US1652836A

US1652836A - Automatic telephone system

Info

Publication number: US1652836A
Application number: US451961A
Authority: US
Inventors: Winfred T Powell
Original assignee: STROMBERG CARLSON TELEPHONE
Current assignee: STROMBERG CARLSON TELEPHONE; STROMBERGCARLSON TELEPHONE MANUFACTURING Co
Priority date: 1921-03-14
Filing date: 1921-03-14
Publication date: 1927-12-13
Anticipated expiration: 1944-12-13

Description

W. T. POWELL AUTOMATIC TELEPHONE SYSTEM Dec. 13, 1927.

2 Shee To NEAT F'HDER INVENTOR s9 \N\NFRED T POWELL TEE: REVERTIVE CALL FWDER BY A.

XZDWF 9506.50

Filed March l4. 1921 a". ZR EQUEHCY SELECTOR.

ATTORNEY Dec. 13, 1927. PoyvE L' AUTOMATIC TELEPHONE SYSTEM Fired March M. 1921 FIGE 52 m jl sL z h n 2 I MU I CONTr\CT RELAYS.

III?

I IIII FINDER BRIDG FINDER ALLOTTER" TEHE REGISTER DATTT} MAIN EXCHANGE I I I l I I I INVENTOR 1 I WINFRED T OW I BY -W ATTORNEY FIGS AT TEN DAHTS STAT \OH.

Patented Dec. 13, 1927,

UNITED STATES PATENT OFFICE.

WINFRED T. POWELL, OF ROCHESTER, NEW YORK, ASSIGNOR TO THE STROMBERG- CARLSON TELEPHONE MANUFACTURING COMPANY, OF ROCHESTER, NEW YORK, A

CORPORATION OF NEXV YORK.

AUTOMATIC TELEPHONE SYSTEM.

Application filed March 14, 1921.

This invention relates to telephone sys tems and more particularly to telephone systems employing automatic switches in com-.

pleting some part of a telephone connection. The main feature of thepresent invention is an improved method of interconnecting telephone lines through the use of non-numerical switches only.

An additional feature of this invention is it the provision of means for signalling party lines in such a telephone system.

A further feature of the invention relates to novel means for completing revertive calls, that is, calls between stations on the same 1 telephone line.

the dotted lines extending across this figure,

represents a very abbreviated disclosure of a second telephone line and the non-numerical switch individual to said line, but in this instance the four substations of the line are M only indicated. The portion of the drawing below this last mentioned telephone line represents a non-numerical finder switch, a numerical frequency selector and Various circuits associated therewith which are emit? ployed in the case of a r-evertive call to intermittently and alternately signal the calling and called stations. At the upper lefthand corner of Figure 2. there is represented a talking bridge or link of which there are suflicient to care for the maximum number of simultaneous conversations. At the lefthand side of Figure 2 and set off by dotted lines there is represented a bridge or link allotter switch which, as the name signifies,

4 operates to assign an idle bridge or link circuit for use. Near the center of Figure 2 and set oil by dotted lines there appears a finder switch, of which there are sufficient to care for the maximum number of calls that are in so the process of being completed. There is as socia'ted with each one of these finders. a sender which includes a tens register and a units register which appear at the lower right-hand corner of Figure 2. At the up- Serial No. 451,961.

per right-hand corner of Figure 2 there are represented three multi-contact test relays, but it will be understood that ten such relays are provided in a system of 100 lines and that each of these relays is provided'with ten distinct sets of contacts. At the lower left-hand corner of'this figure there appears a finder allotter which functions to assign an idle finder as well as its associated register sender for use.

Figure 3 represents an attendant opera tors station andshows a portion of an individual line switch assigned to that station. A portion only of the incoming'trunk and of the operators equipment are indicated, but it will be understood that the portions which have been omitted may be arranged after the manner of that now in use.

The switches which are employed in this system may be of substantially the same structure as that disclosed in the patent to Clement. 1,107,153 patented August 11. 1914.

It is believed that the invention will best be understod by describing the operation of establishing a telephone connection from substation such as that indicated at A to a called line such as that indicated at B, which it is assumed is designated #88.

When the subscriber at A removes his receiver from its switch-hook. a circuit is closed from grounded battery through the left-hand Winding of line relay 1, inner back contact and armature of the cut-off relay 2 over the lower side of the calling line and through the calling substation circuits, over the upper side of this line and through the uppermost armature and back contact of the cut-off relay 2 to ground. The line relay is energized in this circuit and closes an operating circuit for the motor magnet 3 extending from ground, winding of this magnet through the ofi'normal contacts 4, armature, front contact and right-hand winding of the line relay, armature and back contact of the motor magnet, resistance to grounded battery. Under the control of this circuit the motor magnet advances the brushes of the line switch one step thereby opening the off-normal contacts 4 and closing the off-normal contacts 5. This completes a circuit for the motor magnet now traceable from ground, winding of this magnet. off-normal contacts 5. lowermost armature and back contact of the cut-off relay 2, armature and back contact of the motor magnet, through the resistance to grounded battery; Under the control of this last-described circuit, the motor magnet advances the brushes of the line switch until an allotted link or bridge circuit is reached, at which time the motor magnet is short-circuited by a circuit completed from grounded battery, resistance back contact and armature of the motor magnet, right-hand winding of the linerelay l, left-hand front contact and armature of this relay, upper low resistance winding.

of the cut-off relay 2, armature and back contact of the relay 6, test brush 7, test conductor 8, lower back contact and armature of the slow releasing relay 9, brush 10 of the bridge allotter, inner armature and back contact of relay 11, upper back contact and armature of relay 12 to ground.

