US2227121A

US2227121A - Printing telegraph system

Info

Publication number: US2227121A
Application number: US198633A
Authority: US
Inventors: William B Blanton
Original assignee: Western Union Telegraph Co
Current assignee: Western Union Telegraph Co
Priority date: 1938-03-29
Filing date: 1938-03-29
Publication date: 1940-12-31
Anticipated expiration: 1957-12-31

Description

3 Sheets-Sheet 1 1940- w. B. BLANTON I rmn'rme TELEGRAPH sYs'n-m 7 Filed larch 29, 1938 U 0 ul' l2 CALLI NG TRUNKS INVENTOR ORNEY W. B. BLAN TON v BYZAQar-OIN Patented Dec. 31, 1940 PATENT OFFICE PRINTING TELEGRAPH SY STEM William B. Blanton, Merrick, N. Y., assignor to The Western'Union Telegraph Company, New York, N. Y., a corporation of New York Application March 29, 1938, Serial N5. 198,633

22 Claims.

This invention relates to printing telegraph systems, and more particularly to multi-oflice systems embodying acentral station-and a plurality of branch ofllces or stations.

The primary object of the invention is to decrease the number of channels or circuits required between the branchoflicesand the main office or central station of a multi-ofilce system, or to increase the telegraph facilities between outlying branch omces and the central station or main oflice.

A telegraph system to which the invention is applicable would be one where a considerable number of branch ofilces or stations are located in a relatively small area remote from the central 1 station, or so located that the installation or maintenance of connecting circuits is diflicult or expensive, as for example where a group of branch stations are located on the opposite side of a river or a bay from the central station so that a connecting cable is required. In order to decrease the size of the cable required or to provide for increased facilities as the number of branch omces increases, in accordance with the 2 invention, switching means would be provided in connection with the signaling channels from the central station arranged to connect the signaling channels to a wanted branch station, or in the case of a call from a branch station, to connect the calling station to an idle one of the signalin channels to the central station. In. this manner a comparatively large number of branch stations may be operated over a small number of common signaling channels to the central station.

It is an object of the invention to provide a multi-ofilce telegraph system having a switching center for controlling the channels between therespective ofiices, which switching center may be remote from the central oilice and all or all but 'one, of the branch oflices. Since the printers in the printing telegraph system embodying the invention may be used by subscribers or patrons as well as in branch oflices of the telegraph company, the term branch office is intended to cover a subscriber's or patron's oifice.

Another object of the invention is to provide a multi-omce telegraph system having switching means for connecting the central oflice to a wanted branch oflice and vice versa in which some of the branch oflice lines are used only in calling from the central ofilce and others only in calling from branch ofllces.

Another object of the invention is to provide a multi-oillce system of the character described 55 adapted for central oflices having a concentrator for selectively connecting operators printers with calling and called branch omces and preferably a concentrator having terminals of direct lines to branch ofllces as well as terminals of branch oflices connected through the switching center. 7 Another object of the invention is to provide a multi-omce system of the above character having concentrator operators sets at the central oifice adapted to be connected either to direct branch-office lines or switching center channels and to provide certain guard features to prevent the operator from sending into switching center channels before connection-has been made to a remote branch office and for other purposes.

Another object of the invention is to provide a telegraph system having selector switches to connect to wanted lines, the switches being controlled by current impulses transmitted over the telegraph lines or circuits, and in which the operativeness of the telegraphv transmitter depends either upon the prior transmission of selective impulses for setting the selector switch or upon the connection to telegraph receiving apparatus.' This feature of the invention prevents an inadvertent attempt to transmit a message before the connection has been extended to the wanted line or oflice.

Other objects and advantages of the invention will appear from the following description of the system shown on the accompanying drawings wherein Fig. 1 is a schematic di-agramof the preferred embodiment of the invention, and

Figs. 2 and 3 are diagrammatic views of the detailed circuits of the system shown in Fig. 1.

Referring toFig. '1, a typical system embodying the invention comprises a central station or main office M, a plurality of branch oflices or patrons offices A and B connected by direct line circuits In and Ii to the main oflice, and other branch offices C, D, E and F adapted to be connected to the main ofiice through the switching center S and branch oflice channels or trunks l2 and Hi. It will be apparent that by the provision of selectively operable switches at the switching center S to control the connection of a callingor called branch office to the channels I! and [3, the number of such channels may be 50 considerably less' than the number of branch offices since the latter are not in continual operation. The invention is of particular value therefore where the installation or maintenance of the circuits i2 and I3 is difiicult or expensive, 5s

by the growth of the system in the proximity of the branch ofiices C, D, E and F, since the additional ofilces may be placed in service without the installation of additional trunk circuits to the main ofiice.

As shown, the trunk circuits l2 are employed in selecting a wanted branch oflice from the main or central station and are designated calling trunks, whereas the trunk circuits ii are accessible to calling branch oflices and are designated "answering trunks. The calling trunks l2 terminate at the switching center S in selectors s which are controlled from the central station or main oilice in order to connect a wanted branch office. 0n the other hand, when one of the branch omces C, D, E or F has a message to send to the central station, the branch oflice operator transmits a signal as by depressing a key of the printer keyboard whereupon one of the finder switches f at the switching center connects the branch ofllce to one of the answer trunks l3 to the main oflice or central station M.

