US1481577A

US1481577A - A corpora

Info

Publication number: US1481577A
Authority: US
Publication date: 1924-01-22
Anticipated expiration: 1941-01-22

Description

Jan. 22, 1924. mmfiw [3. D. WILLIS ET AIL AUTOMATIC TELEPHONE SYSTEM Jan. 22 1924..

I D. WIILLIIS ET AL AUTOMATIC TELEPHONE SYSTEM Filed Nov. 29" 3.920 55 fim-wts fiheet 2 gv EL 1%. NIILM'EQ ET AL.

AUTOMATIC TELEPHONE SYSTEM Filed Nov. .29, 1920 I5 $heats fiiheet 3 www.-

Patented Jan. 22, 1924.

UNITED STATES PATENT @FFIQE.

BERNARD D. WILLIS, OF OAK PARK, AND ARTHUR J. RAY, OF CHICAGO, ILLINOIS, AS- EJIGNOlEtI-El TO AUTOMATIG ELECTRIC COMPANY, 035 CHICAGO, ILLINOIS, it CORPORA- TION E ILLINOIS.

AUTOMATIG TELEPHONE- $"Z51EM.

Application filed November 5&9, 1920. Serial 1%. 22,177.

EU tion.

The present invention relates in general to automatic telephone systems, but more particularly to such automatic systems as include rural party lines; and the object oi? the invention, briefly stated, is the provision of new and improved means for signalling the subscribers on rural lines.

More specifically, the invention provides a system of code ringing whereby a large number of subscribers on a rural line may be selectively signalled in accordance with pre-assigned codes, and the, principal feature is concerned-with means for preventing false signals which might otherwise be produced either by the calling subscriber hanging up or by the called party answering during. the transmission of a code signal.

This feature and other improvements related thereto will be described fully hereinafter, reference being had to the accoinpanying drawings.

In the drawings, comp-rising Figs. 1, 2, and 3, there is shown by means of the usual 5 circuit diagrams sufiicient oi the apparatus of an automatic telephone system to enable the invention to be readily understood. For convenience, a calling station A is shown in Fig. 1, and a called station A, in Fig. 2, the latter station being one off the stations on a rural line, together with the exchange switching equipment required to connect the two stations. This equipment comprises the line switch (l, individual to the line of staticn A, the selector 1), and'the connector H.

The line switch C is oil the well known rotary type, in which the wipers move in a forward direction only and have no normal position. Other types of line switch may be used, however, such as the plunger type, for example. g

The selector l) and connector H are mechanically oi the well known Strowger vertical and rotary type such as is in common use in many automatic exchanges at the present time. Ordinary two wire circuits are used, which are shown in full and will be described.

In Fig. 3 is shown a code selecting switch which is indicated b the reference character F. This switch is also of the Strowger type, similar to the selector D and connector H. It has radically difl'erent circuits, however, which will be explained fully.

The reference character E indicates a code ringing switch which cooperates with the code selecting switch F. The switch E is a simple rotary switch comprising the two wipers 236 and 237 with their associated banks, and a stepping magnet 214i. .Both switches E and F are individual to the connector H.

A relay interrupter is shown just to the lef of the switch E, where it is indicated by reference character I. This interrupter may be common to the exchange, or to a group of connectors.

Having described the apparatus briefly, its operation may now be explained more in detail. For this purpose let it be assumed that the subscriber at substation A desires to call the subscriber at substation A on the rural or party line X. Let it be further assumed that the number of party line X is 123 and that the code call for sub station A is a5. In this case the calling subscriber must dial the number 12345.

When the receiver is removed at the cal ing substation a circuit is completed over the conductors 11 and 12 for the line relay 15 of the line switch C. Upon energizing, relay 15 closes a circuit at its armature 20 which includes the winding of the switch ing relay let and the stepping magnet 16 in series, and at its armature 21 connects test wiper 26'to the above circuit at a point mic way between the switching relay and the stepping magnet. The operation now depends upon whether the trunk line with which the line switch wipers are associated is busy or idle. It the trunk line is busy there is a ground potential upon the test contact 29 with which the test wiper 26 is in engagement; the switching relay 1% is short circuited and the stepping magnet 16, which interrupts its own circuit, is operated in the manner of a buzzer to advance the switch wipers in search of an idle trunk line. However, we may assume in the present case that when the call is initiated the trunk line "upon which the wipers of the line switch are standing is idle. Under these circumstances when the line relay 15 isenergized the switching relay 1 1 is not short circuited and the stepping magnet 16 is not operated because of the high resistance of said switching relay. The latter relay, however, is energized, grounds the test wiper 26 at its armature 18, and at its armatures 17 and 19 disconnects the line conductors 11 and 12 from "the windings oi relay 15 and'from ground, respectively, and extends them by way of wipers '25 and 2'7, and bank contacts 28 and 30, to=the line relay 31 of the first selector D. The line relay 31 and the release relay 32 of the selector 1) are now energized in the usual manner and the latter relay grounds the release trunk conductor leading to test contact 29 of'the trunk line in order to establish a holding circuit for the switching relay 1% of the line'switch C. This operation is well understood and need not be explained further.

