US2058605A - Printing telegraph system - Google Patents

Description

Oct. 27, 1936. c. c. LANE PRINTING TELEGRAPH SYSTEM Filed May 28, 1935 /NVENTOR CC'. LANE TTORVFV Patented Oct. 27, 1936 UNITED STATES PATENT OFFICE PRINTING TELEGRAIH SYSTEM Application May 28, 1935, Serial No. 23,835

8 Claims.

This invention relates to the art of telegraph communication and particularly to selective calling and remote control circuit arrangements at each of a plurality of stations connected in series in a normally closed loop circuit of a printing telegraph system.

An object of the invention is to convert upon the initiation of a call from any one of the plurality of stations, an alternating current source of power at each of said stations into a suitable rectied current for operating at each of the stations, a selective calling circuit whereby the desired station is connected for communication with the calling station.

Another object is to employ the source of alternatng current only at such times as the system is in use for initiating a call and transmitting messages.

Heretofore, in systems of this character, that is, in systems wherein a plurality of stations are connected in series in a transmission line, a source of direct current was continuously connected at each of the stations for normally maintaining the calling and control arrangements at each of the stations in an operated condition, thereby increasin series connection at each of the stations, two

polarized relays, one of which is held in a normally operated position and the other in a normally unoperated position. In initiating a call, the line is momentarily opened at the calling station whereby the normally unoperated relays operate to prepare each of the selective calling circuit arrangements for the reception of the code signals of the desired station which are transmitted from the calling station subsequent to the opening of the line, and the normally operated relays release to close the circuits for connecting the rectied current sources for operating the selective calling circuits to the position where each is capable of responding to the code signal of the desired station. The printer set of the desired station only will be automatically connected, in response toits code signal, to the calling station. It is obvious that only one station in the system may establish a connection at any one time, there appearing at each of the stations a busy signal indicating that the line is engaged. However, the system is adapted to permit an operator to call more than one station by individual signal codes or all stations by a single code.

The invention disclosed herein is shown as being applied to a single loop circuit although it is understood that it may readily be applied to a multi-party loop circuit operating through a special exchange provided with automatic switching devices or manually operated switchboards.

The invention as disclosed in the accompanying drawing is being applied to a party line in a printing telegraph system such as disclosed in U. S. Patent 1,946,216 granted to F. S. Kinkead on February 6, 1934.. In that patent, a station A63 is shown on a line with one other station BX, it being understood that any number of stations within the limits hereinafter specified may be connected to the line. All the apparatus at the station Ae`3 is diagrammatically indicated Whereas only the principal essential elements at the station BX are shown. In the drawing the main line circuit in the normally idle condition is shown in continuous heavy lines and the remaining conductive connections are shown in lighter continuous lines.

The system disclosed in the Kinkead patent, supra, may be operated to perform the following functions:

1. One or more stations may be called by individual codes from any o-ther station or all stations may be called by a single code.

2. Complete remote control of the teletypewriter motor circuit is provided,

3. Teletypewriter signals will not cause false selections of the station selecting apparatus.

4. A calling signal is operated at all called stations to indicate that the station is being called.

5. A lamp is lighted whenever the circuit is being employed to call stations to give a warning that calling operations are going on.

6. A busy signal is displayed at all stations when the telegraph circuit is in use for communication.

7. At any time during operation of the teletypewriters additional stations may be called in on the line Without the necessity of redialing those originally called.

8. At the completion of any communication, any operator may stop all stations and restore the apparatus thereat to normal by a single operation.

9. Complete remote control for the current sup-l ply for the circuit is provided.

The principal apparatus at each station consists of the usual teletypewriter machine diagrammatically indicated within the rectangle 509, a calling dial 404, main line relays |02 and |94, step-by-step selector switch SE, busy and guard lamps A and 402, respectively, an alternating current supply 3| I, an alternating current recticonductor |00 of line L.