After a connection is established between one of the branch oilices C, D, E or F, and the main oiiice M over either a calling trunk or an answering trimk, two-way communication may be had between the main and branch ofllces. On the other hand, if the main oflice places a call for a branch ofilce which is already connected to the main office or has initiated a call thereto, a busy signal is transmitted from the switching center .be employed to connect the operators printers Ii at the main omceto any calling or called branch oflice. As indicated, the concentrator switchboard may include terminals of both direct lines In and II- to branch omces and channels l2 and I3 to the switching center S. Certain of the operators printers at the main ofllce are provided with a calling dial l1 and a key or switch l8 whereby the printer may be connected to one of the calling trunks and impulses transmitted over the calling trunk for controlling the selector switches s. In accordance with another feature of the invention, the selection, control and intelligence signals, and in the case of an attempted call to a busy branch oflice, the busy signal, are transmitted over a single line conductor. In accordance with a still further feature of the invention provision is made whereby the operator's printer [6 will not function after actuating the key I8 if ,an attempt is made to transmit message signals over a calling trunk l2 before th. dial I! has been operated or a branch office has been connected by the associated selector switch S.

For abetter understanding of the present in-' vention, reference may be had to Figs. 2 and 3 illustrating the detailed circuits of the system ,shown in Fig. 1. IngFig. 2 is shown the operthrough the switching center, together with two oi the branch oflices A and 3 connected by direct line circuits to the main oflice M.

The apparatus at the main office M includes a concentrator or switchboard for connecting operators printers to the branch omce lines of the type disclosed in the patent to Drake and Blanton, No. 1,804,327 dated May 5, 1931. Reference may be had to said prior patent for a complete description of the main office equipment, certain features of which have been omitted for the sake of simplicity. In general, the concentrator comprises manual switching equipment such as plugs and jacks for connecting any printer to any branchoflice line to answer calls irombranch oflices and to originate calls to the branch offlces.

4 tion, the call lamp l9 being lighted when a call is initiated to the main oflice from a branch ofllce, as for example by the branch oihce operator momentarily interrupting the line circuit.

The line circuits are normally connected to positive battery at the main ofiice until an operator plugs in a printer to originate or answer a call,

whereupon the polarity of the line circuit is reversed.

The printer lishown in Fig. 2 is arranged to be used in connection with transmission to or from the branch ofllces A and B (Fig. 3) connected by the direct line circuits l0 and H to the main oflice M and also for transmission of messages through the switching center S to and from the remote branch oilices, such as C and D (Fig. 2). The calling trunk I2 shown in Fig. 2 is representative of the several calling trunks provided, the number of which depends upon the peak message load. Since each of the calling trunks is similar to the trunk l2, and the apparatus associated with each of the answering trunks I3 is also similar to that shown, a description of the operation of one calling trunk and one answering trunk will suflice.

Call from main oIfice to branch. ojfice A polarized relay 24 is connected in series relation with the calling trunk l2 to respond to current impulses for controlling the selector 8 transmitted over said trunk. The armature of said relay is provided with mechanical bias as shown, 'or with electrical bias tending to hold said armature against its right hand contact.

The armature of relay 2|, however, is held in engagement with its left hand contact by the current traversing the calling trunk l2 when idle and thereby energizes associated relay 25 during this period. The circuit of relay 24 may be traced from positive battery at the main office through the right hand break contacts of the key switch l8, conductor l2, the winding of relay 24, .the make-before-break contacts associated with the middle right hand armature ofrelay 26, resistance 21, the inner right hand armature and backcontact of relay 28 and a rectifier 29 to ground. The rectifier 29 is poled to pass the line current flowing when the trunk I2 is connected to posi tive battery at the main oflice.

when the operator atthe main oflice desires to initiate a call through theswitching center S to one of the branch offices, for example branch offlce D, the key or switch I8 is operated, it being assumed that the printer I6 is idle and the plug 2.2. associated therewith is removed from the of key IS, the above-described circuit of relay 24 is interrupted at the break contacts of said-key and a new circuit is established through'the right hand make contacts of 'saidke'y, the off-normal contacts of the dial H, the contacts and printer magnet of the printer l6 and resistance 2| to negative battery. As a result of the reversal of polarity, the flow of current in the conductor l2 and winding of relay 24 is decreased to a relatively small value by the rectifier 29 and the armature of relay 24 is actuated into engagement with its right hand contact by the retractile spring or bias of said relay;

Upon the release operation of relay 24 the circuit of relay 25 is broken and a circuit is closed through the right hand contact of relay 24 for energizing relay 3|, relays 25 and 3! being both 'of the slow-to-release type. The apparatus at the switching center is now in condition for operation in response to the transmission of selector impulses from the dial IT at the main office.

It will be noted that a different switching 0D- eration, l. e., operation of the key l8, precedes the dialing of a call through the switching center whereas in the'case of calls to the branch -oiiices 'A and B, the operator plugs the connection into a jack representing the wanted office. In the latter instance, the operator may commence transmission immediately or upon the. reception of GA (go ahead) from the branch ofiice. In order to prevent the operator from proceeding in this manner inadvertently inthe case of a call through the switching station, the line circuit is opened in efiect by the rectifier 29 until after the number of the wanted station has been dialed. The printer I6 is of the start-stop type, operating in response to rest and mark ng current impulses and start and spacing impulses of zero current. Thus the printer runs idle while the line current is zero and the operator cannot send until normal line current corresponding to the normal'rest condition is established.

