US1251604A - Ringing control system for telephone-exchanges. - Google Patents

Description

for:

" AWE/r Patented Jan. 1, 1918.

. 9 was S. B. WiLHAMS, JR

APPLICATION mu) DEC. 28. 1915.

new

RINGING CONTROL SYSTEM FOR TELEPHONE EXCHANGES..

UNITED STATES PATENT @FFTCE.

SAMUEL E. WILLIAMS, 33., OF BROOKLYN, NEW YORK, ASSIGNOR TO WESTERN ELEG- TRIC COMPANY. INCORPORATED, OF NEW YORK, N. Y., A CORPORATION OF NEW YORK.

RINGING CONTROL SYSTEM FOR TELEPHONE-EXCHANGES:

moron-a.

Specification of Letters Patent.

Patented Jan. 11, 1918..

Application filed December 28, 1915. Serial No. 69,066.

T 0 all whom it may concern:

Be it known that I, SAMUEL B. 'Wliiunzvts, J12, a citizen of the United States, residing at Brooklyn, in the county of Kings and State of New York, have invented certain new and useful Improvements in Ringing Control Systems for Telephone-EXchanges, of which the following is a full, clear, concise. and exact description.

This inventioii relates to a ringing control system for telephone exchanges. and is ringing current that is automatically ap plied in establishing connection with a'line, to ring a particular station ot that line, and to ascertain the sort oi? ringing current a particular connecting circuit is set to apply.

The system of this invention is such that the setting of the operators switching apparatus to predetermine the character of ringing current that to be applied automatically by a particular connecting circuit, brings about certain changes in said circuit which not only are instrumental in controlling the charactcr of the signaling current that this circuit is thus adapted to apply, but also control the display or a corresponding one of a number of signals associated with the operators switching apparatus to indicate to the operator, when she listens in on this connecting circuit. the sort of ringing current for which the connecting circuit is set. The organization ot'the. system is such that when a connecting circuit is changed through the agency ot the operator's switching mechanism to adapt it for the application of a certain sort of ringing current, it remains set to apply'this sort of current until the connection is taken down or until the operator manipulates her switching mechanism to change the setting while switch of the eflccted through the agency of an automatic sequence switch type, this switch being arranged to establish the different ringing current combinations in different positions of its movement, and being arranged to move to any predetermined one of its ringing positions under the control of the individual connecting circuit controlling mechanism set by the switching apparatus common to the position.

The above mentioned and other features of the invention will be described in detail in connection with the accompanying drawing. which illustrates one of the forms in which the invention may be practised. v

In the particular embodiment illustrated, the invention is shown applied to a connccting circuit terminating in a plug 11, the plug being adapted to be inserted in a spring jack 12 upon which the telephone line terminates. The telephone line 13, 14: 1s lllustrated as extending to four substations, M, J, R and W, each of which is provided with the usual substation equipment, which may comprise a telephone transmitter and receiver, an induction coil, a condenser and a switch hook for controlling the circuit. In addition, there is at each substation a bell which is bridged, through the condenser, from one side or the other of the telephone line to ground. The bells at substations M and J are bridged to ground from the conductor 13, and those at stations R and i from conductor 14: of the telephone line.

Only the calling end of the connecting circuit E is illustrated. The other end of the connecting circuit may be assumed to extend to apparatus suitable for making connection with a calling line and "for controlling such connection. the circuit between the answering and calling ends of the connecting circuit having included in it a repeating coil 10 with a bridged battery 15, in the usual way.

The talking eoiuluctors 1.6 and 17 of the conn cting circuit terminate upon the tip and ring contact surfaces, respectively, of the calling plug 11. The sleeve contact surface of the plug is the terminal of a conductor 18, which extends from the free pole of the battery 15 and includes the windings of two relays 19 and 20. When the plug 11 is inserted in a spring jack 12, the circuit of this conductor 18 is completed to ground by way of the winding of the cut oit relay 21, thus bringing about the energization of the relays 19, 20 and 21. The relay 21 has the usual function of disconnecting from the line, during its use, the branches that lead to the usual line signal apparatus (not shown). Relay 19 in operating, disconnects the tip of the plug from the operators busy test circuit (not shown) and connects it with the talking conductor 16. The relay 20 in operating, closes a circuit 501' the How of current through the calling super visory lamp 22, subject to the control of contacts 114 closed in position 17 ot' a calling cord sequence switch that will be referred to hereinafter. After the circuit of the calling lamp is closed by the actuation of the relay 20, when the calling plug is inserted in the spring jack, the illumination of the lamp is under the control. of the called subscriber in the usual way through the medium of the calling supervisory relay 2 1, the shunt of the lamp controlled by this relay being also under the control of contacts 112 closed in position 17 of the calling cord sequence switch.