This last described circuit is also effective to energize the cut-01f relay 2 which disconnects the line relay 1 from the calling line and-alsoopens the operating circuit of the motor magnet 3 at the lowermost armature andback contact of this relay. When the cut-01f relay operates to extend the calling line through brushes Band 1% of the line switch to'conductors and 16 thereby completing the impulse circuit, conductor 15 extends the impulse circuit through the up permost armatureand back contact of relay 17 lower winding of relay 18 to grounded battery, while conductor 16 includes the other side of impulse circuit which extends through the lower back contact and armature of relay 17 and through the upper winding of relay 18 to ground. As a result of the closing of this circuit, relay 18 attracts'jits armatures and thereby closes a circuit for energizing the slow re'leasing relay 9 'from grounded battery, winding of this relay, up

per front contact and armature of relay 18; conductor 19, low resistance'winding of relay 11 to ground. Relay 11, however, is shortcircuited by ground at the inner armature and back contact of a relay 9 of an idle' bridge. Relay 9 thereby closes aholding circuit for the'line switch extending from ground, its inner upper armature and front contact upper armature and back contact of the holding relay 20, outer backcontact and armature of relay 87, conductor 21, holding brush 22 of the line switch, inner lower armature, front contact and the high resistance winding of the cut-off relay 2 to grounded battery. Relay 6 is alsoenergized in a circuit in multiple of that justdescribed which extends to grounded battery through the lower winding of this relay. As soon as relay 9 is actuated, it closes at its uppermost armature a circuit for energizing the relay 78. It shouldbe noted at this point that contacts designated X on relay 9 are closed before contacts Y are opened.

In the usual operation of the system such a bridge circuit as that described is' in readiness to receive a call. This is due to the fact that as soon as the holding relay of any bridge circuit is energized upon the location of this bridge by an allotted Te finder, a circuit is closed from ground, lower armature and front contact of the operated holding-relay, conductor 23, brush 24 of the bridge allotter, back contact and armature of the motor magnet 25 of this allotter,

outer armature and back contact of relay 11, Winding of magnet 25 to grounded battery. The motor magnet 25 will thus advancethe brushes of-the bridge allotter as long as the brush 24 engages the terminal having a ground potential thereon due to the energizetion of a holding relay 20 of engaged bridge circuits. lVhenever an idle bridge isreached, the motor magnet 25 will remain inert until the allotted bridge is seized by some succeeding calling line. Also when the line'relay 1 is energized on the initiation of a call it closes a circuit for relay 26 includingthe conductor 121. With the relay 26' energized a circuit is completed from ground through its left-hand armature and front contact, brush 27 of the finder allotter, back contact, armature and winding of the motor magnet 28 of the allotted finder switch through resistance 29, back contact and armature of re--- I lay 30 to grounded battery. Under thecontrol of this circuit the finder will advance its

brushes

31, 32, 33 and 34 until its brush 31 encounters a terminal individual to the allotted bridge circuit, at which time the relay contact of a relay similar to 30 of an idle finder switch, over conductor 37, winding of relay 30,'righthand winding of relay 35, inner armature and front contact of this relay, conductor 38, finder brush 32, outer back contact and armature of the ringing relay 39, outer back'contact and armature of relay 40, lower winding of relay 20, inner front contact and armature of relay 9 to ground. Relays 30 and 20 are energized and relay 35 held energized in this circuit. The high resistance rlght-hand-winding of relay 35 serves to hold it operated aslong'as'its finder switch is in use even after the bridge allotter has advanced to some other position. The release relay is energized in a lit) circuitin multiple of that last disclosed, and at its left-hand armature and front contact closes a locking circuit for itself independent of the control of the relay 35. With relay 60 operated an energizing circuit is closed for relay 59 from grounded battery, its Winding, outer back contact and armature of relay 54, conductor 61, outer front contact and armature of relay 60 to ground. WVhen relay attracts its armature it closes a circuit from grounded battery, brush 41 of the finder allotter, winding of relay 42 to ground. This energizes relay 42 and closes a circuit for the motor magnet 143 of the finder allotter, from grounded battery, inner armature and front contact of relay 42, winding back contact and armature of this. magnet, lower armature and back contact of relay 12, back contact and armature of relay 26 to ground. Under the control of this circuit the motor magnet 143 advan the brushes of the finder allotter until its brush 41 encounters the terminal individual to a finder switch that is idle, at which time relay 42 deenergizes and opens the operating circuit of the motor magnet 143.

The operations just described have been effective to connect the calling line to an idle bridge circuit and to connect an idle register sender to this link circuit through the brushes of its associated finder switch. The remaining operations have allotted another bridge circuit for the next call that it originated, and have advanced the finder allotier to assign an idle finder and its associated register sender for use in the next succeed: ing call.

