US2274759A - Telephone system - Google Patents

Description

March 3, 1942.Y J. wlcKs TELEPHONE SYSTEM Filed June 30, 1939 2 Sheets-Sheet l QQ @QQ NQ w: @v

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March 3, 1942. J, wlcKs TELEPHONE SYSTEM 2 Sheets-Sheet `2 Filed June 3o, 1959 w EN c N @QN E @Q83 x USN 6N .m6 Qwl m f UY E 6.52 @Q M NQQN D @QN NW @uw r IIIIIIIIIII I1 l I||||l IIIIIIJ QN QN NN mw n TSW w @wlw @www www# W% Ind @SN SNITI.. www wl .SN im www. www. EN QMNSOQ @N m H NNN OWN l @mw DNN OOM @QN @QN t, www l n www Rfo www www .M .NEN www2* BNSNUL. Et L i M2314 JF@ EINRUI @Q Sw @WJ f EN Q om ATTORNEYS.

Patented Mar. 3, 1942 UNITE TELEPHONE SYSTEM .lohn Wicks, Oak Park, Ill., assignor to Associatedy Electric Laboratories, Inc., Chicago, Ill., a corporation of Delaware Application June 30, 1939, Serial No. 282,006

19 Claims.

The present invention relates to automatic telephone systems and has for one of its objects the provision of improved apparatus for automatically forwarding calls intended for a first substation of an automatic telephone system to another substation selected by the subscriber or party for whose service the first substation is provided.

It is another object of the invention to provide in an automatic telephone system, improved call forwarding apparatus of the character described which is economical to manufacture and install, is adapted for use in conjunction with automatic switching apparatus of substantially all types, and is thoroughly reliable in operation.

It is another object of the invention to provide in an automatic telephone system, improved call forwarding apparatus of the character described which is normally inactive and is automatically rendered operative to respond to calls incoming to the associated substation through operation of the apparatus to select a substation to which the calls are to be forwarded.

It is another object of the invention to provide in an automatic telephone system, call forwarding apparatus of the character described which is arranged in an improved manner such that no auxiliary lines are required between the automatic switching apparatus of the system and the substation with which the call forwarding apparatus is associated.

It is a further object of the invention to provide in an automatic telephone system, improved call forwarding apparatus which is so arranged that alternating current pulsing over the line extending to the substation with which the apparatus is associated, is utilized for directively controlling the automatic switching apparatus through which the calls are forwarded; thus eliminating the necessity of providing an auxiliary line between the substation and the automatic switching apparatus of the system.

'Ihe invention is illustrated in its embodiment in an automatic telephone system which comprises a. plurality of substations and automatic switching apparatus including non-numerical and impulse responsive numerical switches for setting up connections between the lines extending to the substations. Two embodiments of the invention are illustrated. In each modification, call forwarding apparatus is provided individual to the lines arranged for call forwarding service. This apparatus includes a motor-driven, cyclically operative device which is operative to transmit to the automatic switching apparatus the impulses of the directory number designating the substation to which the calls are to be forwarded. This device includes a plurality of control elements individually corresponding to the substations to which calls may be forwarded, a station selecting element having a normal position and operative to off-normal positions individually corresponding to the control elements, and pulsing means adapted to be controlled by any one of the control elements for transmitting to the automatic switching apparatus the impulses of the directory number designating the substation corresponding to the off-normal position occupied by the station selecting element. For the purpose of initiating the operation of the call forwarding apparatus, `there is provided a relay which is adapted to be connected to the line arranged for call forwarding service and to respond to ringing current transmitted over the line. connect this relay toV respond to ringing current transmitted over the line, there is provided switching means operative in response to operation of the selecting element to any one of its off-normal positions. This relay functions -to complete the operating circuit for the motor which drives the cyclically operative pulsingfdevice, and the arrangement is such that the pulsing device is caused to operate through repeated cycles, thereby repeatedly .to forward an incoming call to theassociated line through the automatic switching apparatus to the substation selected for call transfer, until the call is aban` doned or is answered at the last-mentioned substation. =In order to arrest the operation of the device and to terminate the transmission of ringing current over the line associated with the call forwarding apparatus there is provided in this apparatus means operative to perform the indicated functions when the forwarded call is answered at the substation to which the call is routed.

In one embodiment of the invention, the irnpulses produced through operation of the call forwarding apparatus are transmitted from the associated substation to the automatic switching apparatus of the system over an auxiliary line extending between the substation and the auto-V In the second emmatic switching apparatus. bodiment of the invention, the use of an auxiliary line is not necessary; the call forwarding apparatus provided at the substation arranged for call forwarding service including means automatically operative in responsive to the presence of an incoming call on the line extending to the substation for transmitting alternating current for call forwardingservice functions to control means for transmitting over the associated line a In order to` Further features of the invention pertain to the particular arrangement of the circuit elements described hereinafter, whereby the above and additional operating features are attained.

The novel features belieted to be characteristic of the invention are ser. forth with parue- L ularityA in the appended claims. The invention, both as to its organization and method of operation, together with further objects and advantages thereof will best be understood byreference-to. the specication taken in connection with the accompanying drawings in which Figure l illustrates one embodiment of the improved call. forwarding apparatus and Fig. 2 illustrates a second embodiment of the improved` call forwarding apparatus; these two embodiments of y.;

the invention being respectively associated with two different subscribers lines forming a part of the same automatic telephone system.

Briefly described, the system illustrated inthe drawings comprisesa vplurality of substations r t A, B, C and D individually associatedzwith lines l, Ii, l2, and I3 in the. order named; which lines all extend to the automaticswitching apparatus provided in the lineterminating exchange. This apparatus comprises line rswitches M, I5, itand Il individually associated with the lines t3, H, I2 and I3, a plurality of impulse responsive selector switches including the two switches. indi-- cated at I8 and l5, and a. plurality of impulse responsive connector switchestwo of which are indicated at 2Q and 2l, respectively. The system further comprises calllforwarding apparatus individually associated with thesubstations B and D, respectively. The arrangement of this apparatus as provided in conjunction with the substation B is such that an auxiliaryA line 22 extending from this substation to the automatic switching apparatus of the line. terminating exchange and anauxiliary line switch 22,3 for serving the line 22are required. The callrorwarding apparatus illustrated in Fig.y 2, inassociation with the substation D, onthe other hand, is Vsuch that no auxiliary line extending from this substation to the automatic switching apparatus of the line terminating exchange is required. This apparatus does, however, require the provision of an auxiliary line switch Ziiwhich functions to forward calls to the selector switches of the system.

The line switches l, l5, it, V, 23 and 2'4 are f This :rc-lay is arranged to fdl cordance with impulses transmitted thereto, to perform line group, subgroup and particular line selecting operations. Preferably, these switches are of the well-known Strowger type, each having embodied therein a Strowger switching mech- ,anism utilizing vertical and rotary motions in its Voperation to select an outgoing line.

Obviously,

Y the control apparatus embodied in the selector and connector switches is different in each instance depending upon the particular character of the switch.

