US2024581A

US2024581A - Telegraph toll system

Info

Publication number: US2024581A
Application number: US704380A
Authority: US
Inventors: Fullerton S Kinkead; George A Locke
Original assignee: Bell Telephone Laboratories Inc
Current assignee: AT&T Corp
Priority date: 1933-12-29
Filing date: 1933-12-29
Publication date: 1935-12-17
Anticipated expiration: 1952-12-17

Description

5 l7;1$35. 5 K|NKEAD ET AL 2,024,581

TELEGRAPH TOLL SYSTEM Filed D80. 29, 1935 2 Sheets-Sheet l POL A RIZE'D CL I POL A/P/ZED POL AR/ZED FIG] INVENTORS F.$.l\lN/(EAD ATTORNEY Dec. 17, 19 35.

F. S KINKEAD ET AL TELEGRAPH TOLL SYSTEM Filed Dec. 29, 1935 2 Sheets-Sheet 2 N 55 6 5 EDT-D in W W M NM rmllhm b uTT vi. UN 5 INVENTORS F S KIN/(FAD By G-.A.LCKE

ATTORNEY ill Patented Dec. 17, 1935 UNITED STATES PATENT OFFICE TELEGRAPH TOLL SYSTEM Application December 29, 1933, Serial No. 704,380

11 Claims.

This invention relates to teletypewriter switching circuits of the manually operated type having link circuits preferably in the form of cord circuits for interchangeably connecting subscribers lines and supervising intersubscriber connections set up over them.

Features of the invention include selector switches together with auxiliary apparatus for discriminating between line interruptions or break signals of difierent length for the transmission and reception of call, recall and disconnect signals, respectively.

To the extent that the apparatus or circuit arrangements are suitable therefor the system may be employed for transfer of messages between subscribers and central offices either through intermediate central oflices or not'as the case may be.

Objects of the invention are to provide arrangements for sending and receiving call and disconnect signals as well as recall signals and generally supervising teletypewriter communication circuits set up to or through one or more central offices.

In accordance with the'invention, central offices are connected by one or more toll lines over which calls between distant places may be transmitted. Each toll line terminates in a jack at a central office into which a cord circuit thereat may be plugged. At each end of the toll line is tell line terminating equipment including selectors or stepping switches which in a preferred embodiment are stepped around under the control of synchronized interrupted current or suitable timed impulses which need not be accurately synchronized. A feature of the toll line terminating equipment is that by making slight modifications therein by interrupting certain connections and making others the equipment may be employed on a subscribers line which is so long as to be of the toll line type and to include one or more repeaters, carrier current links, radio links or the like. In general, it will be understood that the toll lines illustrated need'not be metallically continuous but may include any sort of links over which the desired make and: break signals may be transferred by methods known in the art. A cord circuit at a central ofiice for interconnecting subscribers lines or toll lines includes a two-relay single line telegraph repeater,

circuit for supervising and monitoring as may be necessary.

Additional features and objects of the invention will appear in connection with the following detailed description and the accompanying drawings wherein:

Fig. 1 comp-rises a cord circuit at the central ofiice together with associated equipment, a subscribers line being diagrammatically indicated at the left. Subscribers lines suitable for connection to other lines through the cord circuit may be of various types; appropriate equipment is shown associated with the subscribers line in the application of Locke-Kinkead Serial No. 459,- 684, filed June 7, 1930, to which reference is made 15 for an understanding of the subscribers line and its operation;

Fig. 2 comprises the line terminating equipment of a toll line which may be assumed to be provided at its distant terminal with similar equipment. This equipment may assume different forms depending upon whether certain switches, which may typify permanent connections or, if desired, may be in the form of actual switches in the system, are openor closed. It will be understood that these switches do not form a part of the operating mechanism but being once set in a given position remain so indefinitely. In the principal modification all the switches marked XI, WI, W2, W3, and W4 are closed. In accordance with another arrangement the switch XI is opened and switches Zl, Z2, Z3, Z4 and Z5 are closed.

The cord circuit shown in Fig. 1 includes equipment for performing the following functions: 3

(l) Answering calls .on subscribers lines.

(2) Receiving an automatic flashing recall signal from either end of the cord.