Any suitable form of selector switch may be employed in the switching center. For the purpose of explaining the invention, a conventional two-motion step by-step selector switch is shown having an auxiliary minor switch 33'- controlled by a stepping magnet 34 and release magnet 35. The selector switch comprises vertical and rotary stepping magnets 36 and 31, respectively, and a release magnet 38adapted when energized to permit the restoration of the arms or wipers of the selector switch tonormal. The upper switch wiper 39 of the selector is adapted to extend the calling trunk I2 to the line extending to the called branch oflice and the lower wiper 40 of the selector is arranged to test the busy or idle condition of the called oilice to guard against the seizure of a busy line. The stationary contacts of the respective selector switches associated with the several calling trunks [2 are multipled together, and in case the called cfiice has already been selected by another operator or a call initiated from said office, the contacts engaged by the test wipers of the other selectors have ground potential thereon which serves to prevent the connection to the busy ofiice in a manner that will be described.

The operation of the selector in response to the actuation of the calling dial ll is as follows:

above, a circuit is closed through the armature when relay 25 becomes deenergized as described,

and back contact of saidrelay for energizing the stepping magnet 34 of the minor switch 33, whereupon the movable switch arm of said switch is stepped into engagement with the second contact thereof. When the operator dials the first digit of the wanted branch oflice D, the off-normal contacts of the dial are opened and the dial-v ing contacts are closed a number of times cor-' responding to the number dialed. The closure of the dialing contacts of the dial 11 connects positive battery to the calling trunk l2 which at this time is disconnected from negative battery by reason of the opening of the oil-normal contacts of said dial, each current impulse from the calling dial ll thus momentarily energizing the polar relay 24 and actuating the armature thereof momentarily into engagement 'with its left hand contact. Relay 25 thus becomes reenergized and again opens the circuit of the stepping magnet 34 of the minor switch. However, since relay 25 is a slow-to-release relay, its armature remains attracted during the series of impulses from the calling dial "and these impulses are reproduced by the armature of relay 24 through" a circuit including the left hand contact ofsaidrelay, the switch arm of the minor switch 33 and the-vertical magnet 36 of the selector switch-f so that the wipers of said switch are actuated a number of steps corresponding to a number 'of impulses dialed by the operator. At the end of the first series of impulses the slow-to-rclease relay 25 becomes deenergized, reclosing the circuit of stepping magnet to step the wiper of the minor switch 33 to the-third contact thereof. Slow-to-release relay 3|, however, remains sufliciently energized to maintain its armature attracted during thev entire dialing operation.

Theoperator now dials the second digit of the number of the called office, whereupon the above operations are repeated except that the selective impulses are diverted through the minor switch 33 to the rotary magnet 31 of the selector switch. In this manner the wipers 39 and of the selector switch are actuated into engagement with the terminals corresponding to wanted oflice D. At the end of the second series of impulses slow-to-release relay 25 again becomes deener-' gized and again closes the contact of the stepping magnet 34 of the minor switch, whereupon the wiper thereof is actuated into engagement with its fourthcontact.

Upon the operation of the minor switch as dc-, scribed, a circuit is closed from positive battery through the winding of relay 25, the minor switch 33 and the winding of relay 28 to ground, whereupon relays 25 and 28 become energized.

Assuming that the wanted branch office is idle,

comes energized and relay 28 is sufiiciently energized to close its inner' right hand armatur and preliminary make contact, whereupon the resistance 43 isshunted by the last-mentioned contact and a much larger current flows through the circuit. This increased flow of current causes relay 28 to become fully'oper'ated whereupon the calling trunk I2 is connected through the middle right hand armature of relay 26, the wiper 39 of the selector 3 to the line 66 extending to the called branch oflice D. Likewise the relay 26, at

its left hand armature and front contact closes a shunt circuit through the rectifier 44 around the winding of polar relay 24. The rectifier 44 is poled so as to oppose the how of current through this shunt circuit when positive potential is applied to the trunk l2 at the main omce, but to offer a relatively low-resistance shunt path around the winding of relay 24 under normal transmitting conditions when negative potential is supplied at the main office. The purpose of this rectifier is to improve the transmission characteristics of the trunk circuit by removing the inductance of the winding of relay 24 from the circuit, while at the same time not to interfere with the signaling and control functions of the system.

The line circuit 60 extending to the branch oflice D is normally connected through the makebefore-break contacts associated with the left hand armature of relay 55, the winding of relay 56 and resistance 51 to positive battery. Relay 56 is thus normally energized, its circuit further including the contacts and printer magnet of the printer 6|, the winding of polar relay62 and resistance 63. When a connection is made as described above to the line circuit 60 through one of the selector switches and relay 55 becomes energized as described above, relay 56 is maintained energized through the left hand armature and make contact of relay 55 to prevent initiating a false call to the apparatus'associated with the answering trunks l3. The connection to positive battery through resistance 51, relay 56 and polar relay 62 maintains the contacts of the polar relay 62 open. However, when negative battery is applied through the selector switch 3 to the line circuit 60 from the main omce, the contacts of polar relay 62 are engaged and light the "call lamp 65. In response to the call the branch office operator closes the switch 66 shunting out the inductance of the polar relay 62, the switch being arranged if desired to start the motor of the printer 6|. Alternatively, the driving motor of the printer if not running continuously may be started by the operation of relay 62. The operator at the branch oflice Dnow sends GA (go ahead) whereupon the main offlce operator is apprised of the fact that the branch omce has answered and transmission proceeds in the usual manner. Since the contacts and operating magnets of the printers l6 and 6| are in series, twoway communication may be had over the trunk v|2 and branch ofllce line 60.