Neglecting for the present the arrangement of the call forwarding apparatus provided in association with the substations B and D, the system as described above is entirely conventional in form and its mode of operation is well understood in thel art. Briey described, if a subscriber at the substation A, for example, initiates a call intended for the substation. B- by removing the receiver provided at the substation A- from its supporting hook or cradley a calling loop circuit is completed by way of the line i!! for initiating the operation of the line switch M. This line switch responds to the completion of the calling loop circuit by operating toselect a trunk line extending to an idle one of therst selector switches. If the selector switch t8, is the first available idle selector switch accessible tor the line switch I4, the last-mentioned@ switch, upon testing the conditionof the trunk line extending to the selector switch i8 and. finding this line to be idle, operates to extend` the calling loop circuit to the selector switch. The control apparatus of the seized selector switch i8 now op.- erates to. return the usual dial tone signal to the calling subscriber. The selector switch I8 responds to the impulses of the iirst digit dialed at the substation A by elevating its wipers to a position opposite the level o bank contacts terminating the trunk lines extending to the con.- nector switches having access to the called line IlY and forming the group including the switch 2i). Further, the control` apparatus of the selector switch operates to terminate the dial tone signal. During the interdigit pause between the first and second digits, the wipers of the selector switch I8 are rotated` step-by-step in the usual manner, successively to.test the condition of the trunk lines respectively extending to the connectorY switches of the selected group. If thecon.- nector switchv 2u is the rst available idle switch of the selected group, the rotary movement of the wipers embodied in the selector switchv I8 is arrested when these wipers engage the contacts terminating the conductors of the trunk line incoming to this connector switch. In addition, the control apparatus of the selector switch I8 functions to extend the, calling, loopcircuit to the seized-connector'switch 2&2' The connector switchli responds to. they impulsesof ythe second digit dialed atthe calling substation by, elevat.- ingits wipers to a position oppositethe level of bank contacts terminating the grouplofv lines including theV calledline H. In response to the impulses ofathe third digit dialed at the calling substation these wipersare rotated into engagement with the particular set oi' bank contacts apparatus embodied in thek connector switch` 2l) functions to determinethe idle or busy. condition 'of the selected line'and'to transmitthe usual 'busy tone signal over the calling loop circuit to the calling subscriber in the event. the called Aune is busy. rf the called une is found to be idle, 'the control equipment embodied in the connector switch functions to transmit ringing current over the called line for the purpose of energizing the ringer conventionally provided at the called substation B and over the calling line to inform the calling party that the called substation is being rung. When the call is answered at the called substation a direct current bridge is connected across the conductors of the line thereby to complete a circuit for energizing the ring cut-off relay conventionally embodied in the Control equipment of the operated connector switch. This relay, upon operating, functions to terminate the ringing operation, to arrest the ringback tone signal and to complete the desired conversational circuit between the calling and called substations. When the ring cut-off relay operates, a loop circuit is established between the connector switch 2o and the substation B, which loop circuit extends through the windings of the 'back bridge or battery reversing relay conventionally embodied in the connector switch 2t. The resulting operation of this back bridge relay causes the direction of current flow over the calling loop circuit to be reversed in the usual manner, and this current reversal may be utilized for various control functions such as call metering or the like. The manner in which the connection is released depends upon the particular arrangement of the control apparatus embodied in the connector switch 2B. For example, this apparatus may be so arranged that the operated switch train is released only when the connection is released at both the calling and called substations. Alternatively, the control apparatus of the connector switch may be so arranged that the release of the switch train is entirely under the control of the calling subscriber. Assuming that the latter arrangement is employed, when the calling party replaces the receiver provided at the substation A upon its supporting hook or cradle the calling loop circuit is interrupted with the result that the connector switch 2|), the selector switch I8 and the line switch |11 are successively released in the order named and in a manner well understood in the art. When these switches are all restored to normal, the calling and called lines Hi and I are marked as idle in the connector switches having access thereto and the apparatus utilized in completing the connection is rendered available for further use. In view of the foregoing description it is believed that the manner in which connections may be established between the other substations of the system will be clearly apparent without further explanation.

Referring now more particularly to the ernbodiment of the call forwarding apparatus illustrated in Fig. l in association with the substation B, this apparatus comprises a cyclically operative control device which includes a plurality of control elernents or cams individually corresponding to the substations to which calls incoming to the line may be forwarded. One such cam is indicated at |60, this cam individually corresponding to the substation C associated with the subscribers-line l2. Each of the control elements or cams is notched around its periphery to provide a camming surface for controlling a pair of impulse shunting springs lol, these springs being transversely movable with respect to the cams to engage the peripheral surface of a selected one thereof in unison with a station selecting element H32 as indicated by the dotted unicontrol line U. The station selecting element |02 is provided with a pointer portion arranged to cooperate with an index |93 which includes indices identifying the substation corresponding to the position occupied by the shunt springs Ill More particularly, the station selecting element |02 is provided with a normal position and a plurality of off-normal positions individually corresponding to the substations to which the calls may be forwarded. This element is arranged to control a pair of switching springs I in a manner such that the springs are disengaged when the station selecting element occupies its normal position and are moved into engagement when thisv element is operated to any one of its off-normal positions. The control device further comprises an impulsing cam |05 which is arranged to operate a pair of pulsing springs |06. Two additional control elements or cams |01 and |03 are provided, which elements are arranged respectively to control the springs embodied in associated spring piles m9 and For the purpose of driving the enumerated control cams there is provided a small synchronous motor of the self-starting type which is arranged to be energized from the usual commercial frequency volt source. More particularly, this motor is arranged to drive a shaft H2 upon which the control elements |61 and IUS are mounted at a reduced speed through a speed reducing mechanism H3. The shaft ||2 is, in turn, geared to drivea shaft Hd upon which the station selecting control elements are mount-v ed through a second speed reducing gear train- ||5. The shaft ||4 is arranged to drive a third shaft ||5 which carries the pulsing cam |65 through a speed increasing gear train It. Since the control cams H31 and |68 are mounted upon the same shaft, these cams are obviously operated in unison, preferably at a speed of approximately one and two-thirds revolutions per minute. The gear ratio of the gear train l5 is such that the station selecting cams carried by the shaft ||4 are rotated three revolutions for each revolution of the cams |01 and m6,' or at a speed of approximately five revolutions per minute. The gear ratio of the train l 6 is such that the impulsing cam |65 is driven at a speed of approximately six hundred revolutions per minute, corresponding to an impulsing rate of approximately ten impulses per second. If desired, the mechanical construction of the portion of the control device comprising the station selecting cams, the gear train H6, the pulsing cam |05 yand the station selecting element H32 may be substantially similar to that disclosed in the copending application of Hans Sengebusch, Serial No. 147,831, filed June 12, 1937.

For the purpose of initiating the operation of the control device there is provided an alternating current relay |26 which includes a winding adapted to be bridged across the conductors of the line in series with a condenser |22 in response to loperation of the station selecting element |92 to one of its off-normal positions so that it will respond to ringing current transmitted over this line. The line connecting equipment of the call forwarding apparatus includes a repeating coil |23, having a pair of windings |24; and |25 adapted to be connected in series circuit relationship with the condenser |22 and the winding of the relay |25) across the conductors of the line and a second pair of windings |26 and |21 adapted to be included in a calling loop circuit including the auxiliary line 22 and extending to the line switch 23. The completion of a talking circuit between the lines I and 22 is under the control of a polarized back bridged relay |30 which is preferably of the permanent magnet type.

Referring now more particularly to the operation of the call forwarding apparatus illustrated in Fig. l, it will be apparent that with the station selecting element |02 occupying its normal position such that the contact springs |04 are disengaged, the series path including the windings |24 and |25 of the repeating coil |23 and the winding of the start relay is not connected across the conductors of the line Accordingly, calls incoming to the substation B and routed through the automatic switching apparatus terminating exchange in the manner previously explained, may be completed and released without in any way affecting the call forwarding arrangement. Also, calls originating at the substation B may be completed without interference occasioned by the associated call forwarding apparatus. In order to condition the call forwarding apparatus to operate in response to calls incoming to the line II, the station seposition the shunt springs |0| to be controlled by the station selecting cam |00. Immediately the element |02 is operated to an off-normal position, the springs |04 are closed to connect across the conductors of the line the series path including the winding of the relay |20.

