is released, removing ground from the circuit through relay 2 I8, which releases, removing ground from the tip of the jack circuit.

, After the plug of cord 30| is inserted in jack 222 a `circuit -may be traced from ground through the winding of relay 226, resistance 223, the tips of jack 222 and plug 30|, the top armature and back contact of relay 308, through the top winding of relay 30S and resistance 3|1 to negative battery. A biasing circuit for relay 306 may also :be traced, from ground .through the bottom winding of relay 306, the bottom, inner armature and back contact of relay 3| I, and resistance 3|9 to negative battery. The relative values of the batteries and resistances in these circuits are such that the effect of the current through the bottom Winding of relay 303 is dominant and the armature remains in engagement with its lefthand or spacing contact. 'lflzie current owing through the relay 226, which controls the timing operation, Vis insufficient to operate it so that timing cannot start.

After the operator has obtained the number of the called subscriber from the calling party in a well-known manner, she connects plug 3|3 to one of the multiple jacks 422 associated with fthe called line. The tip, ring and sleeve connections of the plug 3|3 are extended through the tip, ring and sleeve connections of jack 422. Relays 3|0 and 42| operate over a circuit from battery through relay 3I0 winding, the sleeves of plug 3|3 and jack 322, through the top winding of relay 42| to ground. When relay 42| is operated, the circuit through relay 420 is broken at its top, outer armature and back contact. The tip of the subscribers loop circuit is transferred from the connection extending to ground at relay 420 through the top, inner :armature and back contact of relay 42|, to a connection to negative battery, extending through said armature and through the armature and back Contact of relay 4 Hi. The ring of the jack is extended through the bottom, inner armature and front contact of relay 42, the bottom winding of relay 4 if and resi- stances 415 and 435 to the front contact as sociated with the right-hand, inner armature of relay 401 where it is open. When the tip of the subscribers loop is extended to negative battery, av circuit is `closed through resistance 4M, the rightehand, outer ,armature and back contact of relay 401, winding of relay 408, through the right-hand, inner armature and back contact of relay 401, to ground. Relay 4i0 operates, but relay 400, which is polarized, `does not operate. When relay 419 operates, relay 418 operates over an obvious cir-cuit. Relay 4l'8 connects ground tothe tip of the jack, through its outer armature and front contact. It also supplies ground, through its top, inner armature and front contact, the top armature and back contact of relay 4H, through the winding of relay 416 to positive battery, operating relay 415. Relay 416 operated, connects positive battery to the tip of the subscribers loop, operating polarized relay 408. Relay IHS operated, also closes the circuit from ground through the bottom, outer armature and front contact of relay 421, through its bottom armature and front contact, to battery through the winding of relay 4 i l. This breaks the circuit through the winding of relay 416, releasing it. Relay 4I? locks through its bottom armature and Vfront contact to the ground which operated it.k The release of relay 44B removes positive battery from the tip of the subscribers loop, and, now

V that relay 400 has operated, reconnects it again Y to negative battery. This releases relay 408.

and front contact of relay 409, through relay 401 .and motor 40S in parallel, to the bottom of `power' source 4l?. Relay '400 operated, locks lthrough its bottom armature and front conta-ct, the winding of relay 4|0, the bottom armature and back Contact of switch 4H to the bottom of power source 412. Relay 401 removes ground from the tip of the subscribers loop at its right-hand, inner armature and estab# lishes the subscribers loop, by connecting said armature to its front contact. Relay 401 also breaks the short circuit around the station teletypewriter apparatus at its right-hand armature and back contact. Relay 4I0 connects -power to solenoid 405 and lamp 4l'3 in parallel. The solenoid in turn operates key 404 on the station transmitter. This sends a signal identifying the called station to the calling station. The circuit per Fig. 2A is now in a condition to receive, and Va message may be received without operating switch 2li. The station operator, in response to the lighted lamp signal can operate key 4H to its alternate position. This releases relay 40 which in turn eXtinguishes lamp 4l3 and ldeenergizessolenoid 405 which releases key 404. Operation of switch 4H also breaks the holding path through relay 400 which releases and provides a path to hold relay 401 and motor 200 in operation. It also provides a path to main-tain the agitata" circuit is now conditioned to either receive or transmit.