The calling cord sequence switch 100 may be similar to that illustrated in Patent #1,127,S08 to J. N. Reynolds and C. F. Baldwin, dated February 0, 1915, or of any other suitable type. The sequence switch 100 controls sequence switch contacts 101 to 114, inclusive. Contact 101 of the sequence switch is arranged to close the local circuit "for the sequence switch operating ma gnct in all positions of the switch except those indicated by the figures adjacent to contact 101. This provides that theswitch may Stop only in the positions indicated. The other sequence switch contacts 102 to 114C inclusive, are closed only in the positions indicated by the figures adjacent to the respective contacts.

The positions of the calling cord sequence switches are as follows:

Ringing current is supplied to the connecting circuit by way of a conductor 25,

which has branche 20 and 27 at one end that are adapted under certain conditions to be completed to the tip and ring conductors. respectively, of the calling plug 11, and branches 28 and 29 at the other end which are adapted under certain conditions to be completed to sources of two different sorts of ringing current. In the present instance, the ringing generator 30 has associated with it three commutators 31, and The commutator 31 is adapted, during each cycle of its rotation, to connect the conductor 29 for an interval with generator 30, and during the balance of the cycle connect it with the free pole of battery 15. Commutator 32 is adapted, during each cycle of its rotation, to connectthe conductor 28 twice with the ringing enerator 30 and twice with the free pole of the battery 15 alternately. The arran ement is such that when the branch, by way of the conductor 29, is connected with the cord circuit, a single long impulse of ringing current is applied to one or the other side of the line, depending upon which of the branches 20 and 27 is closed at the time; while. when the branch 28 is connected with the cord circuit, two short ringing impulses are applied. to one side or the other of the line. with a relatively long interval of silence between each group of two short rings. The pick-up commutator 33 rotates with the commutators 31 and and is arranged to send one impulse of current per rotation from the battery 15 out over the circuit in a manner hereinafter to be described, "tor the purpose ol marking the cycles of rotation of the commutators.

The organization described abovc provides ringing current for a plurality of the connecting circuits. and is one'ot' those that may be employed for producing ditterent sorts of ringing current for the selective or distinctivc ringing of bclls at the various substations of a party line. nmnhcr ol other methods of selectively or distinctively ringing party line bclls are available in the art and may be employed, such as those which depend upon thc use of polarized pulsating currents in conncction with polarizcd and biased bells. and those depending upon dittercnt trcqucncv currents and so-called harmonic or tuned bclls, and it will be un lerstood that ringing generators and bells oi' tho th r orts may be substituted for those particularly disclosed herein, without dcparting from the spirit and scope of this invcntion.

The branch 20 of the conductor '25 has its connection with the tip side of th connecting circuit controlled in sequence switch contacts l0l-5 and l0--l8 \vhilc branch "2. has its connection with the ring side of the connecting circuit controlled in sequenciswitch contacts 10511 and 105-13. The

connection between the other end of the con ductor 25 and the two branches 2S and 2 over which the two sorts of ringing currents are supplied from con'nnutators 32 and 'll. is controlled by sequence switch contacts 100. branch 28 being connected with cinnluctm' 25 in positions 100-5 and 100-ll, while branch 29 is eonncctedin positions 106-8 and 100-13 of the switch contacts. That is, in position 5 of the sequence switch 100, source 30, 32 of ringing current is connected with the tip strand of the connecting circuit; in position 8 of the sequence switch, source 30, 31 is connected with the tip strand, in position 11, source 30, 32 is connected with the ring strand, and in position 13, source 30, 31 is connected with the ring .strand of the connecting circuit. Contacts 1055, 105S, 104*11 and 1041'3 of the sequence switch operate to establish a ground connection from one side o:t the connecting circuit when the other side of the circuit is connected to one or the other of the sources oi ringing current.