At the end of the exchange of business, the main ofllce operator restores the key l6 thereby disconnecting the trunk circuit l2 from the printer and connecting the same to positive battery through the right hand break contacts of the key. The reversal of the current in the line circuit as the result of the reversal of the polarity of the battery connected thereto at the main office causes the armature of polar relay 24 to move against itsleft handcontact thereby interrupting the circuit of relay 3|. Relay 3| becomes deenergized and closes through its armature and back contact, and the off-normal contacts 4| and 42 of the selector switch and minor switch, respectively, circuits for energizing the release magnets 38 and 25 of said switches, whereup n the switches are restored to normal. When the wipers of the selector and minor switches are restored to their normal positions,

; switch I as will be described hereinafter.

the off-normal contacts 4| and 42 are opened. 2

The restoration of the minor switch 33 also interrupts the above-described circuit of relay 28 whereupon this relay becomes deenergized and interrupts the circuit of relays 26 and 55 through its left hand armature and front contact. The circuit of relay 55 is also interrupted by the restoration of the test wiper 40 of the selector switch to normal. Relays 26 and 55 are thus deenergized so that all equipment and circuits at the main ofllce and the switching center are restored to normal in readiness for use in establishing another connection.

Upon the deenergization of relay 55, the branch office line circuit 60 is reconnected through the make-before-break contacts associated with the left hand armature of said relay to the positive battery at 'the relay 56. The polar relay 62 at branch oflice D is thus operated in such a manthe selector switch s connected the calling trunk |2 to the terminals of said branch oifice. If the branch ofllce D had been busy, the lower bank contact engaged by the test wiper 40 would have been at or near ground potential. In the case of a previous call initiated from the main oflice through one of the other selectors s, the test bank contact would have been grounded through the left hand armature of a relay corresponding to relay 28 and the winding and right hand inner armature and front contact of the relay corresponding to relay 26. In the case of a previous call initiated from the branch oflice D, the bank contact'would have been grounded at the finder The bank contact may also 'be grounded by the busying key 5| in case a branch oflice circuit is to be disconnected from service during testing or repairs being efl'ected on the branch omce circuit.

When the selector switch ,3 is operated to connect to the branch office D when the latter is busy, the ground potential on the test contact which is connected through the test wiper 40 and the left hand armature and front contact of relay 28 to the test relay 26 does not operate relay 26-since this relay is also connected to ground through the resistance 43. Relay 26 thus does not become energized in case an attempt is made to connect to a busy branch office and therefore the calling trunk I2 is not connected through the middle right hand armature and front contact of said relay to the switch wiper 39, but remains connected through the make-before-break contacts associated with said relay, the resistance 21, the right hand inner armature and front contact of relay 28 to the busy signal transmitter having interrupter contacts 46 connected to the front contact associated with the inner right hand armature of relay 28. The transmitting device 45 may be a motor driven commutator arranged to send signaling impulses of any desired character to the printer IE to indicate that the desired branch office or patro'ns office is busy.. The transmitter may be running continually or started if desired upon the closure of a circuit through the outer right hand armature and front contact of relay 28 and the outer right hand armature and back contact of relay 21 as shown.

- Thus, if an attempt is made to connect to a bu y branch oflice, the connection is not effected but the calling operator is signaled that the branch office dialed is busy. v

If the operator restores the key I8, the switching center equipment is restored to normal in the same manner as in the case of a completed call described. However, if the operator does notrestore the key I8 but waits until the wanted branch ofiice is idle, the connection will be automatically effected between the calling trunk I2 and the branch ofiice when the latter becomes idle. The idle'condition of the branch office will be indicated by the removal of ground potential from the lower bank contact associated with the test wiper40 whereupon test relay 26 will be energized in series relation with the relay 55 as described above in the case of a call to an idle branch ofiice. The energization of relay 26 .will interrupt the busy signaling circuit from the busy signal transmitter 45 and will connect the calling trunk I2 through the switch wiper 39 to the called, branch ofilce. Subsequent operations of the system will be the same as described above in connection with a completed call to an idle line.

Call initiated from a branch ofllce Assuming that the driving motor of the printer at the branch ofiice D is running continually or hasbeen started by the operation of a conventional manual starting switch, the branch office operator initiates a call to the main omce by pressing any key on the printer, thereby momentarily opening the line circuit 60 entending to the switching center and interrupting. the

current through series relay 56. As explained above, relay 56 is normally energized when the of printer 6|, the winding of relay 62and resistance 63'to ground at the branch oflice. When relay 56 becomes deenergized as described above, a short-circuit around the winding of said.