(3) Ringing manually over the calling cord only.

(4) Sending disconnect signals or recall signals over toll lines from either end of the cord.

(5) Giving a steady disconnect signal at either end of the cord.

(6) Ringing or calling subscribers or distant toll operators.

('7) Making a busy test with either end of the cord circuit.

(8) Repeating telegraph signals over the single line repeater contained in the cord circuit from or to subscribers lines or toll lines.

(9) Splitting the circuit for typing or signaling in either direction independently of the other.

(1-0) Closing the repeater of the cord circuit automatically when either terminal thereof is connected to the line circuit.

(11) Connecting the operators teletypewriter set into the cord circuit for sending or receiving teletypewriter messages.

The toll line equipment shown in Fig. 2 includes devices and circuit arrangements forperforming the following principal functions:

(1) Receiving a calling signal.

(2) Receiving a disconnect signal.

(3) Transmitting a disconnect signal.

(4) Transmitting a flashing recall signal.

(5) sleeve of the toll line during the time the line is busy or upon an accurate reception of a calling signal.

(6) Receiving a flashing recall signal.

('7) When properly modified, sending or receiving call or disconnect signals from a subscribers station over toll line equipment, that is, one or more repeaters and/or other apparatus commonly employed in long telegraph circuits.

An important feature of operation consists of arrangements whereby difference in phase of the stepping im ulses supplied at different offices will not detrimentally affect the operation.

A feature of operation when disconnect signals are sent over toll line equipment from a subscribers station to a central ofifice is that the subscriber produces a long open impulse upon the line to cause the disconnect signal indication at the central ofiice but devices at the central oflice limit the length of the open impulse transmitted from the central ofiice to connecting lines or stations.

In the cord circuit the relays AL and CL constitute a two-way, single line repeater which is closed for operation when the relay M is operated. We may now assume that the switches XI WI, W2, W3 and W4 are closed and that the circuit arrangements are in normal condition and. that the operator observes a calling signal upon a subscribers line lamp LL. The answering plug AN is inserted into the line jack. Ground over a relay winding is present 'on the sleeve of the jack. The circuit is then completed from ground through the sleeve of the plug and jack through the winding of the relay AB to battery, operating the relay AB. The tip of the plug is norm-ally connected through the winding of the polarized relay BY which is connected to the busy test lamp BL. Upon operation of the relay AB the tip of the plug is taken off the connection to the relay BY and transferred to the winding of the AD relay. A momentary ground is present on the tip of the jack in the line circuit. This operates the relay AD, which in turn operates the relay AE. Upon cessation of the momentary ground the relay AD releases but the relay AE locks up over a circuit extending from ground on the upper inner contact of the relay AB and passes through the locking winding of the relay AE to battery through a resistance. If the operator throws the typing key TYP the relay AB is released. If the operation of the typing key is delayed the answering lamp AL may 'flash but no harm results therefrom. 7

Operation of either relay AB or CB operates relay'M and hence conditions the repeater for operation whenever the cord circuit has one of its plugs in a jack.

Placing the busy test indication upon the ground supplied thereto.

Upon operating, the relay AB closes a circuit from negative battery in the line over the ring through the outer lower back contact of the relay AB, the splitting key SPL, the typing key TYP and the winding of the relay AL to positive battery through the back contact of the relay CL. The relay AB also closes the lower winding of the relay CL to negative battery over a contact of the relay CR and the lower break contact of the relay CB and the inner lower make contact of the relay AD. The calling side of the repeater is now closed to line and the operator may communicate with the subscriber andinquire what number is wanted. If the subscriber wishes a local connection, connection will be made to another line with the calling side plug of the cord circuit in a. manner which is not essential for purposes of the present invention and we, therefore, pass onto the case where connection is to be completed over a toll line.

OPERATOR CALLS oven TOLL LINES Operation of cord circuit erates the relay CR and opens the toll line for that period of time. The relay CD is released so that any operation of the relay CR opens the line. The result of this will be the lighting of a lamp in the toll multiple at the distant end of the toll line in a manner which will be hereinafter described. It will be noticed that the calling side of the repeater is held closed over another path while the line is opened at the relay CR.