The calling subscriber lll'ity now operate his calling device in accordance with the first digit 1 of the desired number. I WVhen th'e'line'circuit'is interrupted by the calling devicethe line re'lay 81 falls back and closes the 'circuit of the vertical magnet 33 in series with slow acting relay 34:. The vertical magnet operates to raise the switch shaft andwipers 'to the desired level. Relay 3 1 is energized in 'se'ries with the vertical magnet and, as soon as the vertical ofl' normal springs '39 are closed, operates the ste ping relay35 over the 'following circuit: rom ground through the working contact of armature 51 and the said armature,armature 53*and its working contact, off normal springs 39, and through the stepping relay 35 to battery. When relay 35 energizes ()Veltlle abovetraced circuit it prepares the rotary magnet circuit at armature and at armature 54 it locks itself toground in series with the interrupter contacts of the rotary magnet 40. When the slow acting relay-34 fallsback after the end of the vertical'impulsesa circuit is closed for the rotary magnet 10 as follows: from ground through the working contact of armature 51 and thesaid -armature,'armature53 and its resting contact, armature 55 and its working contact, and through rotary magnet 40 to battery; The rotary magnet energizes over this circuit and rotates the wipers onto the first set (if-contacts in the level opposite which they were raised, and also interrupts the circuit ofthe stepping relay 35'allowing it to "fall back and break the circuit of the rotary magnetwhich deenergizes and closes its interrupt'er contacts again. The operation 'nowdepends upon whether the trunk connected to the first set of contacts is busy or idle. If the trunk is busy ground is present on the test contact, and a circuit for the stepping relay 35 is closed allowing it to energize again to operate the rotary magnet 10 to step the wipers over to the next set of contacts. This operation continues until an idle trunk is found.

lVhen an idle trunk is found, which we will assume is the trunk line shown in the drawing, the switching relay 36, being no longer short circuited, energizes over the following circuit: from ground through the working contact of armature 51 and the said armature, switching relay 3(3. interrupter contacts 75 oi? rotary magnet 10, oil normal springs and through stepping relay 35 to battery. lielay 85, however, be ing wound with relatively few turns. does not energize in series with relay 21o. When relay 36 energizes it extends the calling line by way of wipers 61 and 63, contacts (3% and 66, and conductors (5? and (31 to the line relay of the connector ll. The line and release relays 100 and 101 of the connector H accordingly energize and the latter grounds release trunk conductor (it), thus holding the selector D and the line switch C in their respective operated positions, and prepares a circuit for the vertical magnet 102.

The calling subscriber may now operate his calling device in accordance with the second digit 2 of the desired number. At each interruption at the calling device the line relay 100 falls back and operates the vertical magnet 102 in series with relay 103, raising the switch shaft and wipers to the second level. Slow acting relay 10 5 i accordingly energized, and, in conjunction with the switching of the vertical ofi' normal springs on the first vertical step, shifts the path of the impulses from the armature 120 of the line relay 100 so that they come through armature 124 and its working contact. hen the slow acting relay 103 deenergizes after the series 01'' vertical inipulses the impulsing circuit shifted from the vertical magnet 102 to the rotary magnet 1.10.

In response to the calling oi? the third digit 3 of the called number. the rotary magnet rotates the wipers 1 114-13, inclusive, into engagement with contacts 144.1l6, inclusive. Slow acting relay 114- is energized in multiple with the rotary magnet and rcmains energized during the entire operation. The operation new dc ds upon whether the called line is busy oi idle. l1? it busy ground is present on test contact 1&5 and busy test relay 11S energizes over the following circuit: from grounded contact 1 15 through wiper 1412, armature 115 and its working contact, armature 181 and its resting contact, and relay 118 to battery. When the slow acting relay 11 1- 'falls back, said relay 118 remains locked up over a circuit ion lit)

that includes its armature 130.

manner a The test relay 118 also opens the rotary magnet circuit at armature 111 in order to prevent further rotation of the wipers in case the calling dial is again manipulated, and at armature 119 completes a connection from the busy signalling machine to the lower line conductor. lhis operation gives the calling subscriber an audible busy signal to inform him that the called line is busy, and he will hear the signal and replace his receiver.

