US1322025A

US1322025A - keith

Info

Publication number: US1322025A
Authority: US
Publication date: 1919-11-18
Anticipated expiration: 1936-11-18

Description

A. E. KEITH.

AUTOMATIC TELEPHONE SYSTEM.

ICATION nuzo AUG.3I, 1914. RENEWED APR Patented Nov. 18, l919.

4 SHEETSSHEET 1.

I WITNESSES HTTOR/VEKS,

A. E. KEH'H.

AUTOMATIC TELEPHONE SYSTEM.

APPLICATION FILED AUG.31. I914. RENEWED APR-5,1919.

Patented Nov. 18, 191%.

4 SHEETSSHEET 2.

W/TA/ESSES A. E. KEITH.

AUTOMATIC TELEPHONE SYSTEM.

APPLICATION FILED AUG.31, 1914. RENEWED APR. 5, 19:9.

knew/701?.-

177' TOP/VH5 JQEXH/YJEEDEEKEYTH W/T/VESSES A. E. KEITH.

AUTOMATIC TELEPHONE SYSTEM. APPLICATION FILED Aue.s1.1914. RENEWED APR. 5, 1919. 1,322,025, Patented Nov. 18, 1919.

' 4 SHEETSSHEET 4.

w w E IMT/VESSES UNITED STATES PATENT OFFICE.

ALEXANDER E. KEITH, OF HINSDALE, ILLINOIS, ASSIGNOR T0 AUTOMATIC ELECTRIC COMPANY, OF CHICAGO, ILLINOIS, A CORPORATION OF ILLINOIS.

AUTOMATIC TELEPHONE SYSTEM.

Specification of Letters Patent.

Patented Nov. 18, 1919.

Application filed August 31, 1914, Serial No. 859,439. Renewed April 5, 1919. Serial No. 287,923.

To all whom it may concern:

Be it known that I, ALEXANDER E. KEITH, a citizen of the United States of America, and resident of Hinsdale, Dupage county, Illinois, have invented certain new and useful Improvements in Automatic Telephone Systems, of which the following is a specification.

My invention relates to improvements in automatic telephone systems and more particularly to systems employing selector and connector switches for establishing connection between tw lines.

Among the features or" my invention are the improved means for controlling the operation of the switches. Heretofore it has been customary for each switch to be provided with its own operating mechanism. By my invention, however, I provide a common operating mechanism which can be brought into operative relationship with any one of a plurality of switches, and it is then automatically disconnected therefrom when the switch has been operated. In this manner the construction of the switches is greatly simplified and the total amount of apparatus necessary in an exchange greatly reduced.

In the acompanying drawings I have illustrated my invention in connection with selector and connector switches of well-known types, and have illustrated the common mechanism as associated only with the selector switches. This, however, is merely for the purpose of illustration, as it will be readily apparent that the form of the switches could be changed and that the common mechanism could be associated equally as well with any of the other types of selector switches, or with the connector switches.

In the drawings Figure 1 is a diagrammatic layout of a telephone system in which I have chosen to illustrate my invention.

Fig. 2 shows a side view of one of the selectors shown at F.

3 is a front view of the same switch.

Figs. i and 5 show a complete connection between two automatic substations in said system.

The telephone system illustrated in Fig. 1 comprises an automatic exchange or" the well-known type comprising subscribers individual preselector or line switches C, so-

called first selector switches E, second selector switches F, control switches I and connector switches H. In the drawings there is represented on a scale of three to ten an exchange of ten thousand lines capacity. The subscribers substations and the lines connected thereto are divided into groups A A etc., of one hundred lines each. 011 a scale of three to ten, therefore, the nine groups (A to A inclusive) represent ten thousand lines. With each group of subscribers lines there is associated a group of individual or line switches C (one for each line), a group of first selectors E, a group of second selectors F and a group of connectors H. Considering the groups A A and A as representing one thousand lines in the ten thousand line office, it will beseen that there is a group of control switches I associated with each thousand lines. The selector and connector switches comprise ianks of contacts arranged in horizontal rows or levels. These levels are represented diagrannnatically by horizontal lines, which, in the case of the first selectors E and the connectors H, extend across a group of switches, thereby indicating that the corresponding contacts of all the switches of the groups are multipled together. In the case of the second selectors F the banks are shown in a different manner, but it is to be understood that the bank contacts are multipled in the same manner as described for the first selectors E and the connectors II. All of the line switches C belonging to a single group of subscribers lines have common access to a group of first selectors E. The corresponding contacts of all the first selectors of the corresponding hundred in each thousand are multipled together. Trunk lines leading from the first level of the first selectors of the first hundred of each thousand extend to the group of second selectors associated with the first hundred in the first thousand. Trunk lines leading from the second level of the first hundred of each thousand extend to second selectors associated with the first hundred in the second thousand, etc. The corresponding bank contacts of all the second selectors in each thousand are also multipled together. Trunk lines leading from the first level of the second selectors of any thousand extend to connectors associated with the first hundred of that thousand. Trunk lines leading from the second level of the second selectors of any thousand extend to connectors associated with the second hundred of that thousand, etc. This trunking arrangement of an automatic system is in general well known in the art and it is not thought necessary to describe it in greater detail herein. The control switch I is equipped with a shaft which operates the wipers of a number of second selectors F. The system is so arranged that this number consists of one second selector in each hundred of the thousand with which the control switch I is associated. l/Vhen connection is made with one of the above-mentioned second selector switches, the said second selector switch grips the common shaft, and at the same time the other second selector switches associated with that particular control switch are made busy. Thereupon .the control switch operates to advance the wipers of th said second selector to an idle contact in the called level, whereupon the wipers of the said second selector are released from the common shaft. The control switch then returns to normal and removes the guarding potential from the re maining second selectors associated therewith.