In the particular embodiment of the invention illustrated, the control of the ringing current so as to ring any one 01": the four stations of a party line is effected through the medium of four'selective keys M, J, R, and 1V, which are common to all of the connccting circuits of the operators position. Other connecting circuits organized similarly to the one shown, are indicated by the taps which are represented as extending from the conductors that lead to the common selective keys and their associated lamps m, j, r, and w. The selective keys M, J, R, and NV act through the medium of relays 38. 39 and 40, individual to each connecting circuit,'to determine which one of four branches 41, 42, 43, and 44 of a controlling circuit 45 shall have its circuit 'closed. These branches 41, 42, 43 and 44 are brought successively into operative relation with the controlling conductor 45 in the movement or the sequence switch 100 and through the medium of their respective associated sequence switch contacts 1073 to 5, 1086 to S, 109-9 to 11, and 110-12 to 13. The completion of the controlling conductor 45 throughtone or another of the branches 41, 42, 43 and 44 in the movement of the sequence switch acts through the medium of relay 36 included in the controlling circuit to complete the circuit of the ringing conductor in the contacts 34 of that relay, and to control the stopping of the sequence switch in position to close the branches of the ringing circuit for ringing the particular party line station that corresponds with the particular selective key M, J, R, or V that has been depressed and the particular branch 41, 42, 43 or 44 of the controlling circuit that has been closed.

Assuming thatthe operator has received a call for station W of the particular line that is illustrated in the drawing, and that the call has come over the connecting C11- "cuit that is shown in the drawing. Under such circumstances the operator has her telephone set and controlling apparatus in connection with the particular cord circuit illustrated, and the switch contacts 202, 203, 204,

205, 207 and 208, which may be contacts as sociated with a listening key sequence switch, of which there would be one foreach connecting circuit, are-closed. The closure of these contacts, only one set of which may be closed at a time, connects the selecting keys M, J, R, and 1V common to the operators position with the particular connecting circuit thatis'to be used in establishing the connection. This places the ringing control devices of this particular connecting circuit under the control of the common selecting keys M, J, R and W'.

The arrangement of the ringing current controlling devices of each connecting circuit is such that normally the branch 44 of the controlling circuit 45 has its connection with earth completed by way of the back contacts 40, 47 and 48 of the relay 38, 39 and 40, respectively; and therefore, if the apparatus is in its normal'condition, itis not necessary for the operator to depress the selecting key lV. She inserts the calling plug 11 into the spring jack 12. This act, through the agency of circuits and apparatus that need not be particularlydescribed, completes the local circuit of the calling cord sequence switch operating magnet by way of sequence switch contact 1021, and moves the sequence switch out of positlon .1 and into position \Vhen the operators telephone set and controlling apparatus is dlsconnected from the connecting cireuit,- which may result either from the operators listening out manually, or from a sequence switch that is assumed to control the switch contacts 202 to 208, inclusive, being moved as a result of the closure of the circuit due to inserting the plug 11 in the spring jack l2,the local circuit of the calling cord sequence switch is closed by way of sequence switch contacts 1032 to move the sequence switch out of position 2.

As sequence switch 100 moves into position 3, it closes in sequence switch contacts 111. a path to ground for whichever of the branches 41, 42, 43 and 44 may be closed in the relay contacts 46, 47 and 48. In the particular case being described, as the relays 38, 39, and 40 are inert, it is the branch 44 that thus is given a ground connection As the sequence switch 100 moves into position 4, its further movement comes under the control of the normal or resting contacts 35 of relay 36 by way of sequence switch contacts 103- 1 to 13. Therefore, beyond position 4 the movement of the sequence switch 100 will continue only as long as relay 36 remains inert. As sequence switch 100 moves l'rom position 3 to position 11 inchisive, it brings the controlling conductor 45 successively into communication with the branches 41., 42 and 43 by the successive closure of the sequence switch contacts 107, 108 and 109. But as each of these branches is open in its associated relay contacts, nothing happens.