relay is closed through the left hand armature andback contact of relay 55. Thus relay 66 remains deenergized until the circuit has been restored and the short-circuit opened by the operation of relay 55. 7 Upon thedeenergization of relay 56 as described, a start circuit is closed from ground through the right hand armature and back contact of said relay, the right hand; break contacts of the key the break contacts of the trunk busying key I05, Fig. 3, the fourth right hand armature and backcont'act of relay I06 and the winding of relay I01 tobattery whereuponrelay I01 becomes energized. --The respective finder switches f are each associated with individual answering trunks I3 to the main oflice and the foregoing description assumes that the first findrelay 56 would be transferred from the fourth right handarmature and back contact .of relay I06 to the front contact associated with said armature through the break contacts of busying key 205 to the control equipment associated with 20I, 202, and 203 and the stepping magnet 204. A plurality of finder switches are thus provided, one for each answering trunk, suflicient to take care of the maximumnumber of simultaneous calls from the group of branch offices C, D, etc. Upon the operation of-relay I01 as described above, the left hand armature of said relay opens the circuit including thetrunk I3 to the main oflice to initiate a call to said ofl'ice. As shown, the trunk J 3 is connected through the winding of polar relay I I0, the make-before-break contacts associated with the inner left hand armature of relay I06, resistance III and the left hand armature and back contact of relay I01, to ground.

The trunk I3 terminates at. the main ofiic'e in signaling and control equipment of any suitable character. equipment comprises relays 15, I6 and I1, arranged to control the call and busy lamps I9 and 20, together with interrupter contacts I9 arranged as shown in the above mentioned prior patent to Drake and Blanton. The trunk circuit is normally connected through the makebefore-break contacts associated with the middle As shown in Fig. 2, the control.

armature of relay 15, the winding of relay 'lland the resistance 18 to positive battery. The I I described circuit normally maintains relay I1 energized and because of the connection to posiat the switching center to maintain, the a'rma:

ture thereof in engagement with its left hand contact.

Upon the momentary interruption of the trunk circuit as described, relay 11 becomes .deenergized and closes through its right hand armature back contact of relay 11 a short circuit around its own winding so that the relay remains deenergized upon the reclosure-of the line circuit.

The deenergization of relay 11 also closes through its left hand armature,..and back con and back contact and the upper armature and tact the circuit of.call lamp I9, whereupon this lamp becomes lighted to indicate'to the, op-

erator that ,a call has been received on the trunk I3 from a remote branch oflice.

When the operator plugs aprinter such-as the through the lower Winding of. relay I6 to-the corresponding jack I5, the plug 22, the left hand break contacts of the key- I8, the contacts and printer magnet of the printer I6 and resistance 2| tonegative battery, whereupon the polarity I5 and the lower interrupter contact 19 a lockcircuit for said'relay including the upper in" terrupter contact 19. Theoperators printer's, the 'main office is now connected to the callinj circuit, but before this connection has been mad a .finder, switch I 'hasoperatedto connect calling branch office' to this main oifice" line: cuitin a manner whichwill now be described The bank contacts associated with-the printer I6 intolthe jack I 5-associated with the trunk'circuit I3, the trunk circuit H3 is extended tive battery operates the series polar relay IIO 3 E ing circuit for relay I6 and-an-operating circuit 9 forrelay' I5. The energization of relay I5 at its .middle armature and front contact opens the above describedcircuit of relay 11," and closes.

the circuit for operating -the busy"- lamp '20..- The energization' of relay I5 further closes at its lower armature and front contact a locking .v

mally grounded by the relays 56 associated with the respective branch 'ofiice circuits. When, however, a call is initiated from. one of the branch ofiices as described above, ground potential is removed by relay 56 from the bank contact in each of the finder switches, corresponding to the calling branch office. Upon the operation of relay I01, as described above, a circuit is closed from positive battery to the stepping magnet of the first idle finder switch, for example, the stepping magnet I04 of the first finder switch and the interrupter contacts thereof, the outer right hand armature and front contact of relay I0I, the third right hand armature .and back contact of relay I00, wiper IM to ground potential, assuming that the wiper IOI is not already in, engagement with the bank contact corresponding to the calling branch oiiice. In response to the energization of stepping magnet I04, the switch wipers IOI, I02 and I03 are stepped until the wiper IOI reaches the ungrounded contact individual to the calling office, at which time the stepping magnet I04 becomes deenergized and the switch wipers remain in engagement with the bank contacts associated with the callingoflice.

Upon the energization of relay I01 as described above, a circuit is also closed from positive battery through the stepping magnet I04 of the finder switch, the outer right hand armature and front contact of relay I101, the inner right hand armature and front contact of said relay and the winding of relay I06 to ground. However, as long as wiper IOI of the finder switch is stepping over grounded contacts the winding of relay I06 is short circuited and the relay is not energized. However, as soon as the wiper 'IOI reaches the contact associated with the calling branch oifice which is not grounded, relay I00 becomes energized. The outer right hand armature and the front contact of relay I00 are adjusted to engage before any of the other contacts of said relay are made or broken and a circuit is thus closed from battery through the winding of relay I01, the outer right handarmature and front contact of relay I00, the. inner right hand armature and back contact of relay] I0 and the left hand armatureand front contact of relay I01 whereby the latter relay is maintained energized in spite of the fact that this original circuit is broken at the fourth right hand arinature and back contact of relay I00. The energization of relay I00 through its fourth right hand armature and front contact. transfers the start circuit through the busying key I06 to the control equipment associated with the second-finder switch through the break contacts of the second busying key 205. Hence the second I finder switch will be started to hunt for the next branch office that initiates a call through the switching center to the main ofiice M. This connection will be established in .the same manner as describedabove in connection with the call initiated in the branch ofllce D through the first finder switch. The energization of relay-I00 also change of business between the respective omces,

' the operator at the main omce will disconnect her .cord circuit by withdrawing the plug from the interrupts at its third right hand armature and back contact the above described circuit between thewiper m of the finder switch and the step- I L'ping magnet I04, and at the front contact associated with said armature connects ground potenf tiple with which said wiper isengaged is grounded tial to the wiper I" so that the bank contact mul and will not be selected by another finder switch.