The automatic substation A (Fig. 4) comprises the usual receiver 2, transmitter 3, ringer 4 and condenser 5. Being an auto matic substation it is also provided with a suitable call-sending mechanism for controlling the automatic switches, which mechanism is represented diagrammatically by a pair of impulse springs 6 and 7 and an impulse wheel 8, which latter may be controlled by a dial provided with finger holes in such a way that the impulse springs may be momentarily separated a number of times corresponding to the respective digits of the number of the called subscriber.

The subscribers individual switch C (Fig. 4) is of the general type of subscribers switch shown in British patent to R. l/V. James No. 26,301 of 1906, being, 110wever, of the particular type disclosed in British patent to T. G. Martin No. 1419 of '1910. This line switch comprises among other details a plunger (not shown) attached to the end of a so-called plunger arm 9 which is controlled by the magnet 10. The magnet 10 comprises four windings, namely, a pull-down winding 11, a cut-off or holding winding 12, a line winding 13 and an auxiliary winding 14. The core of the magnet 10 is so constructed that the magnetic circuit of the windings 11 and 12 is separate from that of the windings 13 and '14. This magnet also controls the cutoff armature 15. The pull-in winding 11 operates both the plunger arm 9 and the armature 15, while the cut-off or holding winding 12 is strong enough only to operate the cut-off armature 15 and to hold the plunger arm 9 in its operated position. When the plunger arm is operated, the

-plunger is forced into a bank of contact springs, forcing the

springs

16, 17, 18 and 19 into engagement with the springs 20, 21, 22 and 23, respectii ely. Although only one set of springs (16 to 23, inclusive) is shown, each line switch is provided with a plurality of such sets, each set forming the terminal of a trunk line leading to a selector switch. Each trunk line is connected in multiple with the corresponding springs of all the line switches of the group which is controlled by the master switch D. The switch C is controlled by the subscriber through the medium of the line relay 13, as will hereinafter be more fully explained.

The master switch D (Fig. 4) is of the same general type as that disclosed in British patent to R. W. James No. 26,301 of 1906, being, however, of the particular type disclosed in British patent to T. G. Martin No. 1419 of 1910. The function of the master switch, as is well known, is to maintain the plunger-s of all the idle line switches in position to engage the terminal of an idle trunk line.

The selector switch E (Fig. 4) is of the general type of selector switch disclosed in United States Letters Patent No. 815,321, granted March 13, 1906, to Keith, Erickson and Erickson, except that the so-called side sWitch is omitted and the circuits are modified to adapt the switch to operate in a system in which the central office apparatus is controlled by impulses delivered over the two sides of the line in series, as shown in British patent to T. G. Martin No. 10,376 of 1913. Among other details the selector E comprises a bank of contacts arranged in horizontal rows or levels, which contacts are adapted to be engaged by a set of wipers 24, 25 and 26 carried upon a shaft (not shown) which has a vertical movement controlled by the vertical magnet 27 and a rotary movement controlled by the rotary magnet 28. The operations of the various parts of the switch are controlled through the medium of the double-wound relay 29. Means for permitting the switch to be restored to normal position are provided in the release magnet 30, which, upon energizing, withdraws the retaining pawls from the shaft. The springs 31 and 32 close only when the switch shaft has been raised one or more steps from its lowest position. The relays 33 and 34 are slow actingthat is, they are slow to release their armatures upon deenergizing.

The control switch I (Fig. 4) is similar to the switch E except that it has neither a bank of contacts or shaft wipers and its shaft (not shown) is of sufficient length to extend through ten of the so-called second selector switches. The springs break contact only when the switch has rotated one or more steps from normal position.