Let us assume, however, that the called line is idle when the connector H is operated, as before explained, to establish connection therewith. Under these circumstances as soon as the slow acting relay 114 deenergizes upon th cessation of the rotary movement, the following circuit is completed: from ground through the working contact or" armature 120 and said armature, armature 130 and its restin contact u" or windin of relay 117, resting contact of armature 115 and the said armature, test wiper 1 .2, test contact 1 15, switching relay 160 oi" the calle ling switch and through the stepping magnet 162 to battery. l'lelays 117 and 160 energize over the above traced circuit. Relay 160, upon energizing, removes the line relay bridge at the line switch *1), while relay 11? looks itself. to ground, completes at armatures 133 and 13? the connection to the line wipers 141 and 143, and closes a circuit for relay 116 which operates to shift the operat ing circuit to conductor 176 leading to the frequency selector F.

In response to the fourth digit 4 of the callednuinber the vertical magnet 201 of the frequency selector 1* receives four impulses over operating conductor 176. The first impulse comes through vertical of? normal springs 211i. and 209, slow acting relay 202 and vertical magnet 201 to battery. Upon the first vertical step the off normal springs operate and relay 202 energizes and completcs a new path for the impulses as :tollows: from conductor 176 through off normal springs 211 and 210, armature 238 and its working contact, relay 202, and vertical magnet 201 to battery. The vertical magnet and the slow relay 202 receive three more impulses over the new circuit which steps the switch shaft and wipers up until they stand opposite the fourth level oi? bank contacts. Soon after the last vertical impulse the slow acting relay 202 deenergizes and when it does so it switches the impulsing circuit to the rotary magnet 203 over the following path: armature 236 its resting contact, armature 227 and its resting contact, slow acting relay/204i and through rotary magnet to battery.

The calling subscriber may now operate his calling device in accordance with the last digit of the desire-flnumher. A series at impluses, as before, come over the operating circuit. in response to these impluses the rotary magnet operates to step the wipers 23 1 and 235 into engagement with the fifth set of contacts in the fourth level, opposite which they were previously raised. Relay a is energized in series with the rotary magnet 203 and at armature 225 closes a circuit for relay 205 which energizes and locks itself to conductor 173 and thence through the resting contact 01" armature 128 and said armature, armature 123 and its working contact to ground. At armature 227 relay 205 opens the circuit for the rotary magnet; however, relay 204; at armature 22lpreviously closed a multiple circuit so that the rotary magnet circuit is held closed until the end of the last impluse when it is opened by the falling back of relay 204:, which prevents further rotation of the wipers in case the calling subscriber should again operate his calling device. Relay 205, upon energizing, also closes at armature 223 a circuit for the interrupter l. Relays 261, 262, and 263 receive a momentary impulse. l lelay 261, being of the ordinary quick acting type, falls back first and closes again the circuit for relay 263. Belay 263 remains energized. for a time and holds the circuit to relay 262 open. ltelay 262, upon deenergizing, closes again the circuit for relay 261 which operates and breaks the circuit for relay which, upon deenergising, closes again the circuit for relay 262. This operation continues until ground is re moved from conductor 239 and, as relays 262 and 263 are both slow to tall back, the relay 261 is energized and dcencrgized at in tervals, thus sending out interrupted ground at armatures 212, 219, and 220.

Relay 204:, upon deenergizing after the last rotary impluse, completes the following circuit: from interrupted ground, conductor 213, through the resting contact oi armature 221 and said armature, working contact of armature 222 and said armature and stepping magnet 2141 or": code sending switch l5. AS soon as ground is sent over this circuit the stepping magnet 21 i; energizes and when the ground is removed magnet deenergizes. Stepping magnet 214., upon deenergizing, advances the switch wipers 236 and 23? into engagement with "he first set of contacts 22? and 228 of their associated banks. l l iper and 23?, upon reaching contacts 227 and 226., complete the following circuit: from grounded contact through wiper 237, conductor 266, wiper 236, conductor 2450, relay 231, and resistance to battery. Relay 231 energizes over the above traced circuit and locks itself to ground over grounded conductor 173. When ground. comes again over conductor 213 it operates stepping magnet 21% over its previously traced circuit and also operates ringing relay 21? over the following circuit:

