US1479250A

US1479250A - Automatic telephone system

Info

Publication number: US1479250A
Application number: US428224A
Authority: US
Inventors: Winfred T Powell
Original assignee: Stromberg Carlson Telephone
Current assignee: Stromberg Carlson Telephone Manufacturing Co
Priority date: 1920-12-04
Filing date: 1920-12-04
Publication date: 1924-01-01
Anticipated expiration: 1941-01-01

Description

W. T. POWELL AUTOMATIC TELEPHONE SYSTEM Jan, 11 y 1924 1,4792%) Filed Dec. 4,

1920 Sheets-Sheet BRHDGE :00 GROUP.

TERPUHAT\ 3006mm? LINE swrrcH see LINE 5WITCH #510 INVENTOR WINFRED T. POWELL.

sv pgzyg ATTOR NEY Jan, 19

4, 1920 3 Sheets-Sheet 5 Filed Dec.

QDOMG 00m MMDEUW MMPW UMM MOL 10.57am JOWFCLOU INVENTOR WIHFRED T. POWELL ATTORNEY Patented Jan. 11,. W24.

il llit llhtl UNHTED STATES- FATENTTDFWEEG WINFRED T. POWELL, OF ROCHESTER, NEW YORK, ASSIGNOR TO THE STROMB- 1 SON TELEPHONE MANUFACTURING COMPANY, OF EH T, YORK,

AUTOMLATIC TELEPHONE SYSTEM.

Application filed December l, 1920. serial 1%. 4%,224.

To all whom it may concern:

Be it known that I, Wmrnno T. PownLL,

a citizen of the United States, residing at Rochester,, in the county of Monroe and 5 State of New York, have invented certain new and useful Improvements in Automatic Telephone Systems, of which the following is a full, clear, concise, and exact description.

The present invention relates to telephone systems and more particularly to telephone systems employing automatic switches in establishing telephone connections between subscribers.

The main feature of this invention is the arrangement of the circuits by which a telephone connection is completed between two subscribers extending through non-numerical switches only.

A further feature of this inventionis the arrangement for testing the calling andwanted lines.

Other features will appear from the detailed description and claims.

The drawings, with Figure 1 placed at the left of Figure 2 and with Figure 3 placed below these last two mentioned figures, diagrammatically represents a portion of a telephone system including the present invention. In Figure 1 that portion of the drawing appearing at the upper left-hand corner of the sheet represents the sub-station circuits and telephone line which will be referred to as the calling line.

I Associated with this line there is represented a line switch of the advance to normal type. At the lower left-hand corner of Figure 1 there appears the sub-station circuits and telephone line of a second euloscriber which circuit will be referred to in this description as the called line. This line is similarly provided with a line switch. At the upper right-hand corner of Figure 1 there appears a portion of the circuits employed in a telephone connection which are referred to as the talking bridge and at the lower right-hand corner there is represented a rotary switch designated a terminating allotter. At the upper left-hand corner of Figure 2 there is represented a portion of the talking bridge, previously referred to, as well as a two-motion switch for locating a desired bridge. At the lefthand side of Figure 2 there is also represented a rotary switch herein referred to as an originating allotter, while at the upper right-hand corner of Figure 2 there appears a group of ten multi-contact relays each of which is provided with ten sets of contacts and at the lower right-hand corner of Figure 2 and bounded b heavy lines is represented a register sen er including a hundreds register, a tens register and a units register. Tn Figure 3 there is represented a so-called control switch which serves to complete circuits in proper sequence. Within the dotted rectangle of Figure 3 there appears a so-called double interrupter which is common to the exchange and at the upper right-hand corner of this figure there is shown a second interrupting device also common to the ex change.

The structure of the line switch used in this system is of the type disclosed in the patent to Clement $1,107,153 patented August 11, 1914, but the brushes of each switch are arranged to be advanced to normal when not in use. Three types of circuits terminate in each line switch; the first circuits lead to register senders and the second type of circuits are link circuits that are employed by a line when it originates a call; the third type of circuit terminating in each line'switch and referred to as a bridge is employed by a line switch when its individual line is called. The numher of each of these sender circuits, talking links and talking bridges will depend upon the traflic existing in the system. The terminating or bridge allotter as well as the originating or link allotter is likewise of the type of switch disclosed in mentioned patent to Clement and one of each of these allottcrs is assigned for the individual use of each group of telephone lines. Any type of multi-contact relay may he employed wherein each relay is provided with ten sets of contacts. A set of these multi-contact relays is provided for the use of each group of lines. A register sender provided with a hundreds, a tens and a units register each of the mentioned rotary type is employed and a controller switch, similar in structure to the previously mentioned switches, is provided for cash register sender.

The

tit)

lit-3 bridge finder may be of any well known ty e of two-motion switch which is provided with a set of group contacts.

This invention is not limited to the number of lines or to the arrangement of these lines, but, for convenience in understanding the same, it has been assumed that the system is arranged to give servlce 1Q00 lines and that these lmes are arbitrarily divided into groups of 100 lines each, Each telephone line is provided with an individual rotar line switch which is provided with 26 xed contacts of which one set of contacts is the normal position of the switch, while five other sets of contacts serve as terminals for circuits leading to five sets of re ister senders, it being un derstood that five sets of register senders are provided for each group of 100 lines. Of the remaining 20 sets of contacts 1n the line switch, ten sets serve as terminals for ten talkin bridges and ten sets serve as terminals or ten link circuits each of which are provided for the common use of the lines of a group. Likewise there is provided for each group of 100 lines a terminating allotter switch, an originating allotter switch and a group of ten multi-contact relays, 1n the contacts of which a test circuit for each telephone line terminates.

Briefly the operation of the system 18 as follows:

On the origination of a call, the line switch of the callin line hunts for an idle register sender and t en the idle register sender is operated from the dial switch of the calling line, in accordance with the designation of the wanted line. -'lhe line switch of the called line is next set in motion to hunt for a previously allotted bridge and the bridge finder connects a previously allotted link circuit to the allotted talking bridge. At this time the calling line switch is released from the sender and immediately proceeds to locate the allotted link circuit. The register sender which has just been used is now released for use with a succeeding call.