The second selector switch F (Fig. 4) is also similar to the switch E except that its shaft 36 (Fig. 2) is hollow, thus allowing the shaft 37 0f thecontrol switch I to pass loosely through its center. At 38 and 39 are shown two solenoids, which, when the switch is at normal, are so placed that the combined effort of the two will cause the pin 40 (Fig. 2) to be forced through the hole 41 in the shaft 36 into the hole 42 in the shaft 37. Thus the shafts 36 and 37 will be locked together and any motion of the shaft 37 will be transmitted to the shaft 36. The solenoid 38 is of suficient strength to retain the pin 40 in an operated position once it has been operated. In Fig. 3 a projection on the shaft 36 is shown as resting upon the arm 43 and in this way keeping the springs shown at 44 in a normal position. Referring to Fig. 2, it will be seen that the armature 45 of the relay 46 is extended in such a manner as to lock the arm 43 in a normal position even though the shaft 36 should be raised. With the shaft 36 raised one or more steps, the energization of the relay 46 unlocks the arm 43, which in turn allows the springs 44 to assume an operated position. At the release of the switch the shaft 36, upon reaching normal position, forces the arm 43 under the armature 45. The second selector switch F has neither vertical nor rotary magnets. The springs 135 make contact only when the switch has been rotated one or more steps.

The connector switch H (lig. is of the same general type of connector switch disclosed in United States Letters Patent No. 815,176, granted March 13, 1906, to K ith, Erickson and Erickson, the circuits, however, being modified to adapt the switch to operate in a system in which the central oilice apparatus is controlled by impulses delivered over the two sides of the line in series. Among other details the connector H comprises a bank of contacts arranged in horizontal rows or levels, which contacts are adapted to be engaged by a set of

wipers

47, 48 and 49 carried upon a shaft (not shown) which has a vertical movement controlled by the vertical magnet 50 and a rotary movement controlled by the rotary magnet 51. The usual side switch comprises the wipers 52, 53, 54 and 55 and is controlled by the private magnet 56 in the usual and well-known manner. The operations of the various parts of the switch are con trolled through the medium of the doublewound line relay 5?. The relay 58 is the usual back-bridge relay through which the called substation receives talking current. The ringing relay 59aifords means by which ringing current is applied to the called line. Means for permitting the switch to be re stored to normal position are provided in the release magnet 169, which, upon energizing, withdraws the retaining pawls from the shaft. The springs 60 and 61 close only when the switch shaft has been raised one or more steps fron'i its lowest position. e relays and 63 are slow acting-that is, slow to release their armatures upon deenergizing.

The called substation A and its individual switch 0 are similar in all respect to the substation A and its individual switch (7.

For the purpose of supplying batter current for operating the apparatus and for talking there is shown the battery B having one terminal grounded at G. For the purpose of supplying ringing current there is shown the ringing current generator it. The busy signaling machine Q, as represented herein, coinorises an induction. coil or transformer, the primary winding of w 'ch is included in a local. circuit with a battery and an interrupter. Through the medium of this interrupter an intermittent current is supplied to the primary winning. which induces an alternating current in the secondary winding, whereby when said winding is connected with the subscribers lines a buzzing sound is heard in the receiver.

A. general description of the apparatus having been given, it will now be explained how a connection can be established ween the line of substation A and the line of the called substation A. The number of the called substation will be assumed to be Since the automatic switching apparatus disclosed herein is .in general. well known in the art, and is oescribed in the publications herein referred to, its opera ion will be or plained in a more or less general manner.

Then the subscriber at substation A removes the receiver 2 preparatory to making a call, an energizing circuit is closed through the line winding 13 of the line switch C. This circuit extends from ground G through th springs 65 and 66, conductor 67 to and through the substation A, conductor 68, springs 69 and 70 and the line winding 13 to battery B. The armature 71, upon being operated, closes a circuit from ground G through the springs 65 and 72, pull-in winding 11, auxiliary winding 14 and the springs 7 3 to battery 13. The pull-in winding 11, upon energizing, attracts both the armature 15 and the plunger arm 9. The plunger arm 9, upon being attracted, forces the plunger which is attached to the end thereof into the bank of trunk terminals to which it has access, forcing the

springs

16, 17, 18 and 19 into engagement with the springs 20, 21, 22 and 23, respectively. The engagement of the springs 16 and 19 with the springs 20 and 23, respectively, closes a circuit through the line relay 29 of the first selector E. This circuit extends from ground G through the lower winding of the relay 29, springs 74 and 75, springs 23 and 19, conductor (37 to and through the substation A, conductor 68, springs 16 and 20, springs 76 and 77 and the upper winding of the relay 29 to battery B. The relay 29, upon energizing, closes a circuit as follows: from ground G through the springs 78 and 79 and the relay 33 to battery B. The energization of the relay 33 closes a circuit extending from ground G through the springs 80, springs 21 and 17 to the point 81, from which point one branch extends over the conductor 82 to the connector private bank contact associated with the calling line and multiples of the same. This guarding potential prevents any party from connecting with the substation A when said substation is calling. Another branch extends from the point 81 through the holding winding 12 to battery B. This circuit through the holding winding 12 is closed before the armature 71 falls back after the circuit through the line winding 13 is broken by the attraction of the armature 15. The armature 71 does not fall back immediately upon the pulling up of the armature 15, due to the fact that simultaneous with the attraction of the armature 15 is the pulling up of the plunger arm 9, which short-circuits the auxiliary winding 14 by closing the springs 83. The short-circuiting of the winding 14 tends to retard the de'e' ner 'ization of the core and thus the armatureTl is held in an operative position until enough time has elapsed for the circuit through the winding 12 to be closed while the plunger arm 9 is held in an operated position.