With the apparatus in this condition if a call intended for the substation B is routed to the line II through the switches I4, I8 and 20 from the substation A in the manner previously described, ringing current is projected over the line I I following the operation of the control apparatus of the connector switch 20 to ascertain the idle condition of the line I I. A portion of the ringing current traverses the winding of the relay |20 over a circuit which may partially be traced as extending by way of the line conductor I Ia, the contact springs |04, the winding |24, the winding of the relay |20, the condenser |22, the winding I and the line conductor IIb. Each time the relay |20 is energized by current traversing this circuit it operates to complete, at its armature |2I, a circuit for energizing the synchronous motor III, this circuit extending from one terminal of the alternating current source, through the windings of the motor I I I, the armature |33 and the armature I2I to the opposite terminal of the current source. When energized over this circuit, operation of the motor III to drive the Various control cams, previously described, is initiated. During the initial operation of the motor, the cam |01 is moved off-normal to operate the contact springs |34 and |35 respectively into engagement. At the contact springs |35 an auxiliary or second circuit is compieted for energizing the motor III, this second circuit extending from one terminal of the current supply source through the windings of the motor III and by way of the contact springs |35 to the opposite terminal of the current source. Thus, operation of the motor III is maintained independently of the energized or deenergized condition of the start relay |20 until the control device driven thereby has been operated through a complete cycle of operation. When the contact springs |34 are moved into engagement a calling loop circuit extending to the line switch 23 is completed, this loop circuit extending by way of the line conductor 22a, the repeater winding |26, the winding of the relay I 30, the repeater winding |2'I, the contact springs |34, |36 and |38 and the opposite line conductor 221i. The direction of current flow over this loop circuit is such that the polarized relay |30 does not operate; this relay being so poled that it only operates in response to the reversal of current flow over the calling loop circuit which occurs when the call is answered at the substation to which the call is forwarded. When the above-traced calling loop circuit is completed, the line switch 23 operates to select an idle one of the selector switches, such, for example, as the switch I9, to which is has access. When this switch is selected, the calling loop circuit is extended thereto and the selected switch is conditioned to respond to the first series of impulses transmitted over the line 22 through operation of the pulsing springs |03 as controlled by the shunt springs IilI. In order to provide ample time for the line switch 23 to perform its switch selecting operation, the transmission of impulses from the control device is delayed for a predetermined time interval after operation thereof is initiated. To this end, the springs |36 and |38, controlled by the cam |03, are held in engagement to shortcircuit the springs |0I and |06 until the cam E00 has been rotated through 'an angle of approximately 45 degrees. It will be understood that during such rotation of the cam |0| the station selecting cams, including the cam |00, are rotated through an angle of approximately 35 degrees since the speed ratio between the shafts I4 and I I2 is approximately three to one. By virtue of this arrangement, transmission of switch control pulses from the control device is delayed for an interval of approximately four and one-half seconds after the calling loop circuit is completed, this interval being ample for the line switch 23 to test the idle or busy condition of all of the selector switches to which it has access. At the end of this interval, the cam follower portion of the spring |38 drops into the notch I08a provided in the peripheral surface of the cam |00. As a result, the springs |36 and 38 are disengaged and the springs |36 and |31 are moved into engagement. Thus the parallel connected shunt springs II and the pulsing springs 05 are effectively included in the calling loop circuit. Shortly following this operation, the cam follower portion of the shunt spring I0|a drops into the notch |0011, formed in the peripheral surface of the station selecting cam |00. Thus, the shunt springs |0Ia and IIlIb` are disengaged so that the puising springs |06 are actively included in the calling loop circuit to transmit thereover to the selector switch I9 the impulses of the rst digit of the directory number designating the substation C. In this regard, it will be apparent that the number of impulses transmitted during the digit is determined by the circumferential length of the notch |00a formed in the peripheral surface of the element of the cam |00. For example, if the directory number designating the substation C is 352, the length of the notch I00a will be so proportioned relative to the pulsing rate and the speed of rotation of the cam |00 that three impulses are www@ transmitted over the calling loop circuit during i the interval when the cam follower portion of the spring Ila, is engaging the peripheral surface of the cam IBD defined by this notch. In a similar manner, the length of the second notch |0019 corresponding to the second digit of the directory number designating the substation C is formed of a length such that five impulses will be transmitted over the calling loop circuit while the cam follower portion of the spring ||||ar is engaging the peripheral surface dened by this second notch. Also, the length of the notch |000 which determines the number of impulses of the third digit is such that two impulses are transmitted over the calling loop circuit by the pulsing springs |06 during the interval when the cam follower portion of the spring |0|a is engaging the peripheral surface of the cam |00 defined by this third notch.

The selector switch I9 responds to kthe impulses of the first digit by elevating its wipers to a position opposite the level of bank contacts terminating the conductors of the trunk lines respectively extending to the connector switches having access to the called line I2. When the cam follower portionrof the shunt spring lilla engages the projection separating the notch Milla and lllb of the cam |661, it is moved into engagement with the associated spring lb to complete an obvious path in shunt with the pulsing springs |06 so that the latter springs are no longer actively included in the calling loop circuit. The circumferential length of the projection separating the two notches |000, and Ib determines the duration of the interdigit pause between the first and second digits of -the directory number designating the substation C. During this pause,

the wipers of the selector switch |9 are rotated.

step-by-step until a trunk line extending to an idle one of the connector switches of the selected group is found. Assuming, for example, that the connector switch 2| is the first available idle switch of the selected group, the selector switch i!! seizes this connector switch and extends the callingV loop circuit thereto. Thereafter, and when the cam follower portion of the shunt spring Illia drops into the notch ltliib of the cam |00, the pulsing springs |06 are again actively included in the calling loop circuit so that the impulses of the second digit are transmitted to the connector switch 2|. The indicated connector switch responds to the impulses of this digit by elevating its wipers to a position opposite the level of bank contacts terminating the ten subscribers linesforming the subgroup including the line I2. When the cam follower portion of the spring ||l|a engages the projection separating thenotches limb and llc, the shunt springs are again moved into engagement to short circuit the pulsing springs |65, thereby to terminate the impulses of the second digit and to provide an interdigit pause .during which the control apparatus of the connector switch 2| is conditioned to respond `to the impulses making up the third digit of the directory number desig` hating the substation C. The impulses of this third digit are started when the cam follower portion of the spring |t|a drops into the notch iililc so that this spring is disengaged from its associated spring itil). The connector switch 2| responds to the impulses of the third digit by operating to select the line l2 from the selected subgroup of lines. The pulses of the third and nal digit are terminated when the cam follower portion of the spring |l||a is moved out of the notch |0|lc and into engagement with its assocated spring |0|b to shortA circuit the pulsing springs |05. Shortly following the endof thethird digit, the cam follower portion of the contact spring |38 moves over the trailing edge of the notch Ia provided in the cam |8 so that the springs |36 and |38 are moved into engagement, following which, the springs |36 and |31 are disengaged. T hus, the shunt springs IDI and the pulsing `springs |06 are effectively shunted from the calling loop circuit so that no further impulses may be transmitted thereover untila second cycle of operation of the control device is initiated. After the Aimpulse transmission is ended, the calling loop circuit is not interrupted for a substantial time interval during which the called line |2 is tested to' determine the idleor busy condition thereof, ringing current may be transmitted overthe line to energize the signal device provided at the called substation and the call may be` answered. Thus, the cams |01 and |08 are rotated through an angle of approximately 135 degrees during the interval when the call is being forwarded through the switches l I5, I9 and 2| to the called line I2. These cams must be rotated through an additional angle of 225 degrees lbefore they are returned to their respective normal positions to `complete theroperating cycle.` Thus, aV period of approximatelyA twenty-fourv seconds is provided during which the called substationmay be signaled and the call answered.

Assuming that the called line i2 is idle at thel time it is selected by the connector switch 2| and,

f further, that the call -is answered during thel above-mentioned time interval required for the control device to complete its cycle of operation, the ring cut-off relay provided in the connector switch2| operates to complete aloop circuit extending through thewindings of the back bridge relay of this switch andincluding the conductorsof the called line l2 in the usual manner. Upon operating, the back bridgel relay of the connector switch functions to reverse' the direction of current flow over the loop -circuit extending from the connector switch 2| to the repeater |23. As a result, the polarized relay |30 is'caused to operate. Upon operating, the relay |30 opens, at its armature |33, a .point in ,the initiallyco1`n pleted circuit for energizing the motor `At t its armature |32, the relay |30 completes .an obvious path for short-circuiting the condenser |22-, thereby to establish av direct current bridge across the conductors of the line ||.v More par` 5 ticularly, a loop circuit is established which extends by way of the conductor Ha, the springs |06, the winding |24, the 4winding of the relay |20, the armature |32, the winding |25 andthe opposite line conductor lib.` When this circuit is completed, the ring cut-off and back bridge relays embodied in the. connector switch 20 are caused sequentially to operate in the manner previously explained so that the ringing operation of the connector switch 2o is arrested and a talkingcircuit is yestablished which includes "the re-rk peating coil |23 and extends from the calling sub,- station A to the substation C.