\Yhen sequence switch 100 comes to position 12, it closes sequence switch contacts 110, and thus completes t path to ground for controlling conductor 45 by way of branch l-t, the resting contacts 18, 47 and 46 of relays '10, 39 and 38 respectively, and sequence switch contacts 111. This atlords a path for current tlow through relay 36, and the consequent energization of that relay opens its back contacts 35 and interrupts in these contacts the local energizing circuit ot' the sequence switch 100 by way of contacts 1(3, thus causing the sequence switch to come to rest in position 13 upon the opening of the alternative energizing path that. it has in position 12 by way of sequence switch contact 101. in position 13 of the sequence switch 100 ringing current from the' source 30. 31 is supplied to the line to ring the bell at station \V', the path of flow being fron'i ringing generator 30 through connnutator ll branch 2 sequence switch contacts IMP-13, winding of relay 49, contacts 3-1 oti relay 3t), conductor 25, branch 27, sequence switch contacts 105-13, registering ring contact surfaces of plug 11 and spring jack 12, line conductor 14, through the. condensers and bells at stations R. and ll" to ground. The subscriber at station it does not respond, because his signal is two short rings instead of the one long ring per cycle that is being given.

When the subscriber at station \V takes his receiver from the hook, the relay 10 included in the ringing circuit in energized and opens its contact 30. The relay 19 is so constructed and adjusted as to be unresponsive to the current that flows through it during the ringiiig of the called station, but to respond when the called subscriber takes his telephone from the book. The opening of the contact 50 ot' the relay 49, on the response of the called subscriber, opens the short-circuit that has hitherto existed around the winding of relay 51, thus permitting the current flowing in the controlling conduc or 15 to pass through and energize relay 51. When this relay operates, it introduces, in its contacts another break in the above mentioned short-circuit to insure the continued energization o't' relay 51 after relay 40 becomes inert. and also in its contacts 3:, closes a path to battery through a relatively low resistance coil 5-1 in shunt. ot' the winding of the relay 36 to' bring about the dei nerigization of the lastv mentioned relay.

When relay I36 becon'ies inert, it permits the closure of its back contact 35, thus again closing the local energizing circuit of the sequence switch 100 by way of sequence switch contacts 103-1bl Therefore the sequence switch moves out of position 13 and continues its n'iovement to position 16, where it is stopped by the opening of its energizing circuit in contacts of its 101 cam. In position 16 ot the sequence switch, the sequence switch contacts 101 and 105 are closed to connect the tip and ring of the plug 11 with the conductors 16 and 17 respectively of the connecting circuit, the plug having been disconnected from its ringing current connections when the sequence switch moved out of position 13. As the called subscriber has his telephone off its hook, supervisory relay 2+ is energized and closes the local circuit of sequence switch 100 by way of sequence switch contacts 10216. This causes the sequence switch to move to position 17, which is the talking position.

\Vhile the conversation is proceeding and the called subscriber has his receiver oti its hook, supervisory relay :24 keeps the shunt of the calling supervisory lamp 22 closed by way of sequence switch contacts 112-1T. When the called subscriber replaces his receiver. relay 24 becomes inert. and permits lamp :2 to light. The operator in taking down the connection brings about the closure of the local energizing circuit of sequence switch 100 by way of contacts 10217, and the sequence switch in consequence moves to position 1, thus restoring the circuits to their normal condition.

The operation described above was under the assumption that it was station 1 that was to be signaled. If it is station R that i to be called, the operator presses key it of her common selecting keys M, R, J, and "\V, while li tening in on this particular connecting circuit. In this condition the switch contacts 202, 203, 201, 205, 201' and 208 are closed and the circuits of the common select-. ing keys are connected with this cord circuit. Pressing the selecting key R energizes relay 40 over the path by way of contacts 201. contacts 59 of key R and resting contgtcts 5S and 56 of keys J and M, respectively, tOiQjl'OlliKl. Upon the release of selecting key 1%, after a momentary depression, a holding circuit is closed for relay 40 by way 0t. t'ront contact 63 of that relay, resting contacts 61 and 65 of relays 39 and 38 respectively. contacts 207 closed while the operator is in on this circuit, and resting contacts 62, 60, 5S and 56 of the selecting keys to ground. Relay -10, thus held energized, completes the circuit ot branch 43 to ground by way of the front contact 48 of relay +10 and the resting contacts i7, -16 of relays 39 and 38 respectively, and sequence switch contacts 111 in positions 3 to 13 of the sequence switch.