Battery over the sleeve of the calling plug and the jack will operate the relay SL. The opening of the line releases the relay L which causes the release of the relay G by opening the energizing path extending through its lower winding. The release of the relay G causes the relay K to operate in accordance with the interrupted Each operation of the relay K will step the selector SEL by energizing the rotary magnet ROT over an obvious circuit. After the selector has stepped one or two steps the line will close. It will be noted, however, that the relay H will not operate, because the Operation of toll Zine equipment relay SL is operated. Upon closing the line the relay L will reoperate which reoperates the relay G. The operation of the relay G closes the circuit through the release magnet RLS of the selector thereby causing it to release.

Distant operator receives calling signal At the distant station the opening of a line for two seconds causes a similar sequence of relay operation to that at the sending station. In

. other words, the release of the relay L will release the relay G which causes the relay K to operate in accordance with interrupted ground and step the selector SEL by energizing the rotary magnet. After one or two steps the line will close. Owing to the fact that the relay SL is not operated the closing of the line will operate the relay H through any one of the first, second or third points of the second bank of selector contacts over a path from battery to selector contact on the second bank, upper back contact of relay SL, lower makeupon-release-contact of relay I-l, winding of relay H, upper back contact of relay D and ground upon lower back contact of relay A. Upon closing the line the relay L reoperates and operates the relay G which closes an obvious circuit to the release magnet of the selector over the off-normal contact thereof and. causes the selector to release. The relay H in operating locks itself up andlights the answering line lamp ANS; it also connects battery through a resistance to the upper winding of the relay SL over an obvious circuit. The relay SL does not operate at this time because its windings are differentially connected. Battery applied to the sleeve in the jack through the winding of the relay SL makes the jack appear busy in the multiple. The distant operator observes the lighted lamp and responds thereto by inserting the answering plug of the cord circuit into the jack associated with the lamp. Battery present upon the sleeve of the plug will cause the completion of a circuit through the winding of the relay SL causing suificient current to flow to overcome the diflerential eifect and cause the relay SL to operate. The operation 'of the relay SL will disconnect the SI side of the toll line loop from the repeater and complete the circuit from the Ti side of the repeater through the ring of the jack and plug into the cord circuit which is normally closed when the cord is in use in the manner hereinbefore described. This completes the communication circuit which passes through the toll line terminating equipment in the incoming direction from the TI side of the loop through winding of the L relay, the upper make-on-release contact of the relay A, the lower make contact of the relay SL and. resistance to the ring R of the jack. The operation of the relay SL operates the relay B over an obvious circuit and also interrupts the holding circuit of the relay H over another obwous circuit which extinguishes the answering line lamp ANS. The operation of the relay B operates the relay C over a circuit from battery, upper make contact of. relay B, winding of relay C and make contact of relay L and it also connects battery to the upper winding of relay G to ground upon the upper make contact of the relay C. The sleeve of the jack is maintained ina busy condition by battery supplied from the cord. The operator scribers line or to another toll line and that the subscriber has answered or that the circuit has been completed through another toll line to put the two subscribers int?) communication. We may, however, alternatively assume that the distant operator has connected her own teletypewriter to the circuit and has been unable to extend the call any further. In any case we will assume that one of the operators upon the toll line wishes to send a flashing recall signal to attract the attention of the other.

Operator sends flashing recall signal Assuming that the toll line circuit is connected up for communication with a cord circuit plugged in at each end thereof and the operator wishes to send a flashing recall signal, she presses the toll signal key TS in the cord circuit which applies ground to the tip of the plug if the splitting key SPL is normal or operated to the calling side. If the splitting key is operated to the answering side, the. ground will be applied to the tip of the answering plug AN. This closes a circuit through the tip of the plug, lower back contact of relay D, back contact of relay R and the secondary winding of relay A to battery on the lower armature of relay B which operates the relay A; this opens up the line and connects in a resistance closing the ring of the cord circuit from the battery through the resistance. The relay L releases when the line opens and the selector SEL will step as previously explained. The relay A locks up on a circuit from battery through its lower winding, a resistance and its lower make contact to ground. When the selector reaches the sixth contact on bank I which is connected to battery at relay B, the relay A will release; however, the relay R has at this time operated on a path from battery through bank 2, winding of relay R to ground. Thus upon the release of the relay A the. line circuit will be closed. and the relay L reoperated which releases the selector. Upon closure of the line ground will be applied to the tip of the jack over a circuit extending from ground, make contact of relay L, make contact of relay R and back contact of relay D to the tip. The line has thus been opened for about seven seconds.