The apparatus is now in condition to receive the impulses corresponding to the designation of the wanted line. The first series of impulses transmitted is effective to select the proper frequency for ringing the bell at the wanted station on the called line, and consists of either 2, 3, 4 or 5 impulses, depending upon whether 16, 33, 50 or 66 cycle ringing current is selected. Let it be assumed that the bell at the wanted station responds to 16 cycle ringing frequency, wherefore in order to select this fre quency, the calling party operates his dial sender to transmit two impulses of current. In response to these impulses the impulse relay l8 retracts its armature twice and on each retrcdio'n closes a circuit from ground, lower arrltllltf and front contact of relay 20, lower back contact and armature of relay l8, conductor 43, brush 44 of the frequency selector in its normal position, winding of slow releasing relay 45, winding of the motor magnet 46 to grounded battery. The slow releasing relay is energized in this circuit and is maintained energized dur ing this firs series of impulses, but the motor magnet is operated in response to each of these impulses and advances the brushes her corresponds to the tens digit of the vwanted number, and in response to each of these impulses the impulse relay l8 vibrates armatures and now closes a circuit from ground, lower armature and front contact of relay 20, lower back contact and armature of relay 18, conductor 43, brush 44 of the frequency selector switch armature and back contact of relay 45, conductor 4?, brush 34,

of the finder switch, continuity spring and back contact of change-over relay 48, outer armature and front contact of relay 35, winding of change-over relay 48, conductor 49, winding of the motor magnet to grounded baits U The change-over relay 48 is operated in this circuit and the impulse circuit is thereby extended through the continuity spring and armature of relay 48 which renders the circuit independent of the control relay 35. In response to each impulse of the tens series the motor magnet 50 advances the brushes of the tens register one step, but at the close of the tens series of impulses the change-over relay 48 of the tens. register deenergizes and the senderis in condition. to receive the units series of impulses. As soon as the brush 122 of the tens register is moved from its normal position, the right-hand winding of relay 35 is short circuited, and since the bridge allotter has been moved to a bridge other than that under consideration, the circuit including the left-hand winding of relay 35 is opened and it deenergizes.

The units impulses, which are eight in number, are repeated to the units register over a circuit closed from ground, armature and front contact of relay 20, back contact and armature of relay 18, conductor 43, brush 44, armature and back contact of relay 45, conductor 47, finder brush 34, continuity spring and back contact of relay 48, outer armature and back contact of relay 35, continuity spring and back contact of units change-over relay 51, the units register brush 52 in its first position, winding ofthe change-over relay 5i, winding of the motor magnet to grounded battery. The changeover relay 51 is energized in this circuit and extends the impulse circuit through its continuity spring and armature which renders this circuit independent of the register brush In response to each of the im pulses repeated over this circuit, the motor a la register one step until the close of this series of impulses when the relay 51 retracts its armatures, and if no other sender is testing any of the lines of the system, the sender under consideration tests the wanted line to determine whether it is busy or idle.

Let it be assumed that no other sender is testing any of the lines, under which assumption the relay 54 of the sender under consideration as well as the

relays

54 and 54 will be inactive. Relay 54 is now operated in circuit completed from ground, continuity spring and back-contact of relay 54 through the continuity springs and back contacts of other similar relays at the other register senders, back contact and left-hand continuity spring and winding of relay 54, conductor 55, back contact and armature of relay51, units register brush 56 which we will assume hasbeen advanced to its eighth position, multi-contact relay 58 of the group of lines in which the called line is located. The relay 54 opens the ei'iergizing circuit of relay 59 but before this relay retracts its armature, a test circuit is closed from ground at the outer armature and front contact of release relay 60, conductor 61, outer armature and front contact of relay 54, continuity spring and armature of relay 59, upper winding of relay 62, tens register brush 3 in its eighth position, conductor 64, innermost armature and front contact of relay to the test wire 65 of line #88, upper winding of relay 66, upper back contact and armature of cut-off relay 67, left-hand winding of line relay 68 to grounded battery. The relay '66 attracts its armature and renders the test brush 72 ineffective totest the outgoing terminals of bridge circuits, but when this'brush reaches the group of incomin terminals of the brid e circuits a contact 71 will be closed to render the test brush 72 effective. l/Vith line relay 68 energized the motor magnet 69 of the called line switch is operated to seize the bridge circuit to which the calling line is connected.

When the terminating line switch reaches the bridge circuit to which the calling line has been connected, a circuit isclosed from grounded battery, resistance, contact and armature of motor magnet 69, right-hand windingof line relay 68, its front contact and armature, upper winding of cut-off re- 67, lower ari'nature and front contact of relay 66, contact 71, test brush 72. test terminal 73, conductor 74, finder brush 33, upper front contact and armature of relay 62, left hand winding of release relay to ground. The cut-off relay 67 is energized in this circuit and closes a locking circuit for itself through its lower front contact andarmature, holding brush 75, test terminal 76, test conductor 77, lowermost annature and front contact of relay 78, winding of ringing relay 39 to ground. Relay 60 is differentially woundand releases because of the previouslydescribed circuit closed through its left-hand winding, and mentioned test circuit of the called line switch. lVith relay 6O deenergized the motor magnet 50 of the tens register and the motor magnet of the units register are operated to restore these registers to normal.

The ringing relay 89 is thus energized'andcloses a ringingcircuit from the source of 16 cycle ringing current, frequency selector brush 80, right-hand winding of the trlp relay -79, inner right-hand front contact and armature of relay 39 conductor 81 ring termina-l82 of the bridge circuit, line switch brush 83 through the bell of the wanted station (not shown) over the upper side of the called line, tip brush 84, tip terminal 85, conductor 86, through the resistance, lefthand front contact and armature'of relay 39,- inner front contact andarmature of relay 78 to ground.

armature, and at its outer left-hand arma ture and front contact it short-circuits the ringing relay 39 which deenergizes, whereupon a locking circuit is closed for the trip relay from grounded battery, its left-hand winding front contact and armature, lefthand back contact and armature of relay 39, inner front contact and armature of relay T8 to ground as soon as this last named relay is operated.