The consequence of this is that when sequence switch 100, in moving beyond position 41, reaches position 9 and closes switch contacts 109 associated with the grounded bra ch 43, an energizing circuit for relay 36 completed, which causes that relay to open its resting contact 35, thus breaking the local energizing circuit of the sequence switch closed in switch contacts 102- and bringing the switch to rest in position 10.

As the ringing code employed in this system depends upon one or more rings having a certain relation to each other, it is desirable that the application of ringing current to the circuit occur only at a particular pointin the ringing cycle. To accomplish this the arrangement is such that the sequence switch is brought to rest at a position one point before that at which the particular ringing current selected is to be applied, and is moved from this waiting t the ringing position by a pickup impulse produced at the beginning of each ringing cycle by the commutator 33. This action is eiiected through the medium of the relay 37. When the to lay 36 is energized, the circuit of the relay 37 is completed to ground by way of the front contacts of relay 36. The connection of relay 37 with the battery is completed once for each ringing cycle by means of the pick-up commutator 33. Therefore, at the start of the first ringing cycle after relay 36 has closed its contacts 35, the relay 37 receives current for its energization by way of the pick-up commutator 33; and in' oper-' ating its contacts (36, relay 37 disconnects its winding from the pick-up commutator and connects it directly to battery, so that thereafter the relay 37 remains energized as long as its circuit is completed in the contacts 35 of relay 36. lVhen the first pick-up impulse, after relay 36 was operated, energizes relay 37, that relay closes in its contact 67 an energizing circuit for sequence switch 100 by way of sequence switch contacts 103 in positions 4, 7 or 10, these three positions being those in which the sequence switch waits upon the receipt of a pick-up impulse before it moves to the immediately succeeding position where the selected ringing current is applied.

The present assumption is that by reason of the depression of the key R having brought about the closureot the branch 43, the sequence switch 100 has been stopped in position 10, where it is awaiting the next pick-u p impulse. Upon receipt of the pickup impulse, the relay 3? closes its contact (57, and the sequence switch is moved from position 10 to position 11. In position 11, sequence switch contacts 106 are closed to direct ringing current from source 30, 32 to ringing conductor 25, and sequence switch contacts 105 are closed to connect the ringing current thus applied to conductor 25 with the ring side of the connecting circuit, and thence by way of conductor 14 of the line circuit to stations R and N". The bells at both stations ring, and the subscriber at station R, whose ringing code signal is being given, answers. The taking'of the receiver from its hook at station it brings about the energization of relays i9 and 51 and the deenergization of relay 3V in the same manner as was described in connection with the ringing of station l \Vhen relay 3G is deencrgized. it closes in its resting contacts 35 the local energizing circuit of the sequence switch 100 by way of sequence switch contacts 1t)34 to 13, thus causing the sequence switch to HIOVO continuously from position 11, through position 13, whence the movement is continued by way of sequence switch contacts 101 to position'lfi, out of which position it'is moved in the manner described in connect ion with the ringing of station W V. If it is assumed to be station J that is to be signaled. the operator, While havingher t'onnnon selecting keys M, J, R and W as. soclated with this particular connectlng ciring contact 65 of relay 38, contacts 207 closed while the operator inon this..circuit, and the resting contacts 62, 60, 58 and 56 of the tour selecting keys, to ground. As a result, branch 42 of the controlling circuit is complei ed to ground by way of the frontcontact 47 ot' relays 3f). resting contact d6 of relay 3S and contacts 1l13 to 13 0t tne sequence witch, while the other branches 41, 43 and H- rcniain open. Consequently, when sequence switch 100 reaches position (3 and closes sequence switch contacts 108 with which branch 42 is associated, relay 36 opens its contact to stop the sequence switclrin the next open position 7 of the controlling contacts 101, and'its contacts 34: to close the ringing conductor in readiness for the application of ringing current to the circuit. Relay 3G, in closing its front contact 35, also places relay 37 in'reaiiiness to be operated upon the occurrence cf the next pick-up impulse, this operation of relay 37 acting, by the closure of its contact 67, to close the local energizing circuit; of the sequence switch 100 by way of sequence switch contacts 103-7, thus moving the sequence switch into position 8'. 1

, In position 8 of the sequence switch, contacts 106 of theswitch connect ringing current from commutator 31 with ringing conductor 25, and contacts 1040f the switch connect conductor 25 with the tip side of the circuit and thence, by way of line conductor 7 13, ringing current flows through the bells at stations M and J. As the current that is being applied is such as to give the code signal to which station J responds, the subscriber at that station takes his receiver from its hook. Thereafter the operation is as has been described in connection with the ringing of stations W and R, the taking of the receiver bringing about the deenergization of relay 36 to disconnect the ringing current and move the sequence switch from the position 8, in which it has been resting, through position 13, and thence to the talking position 17.