' It is believed that the operation of the system will best be understood by describing the method of extending a telephone connection from the subscribers line, designated #366, to a called subscribers line, whose designation is #370. When the calling subscriber at sub-station #366 removes his receiver from its switch hook, the line relay 5 is energized in a circuit extended from grounded battery, righ-hand winding of this relay, continuit spring and contact 6 of the cut-0E relay through the lower side of the line and substation circuits over the upper side of the line, continuity springncraaeo magnet 9 advances the brushes of the line switch one step which operation 0 ens the normallyclosed contacts of the 0 -normal switch and thereby interrups the initial operating circuit of the motor ma net 9, but a second operating circuit for t is ma et is immediately closed from ground, win ing of this magnet, through the contacts 11 of the ofi-normal switch, lower inner armature and back contact of the cut-ofi' relay 7, armature and back contact of the motor magnet 9, resistance to the grounded battery. Under the control of this last mentioned circuit the motor magnet of the line switch advances its brushes until an idle register sender is located at which time a circuit is closed from grounded battery, resistance, back contact and armature of the motor magnet 9, left-hand winding, front contact and armature of the line relay 5, upper winding of the cut-off relay 7, left-hand armature and back contact of the relay 12, sender test brush 13, conductor 14, ofi-normal contact 15 of the units register, off-non mal contact of the tens register and ofi-normal contact 170 of the hundreds register, each of which ofi'-normal contacts are closed in case the registers of a sender are idle, conductor 16 to the normally closed contact 17 of the controller switch, to ground. This last described circuit shunts the motor magnet 9 but causes the operation of the cut-off relay 7, which relay on operation extends the calling line through its upper armatures and continuity springs 6 and 8 to the brushes 18 and 19 of the line switch. A lockingcircuit is also completed at this time for the cut-0E relay by its operation which circuit extends from ground, winding of the motor magnet 9, contacts 11 of the oil-normal switch, inner lower armature, front contact and lower winding of the cut-off relay 7 and in multiple therewith a circuit including the left-handwinding of the slow releasing relay 12, holding brush 20 of the line switch, conductor 21, continuity spring and contact of relay 22, resistance to grounded battery. 7

The mentioned shunting circuit of the motormagnet 9 of the line switch extends through the left-hand winding of the line relay 5, so that, even though the line circuit is disconnected from the line relay by the operation of the cut-off relay 7, neither the line relay nor the cut-0d relay will release before the mentioned holding circuit for the reraaeo cut-E relay is established. At the time when the cut-off relay 7 operated, it opened at its lowermost armature and back contact the test circuit including conductor 23 for the calling line so that this line cannot be disturbed while it is in use, and, when the cut-0E relay attracted its upper armatures, it disconnected the battery bridge including the right-hand winding of the line relay 5 from .the calling subscribers line, con

nected the line switch brushes 18 and 19 to the calling subscribers line, thus completing an operating circuit over conductors 24 and 25 including both windings of the impulse rela 26 of the register sender. Relay 26 is t us energized and at its armature and front contact closes a circuit through the upper Winding of relay 27 which relay prevents the release of the register sender during the period when the impulse relay 26 is vibrating its armatures in response to dlrective im ulses.

At this point it may be well to indicate the purpose of the double interrupter shown in the dotted rectangle at the center of Figure 3. This so-called double interrupter is preferably in the form of a constantly rotating shaft provided with cams represented by discs 28 and 29 which are arranged to connect brushes 30 and 231 in circuit in predetermined intervals. These interrupters cooperate with relay 27, as will be pointed out, to prevent the release of the registers until the proper time and also co-operate with the relay 31 which is known as the change-over relay to separate the series of hundreds, tens p and units impulses so that these impulses are transmitted to the proper register. The detailed operation of these relays with the double interrupter will appear 1n the course of this description.

As soon as the relay 27 attracts its armatures, a circuit is closed from ground, winding of the motor magnet 32 of the control switch of Figure 3, back contact and armature of this magnet, inner armature and back contact of relay 33, brush 34 of the control switch in its first position, lowermost front contact and armature of relay 27, conductor 35, resistance to grounded battery. Motor magnet 32 is operated and interrupts its own circuit to advance the brushes of the control switch into their second position. The circuits are now in condition for the impulses corresponding to the first digit of the wanted number and the subscriber at sub-station #366 operates his dial switch to send three impulses corresponding to the hundreds digit of the wanted number. In response to these three impulses the impulse relay 26 vibrates its armature three times and on the first retraction of its armature, a circuit is closed from ground through upper winding of the change-over relay 31, brush 36 of the control switch which Is now. in its second position, conductor 37. winding of the motor magnet 38 of the hundreds register to grounded battery. The closure of this circuit causes the motor magnet 38 to advance its

brushes

39,40, 41, 42 and 43 one step. Relay 31 is operated in this circuit and closes a locking circuit which is from grounded battery, its lower winding, front contact and armature to ground through the brush 30 of the interrupter, provided the interrupter is at a certain point of its cycle of rotation.

The adjustment of cams 28 and 29 is such that they will measure off an interval of time greater than the intervalbetween two successive impulses of a series, before the circuit through brush 231 is closed.

On the first energization of the changeover relay 31, the motor magnet 32 is again energized over a circuit now traceable from ground, through its winding, back contact and armature, back contact and armature of relay 33, control brush 34 in its second position, lowermost armature and front contact of relay 31, conductor 35, resistance to grounded battery. The motor magnet 32 thus advances the control switch brushes into their third position but the operating circuit for the hundreds register is still maintained through the control switch brush 36 which is connected to conductor 37 in positions 2 and 3. The remaining impulses corresponding to the first digit of the wanted number are effective to operate the motor magnet 38 of the hundreds register to cause this register to advance its brushes into their third osition.