When the subscribers loop is established, current `is supplied to .both windings of relay 49 which neutralize the effect, each of the other, and the relay releases. Relay 449, we have seen supplied ground, while operated, for the operation of relay 4l8. During the interval that relay 4l8 is oper-ated ground was connected to the tip of jack 222. When the station teletypewriter apparatus was `started and the loop closed, as a result ofthe release of relay 4I9 and in turn 4I8, the ground on the tip of the jack 422'and cord 353 is removed. This controls the operation of the timing apparatus as will now be described.

When ground was Iconnected to the tip of the cord, through the top, outer armature and front conta-ct of relay 410, a circuit was established, through the tips of jack 422 and plug 313, the top `armature and back contact of relay 309, through the winding of relay 3M, operating relay 3l4. This momentarily lights lamp 3l5 over an obvious circuit as a signal that the called station has not yet responded. It also opens the circuit from battery through the front contact and armature of relay 3l0, which is operated, the bottom armature and .back contact of relay 309, through the bottom armature `and back contact of relay 3l4, through the winding of relay 3H to ground. When, after the called station apparatusresponds, ground is removed, as We have seen, at relay 4%0, relayV 3I4 releases, extinguishing lamp 045 and operating relay .3l l, over the circuit last traced. Relay 3H operated, locks thrcugh its top armature and front contact to the .battery supplied by the operation of relay 3l0.

The operation of relay 3H increases the cur rent through relay 22B in Fig. 2B by connecting resistance 320 through its bottom, outer armature and front contact in parallel with the path through the top winding of relay 306, heretofore traced. Relay 225 operates on the increased current to start the operation of the timing mechanism to be described in detail hereinafter.

The operation of relay 3l I, by connecting a resistance :in parallel with the top winding of relay 303 to'increase the current through relay 226, decreased the current through the top winding of relay 306. Since it is necessary to maintain ythe armature oi relay 30B from engagement with its right-hand contact, to prevent the reception of a supervisiory signal on the answering side ofthe cord, the current through the bottom or biasing winding of relay 300, the effect of which is tok tend to operate the armature of relay 306 engage its vright-hand contact, must be correspondingly reduced. This is effected by l, substituting resistance 3l3 in series with 320 for ly to provide an .interrupted ground supply for motor in operation. Relay 401 is held operated which 4,holds the subscribers loop closed; The

theYi-ntermittent operation of rotary magnet 223, which drives the arm of selector 22,1, `so that it engages,the/.associated contacts, ,indicated by small circles arranged in an arc, successively. The timing may be xed in yany ,desired manner. As arranged in the 'gure herein, when the arm `the Winding of relay 209, the contact and arma- .ture lof relay 2 08, to the negative terminal of of the switch is stepped onto the rst contact an obvious circuit is established to energize register magnet 233 which in turn operates register 234. The switch 221 is operated continuously while the circuits are conditioned for communication, stepping around to the last contact and then returning to the first, to repeat the cycle in a well-known manner. As the arm passes over `the first contact in each cycle, the register is operated. While the arm is operated from the normal position, the off-normal springs 23| are in engagement, but the circuit through the switch release magnet 230 is disconnected from ground at the right-hand armature and contact of relay 226 which are open.

At the conclusion of communication the calling subscriber restores switch 2|| to normal. 'Ihis opens the circuit to the motor 20B. It also releases relay 201, which opens the ring of the subscribers loop circuit and grounds the tip. Ground on the tip shunts timing relay 226 which releases, deenergizing the rotary magnet 228 and operating the release magnet 230 associated with switch 221 which is restored to normal, stopping the timing mechanism.

Ground on the tip also increases the current through the top winding of relay 306, the effect of which now becomes dominant over the effect of the current in the bottom winding and the armature of relay 305 is actuated to the right to engage its right-hand contact. A circuit may now be traced from ground through the armature and right-hand contact of relay 306, the top ar- -mature and back contact of relay 304, through the winding of relay 302 to battery. Relay 302 operates, supplying ground through its bottom, front contact and armature to light lamp 303 as a disconnect signal to the operator who takes down the cord.

In the case of the called station the attendant may stop the station equipment and transmit a disconnect signal as follows.