Upon connection of this ground to the tip momentarily the relay AD in the cord circuit is operated, which in turn operates the relay AE. As soon as the ground is removed the relay AD releases but the relay AE stays locked up through its primary winding. The operation of the relay AE opens the operating circuit of the relay AD so that when ground is taken from the tip and the relay AD releases, subsequent operations of the recall key will not cause the relay AD to reoperate. The answering lamp AL is connected over the back contact of the relay AD and the front contact of the relay AE to a source of current interrupted sixty times per minute. If the recall happens to be on the calling end of the cord circuit the operation is similar. Upon noting the flashing recall signal the operator may operate the typing key TYP which closes a short circuit path to ground over its upper contact to release whichever relay AE or CE happens to be operated by short-circuiting the winding to ground and this stops the flashing of the lamp. The operator may then receive inquiries over the circuit by means of the teletypewriter and inform the inquiring distant operator the reason for the recall signal.

Distant operator receives a flashing recall signal The release of the relay G causes the relay K to operate in accordance with the interrupted ground connected in series with its winding. The selector SEL will step and continue to step until the brush in the second bank of contacts reaches the seventh contact at which time the line circuit Cal will close and cause the selector to release by the reoperation of the relay L which operates the relay G and energizes the release magnet of the selector in a manner previously explained. When the brush of the second bank of contacts reaches the fourth contact the relay R will operate and. transierthe tip of the jack to a lead extending to the open upper contact of the relay L. In this condition negative battery is applied to the tip both in the cord circuit and from the upper contact oi the relay B and no current will flow. As soon, however, as the relay L reoperates ground is connected to the cord circuit over the tip through the make contacts of the relays R and L. Upon connection of this ground to the cord circuit the supervisory lamp will be caused to flash therein by a sequence of operations similar to those which caused the supervisory lamp'to flash at the station sending the flashing recall signal. Even though the selector should release somewhat sooner than it should ground will be applied to the tip in the cord circuit because of the slow release characteristic of the relay R. The operator receiving the flashing disconnect signal will then connect her teletypewriter to the circuit by means of the typing key TYP which causes the release of whichever relay AE or CE happens to be operated by short-circuiting the winding thereof to ground and stopping the flashing of the lamp. The operator will then send an inquiry over the circuit by means of her teletypewriter and endeavor to learn the reason why the recall signal was sent.

Flashing recall signals will, in general, be received by all toll switchboards connected in the circuit.

Sending of a. disconnect signal To send a disconnect signal the operator presses the toll signal key TS in the cord circuit and then immediately removes the plug from the jack of the toll line over which the disconnect signal is to be sent. Pressing the key applies ground to the tip which operates the relay A causing the relay A to operate and'lock up. When the plug is removed the relay SL is released and this releases the relay B. The operation of the relay A opens the line and the selector steps up to the tenth terminal which is connected to battery, thus causing the relay A to release. When the relay A releases the line is closed and the disconnect signal is given to the distant oflices in a manner which will now be described.

Reception of disconnect signal As stated above, the sending of a disconnect signal holds the line open for ten seconds. At a station or stations receiving the signal the relay L releases and the selector starts stepping in a manner and for reasons as previously described. The selector steps until the tenth terminal is reached. When theeighth terminal is reached the eighth contact on bank 2 closes the circuit from battery through the lower winding of relay D to ground, thus operating the relay D which prepares its own locking path over the off-normal contacts of the selector switch and later over the make contact of relay B. The relay D also prepares a path to ground on the tip of the jack when the line is closed. This path extends from ground through the then opened contacts of relay L, make contacts of relay D and thence to the tip. Upon closing the line the relay L operates to connect ground to the tip of the jack. This ground will remain on the tip until the cord plug is pulled down from the 'jack, thus maintaining a steady light in the cord. circuit over a path extending from the tip of the cord. In the case of the answering end of the cord this ground causes the operation of the relays AD and AE. The relay AD closes the circuit through the answering lamp AL which constitutes the disconnect signal on that cord terminal. When the cord plug is removed from the jack the relays AD and AE will release and the lamp will be extinguished. In the case of the calling end of the cord the relays CD and CE will operate in a similar manner. Returning to the toll line terminating equipment, upon the removal 01' the plug from the jack the relay SL will release which releases the relay B, which in turn releases the relay D and restores the circuit to normal.