At the close of this series of impulses the impulse relay 26 attracts its armature for a relatively long interval thereby interrupting the operating circuit extending through the upper winding of the change-over relay 31. however; if brush 30 is in contact with the cam 28, the locking circuit through the lower winding of the change-over re la 31 will be maintained, during which perio the change-over relay 31 will hold its armatures attracted and at its middle armature and back contact holds open the circuit which is effective to advance the control switch into a succeeding position. If, however, the circuit at brush 30 is open and the relay 31 is deenergized, the circuit-for advancing the control switch into position four, although closed at the middle armature of the changeover relay 31, will be open at brush 231 for a predetermined period after the deenergization of the change-over relay which period is greater than that between two successive impulses of a series. However, after the double interrupter has measured an interval of time which indicates that the first series of impulses is terminated, a circuit is closed from grounded battery, resistance, cam '29 and brush 23L middle armature and back contact of relay 31, brush 34 in its third position, back contact and armature of rela 33, armature, back contact and Winding 0 the motor magnet 32 to ground. This circuit operates to advance the control switch brushes into their fourth position in which position the sender is in readiness to receive the impulses corresponding to the second digit of the wanted number.

The calling subscriber again operates his dial switch which this time transmits seven impulses andjthe impulse relay again v1- brates its armature to repeat impulses to the tens register. The first of these impulses is repeated over the circuit traceable from ground, armature and back contact of the impulse relay 26, upper winding of the change-over relay 31, brush 36 in its fourth position, conductor 44, winding of the motor magnet 45 of the tens register to grounded battery. On the energization of the changeover relay 31 the control switch is advanced to position five by a circuit completed from ground, winding, back contact and armature of the motor magnet 32, armature and back contact of relay 33, brush 34 in its fourth position, lowermost front contact and armature of relay 31, conductor 35, resistance to grounded battery. The remaining impulses ofthis series are transmitted through the brush 36 in its fifth position, over conductor 44 and the remainder of the circuit previously described. In response to each of the impulses repeated by the impulse relay 26 over this operating circuit, the motor magnet 45 advances the brushes 46 to 55, inclusive, of the tens register into their seventh position.

After the last of this series of impulses, relay 26 will hold its armature attracted and in due time the relay 31 willretract its armatures and thereafter when cam 29 is engaged by brush 231 the previousl described circuit extended from grounde battery resistance, cam 29, brush 231, middle armature and back contact of relay 31,

brush 34 in its fifth position, back contact and armature of relay 33, winding of motor magnet 32 to round, to move the control switch into posltion six. The sender is now in condition to receive the last or units series of impulses corresponding to the wanted number. The calling subscriber again operates his dial switch this time to transmit ten impulses to the impulse relay 26. The first of this series of impulses is repeated to the motor magnet 57 of the units register of Figure 2, over a circuit completed from ground, armature and back contact of the impulse relay, upper winding of the changeover relay 31, brush 36 in' its sixth position, conductor 56, winding of the motor magnet 57 to grounded battery. This circuit causes the motor magnet 57 to advance the register brushes 57 to 66 inclusive one step.

The change-over relay 31 is energized in this I.

neraaeo circuit and again completes the circuit for the motor magnet 32 through its lowermost armature and front contact to advance the control switch into its seventh position. The remaining impulses of this last series are repeated over brush 36 in its seventh position and conductor 56 to the motor magnet 57 of the units register. The impulses thus repeated are efi'ective to place the brushes of the units register onto their tenth set of contacts. When the change-over relay 31 has retracted its armatures and when the brush 231 engages the cam 29 of the double interrupter the motor magnet 32 is operated over the circuit previously described through brush 34 in its seventh position, to move the control switch into position 8. A circuit is thereupon completed from grounded battery, right-hand winding of relay 67, conductor 68, brush 34 in its eighth position, armature and back contact of relay 33, armature, back contact and winding of the motor magnet 32 to ground. Relay 67 attracts its armatures and completes a looking. circuit for itself from ground, its lefthand winding, front contact and armature, brush 187 in its positions 8, 9 and 10, conductor 35, resistance, to grounded battery. Relay 67, however, is locked operated while the control switch brushes are in positions 8, 9 and 10 but as long as the relay 67 is operated, it closes a circuit for advancing the control switch, which circuit extends from ground, winding of the motor magnet 32, its armature and back contact, conductor 69, inner right-hand front contact and armature of relay 67, conductor 35, to grounded battery. The control switch is thus operated until its brushes arrive in position 11 at which time the relay 67 deenergizes and opens the circuit just described for the motor magnet 32.