The calling subscriber now operates his calling device for the first digit 2 of the called number, whereby the substation impulse springs 6 and 7 are separated twice momentarily, each time breaking the circuit of the lin relay 29 of the selector E. The relay 33 of the selector being slow acting does not deenergize during the momentary interruptions of its circuit by the relay 29, and consequently, each time the latter relay denergizes, an impulse is transmitted over the circuit extending from ground G through the springs 78 and 84, springs 85, springs 86 and 87, relay 34: and the vertical magnet 27 to battery B. The vertical magnet receives two impulses over this circuit and operates to raise the switch shaft and wipers two steps to a position opposite the second row or level of bank contacts, and at th same time the shaftcontrolled contacts 31 and 32 are closed. The slow acting relay 34 is maintained in its energized position continuously while impulses are being transmitted to the vertical magnet therethrough, and in its energized position closes a circuit extending from ground G through the springs 88 and S9 and the relay 90 to battery B. The relay 90, upon energizing, forms a locking circuit for itself extending from ground Gr at the relay 33 through the springs 80, springs 91, off normal springs springs 92 and 93 and the relay 90 to battery B. Thus, upon the de'oinergization of the relay 341- after the last impulse is delivered to the vertical magnet, the relay 90 remains energized and the circuit of the rotary magnet 28 is closed, which circuit extends from ground G at the relay 33, springs 80, springs 91, 011' normal springs 32, springs 92 and 93, springs 89 and 94, springs and the rotary magnet 28 to battery B. The rotary magnet 28, upon energizing, rotates the shaft wipers one step and, by opening the springs 91 and 95, disconnects the ground G from itself and from the relay 90. If the first trunk line of the second level is idle, the relay 90 deenergizes as soon as th springs 91 are opened. If this trunk line is busy, however, the private wiper 25 finds the contact which it engages provided with a guarding ground potential which is transmitted to the relay 90 through the springs 92 and 93, and thereby, prevents it from deenergizing. The rotary magnet 28. however, de'e'nergizes when the springs 95 are opened, regardless of whether the relay 90 remains energized or not. If the relay 90 remains energized, the circuit of the rotary magnet will be again closed as soon as its armature drops back far enough to close the springs 91 and 95. The rotary magnet will therefore operate in a. manner similar to that of a buzzer to advance the wipers step by step over the contacts, until the nongrounded contact of an idle trunk line is reached by the wiper 25, whereupon the relay 90 deenergizes. The relay 90, upon deenergizing, whether after one or several operations of the rotary magnet, permanently breaks the circuit of said rotary magnet and closes the circuit of the switching relay 96. Said circuit extends from ground G* through the springs 80, springs 91, off normal springs 32, springs 92 and 97 and the relay 90 to battery B. The relay 96, upon energizing, disconnects the line relay 29 from the line and extends the line connection over the heavy conductors shown through the wipers 24: and 26 to the second selector F. A circuit may now be traced from ground G through the upper winding of the relay 98, springs 99 and 100, wiper 26 to and through the substation A over the circuit previously traced to the wiper 24:, springs 101 and 102, relay 103, and the lower winding of the relay 98 to battery B. The relays 98 and 103 energize over this circuit and the relay 103, upon energizing, completes a circuit from ground G through the springs 104, 105 and 106, private wiper 25, springs 92 and 97 and the relay 96 to battery B. A branch of the above circuit may be traced from the private wiper 25 through the off normal springs 32, springs 91 to the holding winding of the line switch C, over the circuit previously traced. This circuit maintains the relay 96 and the winding 12 energized after their original energizing circuit is broken by the relay 33, which deenergizes shortly after the line relay disconnected from the line. A branch of theabove circuit extends from th spring 106 through the springs107 and 108 to one of the conductors 109, which extends to the private bank contacts associated with each of the other idle selectors which are controlled by the control switch I. As soon as the relay 103 of any selector is energized, the remaining idle selectors in the group of which it forms a part are protected from being seized. Upon the energization of the relay 103 another circuit is formed extending from ground G- through the springs 104 and 105, solenoid 38 and solenoid 39 to battery B, whereupon the solenoids 38 and 39 operate, as previously explained, to lock the shaft of the selector F with the shaft f the control switch I. The solenoid 39, upon energizing, closes a circuit from ground G through the springs 112and 113 and the relay 114 to battery B. The relay 114, upon energizing, prepares the circuit of the vertical magnet 115. It will be seen that when the solenoid 38 becomes energized, the resistance 111 and ground G are placed in parallel with ground G the reason for which will be hereinafter explained.