Disconnect signals under the above condition will be received at every toll station in a tandem circuit including more than one in addition to the sending toll station.

Subscribers toll line In the case of a subscriber connected to an exchange by means of a long line which is too long for operation as a simple loop it may be necessary to send calling and disconnect signals over the subscribers line in a manner similar to that herein described. Call and disconnect signals sent in such case will not be repeated beyond the first switchboard to which the subscriber is connected. Such subscribers toll lines, in general, will include a repeater and the terminal corresponding to the toll line terminal TI will ordinarily be supplied with negative battery from the repeater. The subscribers station will not be equipped to send or receive flashing recall signals. In the case of such a subscribers long toll line the line equipment at the central ofiice may be modified for operation by changing permanently or by means of switching the circuit in such a manner that all points marked XI, WI, W2, W3 and W4 which are normally closed will be opened and all points Zl, Z2, Z3, Z4 and Z5 will be closed.

In such case if the subscribers station operator wishes to send a calling signal this will be done by opening the line for two seconds. The operation of the line terminating equipment at the central oince will be the same as hereinbefore described under the heading Distant operator receives call signal.

If a subscribers station operator wishes to send a disconnect signal this will be done by interrupting the line for five seconds, which interrup tion may be accomplished, if desired, by a special automatic timing key. The interruption may, however, be longer than five seconds. This interruption releases the relay L and starts the selector stepping. When the brush on the first bank reaches the third contact the ring of the cord in the line circuit is connected over the third contact and the brush to battery and ground through a resistance. Disconnection of the third contact on bank I prevents any interruption of the line for more than three seconds from being effective in the cord circuit. This prevents any long open or break signal of more than three seconds from being relayed through the exchange nearest the subscriber to another exchange or exchanges upon the circuit. When the brush on bank 2 reaches the fourth contact the relay R is operated. which prepares a path for sending ground over the tip to operate the flashing relays in'the cord circuit. When the line closes the tip of the cordwill be grounded over a path extending from a make contact of relay L, make contact of relay R and lower back contact of relay D to the tip of the cord. The disconnect signal for this condition will be a flashing light in the cord circuit which will be advantageous because the operator may challenge on the line and inquire if the subscriber at the end of the long toll subscribers line has finished communicating. When the line is closed the selectorwill return to normal and the relay SL will be released when the cord is removed from the 'jack.

Non-automatically flushing recall In accordance with another condition of this circuit all the switches at points designated M, XI, Zl, Z2, Z3, Z4-and'Z5 may be opened and all the points WI, W2, W3 and W4 connected. In order to send a recall signal under such condition the toll key TS in the cord circuit which applies ground to the tip of the jack will be operated. The relay L releases and the selector will then step until the brush on the first bank reaches the tenth contact upon which is found a battery potential which releases the relay A by short-circuiting its winding. The relay D operates from the second bank of the selector over a path to battery through the eighth, ninth or tenth contacts and winding of relay D, to ground. Relay D locks up upon the contact of relay L which reoperates when the relay A releases. This ground supplied over the make contact of the relay L operates the relays AD and AE in the cord circuit which causes a steady light to appear in the cord circuits because the ground remains upon the tip. The reception of a non-automatically flashing recall signal will produce a cycle of relay operations at the receiving station similar to that at the station sending a non-automatically flashing recall signal and the selector will advance to the tenth contact. Relay D will be locked up, relay L reoperated and relays CE and CD operated. The signal sending operator may then operate the ringing key or send any character over the line from her printer. Either operation will open the line momentarily, which will release the relay L and thus remove the ground from the tip. This will release the relay AD or its corresponding relay CD in the other end of the cord circuit and change the steady light to a flashing recall at the sending and receiving o-flices.