While thecontrol switch is passing through positions 9 and 10, a circuit. is closed from ground at the armature and back contact of relay 70 of Figure 1, conductor 71, lower armature and back contact of relay 72, back contact and armature 'of relay 73, conductor 74, brush 75, conductor 76, lowermost back contact and armature of relay 33, right-hand winding of relay 77, conductor 78, hundreds register brush 40, conductor 79, armature and back contact of relay 70, back contact and armature of relay 80, conductor 81, inner back contact and armature of relay 72, resistance to grounded battery. Relay 77 is energized in this circuit and closes a locking circuit for itself extending from ground, its inner armature, front contact and winding, conductor 282, brush 36 in any of its positons from 8 to 20 inclusive, conductor 35 and resistance to grounded battery. At the right-hand armature and contact, a circuit is closed from grounded battery through the resistance and conductor menace 83, control switch bra in positions 10 to 20 inclusive, back contact and armature o relay 33, armature, back contact and winding of motor magnet 32 to ground, to advance the. control switch into position 21. The operation of relay 77 also closes a circuit from battery, resistance, conductor 83, ri ht-hand armature and front contact of re ay 77, conductor 84, lower winding 01E relay 82 to ground. Relay 77 on operating also closes a circuit from ground, its armature and front contact, conductor 85, hun= dreds register brush 43 in its third position, brush 48 of the tens register in its seventh position, windin of t e #7 group relay erein designate 86, conductor 87, ri hthand winding of relay 7 0, to grounded attery Relays 86 and 7 0 are thus operated in series and the operation of relay serves to open the main test circuit so that no other relay similar to 7 7 can be operated until the connection under consideration is established. Relay 77 on operation also closes another circuit from ground, its left-hand armature and from contact, conductor 88, right-hand winding of relay 89, conductor 90, hundreds register brush 42 in its third position, units register brush 59 in its tenth position, conductor 91, outermost armature and contact of relay 86, conductor 92, lowermost armature and back contact of the cutofi relay 93 of the called line, continuity contact 94 and spring of relay 95, righthand winding of this relay, continuity spring and contact 96 of the cut-0d relay, conductor 97, right-hand winding of line relay 98 of the called line to grounded battery. The relay 89 of Figure 3 and the relays 95 and 98 of the called line are energized in this series circuit and attract their armatures. The operation of relay 95 closes a locking circuit for itself extending from grounded battery, right-hand windin of relay 98, conductor 97, contact 96 an continuity spring of the cut-ofi' relay 93 right-hand winding, continuity spring and armature of relay 95, armature and front contact of line relay- 98, conductor 105, winding of relay 106 to ground. Relays 95 and 98 are thus held operated independent of the test circuit extending over conductor 92, while the relay 106 is operated for a purpose to be described. The left-hand armature of relay 95 is actuated at this time to render the sender test brush 103 inefiective and connects the test brush 102 to the cut-ofi relay, so that at this time the line switch of vthe called line will not seize an idle reer sender but instead will hunt for an allotted talking bridge circuit. As soon as the line relay 98 is operated, it closes a circuit for the motor magnet 107 of the called line switch, this circuit extending from ground, winding of this magnet, the oil-normal spring and contact of this E il line switch, armature, front, contact and f left-hand winding of line relay 98, armature and back contact of motor magnet 107 and resistance, to grounded battery. This circuit is effective to advance the line switch one step whereupon a substitute operatin circuit is closed for the motor magnet 10 which may be traced from ound, its windll'ilfg, through the now close contacts of the 0 -normal switch, conductor 108, inner armature and back contact of the cut-0d relay 93, armature and back contact of motor magnet 107 and resistance, to grounded battery.

As soon as the relay 89 is operated, it closes a circuit from grounded battery (shown at the upper left-hand corner of Figure 3), resistance, upper armature and back contact of relay 33, conductor 208,1efthand armature, front contact and winding of relay 89, conductor 109, hundreds register brush 39 in its third position, conductor 110, winding of relay 111, terminating allotter brush 112, right-hand back contact and armature of relay 113 to ground. Relay 111 operates in this circuit.

The motor magnet 107 continues to advance the brushes of the called line switch until test brush 102 encounters the test contact 114 of allotted bridge, at which time a circuit is closed from grounded battery, resistance, back contact and armature of the motor magnet 107, left-hand winding, front contact and armature of line relay 98, upper winding of the cut-off relay 93, armature and front contact of the relay 95, test brush 102, test contact 114, conductor 115, terminating allotter brush 116, front contact and armature of relay 111 toground.

As long as the called line switch is opcrating, relay 106 will be maintained operated over conductor and the contacts of line rela 98 and rela 95. With rela 106 operate a circuit is c osed from groun right-hand armature and front contact of this relay, left-hand windin of the relay 70, terminating allotter brus 120, winding of slow releasing relay 121 to grounded battery. The relay 70 is maintained energized in this circuit and the relay 121 attracts its armatures and at its left-hand armature and front contact closes a circuit from ground, winding of the slow releasing relay 122, resistance to grounded battery to o crate the relay 122 and thereby close a brea point in the holding conductor 123 of the allotted bridge. As soon as the cut-off relay 93 of the called line operates because its test brush 102 has located the allotted bridge, the cutofi relay is locked operated in a circuit closed from ground, winding of the motor magnet 107, oil-normal switch, conductor 108, inner lower armature, front contact and lower winding of relay 93, line switch holding brush 104, holding contact 124 of the allotted bridge, conductor 123, front contact and armature of relay 122, winding of relay 113 to grounded battery.

Also when the cut-ofi rela 93 operates,

the conductors of the calle line are extended to the

brushes

100 and 101 of its switch so that when the ringing relay 125 is operated signalling current Will be applied to the called line as will be described. The

1 ringing relay 125 is energized in a circuit traceable from the grounded battery,

through the resistance and back contact and armature of relay 126, winding of relay 125, ri ht-hand front contact and armature of 1 re ay 113 to ground. With relay 125 0perated, interrupted si allin current from the ringing generator 1s applied through the right-hand winding of t e trip relay 127, ri ht-hand front contact and armature of re ay 125, conductor 128, bridge contact 129, throu h the line switch brush 101 and lower side 0 the line and the bell at the called substation over the upper side of the called line, line switch brush 100, bridge contact 130, conductor 131, resistance, left-hand armature and front contact of relay 125, front contact and armature of relay 113, to ground. As soon as relay 113-operated, it opened the circuit of relay 111 of the terminating al- 80 lotter and also the circuit of relay 89 which it will be remembered have been operated from the time when the main test circuit was completed. With the relays 89 and 77 of Fig. 3 deenergized, the circuit through the 8 lower winding of relay 82 is opene but, since it is slow to release its armatures, a substitute holding circuit is completed throu h its upper winding, as will be later descri ed. With the rela 89 deenergized and with relay 82 operated and the control switch of Fig. 3 in position 21, a circuit is closed to energize relay 22, which operation is 'efi'ective to start the bridge finder of Fig. 2 into operation and release the line switch of the calling line from the register sender with which it has been associated, but holds this register sender o erated, until the calling line switch and t e bridge finder have completed the connection. The operating circuit of relay 22 extends from 'the ounded battery, resistance, armature and ack contact of rela 33, conductor 208, lefthand armature an back contact of relay 89, inner, lower front contact and armature of relay 82, conductor 133, winding of relay 22, brush 34, in its 21st position, back contact and armature of relay 33, armature, back contact and winding of the motor magnet 32 to ground. The relay 22 at its continuity spring and contact opens the holding circuit for the calling line switch which extended throu h conductor 21. An energizing circuit is also closed for the impulse rela 26 extendingfrom ground, right-hand win ing of this relay, armature aeraaao and continuity spring of relay 22, resistance to grounded battery. With relay 26 operated, the release of the register sender is prevented.