Normally, all relays are released except relays |02 and |04. 1

General outline of operation n Let it be assumed that the apparatusv is ink normal position and it is desired to call another station. The operator at the calling station operates a dial and release key sim'ilarto key 405 at station A63, or what is assumed hereinY to be a called station, and the code of the desired sta- Y tion is dialed on a calling dial, such as dial 404 shown at station BX. When the key 465 is operated, the calling dial has its operating contacts included in the main line circuit. After the code of any desired station, the digit l is dialed ex- @similar to switch 'sE at the Called station is orfcept that in the case of the last station of several which are to be called in upon the line, the digit 0 is dialed. A guard'lamp at the calling station BX, similar to lamp 402 shown at the called station, is lighted during the dialing of each code digit and extinguished during the intervals betweendial operations'. This occurs because whenever the selector switch at the calling station BX,

normal, its off-normal contact 200 closes the circuit of the guard lamp 402 `to positive potential. If the guard lamp remains lighted, it indicates an open signal line circuit because an open line will cause every selector SE` upon the line to re- Y main advanced one step and consequently the offnormal contacts 200 of every selector will furnish a Ypositive potential and light every lamp 402. After the 0 is dialed, the busy lamp 400 and the auxiliary busy lamp 40| will light at all stations, indicating that the circuit is in use.

To call all stations uponY the line, the code Y number 90 is dialed.

After the dialing operation is completed for any desired number of stations by dialing 0, the teletypewriter motors of the called and calling stations will start and an audible signal will be given at all called stations. rEhis audible signal may be stopped by operatingthe key 405. Teletypewriter communication may noW be carried on by any of the called stations or the calling station without any further eirect on the selectors. Accidental operation of the dials at any of the stations will not interrupt the teletypewriter com munication.

A recall key 401 is employed if it is desired to Ycall additional stations without redialing those originally called. When operated, this key causes three break signals to be transmitted, all the teletypewriters stop and all of the busy lamps 400 Ywill be extinguished. The means for causing three break signals to be transmitted is hereinafter described under caption Calling in additional stations after communication has commenced. Additional stations may then be dialed in the usual manner of dialing an additional station. When the dialing of the additional stations is completed, the dialing of 0 starts the motors at all stations just called as Well as the previously called stations and the calling station. The audible signals 403 at the called stations will operate and the busy lamps 400 at all stations will light.

Y When the nal message is completed, the operator at any station may stop all stations by operating the stop key 406 which causes the circuit to transmit ve break signals as hereinafter described under caption Stopping all stations. This causes al1 the teletypewriters to stop, all lamps to be extinguished and all the apparatus to return to normal.

Start of operation Considering the station A63 (which typifies a station Whose call designation is 63) to be called, it will be noted rst that all relays are in their released positions except the relays |02 and |04. Relays |02 and |04 are polarized relays and are operated to their lower contacts by current iiowing over the line L. When another operator on the line dials the rst digit 6, the relays |02 andv|04 follow the dial pulses. During each open period of the line, relay 02 in following the pulses closes its upper contact, thereby completing a circuit through conductor 303, the upper winding of the bell ringing transformer 300, winding of relay 30 I, conductor 302, thereby causing relay 30| to become energized. Operation ofrelay30| closes the input circuit to a. type of rectier 304, such as referred to in U. S. Patent 1,867,638, granted to A. Weaver on July 19, 1932, and which will function to supply positive and negative potential to the apparatusat station A63. Positive potential is supplied to the station over conductor 305 and negative potential is supplied to the station A63 over conductor 306. Slow-to-release relay 3|0 operates from the output of the rectifier 304 in aV circuit extending from the positive terminal of the rectifier 304 through the winding of relay 3 I0, the right outer back contact of relay 308 to the negative terminal of rectier 304. Operation of the relay 3|0 closes a locking circuit for relay 30! in series with the upper winding of transformer 300. Relay 3|0 being of the slow-to-release type remains operated during the train of pulses and as long as the relay 308 is not operated, thereby keeping relay 30| locked in the operated position to insure the functioning of rectifier 304 during the reception of the train of pulses. Relay |04, during the openV period of the line, closes a circuit from conductor 305ithrough the upper contact of relay |04, conductor |06, the left back contact of relay |01, conductor |08, the winding of the rotary magnet ofV selector switch SE to the negative terminal of rectier 304. Closure of the upper contact of relay |04 also completes a circuit from positive potential on its armature to the right back contact of relay I5, conductor |09, winding of relay ||0, to negative potential on conductor 306. The rotary magnet 20| operates and steps the wipers. up one contact for each pulse. Relay ||0, however, being sloW-to-release remains operated during the train of pulses. When operated, relay ||0 applies a positive potential to the winding of relay and causes relay I to operate over a circuit extending from negative potential on conductor 300, winding of relay the right fro-nt contact of relay H0, the right back contact of relay I2, conductor ||3, the front contacts of off-normal springs 200 to the positive terminalof rectier 304. After the last pulse, the relay I0 releases and applies a positive potential from conductor 3 through the right back contact of relay 2, the right back contact of relay l I0, the left outer front contact of relay I I I, the right outer back contact of relay |0I to the wiper of arc 203 of the selector SE. At the last pulse, the wiper is on the sixth contact and, therefore, positive potential will be, applied to the Winding of relay |I4 and the circuit will be completed through the left back contact of relay |24, the right back contact of relay II'I to negative potential on conductors I I8 and 306. The relay I I4 operates and locks through a locking circuit closed over its right inner front contact to positive potential on conductor 305. The guard lamp 402 is lighted over a circuit extending from positive potential on the rectier 304 through the front contacts of the off-normal springs 200, filament of lamp 402 to negative potential on conductor 306, while the selector SE is olf-normal.