When it is station M that is to be signaled, the operator momentarily depresses the common selecting key M wlnle listening in on the connecting circuit that is to be used. This causes the initial energization of relay 38 by way of switch contacts 202 and contacts 55 of the selecting key M, and the continued energization of relay 38, after the key M is released, by way of switch contacts 207 and contacts 62, 60, 58 and 56 of the four selecting keys in series. This closes branch 11 to ground in the front contacts 10 of relay the other three branches l2, l3 and 4st being left open. In this case, therefore, relay is energized as soon as the sequence switch 100 reaches position 3, in which it closes its contact 107 associated with branch 41-. and the sequence switch comes to rest in the next open position 1. Here it awaits the next pick-up impulse, which operates through relay 37 to close the local energizing circuit of the sequence switch by way of contacts 103st and move the sequence switch into position 5. In position sequence switch contacts 106 connect ringing current from the commutator 32 with conductor 25. and sequence switch contacts lUl connect the ringing current thus applied to conductor 25 with the tip side. of the connecting circuit, and thence by way ol line conductor I to the bells at stations M and J. Under these conditions the bells ring the code signal of station M", and the subscriber at that station responds. The taking of the receiver from its book at. the called station acts, in the manner already described. to del nergize relay 36. thus disconnecting ringing current 'lrom the line and closing the local energizing circuit ol sequence switch 100 to move that switch out. of position 7). in which it has been resting, through position 125, and eventually into the talking position 17, as has already been described.

In each rase relay 51, locked up as a result of the response of the called subscriber, is released, upon the resumed movement of the sequence switch, by the breaking of its circuit in whichever of the sequence switch contacts 107, 108, 100 or 110 had its branch closed to effect the signaling of the corresponding station.

When the operators common selecting keys M, J R and .V have been brought into association with any one of the connecting circuits, and have been manipulated to set the apparatus associated with that circuit for the application of a particular sort of ringing current to the line, that setting of the connecting circuit apparatus is maintained until the connection is taken down or until the operator brings about a different setting of the cord circuit apparatus by pressing some other selecting key while listening in on this circuit. This, in the particular embodiment of the invention illustrated, is accomplished by the manner in which the holding or maintaining circuits for the setting relays 38, 39 and 10 of the connecting circuit are made subject to the control of switch contacts associated with the selecting keys, the operators controlling circuits and the connecting cord circuit itself. The common holding or maintaining circuit for the relays 88, 39 and 40 has two branch paths to ground. one of these branches being' closed in the .switch contacts 207, while the operator is listening in on the connecting circuit. and the other being closed in contacts 206 while the operator has her telephone and controlling apparatus disconnected from the connecting circuit. The contacts zoo and 207 are so arranged that one of them is always closed before the other is opened, so that one or the other of the branches of the holding circuit is closed at this point at all times. of the contacts 'illli extends to earth by 'ay of contacts 113 closed in positions 15} to 17-}; of the sequence switch lltt). while the branch completed in the contacts 207 extends to ground by way of the normal or resting contacts (32. (30, 58 and so in series ol the selecting keys \V, R, .l and M.