When the holding circuit of the calling line switch is opened, the cut-off relay 7 deenergizes but the slow releasing relay 12 will be held operated and the cut-off relay 7 remains deenergized to reconnectthe line relay bridge to the line causing this line relay 5 to energize. With relay 7 inert and relays 5 and 12 operated, the calling line switch Will start to hunt for a stopping ground potential which will be found at the brush 134 of the originating allotter switch which is individual to the 300 group of lines. This ground potential indicates the idle link circuit which has been allotted for use and therefore, when the calling line switch is stopped, it will be in engagement with the terminals corresponding to an idle link circuit in the calling 300 group. As long as the calling line switch is advancing, the relay 106 is operated so that a circuit is now closed from grounded battery, resistance, lowermost armature and back contact of relay 111, armature and front contact of relay 106, conductor 208, upper armature, contact and upper winding of relay '82, conductor 209, brush 41 of the hundreds register, conductor 211, winding of relay 148 to ground. The bridge finder of the allotted link circuit will be started by a circuit extending from grounded battery, resistance (shown in the left-hand corner of Fig. 3) armature and front contact of relav 22, conductor 135, originating allotter brush 136, contact 137 of the primary elf-normal switch, winding of relay 138 to ground. This circuit causes relay 138 to attract its armatures and it closes an operating circuit for the primary motor magnet 139 of the bridge finder, continuity contact and spring relay 140, righthand armature and continuity spring of relay 138, lower back contact and armature of relay 141 to grounded battery. Under the control of this circuit, the primary motor magnet 139 advances its

brushes

142, 143, 144 and 145 in a group selecting movementuntil the group brush 146 of the bridge finder encounters group contact 147 at which point, ground is extended from the upper armature and front contact of relay 148, conductor 149, group contact 147, group brush 146, winding of relay 140, continuity contact and spring of relay 140, armature and continuity spring of relay 138, back contact and armature of relay 141 to grounded battery. This last described circuit is effective to shunt the motor magnet 139 and therefore stop it and also energize relay 140 which closes a locking circuit for itself from ground through its left-hand winding, inner armature and continuity spring, armature and continuity spring of relay 138, back conaeraaeo tact and armature of relay 141, to grounded battery. With the relay 140 operated, the operating circuit of the primary motor magnet 139 is opened and the operating circuit of the secondary motor magnet 150 is closed from ground, winding of this magnet, its armature and back contact, inner armature and continuity spring of relay 140, armature and continuity sprlng of relay 138, backcontact'and armature of relay 141 to grounded battery. Under the control of this circuit the secondary motor magnet 150 advances the brushes 142 to 145, inclusive, over the terminals of the bridges of the selected group.

When the proper bridge in the 300 group is reached, a circuit is closed from ground through the left-hand winding of relay 140 its armature and front contact, winding of relay 155, test brush 145 of the brid e finder switch, conductor 156, brush 157 o the terminating allotter to ground. Under the control of this circuit the relay 140 is maintained operated, while the secondary motor magnet 150 is stopped and relay 155 is energized to close a holding circuit for the cut-off relay 7 and relay 12 of Fig. 1 and to complete an energizing circuit for the cut-through relay 141 of Fig. 2. This last mentioned circuit may be traced from ground, winding of the motor magnet 9, contacts 11 of the gifnormal switch, lower armature, front contact and lower winding of the'cut-ofi' relay 7 and in multiple therewith the left-hand winding of relay 12, holding brush 20,- link contact 161, conductor 162, winding of relay 141, armature and front contact of relay 155, bridge finder switch brush 144, conductor 159, front contact and armature of relay 121, winding of relay 160 to grounded battery.

Relays

160 and 141 are energized in this circuit and relay 158 is energized in multiple therewith in the circuit extending over'conductor 162. As soon as relay 141 operates, it extends the calling line to the calling end of the selected bridge and at its lower armature and back contact opens the circuit which has been maintaining the relay 138 operated. At the lower armature and front contact of relay 141 battery is supplied through conductor 163 so that the motor magnet 164 is operated through the originating allotter brush 165 to move the brushes of this allotter to an idle link which condition is indicated when the test brush 165 of this allotter no longer engage-s test contacts having a battery potential. As soon as the relay 138 deenergizes, it opens the holding circuit of the relay 82 of Fig. 3 and since the relay 106 deenergizes as soon as the calling line switch has located the allotted link circuit, all the holding circuits for the relay 82 are now open and this relay releases. At this time the relays 148 and of Fig. 1 and relay 72 of Fig. 2 will be rethrough its lower winding, provide leased to permit the closure of the main testing circuit in connection with other uncompleted' calls. The release of relay 82 opens the circuit which has been maintaining the relay 22 operated and the deenergization of relay 22 causes the impulse relay 26 to retract its armature and in turn open the energizing circuit through the upper winding of the release relay 27 of the register sender which has just been in use. Thereafter the relay 27 Will be maintained ener ized cl the brush 30 is in engagement with the raised portion of the cam 28 of the double interrupter. When the brush 231 engages the raised ortion of cam 29, after the release relay has been deenergized, a circuit is closed from rounded battery, cam 29, brush 231 mi dle armature and back contact of relay 27, continuity contact, spring and winding of rela 33, the normally opened contact 167 o the control switch. This energizes relay 33 thereby closing a lock circuit for itself from ground through contact 167, Winding of relay 33, its continuity spring and upper armature, resistance to grounded battery. At the lower armature and continuity spring of relay 33 an operating circuit is closed for the motor magnet 32 of the control switch which advances this switch into position 1, thereby opening the contact 167 to efiect the release of relay 33. The restoration of the control switch closes contact 17 and completes circuits for restoring the hundreds, tens and units registers of the register sender which has just been in use. This circuit extends from ground,vthro-ugh contact 17, conductor 16, through the normally opened contacts of the off-normal switch, back contact, armature and winding of the motor magnet 38 of the hundreds register to grounded battery. Under the control of this circuit the motor magnet advances its brushes to normal position whereupon contact 169 is opened to prevent further operation of the motor magnet 38 and the release circuit extending over conductor 16 is now completed through contact 170 and through the normally opened contacts of'the off-normal switch, back contact, armature and winding of the motor magnet 45 of the tens register, to grounded battery.