At its armature |3I, the back bridge relay i3d, upon operating, effectively shunts the contact springs |34 from" the loop circuit including the line 2 2. As aI result', this loop circuit is not interrupted when the control cams |01 and |08,

are returned to their respective home positions to end the operating cycle of the `control device. When the cams |01 and IUS are rotated back to normal, the cam follower portion of the'lower control spring |35 drops into the notch provided in the peripheral surface of the cam |01 so that the springs |34 andf|35 are respectively disengaged. When the springs |35 are'moved out of engagement, the previously traced second circuit for energizing the motor is interrupted. Accordingly, this motor is deenergized and operation of the control device is arrested with the various cams occupying the positions illustrated in Fig. l of the drawings.

Assuming that the connector switches 20 and 2| and the other similar switches embodied in the system are of the calling party release type, when the call is cleared out at the calling substationv A the switches 20, |18 and I4 included in the operated switch train are released in the order named and in the manner previously eX- plained. When the connection is cleared out at the called substation C, the back bridge relay embodied in the connector switch 2| is caused to restore so that the direction of current flow over the loop circuit including the line' 22, is again reversed. As a result, the polarized relay |30 restores to open the loop circuit at its armature |3|. At its armature |32, the relay |30 opens the path short-circuiting the condenser |22. At its armature |33, the relay |30 reprepares the operating circuit for the motor III. When the loop circuit including the line 22 is thus interrupted, the connector switch 2|, the selector switch I9 and the line switch 23 are successively released in the order named. Thus, the automatic switching apparatus utilized in forwarding the connection to the substation C is fully restored to normal.

1f, for any reason, the call as forwarded to the substation C is not answered at this substation within the interval required lfor the'control device to complete its cycle of operation after the impulse transmission is ended, the switch train through which the call is forwarded is released and a new cycle of operation of the control device is initiated; assuming that the call is not abandoned at the calling substation A during this interval. Thus, if the called line l2 is busy at the time it is selected by the connector switch 2 the connection obviouslycannot be completed. In such case, the control apparatus of the connector switch 2| functions to return busy tone over the loop circuit including the line 22 and extending to the repeating coil |23, in the usual manner. Since, however, no talking circuit is as yet established betweenA the calling line I and the repeating coil |23, this busy signal is not transmitted to thev calling subscriber. lOn Athe contrary, the usual ring-back tone signal is transmitted to the calling substation continuously un-` til the call is abandoned or is successfully completed` Hence, it will be apparent that the calling party may not abandon the call for a substantialperiod, during which the control device of the call forwarding apparatus may operate through a number of cycles. This may also occur in the case when the line to which the call is forwarded is idle, but the call as forwarded to the substation associated with this line is` not answered promptly. In any event, when such a situation arises, the control device upon completing its first cycle of operation interrupts, at the contact springs |34, the loop circuit extending by wayof the line 22 to the line switch 23.

As a result7 the operated switch train comprising the switches 2|, I9 and 23 is released. Since the start relay |20 is, underlthe conditions as sumed, still operating intermittently in response to the ringing current being transmitted over the line I the motor is deenergized only for a short time interval, if at all, following the completion of the first cycle of operation of the control device. During the first ringing period following the end of the first cycle of operation of the control device, the relay |20 reoperates, the motor is again energized, and a new cycle of operation of the control device is initiated. From this point on, the manner in which the call is again forwarded to the called substation C is exactly the same as explained above. A

In the event the call is abandoned at the calling substation A while a cycle of operation of the control device is in progress and before the call is answered at the substation C, the operated switch train through which the'call is routed to the line is released, but the control device of the call forwarding apparatus continues to operate until the cycle of operation in progress is completed. Thus, so long as the contact springs |35 are engaged, the secondary circuit for energizing the motor is not interrupted. Accordingly, if the call is abandoned while a cycle of operation of the control device is in progress, the control device continues to operate. In such case, if the call is answered at the called substation C to cause the operation of the polarized relay |30 in the manner previously explained, the called party is informed by the failure of the calling party to respond to his answering salutation that the call has been abandoned, and may cause the operated switch train through which the call is forwarded to the line |2 to be released by restoring the receiver provided at the substation C to its supporting hook or cradle.

The call as routed to the line from the substation A may be answered at the substation B even though the call forwarding apparatus is conditioned to operate in response to ringing current transmitted over the line I. In such case, the ringing operation of the connector switch 20 is arrested when the party answering the callremoves the receiver provided at the substation B from its supporting hook or cradle to establish a direct current bridge across the conductors of the line Since operation ofthe control device is initiated when ringing current is first transmitted over the line the call forwarding apparatus operates to forward the call to the substation C. If the call is answered at the last-mentioned substation before the control device completes its cycle of operation, a three way connection is established between the substations A, B and C. Completion of the branch connection to the substation C in no way interferes with the release of the call forwarding apparatus or the automatic switches through which the connections are routed. s

Referring now more particularly to the embodiment of the call forwarding apparatus illustrated in Fig. 2 in association with the line I3 extending tothe substation D, this apparatus includes a control device which is substantially identical in construction and arrangement with the corresponding device illustrated in Fig. 1 and included in the call forwarding apparatus associated with the substation B. For this reason, corresponding elements of the two control devices have been indicated in the two iigures of the drawing by reference characters having the same tens and units digits but different hundreds digits. It will be noted that the only difference between the two control devices is that in the arrangement illustrated in Fig. 2 the spring pile associated with the control cam 208 comprises only two contact springs 236 and 238, whereas the corresponding spring pile IID embodied in the control device shown in Fig. 1 includes an additional contact spring |31. In the Fig. 2 arrangement, no auxiliary line between the substation arranged for call forwarding service and the central exchange switching apparatus is required, the switches utilized in forwarding a call from the line I3 to another of the substations of the system being directively controlled through the provision of apparatus for transmitting over the line I3 alternating'current impulses designating the substation to which the call is to be forwarded. This apparatus, as provided at the substation D, comprises, in addition to the control device mentioned above, an alternating current start relay 220 for initiating operation of the control device and an alternating current relay 240 which is operative to connect the conductors of the line I3 to an alternating current pulsing circuit which includes a condenser 243 and the secondary winding of a voltage stepdown transformer 2M. This alternating pulsing circuit is arranged `to be controlled by the contact springs 2I0, 25| and 255 of the control device in the manner more fully explained subsequently.

For the purpose of repeating alternating current pulses transmitted from the substation D as direct current impulses over the line I3 to the automatic switching apparatus provided in the line terminating exchange, there is provided in the exchange in association with this line a special line circuit 30. More particularly, the line I3 is divided at the main distributing frame of the exchange into two normally connected line sections |30 and |3d, the first of which extends to the substation D and the second of which extends to the automatic switching apparatus provided in the exchange. Briefly described, the special line circuit 35 comprises an alternating current relay which is normally bridged across the conductors of the line section in series with a condenser 252 and is arranged to operate in response to ringing current transmitted over the line. The apparatus 3|] further comprises a slow-to-release hold relay 255, a

switching relay 269, an alternating current pulsing relay 255, a slow-to-release line switching relay 21|) and a slow-to-release pulse responsive relay 215. There is also provided a repeating coil 223 which corresponds to the repeating coil |23 of the Fig. 1 arrangement, and a polarized back bridge relay 230 of the permanent magnet type which corresponds to the back bridge relay embodied in circuits shown in Fig. l.