The operation of restoring the selector to no-rmal after dialing of the first digit is as follows: The slow-to-release relay |I0, upon releasing, removes positive potential from the Winding of slow-torelease relay III. When the relay III releases, it opens the circuit from positive potential to the first wiper and applies a positive potential from conductor II3, the right back contact of relay ||2, the right back contact of relay |I0, the left back contact of relay III, the left outer back contact of relay ||5, winding of release magnet 202 to negative potential on conductor 306. The release magnet 202 operates and the selector SE is restored to the normal position where the front contacts of the off-normal springs 200 open the energizing circuit for the release magnet 202 which is then deenergized.

When the second digit 3 is dialed, relays I I0 and III function as outlined above in describing the operation following the dialing of digit 6. The selector SE steps up to the third position and positive potential is to be applied to the Winding of relay I I6 over a circuit extending from positive potential on conductor I I3 through the right back contact of relay I|2, the right back contact of relay ||0, the left outer front contact of relay III, the right outer back contact of relay |01, the Wiper and the third bank terminal of arc 203, the right outer front contact of relay I I4, the winding of relay I I6, the left inner back contact of relay 308 to negative potential on conductor 306. Relay I I6 operates and locks to positive potential through its right inner front contact. The selector SE will be restored to normal in the same manner as described above in connection with dialing o-f the digit 6. The relay |I6 closes a circuit from negative potential o-n conductor 306 through the iilament of busy lamp 400, the right middle front contact of relay I I6 to positive potential on conductor 305. This causes busy lamp 400 to light. The auxiliary busy lamp 40| is connected in parallel with busy lamp 400 and is lighted over the same circuit. The closure of the left front contact of relay ||6 partly cornpletes a circuit to the audible signal 403 which will hereinafter further be described. Closure of the right outer front contact of relay ||6 partly establishes, a circuit to the power relay 50 I, which will also be hereinafter described.

When the digit 0 is dialed, relays I I0 and III will function as heretofore described when the digit 6 is dialed and a positive potential will be applied to the relays I0'I and ||1 in a circuit extending from conductor I|3 through the right back contact of relay |I2, the right back contact of relay H0, the left outer front contact of relay III, the right outer back contact of relay |01, the Wiper and tenth bank terminal of arc 203, the windings of relays |01 and I|1.connect ing in parallel, the left inner front contact of relayv I| I to negative potential on conductor 306. The relays |01 and I II are held operated through the left inner front contact of relay |01 supplying a positive potential from conductor 305. In operating, the relay |01 short-circuits the right middle front contact of relay |I6 which controls the busy lamps 400 and 40|. The rotary magnet 20| of the selector SE will be transferred from the upper contact of relay |04 to the left outer front contact of relay I0'I. The circuit through the left outer front contact of relay is transferred from the wiper of the first arc 203 to the wiper of the second arc 204 by the operation of the right outer transfer springs of relay I 01. The operation of relay III opens the holding circuit for relay ||4 at the right back contact of relay II'I and the relay II'I also short-circuits the pulsing contacts of the dial 404 over a circuit extending through the left outer front contact of relay II'I.