Similarly when the tens register has advanced to normal, the operating circuit of its motor magnet is interrupted and the release circuit is extended to the motor magnet 57 of the units register, which thereupon operates to restore the brushes of this register to normal position.

At the time when the calling line was extended to the calling end of the selected bridge by means of the switch brushes 142 and 143 of Fig. 2 the relay 171 is operated and through its armature and front contact closes a holding circuit for the slow releasing relay 121. The operation of relay'160 closes an operating clrcuit for the motor magnet 172 of the terminating allotter and brush 173 of the switch as lon as the allotter is testing talkin bridges t at are in use. The relay 174 is a so operated in'a circuit completed at the right-hand front wntact and armature of relay 160 to ground. The purpose of relay 174 is to prevent the terminating allotter from being advanced, if the called party should have answered before the calling switches have been stopped. It has been pointed out how the terminating allotter is advanced under the control of its motor magnet 172 when the relay 160 is energized. It should also be noted that a branch of this circuit is controlled at front contacts of the rela 174 to prevent the improper operation 0 the terminating allotter as "ust mentioned.

hen the called party answers, the trip relay 127 is operated in the well known manner and at its right-hand armature and front contact closes a short circuit! about the relay 125 which causes this last named relay to deenergize. As soon as this takes place, the slow releasing trip rela 127 is locked energized through its leftand winding, front contact and armature, left-hand back contact and armature of relay 125, front contact and armature of relay 113 to ground. Also when the ringing relay 125 deenergizes, it connects the called line to the windings of relay 126 and energizes this relay which thereupon completes the maintaining circuit for the relay 122 independent of the slow releasing relay 121. The relay 126 upon operation also closes a lock circuit for the relay 174 and extends a bus potential to the allotter test contact 182 of t e talking bridge that is now in use. This mentioned circuit insures that the bridge will be held unselectable if the called party hangs up last.

The telephone connection is now completed and talking battery for the calling line is supplied through windings of relay 171 and talking battery for the called line is supplied through the windings of relay 126.

The release of the established connection is efiected by placing the receivers on the switch books. When the calling party re-- places his receiver on its switch hook, the battery feed relay 171 deenergizes and in turn effects the deenergization of the slow release relay 121 and as soon as relay 121 retracts its' armatures, it opensthe holding circuit including conductor 159 by which the cut-through relay 141, the cut-ofi relay 7 and the relay 12 have been maintained energized. These last named relays thereupon retract their armatures and a circuit is then closed from ground, winding of the motor magnet 9, ofi-normal contact 11, inner armature and back contact of cut-ofl relay 7, armaintense ture and back contact of motor, ma net 9,

resistance to grounded battery. Un er the control of this operating circuit the motor 'magnet advances the brushes of the calling opened and the switch is stopped. When the cut-through relay 141 deenergized, it

closed a release circuit for the bridge finder switch completed from grounded battery, armature and back contact of relay 141, continuity spring and contact of relay 138, winding of release magnet 215 and primary ofi-normal switch to ground. Similarly when the called party replaces his receiver on its switch hook, the battery feed relay 126 deenergizes and thereby efiects the demoergization of the slow releasing relay 122, which has held closed the holding circuit of the called line switch. As soon as this holding circuit is opened, the cut-ofi relay 93 and relay 95 deenergize and the motor mag net 107 advances the brushes of the called line switch to their normal position in the same manner as the calling line switch was restored.

If the called line is bus the operation is the same as that previous y described up to the oint where the circuit through the relay 89 is closed by the operation of relay 77 (both of Fig. 3). If the line is busy, the relay-89 will not operate because the test wire is open at the lowermost armature and back contact of the cut-ofi' relay 93. Therefore when the control switch reaches position 21, relay 22 is immediately operated and the calling line switch and the bride finder switch will be operated as before. en relay 160 of Fig. 1 is o erated as a result of the extension of the calling line to the allotted bridge, a busy tone is ap lied to the calling line from the source 0 busy tone current lBZ, left-hand armature and front contact of relay 160, back contact and armatureofi relay 113, over conductor 131, to the calling sub-station circuits and through the other side of the established connection to grounded battery.

Reference has been made in the course of this description to the fact that only one main test can be made at the same time into or out of the group of a hundred lines in which the calling and called lines making the main tests are located. The method by which this is accomplished will now be described more in detail. The main test circuit is from round at the armature and back contact 0% relay 70, conductor71, lower armature and backcontact of relay 72, back contact and armature of relay 73, conductor 74, control switch brush of any control switch in the group of a hundred lines, in

which the calling line is located in its positions 9 or 10, conductor 7 6, back contact and armature or relay 33, right-hand ding of relay 77, conductor 78, hundreds register brush 40 and through the contact with which it is in engagement to the allotter for the group in which the called line is located, by way of conductor 7 9, right-hand armature and back contact of relay 70, back contact and armature of relay 80, conductor 81, inner back contact and armature of relay 72, resistance to grounded battery.

If either the terminating or originating allotters oi the calling or called group of 100 lines is advancing, their respective relays such as 80 of Fig. 1 and 73 of Fig. 2 will be operated to prevent the main test circuit just described from being closed; on the other hand, if a line switch in either the calling or the called group of a hundred lines is hunting for a bridge or link circuit, relays 70 of Fig. 1 and 72 of Fig. 2 will be actuated to open this main test circuit. Again if a bridge finder switch of a certain hundred group is operating, neither the main test circuit for a called line into this hundred, nor for a calling line from this hundred group may be made because a relay such as 82 of Fig. 3, of a register sender in the same hundred group with which the bridge finder switch is associated will be actuated thus holding the relay 72 (Fig. 2) of the originating allotter energized. While the bridge finder is testing and a relay such as 82 is operated, the main test circuit is not completed into or out of the hundred group in which this bridge finder is hunting because relays 1 18 and of Fig. 1 are energized.