Referring now to the operation of the call forwarding apparatus illustrated in Fig. 2, it will be apparent that so long as the station selecting element 202 of the control device occupies its normal position, the alternating current relay 22|! is effectively disconnected from the conductors of the line I3 and cannot respond to ringing current transmitted over this line. With the apparatus in this condition if a call originating at the substation A, for example, is forwarded by way of the line Io, the line switch I4, the selector switch I9 and the connector switch 2| to the line I3 at a time Vwhen the latter line is idle, ringing current is projected over the line I3 by the control apparatus embodied in the connector switch 2| immediately following the operation of this apparatus to determine the idleconditionof the line. A portion of the ringing current traverses the Winding of the relay 250 over a circuit which may partially be traced as extending by way of the armature 21|, the armature 25|, the condenser 252, the winding of the relay 25|), the armature 262 and the armature 212. Each time this relay is energized by the ringing current it operates to complete, at its armature 25|, an obvious circuit for energizing the slow-to-release hold relay 255. The relay 255, upon operating, prepares, at its armature 256, a circuit for energizing the relay 260. This latter circuit, which extends by way of the armature 25 I, is completed at the end of each ringing interval in response to the release of the relay 255. Upon operating, the relay 26|) connects the winding of the alternating current relay 265 across the conductors of the line I3 in series with the condenser 261. Substantially simultaneously with the completion of the operating circuit for the relay 25|), the operating circuit for the slow-to-release relay 255 is interrupted. The period between ringing intervals is such that the relay 255 restores to cause the restoration of the relay 250 shortly following the end of each ringing interval and before the next ringingv interval occurs. Accordingly, the relays 250, 255 and 26|) sequentially respond to each splash of ringing current transmitted over the line I3, but perform no useful function and do not function to cause the operation of any of the other relays embodied in the line circuit 30. When the call is answered at the called substation D to cause the operation of the ring cut-off relay provided in the connector switch 2 I, thereby to terminate the ringing operation, the three relays 250, 255 and 260 are caused to restore. These relays remain in their respective restored positions until another call is routed to the line I3.

If the call originating at the substation A is forwarded through the automatic switches I4, I9 and 2| to the line I3 at a time when the station selecting element occupies one of its offnormal positions, the call forwarding apparatus illustrated in Fig. 2 operates to cause the call to be forwarded to the substation corresponding to the off-normal position occupied by the station selecting element. For example, if the element 202 is set in the off-normal position corresponding tothe substation B, the shunt springs 20| are positioned to be controlled by the cam 200 and the contact springs 204 are engaged so that the relay 220 is bridged across the conductors of the line |3. With the apparatus in this condition, if ringing current is projected over the line I3 the relays 250 and 255 are caused to operate in the manner explained above. In addition, the alternating current relay 22|! is energized by a portion of the ringing current, the circuit traversed by this current extending by way of the armature 21|, the line conductor |3a, the armature 242, the condenser 222, the winding of the relay 220, the contact springs 204, the armature 2d I, the line conductor |31) and the armature 212. When energized at the beginning of the first interval during which ringing current is transmitted over the line I3, the relay 220 operates to complete, at its armature 22| and the associated working contact, a circuit for energizing the motor 2| I, this circuit extending from one terminal of the alternating current supply source through the windings of the motor 2I| andr -by way of the armature 22| to the opposite terminal of the current source. Operation of the motor is thus started toinitiate a cycle of operation of the control device. During the initial rotary movement of the control cam 291 carried by the shaft 2 I2, the springs 235 are closed to complete an obvious secondary circuit for energizing the motor 2| I, whereby operation of the motor is continued after the release of the relay 226 at the end of the rst ringing period. At the Contact springs 234 a circuit is prepared for connecting the primary winding of the transformer 2M across the conductors of the alternating current supply source in parallel with the winding of the alternating current relay 242. At the end of the first ringing interval, the relays 226 and 256 are deenergized and restore. The relay 256, upon restoring, completes the operating circuit for the relay 260, which latter relay in turn operates its armatures 26| and 262 to connect the winding of the relay 265 across the conductors of the line section |30. Upon restoring, the relay 226 opens, at its armature 22| and the associated working contact, the initially completed circuit for energizing the motor 2||. At its armature 22| and the resting contact associated therewith, the relay 220 completes the above-mentioned circuit for energizing the relay 240 and the primary winding of the transformer 264 in parallel. This circuit may be traced as extending from one terminal of the alternating current supply source by way of the contact springs 235 to the armature 22| where it divides; one branch extending through the primary winding of the transformer 244 and the contact springs 235 to the opposite terminal of the current supply source and the other branch extending by way of the condenser 265, the winding of the relay 240 and the contact springs 235 to the opposite terminal of the current supply source. When energized over this circuit, the relay 256 operates to open, at the armatures 24| and 242 and their respective associated'resting contacts, two points in the above-traced circuit for energizing the relay 220. At these same armatures and their respective associated working contacts, the relay 246 completes the previously mentioned circuit for energizing the pulsing relay 265, this circuit extending from the upper terminal of the secondary winding of the transformer 264 by way or" the armature 242, the line conductor |311, the armature 26|, the condenser 261', the winding of the relay 265, the armature 262, the conductor |3b, the armature 24|, the condenser 263 and the contact springs 2|!) to the lower terminal of the transformer secondary winding. Upon operating, the relay 265 completes, at its armature 266, a circuit for energizing the slow-to-release relay 216, this circuit extending from ground at the armature 232 by way of the armature 266 and the winding of the relay 210 to battery. At its armature 261, the relay 265 completes a calling loop circuit including the repeater coil windings 226 and 221 and the winding of the polarized relay 236, and extending to the line switch 26. The relay 210, upon operating, completes, at its armature 213, an obvious holding circuit for the relay 260, whereby the latter relay is held energized following the release of the relay 255 which occurs shortly after the operation of the relay 210. At its armatures 21| and 212, the relay 21D disconnects the line section |3d from the line section |3c, thereby to prevent the alternating current impulses transmitted over the line section |30 from being transmitted back over the calling end of the connection. At these same armatures and their respective associated working contacts the relay'210 partially completes a connection between the line section |3d and the repeater coil windings 224 and 225. At its armature 214, the relay 216 prepares a circuit for energizing the slow-to-release relay 215.

When the relay 265 operates to complete the above-mentioned loop circuit extending between the repeater coil 223 and the line switch 25, this line switch operates to seize an idle one of the selector switches, such, for example, as the selector switch |8, and to extend the loop circuit thereto. The direction of current flow over this loop circuit is such that the polarized relay 236 does not operate at this time. Following the operation of the relay 216, the relays embodied in the line circuit 30 are conditioned to respond to alternating current impulses transmitted thereto from the substation D over the line |3. In this regard it is pointed out that the transmission of alternating current impulses to the line circuit 36 is delayed for an appreciable time interval after the above-traced circuit is completed for energizing the relay 265. This time interval is necessary in order to give the line switch 21| ample opportunity to select an idle one of the selector switches to which it has access. To this end, the spring 238 is held in engagement With its associated spring 236, to maintain the pulsing springs 206 and the shunt springs 26| short circuited, during the interval required for the cam 268 to rotate through an angle of approximately degrees corresponding to rotation of the cam 206 through an angle of approximately degrees. At the end of this interval, the cam follower portion of the spring 238 drops into the notch 26311 formed in the peripheral surface of the cam 268 so that the pulsing springs 266, as shunted by the shunt springs 26|, are actively included in the above-traced circuit over which the pulsing relay 265 is energized. The manner in which the pulsing springs 206 and the shunt springs 26| cooperate to interrupt this circuit in accordance with the impulses of the impulse digits determined by the respective lengths of the notches 26M, 2666 and 266e is exactly the same as described above with reference to the operation of the control device illustrated in Fig. 1. These notches are formed of such lengths that the impulses of the directory number designating the substation B are transmitted over the line section |30 to the pulsing relay 265. The relay 265, through operation of its armature 261, functions to repeat these impulses over the calling loop circuit to the automatic switching apparatus utilized in forwarding the call. When the relay 265 restores at the beginning of the rst impulse of each digit, it opens, at its armature 266, the above-traced operating circuit for the relay 216. At this same armature, the relay 265 completes a circuit for energizing the slow-torelease relay 215, this circuit extending from ground by Way of the armatures 232, 266, 214 and the winding of the relay 215 to battery. Upon operating at the beginning of the first impulse of each digit, the relay 215 completes, at its armature 216, an obvious path for shortcircuiting the series path including the winding 226, the winding of the polarized relay 236 and the winding 221, thereby to exclude the impedance of these windings from the impulsing circuit over which the impulses are transmitted to the automatic switching apparatus. Due to their slowto-release characteristics, the relays 210 and 215 remain operated during impulsing. At the end of each digit the relay 265 is held operated for a suflicient time interval to permit the release of the relay 215, which latter, relay upon restoring,`V

nector switches having accessy to the` line II to.