As a result. after any one of the relays 3h. 2}!) and ll) has been operated by the depression ol' the corresponding selecting key, it is held operated by one or the other of the ln'nlltllts ol the holding circuit as the operator listens in or listens out on the circuit. When the connection is taken down. it being assumed that the operator is not in on the circuit at the lime and that the contacts 206 are. therefore closed. the relay 23S, 39 or stO that has been operated is released by the opening ol the holding circuit in the sequence snitch contacts 113 as the sequence switch [00 returns to its normal position l. The sequence switch llltl is moved out of position 17 and into position 18 upon the de ucrgization of relay ltt resulting from the removal of plug ll from the jack [2. The driving circuit may be traced from ground, through the armature and back contact of relay 19, the sequence switch contact 102, positions 2 to 17, and the power magnet of sequence switch 100 to grounded battery. It the operator desired to change the setlhe branch by way ting of the connecting circuit in order to bring about the application of a different sort of ringing current to the called line, she listens in on the circuit, and then may withdraw the calling plug 11, press the particular one of the selecting keys M, J, R and W corresponding with the desired setting, and reinscrt the plug; whereupon the sequence switch lOO, which was returned to its normal position by the withdrawal of the plug, is moved to the position determined by the new setting of the selecting keys.

in the operators listening-in position, the closure of switch 'contacts 207 places the holding circuit for the relays 38, 39 and i0 under the control of the series of normally closed contacts (32, (50, 58 and 56 of the four selecting keys. Consequently, the depression of any one of these keys releases whichever of the relays 38, 39 and 40 is locked up by opening the corresponding set of holding contacts (32, G0, 58 or 56. The accompany ing closure of the contacts 55, 57 or 59 closes the circuit for the energization of the corresponding relay 38, 39 or L0, depending upon the new setting desired, and the release of the selecting key M, J or R closes the common holding circuit for the operated relay by way of the contacts 56, 58 or 60 before it opens the individual operating circuit of the relay by way of the contacts 57 or 59. As the setting corresponding with the selecting key W is the normal setting or the connecting circuit, that key when depressed op rates merely to restore the normal setting by releasing any one of the relays 38, 39 and 40 that may be held up through the common holding circuit.

In order that the operator may know the ringing current for which a connecting circuit is set, each of the selecting keys M, d,

it and d has associated with it a lamp, '/)L,

j, r and 10, respectively, and the circuit ar rangement is such that when the operator listens in on a connecting circuit. the lamps. corresponding with the sort oi ringing current for which the circuit is set. lights. This is accomplished bv connecting the lamps m, j. 7', and to with the circuits which extend from their mirres 'mnding keys to the switch contacts 202, 203. 304;, and 305, and providing the lamps with a common connection to battery by way 0 5 switch contacts 208 closed when the operator listens in on the circuit. If any one of the three relays 38, 39 and 40 is up at the time the contacts 202, 203, 20% and 205 are closed by the operator going in on the connection, a path to ground for the circuit including the corresponding lamp m, y', or r is closed by way of the front contact 63, 64 or 65 of,

none of the relays are up when the operator listens in. and the setting consequently is the normal setting for the ringing of station W, the path for the flow of current to lamp to is completed by way of the resting contacts 63, (it and (35 ot' the three relays, contacts 207, and the resting contacts of the tour selecting keys in series.

hat is claimed is:

1. The combination with a telephone connecting circuit, of a ringing circuit having a plurality of branches a controlling circuit having a corresponding number of branches with a key in each branch for closing the same, and an automatic switch adapted in its movement successively to establish the branches of said ringing circuit and simultaneously bring itself under the control of the con-responding branch of said controlling circuit.

2. In a telephone system. the combination with a plurality of connecting circuits, of a plurality of electromagnetic ringing control switches for each connecting circuit, operatorsmean's common to said connecting 'cir units for selectively operating the electromagnetic ringing control switches of any one of the connecting circuits, and signals as-' sociated with said operators means, said signals being selectively controlled'by the electromagnetic switches of an associated connecting circuit.

3. in a telephone system, the combination with a plurality of connecting circuits each ln ving a. plurality of ringing control switches associated therewith, of operators indicating means common to said connecting circuits. said iiulicating means being selectively responsive to said ringing control switches to. indicate which one of said switches is operated. and means for bringing said indicating means into operative re lation with any of said connecting circuits.

--l-. In a telephone system, the combination with telephone lines, of a connecting circuit for establishing connection therewith, a switch closed while the connection is established, means for supplying ringing current of different characteristics, switching mechanism i'or selectively controlling the application of ringing current of said different characteristics to said connecting circuit, selecting keys for setting said switching mechanism to appplv current of one sort or another, and holding means for maintaining the setting of said switching mechanism, said holding means being under the alternative control of said first mentioned 1 switch and said selecting keys.