Relay 117 causes motor circuit to start Relay II'I, in operating, also completes a circuit to the audible alarm 403 from negative potential on conductor 306 through the winding of alarm 403, the left front contact of relay I I6, the right outer front contact of relay II'I, the left back contact of relay I2I to positive potential on conductor 305. Relay II'I also closes a circuit from negative potential on conductor 306 through the left inner front contact of relay II 1, the right outer front contact of relay H6, winding of power control relay 50| to positive potential on conductor 305. Operation of relay 50| closes the circuit from the source of alternating current supply 3 II to the teletypewriter motor 502 which operates and permits messages to be transmitted by operating the keys in the usual manner. The

audible alarm 403 may be stopped by operating l' the dial and release key 405 which causes relay |24 to'operate over a circuit established from positive potential on conductor 305, the right front contact of the dialand release key 405, winding of relay I2I, the left front contact of relay IIT to negative potential on conductor 306. Relay |2| locks tof positive potential through its right front contact from conductors 305 and |20. Opening the left back contact 0f relay |2| opens the circuit to the audible alarm 403.

Stopping all stations-Operation station sending the stop signal When it is desired to stop all stations and clear out all connections preparatory to making the next call, the stop key 406 is operated and held operated until the guard lamp 402 lights over the circuit established from negative potential on conductor 306, through the iilament of guard lamp 402, the right front contact of stop key 406, the right middle front contact of relay II6 to positive potential on conductor 305. When the stop key 406 is operated, a circuit is established for energizing the relay |25 from negative potential on conductor 306 through the left inner front contact of relay II'I, winding of relay |25, left front contact of stop key 406, the back contacts of off-normal springs 200 to positive potential on conductor 305. Relay |25 is energized and locks through its left front contact to positive potential on conductor 305, which is applied over conductor |20. Closure of the right front contact of relay |25 establishes a circuit from positive potential on conductor |20 to the winding of relay |I5, the left inner front contact of relay ||1 to negative potential on conductor 306. Relay I I5 is energized and locks through its right inner front contact to positive potential on conductor 305. Opening of the Vleft outer back contact of relay |I5 opens the circuit through the release magnet 202. Opening of the left inner back contact of relay |I5 opens the short circuit around the right back contact of relay I I I. Closure of the right outer front contact and opening of the right back contact of relay II5 transfers the circuit through the Winding of relays I|2 and IIO from the upper Contact of the relay |04 tothe left front contact of relay 22|. As the relay 22| is operated at this time, the relays I|2Yand IIO operate. When the stop key 406 is operated, `the line circuit is opened by the opening of the back contact of stop key 406 thereby permitting relays |02 and |04 to release.

Release of relay |02 performs no function at thisV Ytime as the alternating current supply is locked into the circuit by relay 30| which is held oper-V ated by relay 3|0 which in turn is held operated under control of the right back Contact of the relay l.308. When the relay |04 releases, the upper contact of relay |04 closes but performs no function at this time. The lower contact of relay |04 opens and permits relays |26 and 22| to become deenergized and release. Relay 22|, in releasing, opens its left front Contact and removes the positive potential from the windings of'relays ||2 and ||0 which relays now release. Release of relay 22| also closes a circuit from negative potential on conductor 306 through'the winding of rotary magnet 207|, the left outer front contact of relay |01, the left back contact of relay I2I torpositive potential on conductor |20.v The rotary magnet 20| is energized and takes'one step.