For stations arranged per Fig. 4A where switch 4|| has been operated in response to the calling signal after the called station identification signal V has been transmitted, the station attendant restores key 4|| to normal. Remembering that relays 409 and 4| 0 were released when switch 4| was rst operated to its alternate position, restoration of switch 4|| to normal breaks the circuit through relay 401 at the top armature and front contact of switch 4| Relay 401 releases and grounds the tip of the subscribers loop. The restoration of switch 4H opens the circuit for motor 406 at the same armature and contact of switch 4| I. Ground on the tip of the called line operates relay 3|4 over a circuit heretofore traced, lighting lamp 3|5 as a disconnect signal. The Operator takes down the cord, releasing relay 3|0, which opens the holding path of relay 3|| which releases, restoring the cord to normal.

The operation of the common identifying signal supply per Fig. 5 will now be described.

The station circuit apparatus other than the identifying signal supply equipment and its controlling relays the same as the station circuit apparatus in Fig. 2. This is indicated by the numerals in the 200 series assigned to corresponding apparatus units in Fig. 2 and Fig. 5.

We will consider first a call incoming to station D of a group of three station circuits D, E and F on a particular subscribers premises. Y

When relay 208 in Fig. 5 responds to remote control, relay 209 is also operated over a circuit from the positive terminal of battery 2|2, through battery 2|2. Relay 209 when operated connects power to the motor 206 through its top armature and front contact and locks, over a path from positive terminal of battery 2|2, through relay 209 winding, the front contact and armature o1' relay 209, the winding of relay 5| I, the bottom, back contact and armature of switch 2| l to the negative terminal of battery 2|2. Relay 5| is 'A operated. Ihe operation of relay 209 also closed a path for the operation of relay 201, from the positive terminal of battery 2|2, through the top 4armature and front contact of relay 209, the

winding of relay 201 to the negative terminal O1' battery 2|2.

The operation of relay 201 closes the subscribers loop circuit and removes the short circuit from the station equipment as heretofore described. The operation of relay 5|| closes a circuit for the operation of relays 5|2 and 5|0 from the positive side of battery 2|2, through the winding of relay 5| 2, the armature and front contact of relay 5| the front and back contacts of the make-before-break combination on relay 5| 2, the top, or operate, winding of relay 5|0, through the top, back contact and armature of relay 524 and the contacts 523 associated with cam 526, fixedly mounted on shaft 525, to ground. Cam 526 operates contacts 523 into engagement only when the shaft 525 is in the position corresponding to the position in which the arm of the distributor is in engagement with segment 6 of 5|4. Relay 5|2 is made slow to operate to 'insure the operation of relay 5|0, as when relay 5|2 operates, it opens the operating path of relay 5|0 and locks from the negative or grounded side of the battery 2|2, through the armatures and contacts of relays 5|2 and 5|| in series, relay 5|2 winding, to the positive side of the battery 2| 2. Relay 5|0 operated, closes a holding circuit from the positive side of battery 2|2, through the bottom, inner, front contact and armature of relay 5|0, through the bottom winding of relay 5| 0,

to ground through the armature and back contact of relay 5| 6, which is normally released. A Relay 5 0 operated, opens the circuit through the back and front contacts of its two make-beforebreak combinations, which normally connect the subscribers loop in series through the contacts of this relay and substitutes the two-wire connection to the transmitter-distributor. Relay 5| 0 operated, energizes the start magnet 524 of the distributor, from the positive terminal of battery 2|2 through the bottom, outer armature and front contact of relay 5|0, through magnet 524 to ground. The operation of magnet 524 breaks the connection to ground through contacts 523 which operated relay 5|0 and also operates a lever 521, unlocking cam 5|8, which permits the transmitter-distributor shaft 525 to revolveunder the influence of worm gears 5| 1, friction clutch 5| 9 and motor 520, driven by power source 52|. -These are parts of the transmitter-distributor mechanism whose operation is. well known. The operation of the transmitter-distributor translates the combination perforated Ain a tape, through the medium of a group of tongues and contacts 5|5, into electric impulses, which are impressed on the line successively by the commutator-distributor device 5|4 as the distributor arm passes over the segments of the commutator. The transmitter-distributor will continue to operate until the tape reaches a position in which the sixth hole is perforated. At