gaged when the test is made of this line after the settingof the'register sender, the test circuit such as 'is open at the back contact and inner upper armature of the cut-off relay 67 so that the called line switch'cannot be started to hunt for the bridged circuit to which the calling line is connected. Also there will be no circuit completed for energizing the relay 62 of the finder (Fig. 2). The relay 62 is inertand when relay 59 deenergizes after the test, a circuit is closed for the relay 40. This circuit is traceablefrom grounded battery, winding of relay 40, its continuity spring and contact, lower front contact and armature of relay 18, conductor 43, brush 44, armature and back contact of relay 45, conductor 47,1[inder brush 34, lower back contact and armature of relay 62, back contact and continuity spring of relay 59, leftkhand front contact and armature of relay 54, conductor 61, outer Also when the calledp'artyresponds, the trip relay 7 9 attracts its I Also when the called party responds, the relay 87 is energized front contact and armature of relay 60 to ground. Relay is operated in this circuit and closes a locking circuit for itself through its continuity sprin and armature to ground at the uymerniosL front Contact and armature of relay 9. lVith relay 4O operated a source of busy tone current is connected with the calling line to inform the subscriber there that the wanted party is busy. It will be remembered that the release relay of the register sender is locked operated through its left-hand winding and a circuit controlled at the back contact of relay 42. Therefore when relay t0 energizes it opens this circuit and relay 60 deenergizes to effect the release of the registers of the sender in the manner already outlined. In. the event that the calling party first terminates the call by placing his receiver on its switch-hook, the relay 1S deenergizes and shortly afterwards the slow-releasing relay 9 retracts its armature and thereby opens the holding circuit 21 of the calling line switch. This permits relays 2 and 6 to deenergize and relay 2 at its lower armature and back contact, close the operating circuit for the motor magnet 3 which restores the line switch to normal. Also when the relay 9 retracts its armatures it opens the operating circuit for the relay 7 8 and when this relay deenergizes it opens the holding circuit for the called line switch, which circuit includes conductor 77. This permits the cut-off relay 67 to deenergize and effect the release of the called line switch. In the event that the called party first replaces his receiver on its switch-hook, the relay 87 retracts its armature and thereby closes a circuit from ground over conductor 88 and resistance to grounded battery. This short-circuits relay 78 which opens the holding circuit of the called line switch, and effects the release in the manner described. The calling line switch,

however, is not released until relay 9 deen-- ergizes which is effected by the restoration of the calling receiver to its switch-hook. "When relay 78 deenergizes it closes a selfinterrupting circuit for motor magnet-46 which restores the frequency selector associated with the bridge circuit, to normal.

hen a subscriber desires to call a station on his own line, he dials a series of impulses corresponding to the designation #100. In case the station #2 is calling station number 3 or station #3 is calling station #2, thenv it is necessary to transmit a series of two impulses. If station #2 is calling station #i or station #4 is calling station then it is necessary to send three impulses If station is calling station #5 or is calling' #2, it is necessary to transmit four impulses. If station #3 is calling station #4. or #a is calling #3, then five impu must be sent. while if station #3 station #5 the dial is operated he send six impulses; and if station #4 is calling station #5, or #5 is calling #4, seven impulses are sent. After dialing this fourth or last series of impulses the subscriber is instructed to hang up until his bell stops ringing or until he desires to abandon the Similarly an allotted finder switch connects an idle register sender to the allotted bridge circuit. The subscriber first dials one impulse in response to which motor magnet 46 of the frequency selector advances its brushes to their first position. At the close of this impulse the slow releasing relay 45 atits contact and armature, connects the impulse circuit to the tens register. The subscriber thereupon transmits a series of ten impulses which advances the brushes of the tens register into their tenth position in the manner previously described. Thereupon the subscriber transmits another series of ten impulses corresponding to the units designation which advances the units register brushes into their tenth position. A test circuit is then completed to start into operation an idle revertive call finder, such as is shown at the lower part of Figure 1. This test circuit extends from a multi-contact relay to conductor 89, appearing at the lower right-hand corner of Fig. 1, winding of relay 90, lower back contact and armature of relay 91 to grounded battery. Relay 90 is energized in this circuit and effects the operation of the finder by closing a circuit from grounded battery,'resistance back contact, armature and winding of the magnet 92. uppermost armature and front contact of relay 90 to ground. Under the control of this circuit motor magnet 92 advances the brushes of the revertive call finder until the test brush 192 encounters the test terminal 93 of the bridge circuitto which the calling line has been connected, at which time relay 91 will be operated and will close a locking circuit for itself. This current extends from grounded battery at the inner, lower armature, frontcontact and lower winding of relay 91, conductor 94, inner armature and back contact of slow releasing relay 95, conductor 96, holding brush 97 to the holding conductor 21 of the selected bridge circuit. At the lowermost armature and front contact 98 of relay 91 the test circuit 89 is extended to the next revertivc call finder of the series. to care for any succeeding revertive call. At the upper arniatul'es and front contacts of relay 91 break points are closed in the signalling circuit over which the fourth series at impulses are transmitted eperate the frequency selector associated with the revertive call finder switch. Over this circuit ringing current of the proper frequency 1s first applied to signal the wanted station on the line, and then ringing current of the proper frequency is applied tosignal the calling station on this line.

This last-mentioned signalling circuit includes both windings of relay 100 in series and as soon as the signalling circuit is closed, this relay attracts its armature thereby closing a circuit from ground at its front contact, back contact and armature of the motor magnet 104, brush 105 in its'first pcsition, windingof the motor 'ma,g ;net104 to grounded battery.

As a result of the closure of this circuit, the frequency selector advances its brushes into their first position in readiness to receive the last series of mpulses correspondlng to the wanted sta' tion on the party line.