Operation'of stop key 400 establishes a circuit from positive potential on conductor |20 through the right middlefront contact of relay IIB, right front Contact of stop key 400, conductor II3, right front Contact of relay I I2, winding of relay III to negative potential on conductor 306. Relay III will operate and open the line circuit through its right back contact. The relays II2 and I I0 are slow to release and hold operated for a suilicient time to permit positive potential at the off-normal springs 200 to operate the relay III if the stop key 406 is operated only momen-V tarily. YThis same positive potential causes the Yguard lamp 402 to light in a circuit through the off-normal springs 200 as outlined heretofore. The lighting of the guard lamp 402 indicates that the stop key 400 may be released. The relay III will remain operated long enough to insure complete release of relay 22| and theoperation of rotary magnet 20|. When the relays I|2 and IIO release, relay III closes the Y line circuit through its right back contact thereby causing relays |04 and |02 to operate to their lower contacts and cause relays 22| and |26 to operate. By this sequence, the line has been opened for a period equal to the sum of the release times of relays |04, |26, 22|, II2 and III plus the operate tmeof relay I I5 at the originating station.Y Subsequent breaks in the line will not include the operate time of relay |I5. The closed period of the pulse is for the duration of the operating time of relays |04, 22|, ||2 and III at the originating station. In the following sequence, the relay |26 operates the relays II2 and IIl which again, in turn, operate the relay I I I, which again opens the line L and permits relay |04 to close its upper contact. The relay |04 releases the relays |26 and 22| and the relay 22| en'e'rgizes the rotary magnet 20| and steps the selector to the second bank terminals. This sequence of operations continues until the selector reaches the v fifth bank terminal to which relay `308'is connected. When the Wiper of the selector SE makes Contact with the fifth bankterminal of arc 204,the relays II2 and IIO release and establish an operating circuit for relay 308 from positive potential on conductor' II3 through theright back Contact of relay II2, the right back Contact of relay |I0, the left outer front contact of relay I II, the right 'outer front Contact of relay |01, the wiper and fifth terminal of arc 204, winding of relay 308 to negative potential on conductor' |I8 which connects to conductor,` 305. When the relay 308 operates, it opens the holding circuit through its left inner back contact to relay IIS which releases and opens the circuit to the power control relay which releases in turn and opens the circuit to the tele-V typewriter motor 502. The relay 308 also opens one side of the parallel holding circuit of relays |01 and I|1. When the slow-to-release relay III releases, it closes the signal line through its right back contact but opens the other side of the holding circuit which releases the relays |01 and |I1 which in turn cause the release of relays |25, II5 and 308, Relay ||I also prepares a cir cuit to the release magnet 202 of selector SE which is completed when the'left outer back contact of relay I5 is closed, thus operating the release magnet 202 and returning the selector to normal. The release of relay ||5 short-circuits the right back contacts of relay I I. The release of relay II5 also releases relay |25 and transfers the operating circuit for relays II2 andA |I0 to the upper contacts of relay |04. The relay 308 also opens the locking circuit through the Win-ding of relay 3I0, thereby permitting it to release androp-en the locking circuit for relay 30| which now releases. Release of relay 30| opens the alternating current supply circuit to the rectifier 304, thereby permitting all relays and the magnet 202 to become deenergized.` The entire selector circuit is now restored to normal and ready for the next call.

Calling in additional stations after communican tion has commenced relay |25 and thus when the selector wiper ofV the bank 204 reaches the third terminal, a circuit is closed through the relay IIS which causes that relay to operate. This circuit is from negative potential on conductor II8, through the Winding of relay II9, the left back Contact of relay |25, the third bank terminal and. the brush of are 204, the right outer front contact of relay |01, the left outer'front Contact of relay III, the right back contact of relayv IIO, the right back contact of relay II2 to positive potential on conductor II3, The relay II9, in operating, opens the holding circuit of the relays |01 and II1. When the relay II1 releases its left inner front contact opens and releases the relay II5 which prepares a circuit through the release magnet 202 from positive potential on conductor H3, the right back Contact of relay H2, Vthe right back contact of relay I I0, the left back con- 15`- tact of relay III, the left outer back contact of relay H5, winding of release magnet 202, conductor 301 to negative potential on conductor 300 so that, when relays ||2 and H0 release, the release magnet 202 operates and the selector SE returns to normal. When the relay |01 releases, as described hereinbefore, it transfers the circuit to the rotary magnet 20| from the contact of slow-to-release relay IIS to the upper contact of relay |04. This makes the circuit responsive to dial pulses so that additional stations may now be called in. When the nal digit is dialed, the teletypewriter motorsI at the additional stations as well as those originally called start and messages may be transmitted in the manner outlined heretofore. The audible signal 403 also is operated.