5. in a telephone system. the combination with a connecting circuit. in ans for supplying ringing current of diti'erent characteristics, switching mechanism for applying ringing current of said different characteristics to said connecting circuit, a plurality of electromagnetic switches for selectively controlling said switching mechanism, a' selecting key associated with each of said electromagnetic switches, an energizing circuit for each electromagnetic switch adapted to be completed by the associated key, and locking circuits for said electromagnetic switches having a common branch controlled in contacts of each of said keys.

6. In a telephone system, the combination with a connecting circuit, of a ringing circuit having a plurality of branches, a controlling circuit having a corresponding number of branches, a locking relay for each of said controlling circuit branches adapted when operated to close the associated branch, a selecting key for controlling the operation of each locking relay, and an automatic switch adapted in its movement successively to establish the branches ofsaid ringing circuit and come under the control of the corresponding branch of said controlling circuit.

7. In a telephone system. the combination with a connecting circuit, of a ringing circuit having a plurality of branches, a controlling circuit having corresponding branches, a selecting key for each branch circuit adapted when operated to change the electrical condition of the associated branch, an automatic switch adapted in its movement successively to establish the branches of said ringing circuit and come under the control of the corresponding branch of said controlling cir cuit, and means I'ESPOl'lSlVG to the changed electricalcondition of any one of said coir trolling branches for stopping said automatic switch.

8. In a telephone system, the combination with a connecting circuit, of a rihgii'ig circuit, having a plurality of branches, a controlling circuit having corresponding b 'anches, means for changing the electrical condition of any'ot' said controlling circuit branches, an automaticswitch adapted in its movement. successively to establish the branches of said ringing circuit, an electromagnetic stopping device For said switch responsive to the changed electrical condition of any of said controlling circuit branches, and means for bringing said stopping device into eom'iection with said controlling circuit branches simultaneously with the establishing of the corresponding ringing circuit branches.

9. In a telephone system, the combination with a connecting circuit, of a normally open ringing circuit having a pluralitiy of normally open branches, a controlling circuit having a corresponding number of branches, means for altering the electrical condition of any one of said controlling circuit branches, an automatic switch adapted in its of said controlling movement successively to close the branches of said ringing circuit and simultaneously bring itself under the control of the corresponding branches of said controlling circuit, and means responsive to the changed electrical condition of any one of said controlling circuit branches for stopping said switch and closing said ringing circuit.

10. In a telephone system, the combination with a connecting circuit, of a normally open ringing circuit having a plurality of normally open branches, an automatic switch adapted in its movement successively to close said branches, means for closing said ringing circuit and stopping said switch at a waiting point immediately preceding a branchclosing position of the switch, and means for moving said switch from said waiting point to said n'anch-closing point.

11. In a telephone system, the combinzv tion with a connecting circuit, of a normally open ringing circuit having a plurality of normally open branches. an automatic switch adapted in its movement to close said branches successively, switching mechanism for closing said ringing circuit and simultaneously stopping said switch at a waiting point immediately preceding a branch-clos ing position. a. source of pi k-up impulses. means responsive to a pick-up impulse 'l'or moving said automatic switch from a waiting point to the corresponding lJl'illltJlht'lUS- ing point. and a switch closed by said switchlug nu-chanism for rendering said means operative. I

12. In a telephone system, the combination with a party line. ol a connecting circuit, a ringing circuit therefor having a plurality of branches. sources ol di llcrenl sorts of cur rent in said branches adapted for distinctively signaling the stations ol said partv line, a controlling circuit having branches corresponding with aid ringing circuit branches. means l'or changing the electrical conditions ol any one of said cont-rolling circuit branches, an automatic switch adapted in its movement to establish successively the branches of said ringing circuit and bring ilscll. under the control of correspoiuling branches ol the controlling circuit. means responsive to the changed electrical condi tion oi any controlling briinch for stopping said switch to apply a particular sort of ringing current to the line, and means operated by the response ol the called subscriber for moving said automatic switch to disconnect. the ringing current and establish the talking condition ol said circuit.

13. A telephone ringing circuit having a plurality of branches, an automatic switch adapted in its movement to establish said branches in succession, means for stopping said switch when a particular branch has been established, and means controlled by

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