which the call is to be forwarded. During the interdigit pause betweenr the iirst and second digits, the selector switchv I3 operates to. seize an idle one of the connector' switches, such, for example, as the switch 2.0.; in the selected group.

The seized.` connector switch 20 responds tothe impulses of the secondy and third digits by operating to select the line I'I in the exact manner previously explained: with reference to the call' routed fromV the substation A to, the substation B.' Assuming that the line III is idle at the time it is selected; the control apparatus of the connector switch 20 operates to transmit ringing current over this linel for the purpose of, energizing the signal device provided at the called substation B. TheA arrangement of the control device located at the substation D is similar to the arrangement of the control device illustrated in Fig. 1 in that a substantial timeV interval elapses between the end of the impulse transmission and the completion of the cycle of operation of the device.

positionls. This return movement` requires an angular rotation of the cams 201'and 208 of approximately 225 degrees, thus providing a relatively long time interval during which the substation By may be signaled and the call answered. Assuming that the call is answered during this interval, a loop circuit is established between the called substation Band the connector switch 20, thereby to cause the operation of the ring cut-off and back bridge relaysembodied in this connector switch. The back bridge relay of the connector switch 20, upon operating, reverses the direction of current flow over the loop circuit extending to the repeater vcoil 223 and including the winding of the polarized relay 230. As a result, the relay 230 operates to complete, at its armature 233, an obvious path shunting the pulsing springs controlled by the armature 2551 of the pulsing relay 255. At its armature 232, the relay 230 interrupts the operating circuit for the relay 210 andcompletes an obvious holding circuit therefor. At its armature 23I, the relay 230 completes a direct current path including the repeating coil windings 224 andy 225 across the line conductors of the line section ld. In response to this operation, the ring cut-oir" and back bridge relays embodied in the connector switch 2| are caused to operate in the manner "f previously explained, thus completing the desired talking circuit between the substation A and the substation B.

When the control device providedat the substation D completes its cycle of operation, the

More particularly, the cam follower portion of the spring 238 is moved out Iii motor 21| is deenergized and the two relays 240 and 265 are caused to restore. More particularly, when the cam 201 is returnedto its home position, the springs 234 and' 235 are respectively l disengaged to open the secondary circuitv for energizing the motor 2II and the above-traced circuit over which the winding of the relay 240 and the primary winding of the transformerV 244 arey connected in parallel across the alternating current supply source. Accordingly, the transformer 244 is deenergizedv and operation of the motor 2II is arrested. When the relay 240 is.. deenergizedV it restores to open two points in the above-traced circuit for energizing the relay 2651 and reconnects the windin-g of the relay 22|)y The relay' acrossl the conductors of the line I3. 25.5, uponrestoring, opens, at its armature 256, a furtherY point in the operating circuit for the relay 210 and, at its armature 261, opens thev path shunting the operated armature 233 of the back bridge relay 230.

The manner in which the connectionl as established between the substationsAand` B isrele'asedl is substantially similar to the release of the con- 5 nection established'through operation of the cally switch I8 to the connector switch 20 with the result that these switches are caused sequentially to restore in the order named.y At its armature 232, the relay 230, upon restoring, opens the holding circuit for the relay 210 causing the latter relay and the relay 250 sequentially to restore. At its armature 23I., the relay 230 opens a point in the loop circuit extending t'o the con-- nector switch 2I. Thus, the callforwarding -apparatus illustrated in Fig. 2 isfully restored to normal.

The arrangement of the call' forwarding apparatus shown in Fig. 2 is similar to thearrangement of the apparatus illustrated in Fig. k1 in that a callextended to the line I3 is repeatedly forwarded to the substation designated by the setting of the element 202 through repeatedoperations of the control device provided. at the substation D until the call is answered or is abandoned at the calling substation. More particularly, if the call as forwarded to the substation B is not answered during the interval which elapses between the end of the last series of impulses transmitted over the line I3 and the end of the cycle of operation of the control device, the switch train through which the call is for,- warded to the substation B is released. Thus, when the cam 201 is returned to its home position the contact springs 234 and 235 are respectively disengaged so that the relays 240 and 265v are caused to restore rin the manner previously explained. Under the circumstancesdescribed, the back bridge relay 230 is not operated. Accordingly, the relay 265, upon restoring, interrupts the operating circuit for. the relay 210, causing the relays 210 and V250 sequentially to restore. At its armature 261, the relay 265, upon restoring, also interrupts the loop circuit extending byy-l way of the, line switch 24 and the selector `switch I8 to the operated connector switch 20. In response to this operation, the switches 20, I3 and 24are caused sequentially to restore in the order named,

thus releasing the connection over which the call was initially forwarded to the substation B. If required, the relay 210 may be equipped with a dash pot or other suitable release retarding device in order to prevent the release of this relay before the switches 20, I8 and 24 are fully released. This release retarding device should be of such type that the relay 210 is fast-to-operate when energized. The relay 210, upon restoring, reconnects the line section I3d to the line section I3c so that if the call has not been abandoned, ringing current is again transmitted over the line section I3c to cause lthe reoperation of the two relays 250 and 220. Hence, a new cycle of operation of the control device is initiated. From this point on, the manner in which the call is again forwarded through the automatic switching apparatus to the substation B is exactly the same as described above.

If the call is abandoned at the calling substation A during a cycle of operation of the control device provided at the substation D, this device continues to operate until the cycle of operation is ended, after which the call forwarding apparatus is released. In this regard, it will be apparent that if the call is abandoned while the control device is in operation and the call is then answered at the substation B during the last part of the operating cycle of the control device, the answering party will be informed by the failure of the calling party to answer, that the call has been abandoned and may then condition the apparatus to be released at the end of the cycle of operation of the control device by restoring his receiver to its supporting hook or cradle. In the event the cycle of operation of the control device is completed before the answering party hangs up, the manner in which the three relays 23D, 210 and 260, embodied in the line circuit 30, are released when the connection is cleared out at substation B is exactly the same as described above. In the event the call is not answered or is answered and released after the call is abandoned but before the cycle of operation of the control device is ended, the call forwarding apparatus is restored to normal linmediately the cam 201 is returned to its home position. In response to this operation, the motor 2| I, the relay 240 and the transformer 2M,A are all Vdeenergized in the manner set forth above. In addition, the 'relay' 265 -is caused to restore to interrupt the loop circuit extending through the line switch 24 and to open the operating circuit for the relay 210. Thus, the relays 210 vand 260 are caused sequentially to restore and the switch train through which the call was forwarded to the line II is released. With' the arrangement illustrated in Fig. 2, a call routed to the line I3 from another line of the system cannot be answered at the substation D if the call forwarding apparatusA is conditioned for operation. Thus, immediately after the rst interval during which ringing current is projected over the line I3 the relay 21|! is caused to operate to disconnect the line section I3d from the line section I3c. Hence, ringing current is only transmitted over the line sectionv I 3c for one short interval and no talking circuit can be completed between the substation D and the connector switch through which the connection is routed to the line I3.