this point ground will be connected to the winding ofH relay 516. Relay 516 will operate, breaking the ground connection through the bottom or holding winding of relay 515 which releases. 'Ihe release of relay 510, in turn, deenergizes magnet 524 which allows the lever 52'1v to be restored to -itsv original position under the inuence of spring 1526. The release of magnet 524 stops the revolutionof the cam 518 by engagement between the .right-hand end of said lever and a raised surface 'on the periphery ofthe cam'. The revolution of shaftj525 and the arm of the transmitter-'distributor keyed to said shaft is likewise stopped as .the 'driven member of friction clutch 519 is held. When the revolution of the shaft stops, ground is furnished again to the operate winding of relay "51j0 Y. through contacts 523, but as the circuit "through this winding is open at relay &2, which -isloperated, relay 515 remains released. Relay 511), released, disconnects the leads to the transmitter-distributor from the station circuit and ',reestablishes the original station circuit loop connection in series through theY contacts of relay The operation; of the circuit per 5 has been described for a call assumed to be incoming to lstation D. We will now describe a call incoming `to station F, and assume that station D is connected to the transmitter-distributor and that station Bis also awaitingv its turn for connection to. theY transmitter-distributor apparatus.

Since the transmitter-distributoris operating for the connection to station D, relay 510 associated with stationD is operated. Relays 511 in fthe Eand F station circuits are operated. With .relay 510 operated, relays 512 in the E and F station'circuits cannot operate, as the connection to 'positive battery 21,2, through the windings of rclays512 is broken at the bottom, outer, back contact of relay 510 of station D'. When relay 510 of station D releases, at the end of the transmis- Sion of the identifying signals, a circuit may be traced from the positive terminal of battery 212, through the armature and back contact of relay 5150i station D, the winding of relay 512 of sta- `tion.E`, the armature and'front contact of relay 511.of. station E, the iront and back contacts of the .make-beore-break combination of relay 512 of'station E, through the top or operate winding of relay 510 of station E, thertop, back contact and armature of relay 524, tol ground, through contacts 523, operating relays 512 and 515 in station E..v 'I'hese relays lock as in the case of station D. When relay 510 in station E operates, the connection to theV positive side of battery 212 in station D; which is necessary for the operation ofirelayl512 in stationF, is broken at the bottom, outer amature and back contact of relay 5111 in station E. t Relay 512 in station F Vcannot operate, therefore, until both relays 5,1@ in stations D ,andLE" are released'.

Iii/any relayV 511 'n a station circuit operates, dueto. an'incoming, call, while another station is connected to the transmitter-distributor, its associated relay 51.5 cannot operate to connect it '.to, the transmitter-distributor, because yground for theoperatewinding of its relay 5113 will not be 'ayailable the distributor until the transmission, ofthe identifying characters is ended and relay 521!A releases to establish the connection to ground through contacts 523. Thus but one station maybe connected to the transmitter-distributor at a time, and preference is given to the station, the operate winding of whose relay 510 is 'directly connected to the positive side of battery 212 and, thereafter, in a definite order to the stathe operate winding of relay 510 of the particu- Ylar station in the chain connection to the positive side of battery 212.

In the case of a station circuit arranged per Fig. 5, it may be observed, as in the-case of circuits per Fig. 2A or 4A, it is not necessary to operate the station power switch in order to receive. In the case of Fig. 5, however, a called station may also transmit without operating the power switch. In the case of both arrangements, if the switch were left in the normall position while a message were being received, in order toV stop the station equipment and; signal the operator at the conclusion of communication, the attendant would operate switch 211, first downwardly, and then restore it to normal. Operation to the down position breaks the locking path through relays 269 and 210 in Fig. 2A or through EEB and 511 in Fig. 5, releasing the relays. The operation of the switch also connects the windingof relay 261 and motor 2136 to positive battery to hold the subscribers loop closed. When the switch is restored to normal, relay 2M' is released and the motor is stopped.

As described above the operation of the timing of mechanism is stopped when the calling station power switch is operated. If it is desired to arrange the timing mechanism so that it may be stopped also by the called subscribers first operating the power switch at the called station, before the calling subscribers power switch is operated, the locking contacts for relay 311l are removed. Then when the called subscriber sends a disconnect signal relay 31 1 is released and the current through relay 225 is reduced so that the relay releases.

The features oi this invention have been disclosed as appliedv to a cord circuit presently used and well known in the art. This cord circuit is at present used to interconnect other types of linev circuits not including the automatic remote control feature shown in the line circuit herein. This new automatic remote control feature functions when a cord circuit isY connected to a line circuit to start the station equipment.` To do thisit is not necessary to operate a key in the cord circuit .as has heretofore been necessary. As modied, however, as shown in Fig. 3 the cord circuit will function with the existing wellknown line circuits in the usual manner, so that, if it is desired, it will not be necessary to modify all existing line circuits in accordancev with Fig. 2B. And until such time as they are modied, it would be possible by marking the jacks associated with the new lines, to indicate to the central station operator the lines on which it is unnecessary to perform the additional operation of operating a key to start a station byy remote control. Further, the operator wouldV know from these markings that it would notA be necessary to spend time monitoring the connection to insure that the calling party was connected tov the proper called party and further the operator would know that it was unnecessary to time the connection as the timing would be performed automatically.