As soon as a control switch, such as that shown in Fig. 3 is advanced into position 9, an attempt is made to make the mentioned main test. If the main test circuit is completed at this time, the relay 77 will immediately operate and this main test circuit will then be blocked to other calls. The main test circuit is wired through brushes such as of five control switches in series which are allotted for the individual use ofa group of a hundred lines so that, if two or more control switches of a group are advanced into position 9 at the same time, only one will complete the test circuit.

On the other hand, it is possible for more than one call to be waiting from difit'erent hundreds groups or to the same hundreds group when the main test circuit becomes efiective. Therefore, it is necessary to guard against completing more than one test circuit into the mentioned groups at the same time when this condition exists. This resuit is accomplished by the use of ten common interrupters with cam cuttings such that each of the ten circuits controlled at the interrupting device are closed one at a time in succession.

If the main test circuit is blocked, the control switch of the sender associated with a calling line will pass to position 11 without operating relay 77. It will be remembered that when the control switch was in position 8 the relay 67 was energized in a circuit extending from grounded battery, right-hand winding of this relay, conductor 68, control switch brush 34 in its 8th position, back contact and armature of relay 33, armature, back contact and winding of the motor magnet 32 to ground. When thus operated the relay 67 is locked in a circuit completed from ground through its left-hand winding, front contact and armature, control switch brush 187 in positions 8, 9 and 10, conductor 35 to grounded battery.

If, when the control switch of Fig. 3 is advanced to position 11, another control switch of the system is at 11, the relay 67 will then be locked operated in a circuit closed from ground through its lefthand winding, front contact and armature, control brush 187 in its 11th position and through a brush similar to 187 at the other control switch, through the back contact and armature of a relay similar to 67 associated with the other control switch and over a conductor similar to 35 to grounded battery. The relay 67 is thus held operated and the control switch is advanced through its subsequent positions until control switch brush 187 encounters an idle contact to stop the control switch. The operating circuit of this control switch extends from ground, winding of the motor magnet 32, back contact and armature of this magnet, armature and back contact of relay 33, conductor 69, front contact and armature of relay 67, conductor 35 and resistance to grounded battery. The deenergization of the relay 67, as soon as control brush 187 encounters an idle contact, of course opens this last described circuit. lVhen relay 67 deenergizes, it applies battery potential over conductor 35 through its back contact and armature to "control switch brush 187 and the contact with which it is in engagement. The main test wire is now connected by control switch brush 75 through relay 190, back contact and armature of relay 67, controlswitch brush 191 to the selected common interrupter. WVhen the main test wire becomes free, it will operate the relay 190 of one of the waiting control switches and only one of these relays will operate because the interrupters close the operating battery to the waiting positions of the control switches in succession. Relay 190 operates relav 77 of its associated register sender which in turn immediately blocks the main test circuit.

While ten difierent control circuits have been extended to the common interrupting device of Fig. 3, the number of these circuits required will depend upon the maximum number of calls from or to the same hundred group waiting to cut in at any one time.

In the event that a subscriber in the first hundred group of lines initiates a call, his line switch automatically connects his line to some one of the group of register senders individual to this group of lines. The call ing subscriber thereupon dials the number of the wanted line on the registers of the selected register sender. Let it be assumed that the designation of the wanted line is 561 indicatin that the wanted line is in the fiftli-hundre group, the hundreds register will, therefore be adjusted into its fifth position, the tens register into its sixth position and the units register into its first position. One of the hundreds register brushes similar to 43 of Fig. 2 thus completes a circuit through a brush similar to 50, throu h the fifth group of contacts of the tens register to actuate the #5 relay of the group of multi-contact relays individual to the fifth hundred group of lines. At the time when the test of the called line takes place, a test circuit, which it will be remembered included a conductor similar to 90, is extended through a brush similar to 42 of the operated'hundreds register in its fifth position, through a brush similar to 61 of the units register and through a conductor similar to 91 and a set of contacts individual to the called line appearing at \the operated #5 multi-contact relay.

The closure of the test circuit just described is effective to cause the line switch of the called line to hunt for an allotted bridge circuit of the group of bridge circuits individual to that line. As soon as the allotted bridge is located the line switch of the called line is stopped in the manner already indicated. Also after the test of the called line has taken place, the calling line switch proceeds to hunt for an allotted link circuit of the group individual to the calling line. When an idle link circuit is located a two-motion bridge finder switch individual to the link, first proceeds to operate its brushes .in a primary direction under the control of its motor magnet until a test brush similar to 146 of Fig. 2 encounters a group contact similar to 1 17 individual to the group of lines in the fifth-hundred group, whereupon the bridge finder ceases its primary movement and proceeds to move its brushes in a secondary direction to locate the other end of the bridge circuit which has been seized by the called line. Thereafter'the ringing and releasing operations take place in the manner already indicated.

It will thus be seen that an automatic system has been provided in which the talking 7 circuit extends only through nonnumerical switches.

What is claimed is:

1. In a telephone system, a plurality of telephone lines arranged in groups, a plurality of link circuits and a plurality of bridge circuits arranged in groups, switches for hunting idle link circuits and idle bridge circuits in said'groups, and means for permitting the hunting operation of only one switch in each group simultaneously.

2. In a'telephone system, a plurality of telephone lines arranged in groups, a lurality of link circuits and a plurality of ridge circuits arranged in groups, a switch for the use of each telephone line and operable to select either a link circuit or a bridge circuit, and means for preventing the bridge selecting operations of more than one switch in each group simultaneously.

3. In a telephone system, a plurality of telephone lines, a plurality of groups of link circuits, allotting means for each group of lines for assigning link circuits for use, a plurality of roups of bridge circuits, allotting means or each group of lines for assigning bridge circuits for use, automatic switches for extending two telephone lines in a telephone connection through an allotted link circuit and an allotted bridge circuit, and means for preventing the simultaneous extending operation of more than one line through a group of link circuits or a group of bridge circuits.