The calling subscriber now operates his calling device for the second digit 2 of the called number, whereby the substation inn pulse springs 6 and 7 are separated twice momentarily, each time breaking the circuit of the line relay 98 of the control switch I. The relay 103 of the selector F, which is included in the above circuit, being slow acting does not denergize during the momentary interruptions of its circuit, and consequently, each time the relay 98 deenergizes, an impulse is transmitted over the circuit extending from ground G through the springs 116, springs 117 and 118, springs relay 119 and the vertical magnet 115 to battery 13. The vertical magnet receives two impulses over this circuit and operates to raise the shaft 37, the shaft 36 and the wipers 120, 121 and 122 two steps to a position opposite the second row or level of bank conta ts, and at the same, time the shaft-controlled contacts 123 and 124 are closed. The slow acting relay 119 is maintained in its energized position continuously while impulses are being transmitted to the vertical magnet through it, and in its energized position closes a circuit extending from ground G through the springs 125 and 126 and the relay 128 to battery B. The relay 128, upon energizing, forms a locking circuit for itself extending from ground G through the springs 104, 105 and 106, springs 107 and 108, springs 129, springs 130 and 131 and the relay 128 to battery B. Thus, upon the deenergization of the relay 119 after the last impulse is delivered to the vertical magnet, the relay 128 remains energized and the circuit of the rotary magnet 132 is. closed, which circuit extends from ground Gr through the springs 104, 105 and 106, springs 107 and 108, springs 129, springs 130 and 131, springs 126 and 127, springs 133 and the rotary magnet 132 to battery B. The rotary magnet 132, upon energizing, rotates the shaft 37 the shaft 36 and the wipers 120, 12 1 and 122 one step, and by opening the springs 129 and 133 disconnects ground G from itself and from the relay 128. At the same time the shaft-controlled contact 35 is broken, while the shaftcontrolled contact 135 is closed. If the first trunk line of the second level is idle, the relay 128 deenergizes as soon as the springs 129 are opened. If this trunk line is busy, however, the private wiper 121 finds the contact which it engages provided with aguarding ground potential which is transmitted to the relay 128 over a circuit extending from the private wiper 1 21 through the springs 136, springs 130 and 131 and the relay 128 to battery B. This circuit prevents the relay 128 from deenergizing. The rotary magnet 132, however, de'e'nergizes when the springs 133 are opened, regardless of whether the relay 128 remains energized or not. If the relay 128 remains energized, the circuit of the rotary magnet willbe again closed as soon as its armature drops back far enough to close the-springs 129 and 13 The rotary magnet will, therefore, operate in a manner similar to that of a buzzer to advance the wipers step by step over the contacts until the non-grounded contact of an idle trunk line is reached by the wiper 121, whereupon the relay 128 deenergizes. The relay 128, upon deenergizing, whether after one or several operations of the rotary magnet, permanently breaks the circuit of said rotary magnet and closes the circuit of the switching relay 46. Said circuit is traced from ground G through the springs 104-. 105 and 106, springs 107 and 108, springs 129, springs 130 and 137, 011 normal springs 135, springs 139 and 138 and the relay 46 to battery 13. The relay 46, upon energizing, releases the springs shown at 44 in a manner previously explained and opens the springs 170. The springs in the group 44 are so adjusted that thev make contact with their front contacts before they break contact with their back contacts. After the springs 44 have operated, a circuit may be traced from ground G through the springs 104, 105 and 106, springs 107 and 171, springs 140 and 138 and the relay 16 to battery B. After the springs 44 have operated, the ground for the protection of the private bank contacts of all the idle selectors in the group of which the selector F forms a part is furnished from the round on the private wiper 121 through the springs 136 and springs 129 to one of the conductors 109. In addition, the operation of the springs 1-1 disconnects the line relay 98 from the line and extends the line connection over the heavy conductors shown through the wiper 120 and 122 to the line relay 57 of the connector H. The line relay 57 thereupon becomes energized and closes the circuit of the relay 62, which in turn, upon energizing, completes a circuit extending from ground G through the springs 111, private wiper 121, springs 140 and 13S and the relay 4-6 to battery B. A branch of the above circuit extends from the private wiper 121 through the springs 171 and 107 to the relay 96 of the selector E and the winding 12 of the line switch C over the circuit previously traced. This circuit maintains the relay 46, the relay 96 and the winding 12 energized after their original energizing circuit is broken by the deenergization ot the relay 103, which takes place shortly after its circuit is opened by the relay 46. The deenergization of the relay 103 also opens the circuit of the solenoid 38 but not of the solenoid 39, as a circuit extends from ground G through the resistance 111, springs 110 and the solenoid 39 to battery B. The solenoid 38, upon deenergizing, disengages the shaft 36 from the shaft 37 and after the pin 40 is removed from the-hole 42, the springs 110 are allowed to break contact, thus opening the circuit of the solenoid 39. The solenoid 39, upon deenergizing, removes the guarding ground potential from the private bank contacts of all the idle selectors in the group of which the selector F is a part, at the same time opening the circuit of the relay 11 1. The relay 111 111 turn, upon deenergizing, closes a release circuit from ground G through the springs 116, springs 117 and 142, off normal springs 124 and the release magnet 143 to battery 13. The release magnet 143. upon energizmg, operates to remove the retaining pawls from the shaft 37, its own circuit being opened at the springs 12% when said shal't reaches its lowest position. The control switch I is now in readiness to be used b another selector switch F (not shown) associated with said control switch. and the apparatus used in establishing this call is now in readiness to receive impulses tor the third digit 2.