What is claimed is: y

1. In a manual teletypewriter switching system, a telegraph line and station circuit, a teletypewriter motor, a, remote control device for starting said motor, a calledstation identifying device, and a call metering device all in said circuit and means whereby said devices are made responsive automatically to the connection of said circuit through a cord circuit to another line and station circuit.

2. In a manual teletypewriter switching system, a calling and a. called local station, means in said system for establishing an operable telegraph channel connecting said stations, a teletypewriter motor at said called station, automatic motor starting means at said called station, automatic station identification means at said called station, communication time metering means connected to said channel, a iirst remote control means connected to said channel for operating said starting means inresponse to the insertion of a plug in a jack both in said system, a second remote control means connected to said channel for operating said station identification means in response to said insertion and a third automatic remote control means also connected to said channel for starting said metering means upon the establishing of said channel.

3. In a telegraph circuit, a first local telegraph station, a second local telegraph station, an operable telegraph channel connecting said stations comprising a cord circuit having a plug therein,

an answer-back device at one of saidstations responsive to automatic control means connected to said channel to transmit an identifying signal to the other of said stations .and Aa metering device connected to said channel responsive to automatic control means connected to said channel for measuring the period of communication between said stations.

4. In a teletypewriter circuit, a calling teletypewriter station, a called teletypewriter stai tion, a telegraph circuit connecting said stations comprising a, manually operated cord circuit, means in said telegraph circuit for transmitting a signal characteristic of said called station to said calling station, means in said tel-egraph circuit for measuring elapsed communication time, means also in said circuit for initiating the operation of said identifying device responsive to control means operated by connecting said cord circuit to said called line and'automatic means for starting said measuring device responsive to control means operating When said telegraph circuit is conditioned for communication.

5. In a manual teletypewriter switching system, a central switching station, a plurality of local stations, a. plurality of telegraph circuits connecting each local station with said central station, a called `station identifying device, located in close proximity to said local stations, common to said local stations and means for connecting said device individually to any one of said telegraph circuits.

6. In a manual teletypewriter switching system, a subscribers line and station circuit, a cord circuit conditioned to cooperate with said circuit, a plug in said cord circuit, automatic teletypewriter starting apparatus in said station circuit, autornatic teletypewriter starting control means in said line circuit responsive to the connection of said plug to said line circuit to start said teletypewriter apparatus.

'7. In a manual teletypewriter switching systern, a subscribers line circuit and a station circuit means for interconnecting said circuits, teletypewriter remote control starting means in said station circuit, a polar relay in said station circuit responsive only to current of a definite polarity to initiate the operation of said starting means, and means in said line circuit, responsive to the -connection of a cord circuit to said line circuit, for supplying directly from said line circuit current of said polarity.

8. In a manual teletypewriter switching system, a line circuit, a station circuit, teletypewriter motor starting means in said station circuit, a telegraph loop circuit having a rst and a second end interconnecting said circuits, means in said line circuit for connecting telegraph transmitting battery of a rst polarity directly to said rst end and means also in said line circuit, responsive to the connection of a cord circuit to said line circuit, for connecting battery of a polarity opposite from said first polarity directly to said irst end to operate said teletypewriter starting means.

9. In a manual teletypewriter switching system, a calling and a called teletypevvriter station, means in said system for establishing an operable telegraph path connecting said stations, a teletypewriter at said -called station, automatic starting means for said teletypewriter at said called station, automatic called station identifying means connected to said path for identifying said called station, automatic communication time metering means connected to said path for measuring the time said path is conditioned for communication, flexible, manually operated means in said system for extending said path toward said called station as said path is being established, means in said path, reponsivc to the extension of said path by said flexible mea-ns, for operating said starting means, means in said path, responsive to the extension of said path by said flexible means for operating said identifying means, and means in said path responsive to the establishment of said path for operating said metering means.

LELAND A. GARDNER. FRED J. SINGER. EDWARD F'. WATSON.

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