The mentioned operations of the revertiye call finder follow the last'series of ten im- "pulses, but before the calling subscriber transmits an additional series of impulses to select the current of the proper frequency. The calling subscriber now dials a series of two impulses corresponding to series No. 3 on his line. These impulses are transmitted over the signalling circuit which extends from grounded battery, upper windingot relay 100, back contact and armature of relay 101, uppermost armature and front contact of relay 91, finder brush 102, conductor 15,1ine switch brush 14 and over lower side of calling line through the impulse contacts of the calling dial and over the upper side of the-calling line, line switch brush 13, conductor 16, finder brush 108, innermost upper front contact and armature of relay 91, innermost armature and back contact of relay 101, lower winding of relay 100 to ground. In response to the first of these impulses a circuit is closed from ground, armature and back contact of relay 100 slow releasing reback contact and armature of relay 100 to ground. The closure of this circuitis effective to advance the frequency selector into its third position. Relay 107 is energized in this circuit and remains energized during this series of impulses.

Since it was assumed that a series of two impulses is transmitted to this frequency selector, its

brush

105, 109 and 118 will remain in their third pos tion. In the case of a re- 'vertive c'all, the'calling party is instructed 'to hang up at the close of this series of impulses until the wanted party answers. Re

' lay 100 deenergizes whereupon switching reergized'a circuit is closed from ground,

brush 109, armature and back contact of relay95. uppermost trout contact and armature of relay 101, brush 123, conductor 124, winding of relay 17 to grounded battery. Relay 17 is energized to maintain relay 18 energized while the calling partys receiver is hung up during the ringing period. Relay 18 holds relay 9 operated to prevent the release of the calling line'switch duringthis period. hen the switching relay 101 operated it closes its contact 139 and armature to ground, thereby closing a circuit including conductor 110 and the winding of relays 111 and 112 through the contact 115 to grounded battery,whenever interrupter #1 has. rotated to the proper position. Similarly the circuit including the conductor 110, is completed through the windings 0t relays 113 and 114, and the contact 116, whenever interrupter #2 is rotated into the proper position. It will be noted that the cam cuttings on these interrupters are so arranged that when interrupter-

s

1 and 2 rotate through an eighth of a revolution from the POSllTlOllQllOWIl, they will actuate relays 111 and 112. 113 and 114 so that the 33 cycle source of current is applied to conductor 117 and thence through. brush 118 over the conductor to signal station #3 on the calling line and back again over conductor 10 through the winding of trip relay to grounded battery. hen the interrupters are rotated through another quarter of a revolution, then only the relays 111 and 112 will be operated. so that the 16 cycle source oi ringing current is then connected to the conductor 117, which conductor in this instance is also included in the ringing circuit just described. This alternate signalling of the calling and called subscribers stations continues until one of the parties responds. at which time the trip relay is energized and at its left-hand tront contact and armature, closes a locking circuit for itself through the frequency selector brush 109 to ground. At the inner right hand armature and back contact of relay 95 the holding circuit of relay 91 is interrupted to release the revertive call finder for use on t if) a succeeding call. This finder is of the stay-put type and it remains in engagement with the bridge last used. Also the operation of the trip relay closes a circuit for re toring the trequency selector to its normal position. This circuit is completed from grounded l 'ittery, winding oi the motor magnet 1.0%. conductor 108, right-hand armature and front contact of relay 95, conductor 119. armature and back contact of the motor magnet, left hand front contact and armature of relay 95, brush 109 to ground. Under the control of this circuit the motor magnet 10% advances the frequency selector until the same reaches its normal position, which time the circuits to ground at brush 109 are opened and the trip relay deenergizes to leave the frequency selector in readiness tor a succeeding call. As soon as this selector reaches its normal position, the circuit of the switching relay 101 opened at brush 105 causing it to release. l'his opens the holding circuit of relay 11'. Fig. 2, whereupon relay 17 releases to permit talking battery to he extended to both stations through the windings of relay 18.

111 this system a so-callerl overflow arrangement is provided so that it all the bridge circuits become busy, a busy signal is transmitted to the calling subscriber until he releases or until a bridge circuit becomes idle.

lVhen all the bridge circuits are in use, all

thereby ground potential is disconnected from all the conductors such as 19. Thereupon the low resistance relay 11 is energized in the circuit now closed from ground, winding of this relay over any one of the conductors such as 19, upper armature and trout contact of a relay similar to 18 and winding of a relay similar to 9 to grounded battery. Relay 11 is operated in this circuit and at its inner arn'lature and back contact disconnects the stopping ground potential from the brush 10 and opens the bridge allotter circuit at its outer armature and back contact to prevent this allotter from continually rotating. This relay also places a ground on the overflow test terminals of the line switches. which is applied at the lefthand armature and front contact of relay 11. It a :all is initiated when the above described condition exists. the calling line switch will be advanced to the overflow trunk where relay will be operated by the closed circuit of the calling line. Relay 120 establishes a holding circuit for the line switch which circuit is opened when a tinder or bridge circuit becomes idle, thus causing the line switch to leave the overflow trunk and. choose the bridge circuit which has become idle. As long as the line switch remains on'the overflow trunk, calling party receives a busy tone from source B Z indicating that the bridge circuits are all busy.

It the finders are all busy, relay 12 will be operated to open the operating circuit of the finder allotter and to place a stopping potential on the test terminal of the overflow circuit so that the calling line switch will he stopped in engagement therewith. When this line switch seizes the overflow circuit, relay 120 is operated as previously described and applies a busy tone signal to the calling line until the subscriber there abandons the call or a finder becomes idle.