The calling subscriber now operates his calling device for the third digit 2 of the called number, whereby the substation impulse springs 6 and 7 are separated twice momentarily, each time breaking the circuit of the line relay 57 of the connector H. The relay 62 of the connector being slow act ing does not deenergize during the momentary interruptions of its circuit by the relay 57, and consequently, each time the latter relay de'e'nergizes, an impulse is transmitted over the circuit extending from ground G through the springs 11% and 115, springs 1 16 and 147, relay 63, vertical magnet 50 and the side switch wiper 52 (in first position.) to battery I). The vertical magnet receives two impulses over this circuit and operates to raise the switch shaft and wipers two steps to a position opposite the second row or level. of bank contacts, and at the same time the shaft-controlled springs 60 and 61 are closed. The slow acting relay 63 is maintained in its energized position continuously while, impulses are being transmitted to the vertical magnet through it, and in its energized position closes a circuit extending from ground G through the springs 14S and 14:9 and the private magnet 56 to battery This circuit is broken when the relay 63 deenergizes after the last impulse has been delivered to the vertical magnet. The breaking of said circuit causes the private magnet 56 to deenergize, thus permitting the side switch to pass to second position. In passing from first to second posi tion the side switch wiper 52 transfers the battery connection from the vertical magnet 50 to the rotary magnet 51.

The calling subscriber now operates his calling device for the last digit 2, in response to which the connector line relay operates to transmit two impulses through the rotary magnet 51, whereby the shaft wipers are rotated onto the contacts 01 the desired line. The circuit of the rotary 11mgnet extends from ground (1 through the springs 11-1 and 115, springs 116 and 117, relay 63, springs 151, rotary magnet 51 and the side switch wiper 52 (in second position) to battery B. The relay 63 operates in response to the impulses for this digit in the same manner as for the previous digit to cause the private magnet 56 to advance the side switch to third position. By the engagement ot the side switch wipers 53 and 5 1- with their third-position contact points. the line connection completed with the called line. 7 I side switch wiper 55 with its third-position contact point, a circuit is completed through the cut-ofi' winding of the line switch C This circuit extends from ground G through the side switch wiper (in third position) and the cut-off winding to battery l). The cut-oil? winding of the line switch (l upon energizing, operates to disconnect the line relay from the called suhstation. The connection of ground G with Upon the engagement of the the connector private bank contact associated with the called line prevents the called line from being seized by some other connector switch. By the engagement of the side switch wiper 52 with its third position contact point, the circuit of the ringer relay 59 is closed. This circuit extends from ground G through the interrupter 153, ringer relay 59, springs 15st and the side switch wiper 52 (in third position) to battery B. The ringer relay is energized intermittently due to the interrupter 153 and operates to disconnect the calling line from the called line and to bridge the ringing current generator R across the called line to signal the called subscriber. Upon the response of the called subscriber, his line is provided with talking current through the windings of the back-bridge relay 58, which relay, upon energizing, closes the circuit through the ringer cut-off relay 155. The said circuit extends from ground G through the side switch wiper 55 (in third position), springs '156 and the relay 155 to battery B. The relay 155, upon energizing, interrupts the circuit of the ringer relay at the springs 154: and closes a locking circuit for itself through the springs 157 independent of the springs 156.

Upon the completion of the conversation, the hanging up of the receiver at the calling substation opens the circuit of the line relay 57 of the connector H. The de'e'nergization of the line relay 57 opens the circuit of the relay 62, which in turn, upon denergizing, opens the holding circuit for the relays 16 and 96 and the winding 12, and in addition closes a circuit from ground G through the sprin 1 1 1 and 1-15, springs 14:6 and 158, 0E normal springs 61 and the release magnet 169 to battery B. The release magnet, upon energizing, removes the retaining pawls from the shaft and its own circuit is opened at the springs 61 when the said shaft reaches its lowest position. The de'e nergization of the relay 46 of the second selector F closes a circuit from ground G through the springs 112 and 159, springs 170, off normal springs 123 and the release magnet 160 to battery B. The release magnet, upon energizing, removes the retaining pawls from the shaft and its own circuit is opened at the springs 123 when the said shaft reaches its lowest position. In addition, the shaft, when in its lowest position, places the springs 1 1 again under the control of the relay 16. The deenergization of the relay 96 of the first selector E closes a circuit from ground G through the springs 7 8 and 84:, springs 85,-

said shaft reaches its lowest position. The

deenergization of the holding winding of the line switch C allows the plunger arm 9 to withdraw its plunger from the bank of springs and thus the line switch is returned to normal.