Operation at stations being stopped As the stop signal consists of opening and closing the signal line five consecutive times, the duration of the open pulse being determined by the sum of the release times of the relays |04, |28, 22|, II2 and III at the originating station and the closed pulse is determined by the sum of the operate times of the relays |04, 22|, H2 and III. When the signal line circuit at any station is opened by operation of the stop key 406, the operation at all the other stations connected to the circuit will be as follows: When the line circuit is opened the relay |04 releases and opens its lower contact, thereby opening the holding circuit for the relays 22| and |26` and closes its upper contact-thereby closing the circuit to the relays H2 and H0. When the relay I2! releases, it closes the circuit through .its left back contact and the left outer front contact of relay |01 to the winding of the rotary magnet 20| which energizes and steps the selector SE to the first bank terminal. The olf-normal contact springs 200 are then closed and establish a circuit from positive potential on conductor 305 through the front contacts of off-normal springs 200, conductor H3, the right front contact of relay H2, the winding of relay to negative potential on conductor 306 thereby causing relay III to become energized. When the signal line is again closed, the relay |04 operates to its lower contact and closes-the circuit for the operation of the relays |2| and |26 and opens the circuit through the windings of relays H2 and H0 as outlined heretofore. Relay H2 is of the slow release type and holds operated during the short closed period of the line. After this short closure, the line is again opened at Athe station sending the stop signal and the above sequence of operations is reproduced. After the last open pulse the line remains closed, thus allowing the relays I I2 and I I0 to release and open the holding circuit to relay I II. The relay III, being of the slow-torelease type, remains operated a short period of time after the relay II2 opens its circuit and thus provides a temporary path from positive potential at the selector off-normal contacts 200, through conductor I I3, the right back contact of relay H2, the right back contact of relay H0, the left outer front contact of relay I I I, the right outer front contact of relay |01, the wiper and fifth bank terminal of arc 204, winding of relay 308, conductor H8, to negative potential on conductor 306, thereby operating the relay 308. The relay 308 operates, releases the relay H6, and locks through its own right front contact and the left inner front contacts of relay |01 to posi- 'of relay `springs 200 to positive potential on conductor tive potential on conductor 305. Relay 308 opens the locking circuit for the relays |01 and H1 and holds operated only until the relay III releases and causes the release o-f the relay |01 which opens the locking circuit for relays |01, H1 and 308. The release of the relay H6 opens the circuit to the busy lamp 400 and also the circuit to the relay I2! and the relay 50| thereby stopping the teletypewriter motor. of relay 308 also opens its right back contact thereby opening the locking circuit for the relay 3| 0 which releases and opens the locking circuit for the relay 30|. Relay 30|, in releasing, disconnects the alternating current supply from the rectifier 304 and restores the selector circuit to normal ready for the next call.

Operation at other station in recalling In case the recall key 401 is operated, the operation of relays |04, |28, 22|, |I2, H0 and III is the same as for sending the stop signal. As the recall signal consists of only three pulses the selector wiper will be stepped to the third bank terminal to which the relay I I9 is connected when the relays II2 and H0 release. When the relays H2 and H0 release, the relay is slow to release and a circuit is closed from negative potential on conductor I I 8 through the winding of relay H9, the left back contact of relay |25, the third bank terminal and the brush of arc 204, the right outer front contact of relay |01, the left outer front contact of relay III, the right back contact of relay I0, the right back contact II2, conductor H3, the off-normal 305. The relay I I0 operates and unlocks and releases relays I01 and H1, thus rearranging the circuit so that additional stations may be dialed in upon the line. However, the stations already dialed remain connected.

Operation dt uncalled station If any code other than 63 is dialed by another station, the relay H0 at the Station A63 will not be operated which thus prevents operation of the audible signal 403 and the teletypewriter motor 502 when the 0 is dialed.

The digit l must be dialed betw-een individual station codes to clear out partial selections. After 1 is dialed, the relay |24 will operate and in turn release the relay I I4 at all stations, if it happens to be operated.

After dialing 0 the relays |01 and H1 will be operated at all stations. At all uncalled stations these relays will be released when a series of three or five pulses are transmitted as the result of the operation of the stop key 408 or the recall key 401 as hereinbefore described.

Operation at a calling station When the calling operator moves the dial 404 off normal, positive potential will be supplied to the relay H0 which operates and locks. When 0 is dialed, the relays |01 and I|1 operate and the relay I1 closes a circuit to the motor control relay 50| which starts the teletypewriter motor 302. When the dial and release key 405 is operated, a circuit will be closed from positive potential onk conductor 305 .through the left front contact of the dial and release key 405, the olfnormal contacts of the dial 404, winding of the relay I I6, the left inner back contact of relay 308, conductor I I8 to negative potential on conductor 300 thus causing relay IIB to operate. A circuit Operation winding of relay l2l, left inner front contact of relay Ill, conductor H8 to negative potential on conductor 305. Relay l2'l operates and opensV the circuit to the audible signal 403, thereby preventing the operation of this signal at the calling station.

Broadcasting ,When 901 is dialed, the relays H6 at all stations will operate because their windings are connected to the 9th contacts of the iirst bank of selectors. Thus, all stations may be dialed in for broadcasting by dialing one single code call.

Any number from 2 to 8, inclusive, may be used for the first digit of station codes. Y Any number from 2 to 8, inclusive, may be used for the second digit of theY station codes except the one which has been used for the first digit. The code to which the selector circuit of a station will respond is determined by segments to which the leads 205 and 206 are connected.