In Figure 3 which appears at the lower left-hand corner of Fig. 2 there is represented a two-way trunk extending from the common battery exchange to an attendant operators position or station associated with the private automatic exchange. In the case of this at endant station there is provided an individual switch similar to that provided tor each of the lines of the private system. The brushes of this individual switch are designated 132. 133, 134 and 135 and engage Let it first be assumed that a call from the main exchange is intended for some subscriber in the private automatic exchange, In this case the calling subscriber's line (not shown) will be extended either manually or automatically to include the conductors of the trunk extending between the main exchange and the branch exchange. As soon as this connection has been completed, signal 126 will notify the operator that the call is awaiting her attention. The operator thereupon depresses her listening key 127 by which her telephone set (not shown) is connected inductively to the incoming trunk and she receives the designation of the wanted station. As soon as the listening key 127 is depressed, the relay 128 is operated in a circuit including the operators telephone set and closes a circuit from ground, its outer frontcontact, armature and left-hand winding of relay 129 to grounded battery. This last named relay is operated and closes a circuit from ground, its outer front contact and armature, winding of the motor magnet 130, its armature and back contact, through the resistance to grounded battery. Under the control of this circuit the motor magnet advances the brushes 132 to 135 inclusive to select an allotted bridge circuit in the manner previously described for a subscribers line of the private exchange. When the allotted bridge circuit is located, the relay 131 is operated in a circuit traceable from grounded battery through the resistance, back contact and armature of the motor magnet, right-hand winding, inner armaturel ill) and front contact of relay 129, armature and back contact of relay 12S, oil normal contacts 136 brush 135, the outgoing terminal of the allotted bridge circuit over a conductor similar to 8 of Fig. 1 to ground as previously described. This last described circuit short circuits the motor magnet 130 and stops the line switch in engagement with the allotted bridge circuit. Also when relay 131 is opt erated it extends the operators telephone set to holding conductor similar to 21.

through its front contacts and armatures to

brushes

132 and 133 of the line switch. These, brushes will thereupon extend the circuit to conductors similar to'15 and 16 of Fig; 1 to serially include both windings of a. relay similar to 18 appearing at the upper left-hand corner of Fig. 2. The operation of relay 18 will energize a relay 9 as previously described to apply a. holding ground The relay 131 ofFig. 3 is thereupon locked operated over acircuit completed from grounded battery, lower winding which in the case of the attendants position is of low resistance, inner front contact and armature of this relay and holding brush 134: which is in engagement with a holding terminal associated with the seized bridge circuit and connected to the holding conductor 21.

The operator thereupon operates the dial sender 136 to set up the designation of the wanted station on the register sender. WVhereupon the connection is completed in the manner that has been described in connection with calls within the private auto-' j the short circuit is removed from relay 140 andalthough it is marginal it operates in series with the lower winding of relay 131', and the circuit of the called line is effective to hold relays 128 and 18 operated because the condensers are short-circuited. However, in the case of calls within the exchange the relaycorresponding to 131 has its lower 'inding of high resistance so that marginal relay 140 will not operate in the series therewith and consequently will not short circuit the condensers of the bridgecircuit.

Supervision. at the main exchange is also permitted by reason of the factthat in case of calls that originate outside of the private automatic exchange, relay l iO short-circuits the condensers which normally conductively separate two sides of each bridge circuit as :has been described. With relay 1 1-0. operated and the condensers short-circuited, the called party at the automatic exchange on hanging up his receiver will actuate a signal at the main exchange, in the case of a manual connection whereas in the case of an automatic connection he eliects the deenergization ofa relay to give supervision in the manner well known.

The release of the switches of the private automatic exchange in the case of a call originating at a main otiice is also controlled by the called party placing his receiver on the switch-hook. This will cause the relay corresponding to 87 to retract its armature and thereby short-circuit relay 78in the manner previously described. Relay 78 on deenergizing opens the holding circuit 77 of the called line switch which thereupon releases, as has been described. This also releases relays 128 and 18 and the line switch of the Figure 3. The release of that portion of the connection completed at the main oflice may be effective in any Well known mannor. 7

Since the trunk as represented in Fig. 3 is of the character referred to as a two-way trunk, when a subscriber at the private automatic exchange desires to obtain a connection at the main exchange, the line switch of Fig.

may be operated in response to a predetermined setting of the register sender whereupon the calling subscriber can then dial impulses to set automatic switches at a distant automatic exchange, or in the case that this exchange is manual, an operater is signalled.

lVhat is claimed is: t V

1. In an automatic telephone system in combination with a plurality of telephone lines, bridge circuits means for assigning bridge circuits for use ahead of the calls, means including a non-numerical switch for extending telephone lines to either end of an assigned bridge circuit, a plurality of senders, means for assigning senders for use, means for associating an assigned sender with an assigned bridge circuit, means for adjusting said sender from a remote point, and means operating under the control of said adjusted sender for controlling the extension of a wanted line to said assigned bridge circuit.

2. In an automatic .telephone system, in combination with a plurality of telephone lines, line switches for said lines, bridge circuits, means for assigning bridge circuits for use aheadot' the calls, means for causing the switch of a calling line to extend the same to an assigned bridge circuit, a plurality of senders, meansfor assigning senders for use, means for associating the assigned sender with an assigned bridge circuit, means for adjusting said sender from a remote point in accordance with the designation of the wanted line, and means operating under the control of said ad usted sender'for causing the line switch of a wanted line to extend the same to said assigned bridge circuit.