The energization of relay through its second right hand armature and front contact, and the wiper I02 of the finder switch I00 also grounds.

' of the selector switches S at the switching center to cause a busy signal to be transmitted to the main office if the main ofllceoperator attempts to call the branch ofiice D .which has initiated a call to the main ofiice.

The inner right handarmature and front contact of relay I00 closes the circuit of busy lamp I09 which may be disposed adjacent the trunk busy key I06 to prevent a repairman from cutting the trunk control equipment out of service by operating said key when the trunk is in use.

The energization of relay I06 further closes through its inner left hand armature and front contact, a circuit for extending the main ofllce trunk I3 through the winding of marginal relay Hi, the wiper I03 of the finder switch and its.

' above, closes a circuit from ground through the armature of relay 0, the right hand contact thereof, and left hand outer armature and front contact of relay I06, the armature and back contact of relay H5 and the winding of relay II6 to battery, whereupon relay IIO becomes energized. The energization of relay IIO closes a shunt circuit through the left hand armature and front contact thereof and the rectifier II6 around the winding of polar relay H0. The purpose of this shunt circuit around thewinding of the polar relay-which is in series relation with the transmission circuit, is the same as the corresponding circuit described above in connection with the polar relay 24. However, relay 1 I0 is not biased, and the armature thereof remains in engagement with either contact when the current through its operating winding is made and broken so long as the polarity of the currentis not reversed.

The outer right hand armature and front con- I tact of relay IIO are adjusted to close before any .ofthe other contacts of said relay are closed or broken. A circuit is thus closed initially from the winding of relay I00 through the outer right hand armature and front contact of relay I I0 and the winding of stepping. magnet I04 for holding relay I00 energized. However, the current nowin: in this circuit on account of the resistance of the winding of relay I00 is not sufiicient to energize the stepping magnet I04. Upon the energization of relay II6 as described, the circuit of relay I0I.is interrupted at the right hand inner armature and back contact'of relay IIO, whereupon the relay I0'I becomes deenergized.

The printers I0 and 0I at the main office and branch office, respectively, are now interconnected for two-way communication through the wiper m ofthe finder switch 1. After the exjack I6, whereupon positive battery is again connected to the answering trunk I0 upon the dewergization of relays 16 and I0 and the apparatus at the switching center S and main ofllce M is restored to normal. Likewise the branch office operator may operate the marginal relay III by closing the key 01, to release the finder switch I00 and restore the apparatus at-the switching center the armature of polar relay III] to be actuated 1 into engagement with its left hand contact, thereby opening at the right hand contact of said relay the energizing circuit of release relay 6. Relay IIB becomes deenergized and opens at its outer right hand armature and front contact the energizing circuit of.relay I96, whereupon said relay becomes deenergized.

The deenergization of relay I05 at its fourth right hand armature transfers the start circuit back to the winding of relay III'I so that the first finder switch will respond to the next call initiated from-on of the branch oilices. Likewise, the restoration of the second right hand armature of said relay removes ground potential from the wiper I02 of the finder switch, from the winding of relay 55 and from the test contacts in the test banks of the selector switches s. Thus the branch oifice line will no longer test busy if an attempt is made to connect thereto from one of the calling trunks I2. Relay 55 becomes deenergized and opens at its 'left hand armature and front contact the circuit of relay 56, but said relay remains energized through the make-beforebreak contacts associated with theleft hand armature of relay 55 in series relation with the printer SI and relay 62 at the branch ofiice D.

The switching equipment at the switching center is thus restored to normal when the operator at the main ofiice disconnects the printer I6 from the answering trunk I3. The disconnection of the printer I6 as described also disconnects the negative battery at the printer from the operating winding of relay I6 and upon the opening of the lower interrupted contact I9 relay I6 becomes deremains energized through the make-beforebreak contacts associated with said armature in series relation with the answering trunk I3 and the winding of relay H0 at the switching center. In this manner, the control equipment associated with the concentrator at the main oiiice is also restored to normal when the operator withdraws the plug 22 from the Jack l5 as described above.

If the branch ofiice operator closes the key 61 before the main operator restores the switching equipment at the switching center to normal; the marginal relay II5 in series relation with the line circuit is operated by the increased line current when the resistance 63 is short-circuited. Upon the energization of relay H5 the circuit of release relay H5 is broken at the armature and back contact of relay H5 whereupon the control quipment at the switching center associated with the finder switch I is restored to normal in the same manner as described above in connection with the release of the'equipment from the main oflice. Thus the branch office is released from the connection and made available for a call from another operator at the main oflice even if the operator who has been connected with the branch oflice fails to disconnect the main ofiice Printer promptly from the branch oflice line circuit.