It having been explained how one subscriber establishes connection and releases the same, it will now be explained how a connection is prevented from being made with a busy line. If the called number is busy there will be a guarding potential upon the connector private bank contact associated with that line, just as explained in connection with the line switch G. The connector private wiper 18, upon engaging this grounded contact and before the side switch has passed to third position, completes an energizing circuit through the relay 162. This circuit extends from ground at the private bank contact through the private wiper side switch wiper 55 (in second position), springs 163 and 16 1, relay 162, springs 165 and 149 and the private magnet 56 to battery B. The relay 162, upon energizing, opens the circuit of the rotary magnet 51 at the springs 151 and connects the busy tone with the line over the following circuit: from ground G through the secondary winding of the busy machine Q, springs 166, side switch wiper 54k (in second position) and the condenser 167, thence over the heavy conductor to the calling substation and back over the other heavy conductor through the upper winding of the relay 57 to battery B and ground G, thence back to the machine Q. The relay 162, upon energizing, also forms a locking circuit for itself extending from ground G through the oil normal springs 60, springs 168 and 16l, relay 162, springs 165 and 149 and the private magnet 56 to battery 13. The calling subscriber, upon hearing the busy tone, restores his receiver to the switch hook and the release of the apparatus follows in practically the same manner as previously explained.

It will thus be seen that I have devised a very ellicient system in which a common switch-operating mechanism is employed for operating a plurality of selector switches, which operating mechanism is automatically released and reverts to common use as soon as it has operated the switch to cut through the connection to the next succeeding switch.

\Vhilc I have illustrated and described one specific embodiment of my invention, and have shown the same in connection with automatic switches 'of a well-known type, it will, of course, be understood that I do not wish to be limited to the exact form of switches employed, and that, furthermore, this common operating methanisni could be employed in connection with any form of selector or connector switch.

W hat I claim as my invention is 1. In a telephone system, a plurality of numerical switches, a common operating shaft normally at rest, and means for op eratively connecting any one of said switches with said shaft and for moving it independently of the others.

2. In a telephone system, a plurality of numerical switches, a common operating shaft normally at rest, means for operatively connecting any one of said switches with said shaft, and means for automatically disconnecting said switch from said shaft when said switch has been operated.

3. In a telephone system, a plurality of numerical switches, a common operating shaft, means for operatively connecting any one of said switches with said shaft, and means for preventing two of said switches being connected to said shaftat the same time.

4. In a telephone system, a plurality of subscribers lines, means including selector switches and connector switches for establishing connection between two of said lines, said selector switches being divided into groups, and a common operating mechanism for controlling the operation of a group of said selector switches one at a time without moving the others, said common mechanism being normally at rest.

5. In a telephone system, a plurality of numerical switches, a common step by step operating mechanism for said switches, means for propelling said mechanism, and a magnet individual to each switch for controlling a circuit therethrough.

6. In a telephone system, a plurality of numerical switches, a common step by step operating shaft, means for operatively connecting any one of said switches with said shaft, means for propelling said shaft, and a magnet individual to each switch for controlling a circuit therethrough.

7. In a telephone system, a plurality of numerical switches, a common step by step operating shaft, means for operatively connecting any one of said switches with said shaft, means for automatically disconnecting said switch from said shaft when said switch has been operated, and means for propelling said shaft.

8. In a telephone system, a plurality of subscribers lines, means including line switches, first and second selectors and connectors for establishing connection between two of said lines, individual operating mechanism for certain of said switches, common step by step operating mechanism for other of said switches, and means for propelling said mechanism to move any one of said other switches independently.

9. In a telephone system, a plurality of subscribers lines, means including selector switches and connector switches for establishing connection between two of said lines, said selector switches being divided into groups, a common step by step operating mechanism for controlling the operation of a group of said selector switches, and means for propelling said mechanism to move any one of said selector switches independently.

10. I11 a telephone system, a plurality of numerical switches, a common operating shaft, means for operatively connecting any one of said switches with said shaft, means for releasing said shaft after operation, and a magnet individual to each of said switches for controlling a circuit therethrough.

11. In a telephone system, a plurality of numerical switches, a common operating shaft, means for operatively connecting any one of said switches with said shaft, means for automatically disconnecting said switch from said shaft when said switch has been operated, and means for releasin said shaft after operation.

12. In a telephone system, a plurality of subscribers lines, means including selector switches and connector switches for establishing connection between two of said lines, said selector switches being divided into groups, a common operating mechanism for controlling the operation of a group of said selector switches, means for releasing said mechanism after operation, and a magnet individual to each selector for controlling a circuit therethrough.

13. In a telephone system, a longitudinal shaft, a plurality of switch wipers, means for operatively connecting any one of said wipers with said shaft, means for releasing said shaft after operation, and a magnet individual to each wiper for controlling a circuit therethrough.

14. In a telephone system, a longitudinal shaft, a plurality of switch wipers, means for operatively connecting any one of said wipers with said shaft, means for automatically disconnecting the selected wiper from said shaft when the said shaft has been operated, and means for releasing said shaft after operation.