3. In an automatic telephone system, in combination with a plurality of telephone lines, an individual switch for each of said lines, bridge circuits each provided with two branches both terminating in each switch, means for allotting bridge circuits for use ahead of the calls, means for causing the line switch of a calling line to seize the outgoing branch of said allotted bridge circuit, a plurality of senders, means for assigning senders for use, means for associating an allotted sender with an allotted bridge circuit, means for adjusting said sender from a remote point in accordance with the designation of av wanted line, and means operating under the control of said adjusted sender for causing the individual switch of the called line to seize an incoming branch of the allotted bridge circuit.

4. In an automatic telephone "system, in combination with a plurality of telephone lines, an individual switch for each telephone line, a plurality of bridge circuits each provided with incoming and outgoing branches terminating in each of said switches, a progressively movable switch for allotting bridge circuits for use ahead of the calls, means for causing the individual switch of a calling line to seize the outgoing branch of an allotted bridge circuit, a plurality of senders, means for assigning senders for use, means for associating an assigned sender with an allotted bridge circuit, means for adjusting said sender from a remote point in accordance with the designation of a wanted line, and means operating under the control of said adjusted sender for causing the individual switch of tl e called line to extend the same to an incoming branch of said allot ted bridge circuit.

5. In an automatic telephone system, in combination with a plurality of telephone lines, a plurality of telephone stations on each of said lines, each station being provided with a signal responsive to current of certain frequency, a plurality of bridge circuits, means for allotting said circuits for use.an individual non-numerical switch for each telephone line operative on the initiation of a call on its line to extend the same to an allotted bridge circuit, sources of current of different frequencies, a frequency selector directively controlled over a calling telephone line to select a source of current of the proper frequency to signal the wanted station, a sender directively adjustable over a calling telephone line in accordance with the designation of a wanted telephone line, means responsive to the adjustment of said sender for causing the line switch of the desired line to seize the allotted bridge circuit, means responsive to said seizure to apply the selected source of current to said wanted line 7 nection.

6. In an automatic telephone system, in combination with a plurality of telephone lines, a plurality of stations on each of said lines, each station being provided with a signal responsive to current of a certain frequency, a plurality of bridge circuits,means for allotting said bridge circuits for use, an individual non-numerical switch for each line operative on the initiation of a call on its line to extend the same to an allotted bridge circuit, sources of current of different frequencies, a frequency selector directively controlled over a calling telephone line to select a source of current of the proper frequency to operate the signal at the wanted station, a sender directively adjustable over the calling telephone line in accordance with the designation of the called line, said sender being adjusted subsequent to the operation of said frequency selector, means responsive to the adjustment of said sender for causing the line switch of the desired line to seize the allotted bridge circuit, means responsive to said seizure to apply the selected source of current to said line and means for releasing the established connection.

7 In an automatic telephone system, in combination with a plurality of telephone lines, a plurality of stations on each of said lines, each station being provided with a signal responsive to current of a certain frequency, a plurality of bridge circuits, means for allotting said bridge circuits for use, an individual non-numerical switch for each line operative on the initiation of a call on its line to extend the same to an allotted bridge circuit, sources of current of different frequencies, means directively controlled over a calling telephone line to select a source of current of the proper frequency to operate the signal at the wanted station, a sender directively adjustable over the calling telephone line in accordance with the designation of the called line, said sender being adjusted subsequent to the operation of said frequency selector, means responsive to the adjustment of said sender for causing the line switch of the desired line to seize the allotted bridge circuit, means responsive to said seizure to apply the selected source of current to said line, means for releasing said sender for common use as soon as the individual switch of the wanted line has seized said allotted bridge circuit, and means for releasing the established connection.

8. In an automatic telephone system, in combination with a plurality of telephone lines, a plurality of stations on certain of said lines, each of said stations on a telephone line being provided with a signal responsive to current of a certain frequency, a plurality of sources of current of the proper frequency to operate each of said signals, a frequency selector for selecting the proper frequency to operate a signal at a wanted station, a non-numerical switch responsive to control from a remote point for associating said frequency selector with a calling line, means controlled over said calling line for variably operating said selector to connect the proper source of current to a calling line to signal a wanted station thereon and means for releasing said non-numerical switch prior to the termination of the call.

9. In an automatic telephone system, in combination with a plurality oftelephone lines, a plurality of stations on certain of said lines, each of said stations on a telephone line being provided with asignal responsive' to current of a certain frequency, a plurality of sources of current of the proper frequency to operate each of said signals, non-numerical switches for said telephone lines, a plurality of bridge circuits, anyone of which is arranged to be seized by a nonnumerical switch, a sender, means for associating said sender with a selected bridge circuit, means for variably operating said sender over a calling line and bridge circuit in series, a frequency selector, a non-numerical switch associated therewith, means operated in response to a pre-determined setting of said sender for causing said non-numerical switch to associate said frequency selector with a calling line, means controlled over said calling line for directively operating said frequency selector to apply a source of current of the proper frequency to signal the, wanted station on the calling line, and means for releasing said established connection.

10. In an automatic telephone system in combination with a plurality of telephone lines, non-numerical switches for the use of said lines, a plurality of bridge circuits each having incoming and outgoing branches terminating in each of said switches, a test brush for each non-nmnerical switch, means for rendering said test brush effective to test outgoing branches of said bridge circuits when its telephone line is callingmnd means for rendering said test brush effective :to test only incoming branches of said bridge circuits when its telephone line is being called.