While there has been described what are at present considered to be the preferred embodiments of the invention, it will be understood that various modications may be made therein, and

it is contemplated to cover in the appended claims all such modifications as fall within the true spirit and scope of the invention.

What is claimed is:

1. In an automatic telephone system including a plurality of vsubstations and means comprising automatic switching apparatus for setting up connections between said substations, a line extending to one of said substations, said automatic switching apparatus including aconnector switch operative to seize said line and to transmit ringing current thereover in routing a call to said one substation, call forwarding apparatus associated with said one line and operative directively to control said automatic switching apparatus to route a call incoming to said line through said automatic switching apparatus to any one of a plurality of other substations, means responsive to ringing current transmitted over said line for initiating the operation of said apparatus, and means operative in response to the answering of said call at said other substation for terminating the ringing operation of said connector switch.

2. In an automatic telephone system including a plurality of substations and means comprising automatic switching apparatus for setting up connections between said substations, a line extending to one of said substations, said automatic switching apparatus including a connector switch operative to seize said line and to transmit ringing current thereover in routing a call to said one substation, call forwarding apparatus comprising a cyclically operative device associated with said line and operative to transmit to said automatic switching apparatus the impulses of the directory number designating another of said substations, a motor for driving said device, means responsive to ringing current transmitted over said line for initiating the operation of said motor, means responsive to the initial operation of said device for maintaining the operation of said motor until the cycle of operation of said device is completed, said automatic switching apparatus including automatic switches operative to extend a connection from said line to said other substation in response to the impulses transmitted thereto from said device, and means operative to terminate the ringing operation of said connector switch when the call forwarded to said other substation over said last-named connection is answered.

3. In an automatic telephone system including a plurality of substations and means comprising impulse responsive automatic switching apparatus for setting up connections between said substations, a line extending to one of said substations, a relay adapted to bev bridged across the conductors of said line to respond to ringing current transmitted to said one substation on calls incoming thereto, call forwarding apparatus comprising a cyclically operative device associated with said line and operative to transmit to said automatic switching apparatus the impulses of the directory number designating another of said substations, a motor for driving said device, a first circuit for energizing said motor, said first circuit being completed in response to operation of said relay, a second circuit for energizing said motor, said second circuit being completed in response to the initial operation of said device, said automatic switching apparatus including automatic switches operative to extend a connection from said one line to said other substation in response to the impulses transmitted thereto from said', device, means voperative to interrupt said first circuit when the call forwarded to said other substation oversaidrlastnamed connection isanswered, and. means 'con'- trolled by said device for interrupting said second circuit after said device has completed a.

cycle of operation.

4. In an automatic telephone system including a plurality of substations and means comprising impulse responsive automatic switching apparatus for setting up connections between saidsubstations, a line extending to one ofsaid substations, a relay and a condenser connectedv in series and adapted to be bridged across the conductors of said line, whereby-saidrrelay responds to ringing current transmitted to said;

substation on calls incoming to said onel substation, said automatic switching apparatus including a connector switch operative to seize said line and to transmit ringing current thereover in routing a call to said one substation; call for.`

said motor, said iirst circuit being completed in response to operation of said relay, a second circuit'for energizing said motor, said second cir-- cuit being completed in response to the initial operation of said device, saidautomatic switching apparatus including automatic'sWitches-operative to extend a connection from said linetor said other substation in response to the impulses.

transmitted thereto from said device, means-op'- erative to short-circuit said condenser, thereby to cause the ringing operation of said connector switch to .be terminated and also operative tov interrupt said rst circuit when the call forwarded to said other substation over said lastnamed connection is answered, and means controlled by said device for interrupting said second circuit after said device has completed a cycle of operation.

5. In an automatic telephone system-` including a plurality of substations and means comprising impulse responsive automatic switching apparatus for setting up connections between said substations, call forwarding apparatus comprising a cyclically operative device associatedl with one of said substations and operative tothe operation of said motor until the cycle ofv operation of said device is ended, said automatic switching apparatus including automaticA switches operative to extend a connection to said` other substation in response to the impulsesl transmitted thereto from said device, and, saidV control elements being so constructed, andl arranged that said switches are held operated for' an interval after said impulse transmission is ended. k

6. In an automatic telephone system including a plurality of substations and means comprising impulse responsive automatic switching appara tus for setting up connections between saidsubi impulse responsive-automatic switching apparastations,A call` forwarding apparatus comprising a cyclically'operative device associated with one l of said substations and operative .to transmit to said automatic .switching apparatus the impulses ,l of the directory number designating ano-ther of said substations, saidA device including an impulsingcontrol element and a switch release control element, Aa motor for driving said. device, means responsive to a: call route-d to said one substation forinitiating the operation of said motor, and means controlled'by said switch release control' element for; maintaining the operation of said motor untilthe. cycle of operation of said device is ended, said automatic switching apparatus including automatic switches operative to extend a connection to said other substation in .response tothe impulses transmitted thereto from said device,.said control 'elements being. so. constructed and arranged that said switches are held, operated for an interval after said impulse. transmission is ended, and means operativein thev event the .call as forwardedv to said'. other substation over said last-named connection-is answered during said interval for holding: said switches operated independently of said device:

7. Inv anautomatic telephone systemincluding a` plurality of substationsandmeans comprising impulse responsive automatic switching apparatusifor setting-up connectionsbetween said substations, call forwarding apparatus comprising a` devicefprovided att onezof said substations and including a plurality of control elements individually corresponding to certain of the other .isubstations of said system, a station selecting element having a normalposition and operative to oit-normal positions individuallyy corresponding'tosaid control elements, and pulsing means adapted toV becontrolled by. any one of said control elements for transmitting to said` automatic switching apparatus the impulses of the directoryf. number designating" the substation corresponding tov thef oni-normal position occupied by said station selectingelement, a motor forl driving said device, a device for-'initiating the operation of said motor, and'means responsive to operationof said station selecting element to any one of said ofi-normal positions for` conditioning. said last-named device to operate in response toa call. routed to said one substation.

8; In an automatic telephone system including a plurality of substations and means comprising tus forsettingup connections between said substations, aline extending to one of said substations, call forwarding apparatus comprising ay device provided at said one substation and including a plurality of control elements individually corresponding to certain of the other substations ofthe system, a station selecting element having a normal position and operative to offnormal positions individually corresponding to saidicontrolelements, and pulsing means adapted. to be controlled by any one of said control elements for transmitting to said automatic switching apparatus the impulsesjof the directory numberV designating the substation corresponding to the oir-normal position occupied by said station selecting'element, a motor for driving said i device, a relay adaptedtovvbe bridged -across the conductors of said line to respond to ringing currenttransmitted over said line, a circuit for energizingsaidmotor, means controlled by said relayfor completing said circuit, and means operative tobridge said relay across the conducstation selecting element to one Ofsaid'oif-normal-positions. 9. In an automatic telephone systemincluding a plurality of substations and means comprising impulse responsive automatic switching apparatus for setting up connections between said substations, a line extending to one of said substations, call forwardingapparatus comprising a cyclically operative device provided at said one substation and includinga plurality of control elements individually corresponding to certain of the other substations of the system, a station selecting element having a normal position and operative to oir-normal positions individually corresponding to said control elements, and pulsing means adapted to be controlled by any one of said control elements for transmitting to said automatic switching apparatus the impulses of the directory number designating the substation corresponding to the off-normal position occupied by said station selecting element, a motor for driving said device, a relay adapted to be bridged across the conductors of said line to respond to ringing current transmitted over said line, a circuit for energizing said motor, means controlled by said relay for completing said circuit, means operativeto bridge said relay across the conductors of said line in response to operation of said station selecting element to one of said off-normal positions, a second circuit for energizing said motor, and means operated during the initial operation of said device for completing said second circuit and for maintaining said second circuit completed until the cycle of operation ofsaid device is ended.