When sending a disconnect signal the operation is the same as described in the preceding paragraph except that the operator also removes the plug of the cord immediately after operating the toll signal key. Under this condition, the sleeve of the line jack at the sending end is maintained in a busy condition until the selector returns to normal.

What is claimed is:

1. Line terminating equipment for teletypewriter communication over systems employing lines having jacks to be connected by cord circuits of the manually operated type, the line terminating equipment comprising stepping devices at each terminal, characterized in this that the stepping devices have different contacts thereof associated with different relays whereby line interruptions of different lengths, such as '7 and.10 seconds, give different indications, namely flashing recall and steady disconnect signals, respectively.

2. A teletypewriter system comp-rising a line connecting two ofiices, terminal apparatus at each end of said line including relays and devices whereby a pulse of relatively long duration as compared to a telegraphic signaling pulse sent upon said line from an office thereon causes a signal to appear at a distantofiice, and additional 5 devices whereby a pulse of still longer duration sent upon said line causes a distinctively diiferent signal to appear-at said distant station.

. 3. A teletypewriter toll'line circuit. provided with terminal apparatus including stepping switches and means for causing said switches to step when the line is interrupted for a time of greater duration than the duration of a normal character transmitting signaling impulse, contacts. upon said switches andrelaydevices connected thereto whereby the. opening of said-line .for av certain .period of time operates a recall signal and fora certain different period of time a disconnect signal.

4. A system according to claim 3 wherein the duration of the open periods of said line is automatically determined by the time required for the stepping switches to step to a given contact upon the operation of suitable circuit elements to start the switches to step in combination with a circuit element selectable by the operator to determine the given contact in accordance with the kind of signal desired.

5. An arrangement in accordance with claim 3 in which the stepping switches are connected to a source of timed impulses to cause them to step and certain of their contacts are tied together whereby a departure of the timed impulses at remote terminals from synchronism to an extent equal to a complete impulse does not adversely affect the correct operation.

6. In a teletypewriter toll line circuit, terminal equipment at each end thereof and a jack for plugging a link circuit thereto at each end thereof, stepping switches in said terminal equipment, 40 relays whereby upon the operation of a special toll signal device in the link circuit the terminal equipment of the toll circuit is operated to produce a signal in a cord circuit connected thereto at a distant station, and means whereby if the special toll signal device is operated and the local link circuit immediately disconnected from the jack of the toll line a relay is actuated and said stepping switch is caused to step at the distant station whereby a different signal is caused to be given at said distant station.

7. A system comprising a subscribers line provided at its central office end with line terminating equipment and a jack for connection to a cord circuit, said terminating equipment including devices whereby when said subscribers line is connected to said cord circuit a long line pulse produced at the subscribers end of said line causes a disconnect signal indication at the central office and including a stepping switch, a contact thereof closed after a predetermined duration of said line pulse, and other devices whereby a line impulse exceeding a predetermined dura-' tion is not transmitted through the repeater of the cord circuit connected to said subscribers line.

8. Line terminating equipment for teletypewriter communication over systems employing lines having jacks to be connected by cord circuits of the manually operated type, the line terand 10 seconds, give different indications, namely flashing recall and steady disconnect signals, respectively, and certain points in said line terminating equipment which may be connected and certain other points in said line terminating equipment which may be disconnected together with a circuit interrupting device associated with a cord circuit whereby initiation of operation of said stepping devices at a receiving terminal produces a disconnect signal indication, and means under the control of the signal initiating operator whereby said signal may be converted to a recall indication.

9. In a telegraph exchange system a line terminating in a jack at a central oflice, a cord circuit adapted for connection to said jack for the intertransfer of intelligence impulses between said line and said cord circuit, line terminating equipment connected to' said line to send supervisory signals thereover, a device in said cord circuit for causing said equipment to' send a supervisory signal, and devices to cause the nature of the indication at a distant station to depend upon the immediate'removal or non-removal or the cord circuit from the jack at the central office originating the signal.

10. A system in accordance with claim 9 including stepping switches as a part of the line 10' FULLERTON S. KINKEAD. GEORGE A. LOCKE.