4. In a telephone system, a plurality of groups of telephone lines, a switch for the use of each line, groups of link circuits and groups of bridge circuits, each group being individual to one group of telephone lines,

means including the switches of two telephone lines for connecting said lines through one of said link circuits and one of said bridge circuits, and means for preventing the simultaneous connecting operations of more than one line through a group of link circuits and a group of bridge circuits.

5. In a telephone system, telephone lines divided into groups, a group of link circuits and a group of bridge circuits individual to each group of telephone lines, a switch for the use of each telephone line, and means for completing a telephone connection between two lines including the switches of said lines, a bridge and a link circuit.

6. In a telephone system, groups of telephone lines, a group of register senders for each group of telephone lines, an automatic switch for the use of each telephone line, a group of link circuits and a group of bridge circuits individual to each group of lines, a switch individual to each link circuit, means operative in response to directive control over the telephone lines of a group for variably adjusting an associated register sender in accordance with the designation of a wanted telephone line, means responsive to the control of said adjusted register sender for causing the switch of the called line to seizea bridge circuit and for causing the switch of the calling line to seize a link crcuit, and means including a link switch for connecting a selected link circuit and a selected bridge circuit to complete a telephone connection.

7. In a telephone system, groups of telephone lines, a non-numerical switch for the use of each telephone line, groups of link circuits and groups of bridge circuits for each group of telephone lines, a progressively movable switch .for each group of link circuits for assigning link circuits for use, a progressively movable switch for each group of bridge circuits for preselectmg bridge circuits for use, and means for connecting two telephone lines through a preselected link circuit and an allotted bridge circuit including the non-numerical switches of these lines.

8. In a telephone system, a plurality of telephone lines, automatic switches, a register sender common to said telephone lines comprising three or more progressively movable switches and con-trolling means therefor for recording the designation of wanted telephone lines and subsequently effecting the operation of said automatic switches, the controlling means of said register sender including switching means by which the progressively movable switches of said register sender are adjusted in succession, and a unidirectional rotary timing device .for determining the period of operation of said switching means.

9. In a telephone system, a plurality of telephone lines, a switch for the use of each telephone line, link circuits used exclusively for ou-tgoin calls and bridge circuits used by said switches exclusively on incoming calls, and a non-numerical switch for interconnecting a link circuit and a bridge circuit.

10. In a tele hone system, a plurality of groups of telep one lines, a line switch for the use of each telephone line, means including the line switches of a calling and a called line for completing a telephone connection between said lines, a set of multicontact relays for each group of telephone lines having a set of contacts individual to each telephone line of the group, and a test circuit for initiating the operation of the line switch of the called line, said test circuit extending through the contacts of said relays which are individual to the wanted line.

11. In a telephone system, groups of telephone lines, a line switch for the use of each telephone line, register senders each including a register for each digit of a wanted number, means for associating an idle register sender with a telephone line when calling, means controlled over said calling telephone line for variably adjusting sai register sender in accordance with the designation of the called telephone line, a group of multi-contact relays individual to each group of telephone lines, sets of contacts in each group of multicontact relays for the telephone lines of the group, means controlled bv the setting of the hundreds register for selecting the group of multi-contact relays having a set of contacts for the called line, and a circuit extending through said set of contacts of the called line for efi'ectmg the operation of the called line switch whereby a telephone connection is extended between the calling and the called telephone lines through the switches of these lines.

12. In a telephone system, groups of telephone lines, each tele hone line having a line switch for its use, Iink circuits, register senders including a hundreds, tens and units register, means for associating an idle register sender with a calling line on the initiation of a call, means controlled over the calling line for adjusting the registers of a register sender in accordance with the designation of the called line, a group of multicontact relays for each group of telephone lines, said actuated hundreds register operatmg to select a group of multi-contact relays individual to the called group of telephone lines, said tens register functioning to select a multi-contact relay of the selected group, a circuit completed through the units register and the contacts of the actuated multi-contact relay for effecting the opera tion of the line switch of the called line to select a link circuit, and means effective thereafter for connecting the calling line to said link circuit through the line switch of said line.

13. In a telephone system, groups of telephone lines, a group of link circuits, a group of bridge circuits for the individual use of each group of telephone lines, means for preselecting an idle link circuit and an idle bridge circuit in each group ahead of the calls, a line switch for the use of each line, means controlled from calling station to cause the line switch of the calling line and the line switch of the called line to seize a preselected link and a preselected bridge circuit, and means including a group and unit selecting switch for connecting the link circuit and the bridge circuit which have been seized by the calling and called line.

14. In a telephone system, groups of telephone lines, a line switch for the use of each telephone line, register senders common to said telephone lines, means including the line switch of a calling line for associating said line with an idle register sender, means including a unidirectional interrupter for controlling the variable adjustment of the associated register sender, means controlled by said adjusted register sender for testing the busy or idle condition of a wanted line and, if idle, for causing the individual switch of said called line to extend said line in the direction of the calling line, and means for, completing said connection through the line switch of the calling line.

15. In a telephone system, a plurality of telephone lines, a line switch for the usevof each telephone line, link circuits used exclusively for outgoing calls and bridge circuits used by said switches exclusively on incoming calls, and a group and line selecting non-numerical switch tor interconnecting a link circuit and a bridge circuit.

16. In a. telephone system, a, plurality of groups of telephone lines, bridge circuits, link circuits, line switches for the use of said telephone lines, non-numerical switches for interconnecting telephone lines, non-numerical switches for interconnecting bridge cireraeeo cuits and link circuits, a set of multi-contact relays for each group of telephone lines havmg sets of contacts for the telephone lines of its roup, a test circuit controlled at one of sai sets of contacts from the calling line to cause the line switch of the called line to select a bridge circuit, and means including a non-numerical switch and the line switch of the calling line for extending said calling line through a link circuit to the selected bridge circuit.

In witness whereof, I hereunto subscribe ilrg name this 2nd day of December A. l).

WINFRED T. POLL.