10. In an automatic telephone system, a plurality of substations, means comprising automatic switching apparatus for setting up connections between said substations, a line extending to one of said substations, and call forwarding apparatus comprising means automatically operative when an incoming call is present on said one line for repeatedly forwarding said call through said automatic switchingapparatus to another of said substations until said call is abandoned or is answered at said other substation. i

1l. In an automatic telephone system including a plurality of substations and means comprising impulse responsive automatic switching apparatus for setting up connections between said substations, a line extending to one of said substations, call forwarding apparatus comprising a cyclically operating device for transmitting to said automatic switching apparatus the impulses of the directory number designating another of said substations during each cycle of operation thereof, and means operative when an incoming call is present on said one line for causing said device to operate through repeated cycles, thereby repeatedly to forward said call to said other substation, until said call is abandoned or is answered at said other substation.

12. In an automatic telephone system including a plurality of substations and means comprising impulse responsive automatic switching apparatus for setting up connections between said substations, a line extending between said automatic switching apparatus and one of said substations, call forwarding means comprising apparatus operative to cause a connection to be extended from said line through said automatic switching apparatus to another of said substator's of said line in response to operation of said' tions in response to Aalternating current impulses' transmitted thereto, and means automatically operative in response to the presence of anincoming call on said line for transmitting alternating current pulses to said last-mentioned apparatus.

13. In an automatic telephone system including a plurality of substations and means comprising impulse responsive automatic switching apparatus for setting up connections between said substations, a line extending between said automatic switching apparatus and one of said Asubstations, call forwarding apparatus comprising an impulsing device at .one of saidv substations,' i means controlled by said device'for transmitting over said line alternating current impulses corresponding to the directory number designating another of said substations, apparatus operative in response to said'alternating current impulses for causing a connection to be extended from said line through said automatic switching apparatus to said other substation, a motor for driving said device, and means operative in response to the presence of van incoming call onV said line for initiating the operation of said motor.

14. In an automatic telephone system including a plurality of substations and -means comprising impulse kresponsive automatic switching apparatus for setting up connections between said substations, a line extending between said automatic switching apparatus and one of said substations, call forwarding apparatus comprising an impulsing device at 'one of said stations;

said impulsing device including a plurality of control elements individually corresponding to certain of the other substations of the system, a station selecting element having a normal position and loperative to' off-normal positions individually corresponding to said control elements,

and means for transmitting over said line alternating current impulses designating the substation corresponding to the OIT-normal position occupied by said station selecting element; apparatus operative in response to said'alternating cur'- rent impulses for causinga connection 'to be extended from said line through said automatic switching apparatus to the substation designated by theposition occupied by said station selecting element, a motor for driving said device, a circuit for energizing said motor, a device operative to complete said'circuit, and means'responsive to operation of said stationv selecting element to one of said off-normal positions for conditioning saidV last-named device to operate in response to a call routed `to said one substation.

15. In an automatic telephone system including a plurality of substations and means comprising impulse responsive automatic switching apparatus for setting up connections between' said substations, a line extending from said automatic switching apparatus to one of said substations, call forwarding apparatus comprising a device operative in response to ringing current transmitted over said line, 'means controlled by said device for transmitting over said line along alternating current pulse followed by alternating current impulses corresponding to the directory number designating another of said substations, a pulsing relay adapted to be connected to said line to respond to said alternating current pulses and to repeat said impulses to said automatic switching apparatus, thereby to extend a connection from said line through said automatic switching apparatus to said other substation, and means controlled by ringing current transmitted over said line for connecting said pulsing relay to said line.

16. In an automatic telephone system including a plurality of substations and means comprising impulse responsive automatic switching apparatus for setting up connections between said substations, a line extending from said automatic switching apparatus to one of said substations, a repeater including a rst winding adapted to be connected across said line and a second winding adapted to be included in a calling loop circuit extending to said automatic switching apparatus, call forwarding apparatus comprising a device operative in response to ringing current transmitted over said line, means controlled by said device for transmitting over said line a long alternating current pulse followed by alternating current impulses corresponding to the directory number designating another of said substations, a pulsing relay adapted to be connected to said line to respond to said alternating current pulses, said pulsing relay being operative to complete said calling loop circuit and to repeat said impulses by way thereof to said automatic switching apparatus, whereby a connection is routed from said repeater through said automatic switching apparatus to said other substation, means responsive to operation of said pulsing relay for connecting said first winding t said line, and means controlled by ringing current transmitted over said line for connecting said pulsing relay to said line.

17. In an automatic telephone system including a plurality of substations and means comprising impulse responsive automatic switching apparatus for setting up connections between said substations, a line extending from said automatic switching apparatus to one of said substations, a repeater including a first winding adapted to be connected across said line and a second winding adapted to be included in a calling loop circuit extending to said automatic switching apparatus, call forwarding apparatus comprising a device operative in response to ringing current transmitted over said line, means controlled by said device for transmitting over said line a long alternating current pulse followed by alternating current impulses corresponding to the directory number designating another of said substations, a pulsing relay adapted to be connected to said line to respond to said alternating current pulses, said pulsing relay including contacts for completing said loop circuit and for repeating said impulses by way of said loop circuit to said automatic switching apparatus, whereby a connection is routed from said repeater through said automatic switching apparatus to said other substation, a hold'relay operative to connect said first winding to said line in response to operation of said pulsing relay, a holding circuit for said hold relay, means controlled by ringing current transmitted over said line for connecting said pulsing relay to said line, and means operative when the call forwarded to said other substation is answered for completing said holding circuit and for shunting sai pulsing contacts.

18. In an automatic telephone system including a plurality of substations and means comprising impulse responsive automatic switching apparatus for setting up connections between said substations, a line including two normally connected sections, one of said sections extending to said automatic switching apparatus and the other of said sections extending to one of said substations, a repeater including a first winding adapted to be connected to said one line y section and a second winding adapted to be included in a calling loop circuit extending to said automatic switching apparatus, call forwarding apparatus comprising a device operative in response to ringing current transmitted over said line, means controlled by said device for transmitting over said other line section a relatively long alternating current pulse followed by alternating current impulses corresponding to the directory number designating another of said substations, a pulsing relay adapted to be connected to said other line section to respond to said alternating current pulses, means controlled by said pulsing relay for completing saidy calling loop circuit and for repeating said impulses by way of said calling loop circuit to said automatic switching apparatus, whereby a connection is routed from said repeaterl through said `automatic switching apparatus to said other substation, means responsive to operation of said pulsing relay for disconnecting said one line section from said other line section and for connecting said one line section to said rst winding, and means controlled by ringing current transmitted over said line for connecting said pulsing relay to said other line section.

19. In an automatic telephone system including a plurality of substations and means comprising impulse responsive automatic switching apparatus for setting up connections between said substations, a line including two normally connected sections-one of said sections extending to said automatic switching apparatus and the other of said sections extending to one of said substations, a repeater including a rst winding adapted to be connected to said one line section and a second winding adapted to be included in a calling loop circuit extending to said automatic switching apparatus, call forwarding apparatus comprising a device operative in response to ringing current transmitted over said line, means controlled by said device for transmitting over said other line section a relatively l'ong alternating current pulse followed by alternating current impulses corresponding to the directory number designating another of said substations, a pulsing relay adapted to be connected to said other line section to respond to said alternating current pulses, said pulsing relay including contacts for completing said loop circuit and for repeating said impulses by way of said calling loop circuit to said automatic switching apparatus, whereby a connection is extended from said repeater through said automatic switching apparatus to said other substation, a hold relay operative to prepare a connection between said one line section and said rst winding in response to operation of said pulsing relay, a holding circuit for said hold relay, means controlled by ringing current transmitted over said line for connecting said pulsing relay to said other line section, and means loperative. when the call forwarded to said other substation is answered for completing said last-mentioned connection, completing said holding circuit and shunting said pulsing contacts.

JOHN WICKS.

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