It will be noted that a very convenient party line teletypewriter circuit is provided by the system in which only desired stations are called in upon the line. Disconnection is accomplished by a single operation on the part of the operator and likewise a single operation suflices Yto prepare the circuit Vfor calling in additional stations without redialing those originally called.

. What is claimed is: Y

l.- In a signaling system, a combination of a normally closed transmission line, normally operated means in said transmission line, normally unoperated means .associated with said transmission line, otherA means for momentarily opening said line whereby Vsaid normally operated means is released, a source of alternating current, driving means and a normally open operating circuit therefor directly connected to said source, a plurality of electromagnetic elements connected to saidsource and arranged to be energized in response to the movement of the normally operated means to an unoperated position, a locking member for said electromagnetic elements, a device Y controlled by said electromagnetic elementsY for converting the current from said alternating current source to a direct current, said electromagnetic elementsrin their energized condition being arranged to maintain the continuous flow of direct currentfrom said current converting device and to thereby cause the operation oi said normally unoperated and said driving means, and manually operated switching means for causing the release of said locking member whereby the plurality of electromagnetic elements are deenergized, said current converting device ceases as a current supply and said driving means ceases to operate.

2. In a signaling system according to claim 1, wherein the normally unoperated means comprises an electromagnetic device controlled by said current converting device for maintaining the operating circuit for said driving means closed. until the manually operated switching means is operated.

3. In a signaling system, a transmission line, a station associated therewith, a source of alternating current at said station, normally unenergilzed means for rectifying the current from said source, means at said station responsive to a signal received over said transmission line to energize said normally unenergized means to thereby furnish rectified current, and other means at said station responsive to a special signal received over said transmission line to energize said normally unenergized means to thereby furnish rectified current.

4. In a signaling system, a transmission line, aV

plurality of stations associated therewith, a

source of alternating current at each of said stations, normally inert means for rectifying the current from said source, means at each of said stations and responsive to a signal received over said transmission line to render said normally inert means effective to' furnish rectified current, and other means at each of said stations and responsive to a special signal received over said transmission line to render said normally inert means ineffective to furnish'rectied current.

5. In a signaling system, a combination of a transmission line, a plurality of stations associated therewith, a selector switch at each of said stations,a source of alternating current at each of said stations, normally inert means for rectifying the current from said source,means at each of said stations responsive to a signal received over said transmission line to render said normally inert means effective to furnish rectified currents for preparing said selector switch for operation, other means at each of said stations responsive to special signal of different character received.V over said transmission line to permit said rectified currents to be used for operating to a predetermined position and for restoring to normal position, respectively, said selector switches.,

6. In a signaling system, a combination of a transmission circuit, a source of signals of varying character accessible to said transmission circuit, a plurality of stations associated with said circuit, a signaling device at each of said stations, a selector switch at each of said stations, a source of alternating current at each of said stations, normallyinert means for'rectifying the current from said source, meansin each of said stations responsive to a signal of one character received over said transmission line to render said normally inert means eii'ective to furnish rectied current for preparing said selector switch forV operation, and other means at each of said stations selectively responsiveV to a certain group of varying signals received from said signal source to connect the signaling device at a desired station with the signal device at the station originating the connection whereby said transmission circuit may be completed through said plurality of stations for signaling purposes between any two of said stations.

'7. In a signaling system, in accordance with claim 6, wherein said other means attwo or more stations comprise arrangements controlled by the rectified current from said normally inert means and selectively and respectively responsive to a plurality of groups of varying signals received from said signal source to connect the signal devices at said two or more stations with the signaling device at the station originating the connection whereby said transmission circuit may be completed through said plurality of stations for signaling purposes between three or more of said stations.

8. In a signaling system, a combination of a transmission line, a source of open and closed signals connected to said transmission line, a plurality of stations associated with said lines, each of said stations being associated with said lines over a plurality of paths, a signaling device at each of said stations, a selector switch at each of said stations, a source of alternating current at each of said stations, normally inert means for rectifying the current from said source, means in each of said stations responsive to an open signal received over said transmission line to render said normally inert means eiective to furnish rectied current for preparing said selector switch for operation, means at each of said stations selectively responsive to diierent groups of open and 10 closed signals received from said signal source for completing any desired path of said plurality of paths at one of said stations to select the signaling device at said one of said stations whereby said transmission line may be completed between the signaling device at said one of said stations and the selected signal device at another of said stations through said plurality of stations.

CUTHBERT C. LANE.

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