In the-case of calls to or from the branch offices A and B the operation of the system is essentially the same except that the main ofiice operator plugs one of the printers I5 into a jack I5 individual to the wanted branch ofilce A or B and, therefore,-does not dial the number of the wanted oflice as in the case of a call to the branch oflices connected through the switching center s. The line circuits In and II extending to the .branch oflices A and B terminate at the main oflice in control equipment associated with the concentrator and designated by the reference characters I20 and IZI, each of which is similar to the control equipment shown in Fig. 2 asso- I21. At the end of the exchangeof business, the

main oflice control equipment is restored to normal as described above in connection with the apparatus associated with the trunk I 3.

In order to initiate a call from one of the branch offices A or B, the branch ofiice operator momentarily interrupts the line circuit as by pressing any key on the printer keyboard. The

interruption of the line current initiates a call to the concentrator and lights the call lamp I9 in the same manner d'secribed above in connection with the initiation of a call over the answering trunk I3. When the main oflice operator plugs the printer I6 into the jack associated with the lighted call lamp I9, the printer magnets and contacts of the printers I 6 and I25 are in series relation so that two-way communication can'be carried on over the line circuit.

The foregoing detailed description of a system embodying the invention is merely for the purpose of explaining the invention. The system shown and described above may be modified in various ways without departing from the scope of the invention. v

I claim:

1. A printing telegraph system comprising a central-station, a plurality of branch stations,

printing telegraph equipment of the current-impulse type at said stations, a plurality of signaling channels terminating at said central station, switching means remote from the central station and responsive to current impulses for connecting certain of said channels to any of said branch stations, means including the connected ones of said channels for controlling said switching means from the central station wherebetween calling branch stations and the central station.

2. A printing telegraph system comprising a central station, a plurality of branch stations,.

printing telegraph equipment at said stations, an

intermediate switching station, signaling channels between said switching station and each of the other stations, switching means at the switching station for connecting central station channels to branch station channels, means for transmitting controlling impulses over a central station signaling channel to operate said switching means to connect a branch station channel to said central station channel, means for controlling said switching means from a calling branch station to connect the channel extending to said branch station to an idle central station signal-' ing channel and means operative after such connections have been completed at the intermediate telegrap over the same channels employed for setting up the connection.

3. A printing telegraph system comprising a central station, a plurality of branch stations, printing telegraph equipment at said stations, a plurality of signaling channels terminating at said central station and common to each of said branch stations, means for impressing a potential of one polarity upon a signaling channel to seize the same switching means for extending said channels to the branch stations and means at the central station to control said switching means to select a wanted branch station, said last mentioned means including means for impressing controlling impulses of opposite polarity upon the seized channel.

4. -A printing telegraph system comprising a central station, a plurality of branch stations,

. printing telegraph equipment at said stations, a

plurality of signaling channels terminating at,

said central station and common to each of said branch stations, switching means for extending said channels to the'branch stations and means including said printing telegraph equipment at the branchstations to control said switching means to connect a calling branch station to an idle channel to the central station.

5. A printing telegraph system comprising a central station, a plurality of branch stations remote from said central station, printing telegraph equipment at said stations, a switching station common to said branch stations and remote from said central station and switching means at said switching station for connecting said central station and any of said branch stations, said switching means including a polarized impulse relay responsive to impulses transmitted from the central station.

6. A "printing telegraph systemcomprising a central station, a plurality of branch stations remote from said central station, printing telegraph equipment at said stations, a switching station common to said branch stations and remote from said central station, switching means at said switching station for connecting said central station and any of said branch stations, and means for controlling said switching means from either said central station or said branch stations depending upon the origin of a call, said means for controlling the switching means from the central station including a polarized impulse relay arranged torespond to impulses of opposite polarity from the normal line polarity.

7. A printing telegraph system comprising a central station, a plurality of branch stations, a plurality of trunks or channels terminating at said central station, a source of signaling current of one polarity, means for connecting the same to said trunks or channels, switching means associated with said trunks or channels and remote from said central station and means for disconnecting said source of current from the line and for transmitting current impulses of ation for operating the printing ment at the connected stations any of said branch stations througlisaitiitrunks orchannels.

plurality of trunks or channels terminatingat said central station, selective switchingi'means associatedwith said channels, means including said switching means for interconnecting said central station and any one of said branch's'ta'f g tions, said means including impulse transmittin means at the central station for transmitting impulses over said channels, and means for rendering a printer at the central station inoperative upon initiating a callfrom said last mentioned station until after said impulse-transmitting means has been operated to control the selective switching means.

9. A printing telegraph system comprising a central station, a plurality of branch stations, a plurality of trunks or channels terminating at said central station, selective switching means at the other terminals of said trunks or channels for extending said trunks or channels to any of the branch stations, impulse-transmitting means at the central station for controlling said switching means, printing telegraph equipment at said central station and branch stations, and means for rendering said trunks or channels initially inoperative for the transmission of printer signals and operative only after a predetermined operation of the selective switching means.

10. A printing telegraph system comprising a plurality of stations, a plurality of trunks or channels between said stations, printing telegraph equipment at said stations, selective switching means controlled over said trunks-or channels for interconnecting said stations for operation, means for controlling said switching means over said trunks or channels and means for preventing the transmission of printer signals over said trunks or channels prior to the transmission of impulses for controlling said switchwinding of said relay after the operation of the selective switching means.