11. In an automatic telephone system n combination with a main exchange, a branch exchange, telephone lines terminating at said branch exchange, an operators position at said branch exchange, a trunk circuit extending between said main .exchange and said operators position, non -numerical switching means associated with said operators position for automatically extending a call from said trunk circuit to a wanted telephone line and from a telephone line to said trunk, andmeanscontrolled over said telephone line for disestablishing a portion of the connection.

12. In an automatic telephone system, in combination with a main exchange, a branch exchange, telephone lines terminating at said branch exchange, an attendant operators position at said branch exchange, a two-way trunk circuit extending between said main exchange and said operators position, means including a nonqnnnerical switch for automatically extending any one of said telephone lines as a calling line over said trunk circuit to the main exchange, means including said non-numerical switch associated with said operators position, for extending a call from said trunk circuit to a wanted telephone line, and means controlled over said wanted-telephone line for disestablishing a portion of a connection.

13. In an automatic telephonesystem, in combination with a telephone line, a plurality of stations on said telephone line, each of said stations being provided with a signal responsive to current of different character from that to which the other stations are responsive, a plurality of bridge or link circuits, a non-numerical switch for extending said telephone line to a bridge circuit, sources of current of different character for actuating said signal, a numerical switch. means for associating said last-mentione .l switch with said bridge circuit and means for operating the same over said telephone line, means responsive to the setting of said numerical switch for applying the proper source of current to said telephone line to signal the calling and wanted stations thereon, andmeans for releasing said numerical switch before termination of the conversation.

1 1. In an automatic telephone system, in combination with a telephone line, a plurality of stations on said telephone line, each of said stations being provided with a signal responsive to current of dill erent frequency from that to which the other stations are responsive, a plurality of bridge circuits. a non-numerical switch for extending said telephone line to a bridge circuit. sources of current of different frequency for actuating said signal, a numerical switch, means for associating said last-mentioned switch with said bridge circuit and means for operating the same over said telephone line, means responsive to the setting of said numerical switch for alternately applying the proper sources of current to said telephone line to signal the calling and wanted stat-ions thereon, and means for releasing said numerical switch before the termination of the conversation. V

15, In an automatic telephone system, in combination with a. telephone line, a pinrality of stations on said telephone line, each of said stations being provided with a, sigltll) nal responsive to current of dilferent character from the other stations, a bridge circuit, a source of talking current connected to each bridge circuit, a non-numerical switch having terminals in which said telephone line and bridge circuit terminate, numerical switch connectible to said bridge circuit and responsive to directive control over said telephone line, means responsive to the setting of said numerical switch for selecting sources ot'current of the proper frequency to signal the calling and wanted stations on said wanted telephone line, and a conversational circuit including said telephone line and bridge circuit but having only one automatic switch therein.

16. In an automatic telephone system, a plurality of telephone lines, a plurality of nonnumerical switches, a plurality of bridge circuits, means for causing a non-numerical switch to extend a calling telephone line to an assigned bridge circuit, a plurality of senders, means for assigning senders for use, means for associating the assigned sender with an assigned bridge circuit, means for adjusting said assigned sender from a remote point in accordance with the designation of the wanted telephone line, and means operative under the control of said adjusted sender for causing a non-numerical switch to extend a called line to said assigned bridge circuit.

17. In an automatic telephone system, a plurality of telephone lines, a plurality of telephone stations on each of said telephone lines, each of said stations being provided with a signal responsive to current of a certain characteristic, a plurality of bridge circuits, a plurality of non-numerical switches, means including at least one of said nonnumerical switches for extending a calling telephone line to a bridge circuit on the initiation of a call, sources of current of different characteristics, means controlled over the calling telephone line and bridge circuits for causing a non-numerical switch to extend a called telephone line to said selected bridge circuit and means directively controlled for connecting current of the proper characteristic to signal the wanted station on the called telephone line.

18. In an automatic telephone system, a plurality of telephone lines, a plurality of stations on each of said lines, each of said stations being provided with a signal responsive to current of a certain characteristic, a plurality of bridge circuits, a plurality of non-numerical switches, means including a non-numerical switch for extending a calling telephone line to a bridge circuit, sources of current of different characteristics to actuate said signals, a frequency selector directively controlled over a calling telephone line to select a source of current of the proper character to actuate the signal at the wanted station, a sender directively adjustable over the calling telephone line in accordance with the designation of the called line, said sender being adjusted sub sequent to the operation of said frequency selector, means responsiw e to the adjustment of said sender for causing a non-numerical switch to extend the wanted telephone line to the selected bridge circuit, means respon sive to said extension to apply the selected source of current to said telephone line, and means for releasing the established connection.

19. In a telephone system, a plurality of telephone lines. a plurality of bridge circuits, an over-flow circuit, a plurality of nonnumerical switches, means including a nonnumerical switch extending a calling telephone line to a bridge circuit on the initiation of a call, and means directively controlled for causing a non-numerical switch to extend the wanted telephone line to the bridge circuit to which the calling line is connected, means for rendering the bridge circuit busy when it is seized by a nonnunierical switch, and means operative when all of said bridge circuits are busy for causing said non-numerical switch to extend a calling telephone line to said over-flow circult.

20. In an automatic telephone system, a main exchange, a local exchange, an operators position at said local exchange, a plu rality of telephone lines terminating at said local exchange, means including a plurality of automatic switches for interconnecting said telephone lines, means including a trunk circuit for extending a call from said main exchange to said operators position, a nonnumerical switch associated with said trunk circuit, and means including a non-numerical switch and certain of said automatic switches for extending said trunk to any of said telephone lines and for extending any of said telephone lines to said trunk.

In witness whereof, I hereunto subscribe my name this 9th day of March, A. D. 1921.

VVINFRED T. POWELL.