15. In a telephone system, subscribers lines, a plurality of numerical switches accessible to said lines, a common operating shaft, means for operatively connecting any one of said switches with said shaft, said common shaft controlled from any of said lines, and a magnet individual to each switch for controlling said means.

16. In a telephone system, subscribers lines, a plurality of numerical switches accessible to said lines, a common operating shaft, means for operatively connecting any one of said switches with said shaft, means for automatically disconnecting said switch from said shaft when said switch has been operated, said common shaft controlled from any of said lines, and a magnet individual to each switch for controlling said means. i

17 In a telephone system, a plurality of subscribers hnes, means moludmg selector swltches and connector switches for establishing connection between two of said lines, said selector switches being divided into groups, a common operating mechanism for controlling the operation of a group of said selector switches, said common mechanism controlled over any of said lines, and a magnet individual to each selector for controlling the operation thereof.

18. In a telephone system, an automatic trunking switch, a directive impulse controlled device temporarily associated with said switch mechanically, trunk lines accessible to said switch, means for operating said device and said switch in synclironism to cause the latter to establish connection with one 0 said trunk lines, and means for then dissociating said device and said switch whereby said device may be released while leaving said switch operated to maintain the connection.

19. In a telephone system, a plurality of lines each line terminatlng in an automatic trunking switch, a plurality of trunk lines accessible to said switches, and a device common to all of said lines and operable in response to impulses transmitted over any line to direct the movement of the trunking switch associated therewith to connect with an idle trunk line.

20. In a telephone system, a plurality of lines, each line terminating in an automatic trunking switch, a plurality of trunk lines accessible to said switches, a device common to all of said lines and operable in response to impulses transmitted over any line to direct the movement of the trunking switch associated therewith to connect with an idle trunk line, and means for restoring said device to normal position after each operation while leaving the operated trunking switch and the trunk line connected.

21. In a telephone system, a plurality of lines terminating in a pair of common busbars extending to a controlling relay, a trunking switch for each line, trunk lines accessible to said switches, and a mechanical device under the control of said relay for moving said switches, one after the other into connection with idle trunk lines.

22. In a telephone system, a plurality of lines terminating in a pair of common busbars extending to a controlling relay, a trunking switch for each line, trunk lines accessible to said switches, a mechanical device under the control of said relay for moving said switches, one after the other into connection with idle trunk lines, and means whereby each line is disconnected from said bus-bars after its associated trunking switch has been operated.

23. In a telephone system, a plurality of niunerical switches, a common operating shaft normally at rest, means for operatively connecting any one of said switches with said shaft, means for automatically disconnecting said switch from said shaft when said switch has been operated, and a magnet individual to each switch for controlling said means.

24. In a telephone system, a plurality of numerical switches, a common operating shaft, means for operatively connect-ing any one of said switches with said shaft, means for preventing two of said switches being connected to said shaft at the same time, and a magnet individual to each switch for controlling said first means.

25. In a telephone system, a plurality of numerical switches, a common step by step operating shaft, means for operatively connecting any one of said switches with said shaft, means for propelling said shaft, and a magnet individual to each switch for controlling said first means.

26. In a telephone system, a longitudinal shaft, a plurality of switch wipers, means for operatively connecting any one of said wipers with said shaft, means for releasing said shaft after operation, and a magnet individual to each switch for controlling said first means.

27. In a telephone system, a dial, a plurality of automatic switches, a common operating mechanism for said switches, said switches having means responsive to a numerical operation of the dial for propelling said mechanism to cause any one of said switches to elect a group of lines, and a magnet individual to each switch for controlling a circuit therethrough.

28. In a telephone system, a dial, a plu rality of automatic switches, a common operating shaft for said switches, means for operatively connecting any one of said switches with said shaft, said switches having means responsive to a numerical operation of the dial for propelling said shaft to cause the switch connected therewith to elect a group of lines, and a magnet individual to each switch for cont-rolling a circuit therethrough.

29. In a telephone system, a dial, a plurality of automatic switches, a common operating shaft for said switches, electromagnetic means for operatively connecting any one of said switches with said shaft, said switches having electromagnetic means responsive to a numerical operation of the dial for propelling said shaft to cause the switch connected therewith to elect a group of lines, and a magnet individual to each switch for controlling a circuit therethrough.

30. In an automatic telephone system, automatic switches of two kinds comprising connecting switches provided with connecting means only and operating switches pro- Yided with impulse controlled operating means only, lines accessible to said connecting switches, means for bringing certain switches of the first kind separately under the control of an operating switch, whereby they may be operated to establish connections by Way of said lines, and means Whereby after each connecting switch is operated the said control lSImmSOd and tl1e01 erating switch released.

,Signed by meat Chicago, Cook county, Illinois, this 24th day of August, 1914.

ALEXANDER E. KEITH. Witnesses:

GEO; A. YANOGHOWS'KI, HERBERT KRKCKE.