12. A printing telegraphsystem comprising a central station; a plurality ofbranch stations, a plurality of trunks or channels terminatingzat said central station, selective switching equip- 'ment associated with each of said channels remote from said central station for connecting any of said channels with any of said branch stations and means for controlling said switching equipment from said centralstation, said means including an impulsing device utilizing a potential having a polarity opposite to that employed for normal printer operation;

13.-A printing telegraph system comprising a central station, a plurality of branch stations, a plurality of trunks or channels terminating at said central station, printing telegraph equipment at said stations, selective switching equipment associated with each of said channels re- ,mote from said central station, means for impressing a normal line condition upon any of said channels, means for impressing av second line condition upon said channels for communication purposes, and means for controlling said switching equipment, said last named means including an impulse transmitter arranged to reverse said llne conditions and periodically interrupt said normal line condition.

14. A printing telegraph system comprising a central station, a plurality of branch stations, a plurality of trunks or channels terminating at said central station, selective switching equipment associated with each of said channels remote from said central station, means for impressing upon said channels different line conditions comprising a positive potential, a negative potential and a zero potential, means for controlling said switching equipment from said central station, said switching equipment including a relay, and means for rendering said relay responsive to only one of said line conditions.

15. A printing telegraph system comprising a plurality of stations, selective switching equipment for interconnecting said stations, a plurality of trunks or channels terminating at one of said stations, mains for controlling the operation of said switching equipment from said one station, said means including any of said channels, means for effecting printer communication over any of said signaling channels, means for releasing said switching equipment from said one station, said means including said signaling channel and means for utilizing said signaling channel to provide an indication at said one station of the busy condition at one of said branch stations to which connection has been attempted. 16, A printing telegraph system comprising a central station, a plurality of branch stations, a plurality oi trunks or channels terminating at said central station, switching equipment associated with each of said channels remote from said central station, and means including printing telegraph equipment at each of said branch stations for controlling said switching equipment from any of said branch stations to connect a calling branch station to said central'station.

17. A printing telegraph system comprising a central station, a plurality oi. branch stations remote from said central station, a plurality of trunks or channels terminating at said central station, selective switching equipment associated with said channels for extending any one thereof to any or said remote branch stations, a plurality of branch stations having direct connection with said central station, printing telegraph equipment at each of said stations, and means for connecting the printing telegraph equipment of said central station alternatively for communication with any or said branch stations.

18. A printing telegraph system comprising a central station, a plurality of branch stations, a plurality of trunks or channels terminating at said central station, selective switching equipment associated with each of said channels remote from said central station, said equipment including means responsive to a reversal oi the normal trunk polarity i'or 'directively controlling and releasing said equipment, and printer means responsive to interruptions oi the normal trunk polarity for communicating between the central station and the connected branch station.

19. A printing telegraph system comprising a plurality of stations including a central station and branch stations remote therefrom, a plurality of trunks or channels terminating at said central station, selective switching equipment remote from said central station for extending any of said channels to any of said remote branch stations, means for controlling said switching equipment from any of said stations, a plurality of other branch stations adjacent said central station, a-plurality of individual trunks or channels directly connecting said adjacent branch stations with said central station, printing telegraph equipment at all of said stations, and means for grouping-all of said channels at the central station to afford the telegraph equipment of said central station access to the telegraph equipment of direct-connected branch stations and the branch stations connected through said switching equipment.

20. In a printing telegraph system, a transmitting circuit, printing telegraph equipment for transmitting and receiving printer signals over said circuit, a selector switch tor extending said circuit to any desired one of a series of terminals,

- means for impressing signaling current of one polarity on said circuit and means for impressing controlling impulses of opposite polarity upon said circuit for stepping and releasing said selector switch whereby the transmission of printer signals does not effect the operation of the selector switch.

21. In a printing telegraph system, printing telegraph equipment, a line circuit, selective switching means associated with said line circuit for connecting the same to any desired one of a series of terminals, said selective switching means including a polarized relay connected to the line circuit, means including the printing telegraph equipment for impressing printer sigmale of one polarity upon the line circuit, means for impressing controlling impulses oi opposite polarity upon the line circuit and means including said polarized relay responsive to said impulses of opposite polarity for controlling the selective switching means.

22. In a printing telegraph system, a plurality oi oflices, printing telegraph equipment at said oflices, a line circuit extending from one or said ofllces, a' selector switch associated with said circuit having a plurality of bank contacts and a movable switch member for engaging the same, means including said selector switch for initiating a call over said line circuit from said one 01' said ofiices to the printing telegraph equipment at a selected one of the other offlces, means for controlling said selector switch including means for impressing controlling impulses 01' one polarity on said circuit to control the stepping of said switch by said impulses transmitted over the line circuit and means for impressing code signalling impulses of opposite polarity on said circuit for effecting signalling, said selector switch being responsive solely to said impulses oi the first-mentioned polarity.

WILLIAM B. BLANTON.

mscLmMER 2,227,121.Willtam B. Blanton, Merrick, N. Y. PRINTING TELEGRAPH SYSTEM. Patent dated December 31, 1940. Disclaimer-filed July 3, 1943, by the assignee, The Western Union Telegraph Company.

Hereby enters this disclaimer to

claims

1, 2, 3, 4, 5, 6, 7, 11, 1

of the patent,

Y [Official Gazette August 8, 1.948.]

3, 15, 16, and 1s