I 1 11, Working contact of armature i vcuit to armature previously traced cirand thence through the resting contact of armature 215 and said armature, armature 216 and its Working contact, and relay 217 to batte j relay 217 operates, its armature 218 shitts conductor 1741 from ground to ground through generator G. Ringing current from generator G flows over conductor 174, through the resting contact of armature and said armature, armature 137 and its working contact, Wiper 1 13, contact 1 16, line conductor 118, through the stations B l-41 inclusive, in multiple, and back over line conductor 1 17, contact 1 14, Wiper 1 said armature, armature126 and its resting contact, upper Winding of ring cut-oft relay 125, conductor 175 and armature 233 and its Working contact to ground. All the bells on party line X are operated but relay 125 is not operated, due to its design and adjustment. When ground is removed from conductor 213, relay 217 deenergizes and shifts conductor 174 back to ground and the stepping magnet 21 1 deenergizes to step the wipers onto the second set of contacts. When ground is again placed on conductor 213 relay 217 operates to connect generator on the called line and the stepping magnet attracts its armature and when the ground is removed from conductor 213 relay 217 shifts its armature from generator to ground and the magnet 214 releases its armature to step the Wipers 236 and 237 onto the third set 01 bank contacts. This process continues until the bells on party line X have been rung four times and the magnet 214;

.has been de energized to step the Wipers from the fourth to the fifth set of contacts. When the Wipers reach the fifth contact set current flows tt'rom grounded conductor 206 through iper 236, the fifth contact in the bank of said Wiper, conductor 265, contact 243 in the fifth set on the fourth level of the banks of frequency selector F, Wiper 23 1, and relay 232 to battery. Relay 232 energizes over this circuit and at armature 215 opens the circuit to ringing relay 217. When groundis again placed upon conductor 213 stepping magnet21 l operates as before but obviously relay 217 cannot operate, as its circuit is open at armature 215 and. there fore, the bells on party line X are not rung.

.However, when stepping magnet 214i. de-

energizes and steps the Wipers 236 and into engagement with the sixth set of contacts relay 232 falls back and reestablishes the circuit for relay 217. hen ground is again placed upon conductor 213 the bells on the called line are rung as before. The effect of energizing relay 232 is to cause a time interval or break to occur in the regular periodic rings sent out to the called line so as to distinguish between the first digit ot the code and the second. Now it will be seen that the bells on party line K have been rung tour times and utter a short interval the have started ringing again. As pointed out, the bells are rung While the wipers are on the sixth sct oi? contacts and they will continue to ring each time the intcrriuitcr 1 places ground on conductor 213 until the eleventh contact set is reached, when the bells will. have been rung live more times thus completing the code call When the Wipers are stepped onto the eleventh contact set current lion's troni grounded conductor 206 through \vipci' 236 and the eleventh contact in its associated hank, conductor 2563, contact 21-4 in the bank ol the frequency selector F, Wiper 235, and resistance R to battery. This circuit shunts the relay 231 and allows it to fall bcclr and when it does so it opens its locking circuit, opens the circuit rin 1g relay 217, and re places batter on conductor ;=.i resistance R. lVhen the step ping magnet energizes and dcenergizes again the wipers 230 and 237 are advanced to the twelfth contact but the bells on the party line X are not rung because the circuit for ringing relay 217 is open and it cannot, therefore, place g'gcncrator on the line. 1

In case the called subscriber does not respond immediately, the code sending switch E continues to rotate step by step and repeats the code as it passes over the remainder of the contacts. because the first contact is multipled with the thirteenth. the second with the fourteenth. etc. The switch E will continue to rotate step by step and the proper code will continue to be sent out on the party line X until the called subscriber answers.

It the called subscriber answers at the end of the code the relay 231 will at that time be in deencrgizcd condition and the following circuit for the ring cut-oil relay 125 is completed: from ground through resting contact of armature 21S and said armature of relay 217, conductor 171 and over previously traced circuit to sulgistation A. of the called party, hrough substation A. and back over previously traced circuit to armature 233, and thence through its resting contact to battery through resistance R. Relay 125 energizes over the above traced direct current circuit, locks itself at armature 127 to grounded conductor 177, extends the called line to the back bridge relay 109, and at armature 128 it disconnects conductor 17 3 from grounded conductor 177.

As soon as the Wipers 236 and 237 are stepped onto either the twelfth or the twenty-fifth contact set in their associated banks, no ground Will be present on conductor 206, for the cnergization of relay 125 removed ground from conductor 173. Relay 205 accordingly deenergizes, removes lid ground from starting conductor 239, opens the interrupted ground at armature 222 in case the interrupter I should be operating due to some other cell, and closes at armature 226 and its resting contact a pointin the release circuit.

Returning now to the connector, when the called line is extended to the baclr bridge relay 109 the talking circuit is completed. The called. subscriber is supplied with tallc ing battery through the windings of the double wound back bridge relay 109. Relay 109 is energized while the receiver at A remains oil the hook and reverses the direction oi" current flowing in the calling subscribers battery loop. This operation. is of no utility in the present disclosure, but on account of its being a standard operation the circuits are shown in this way.

Conversation may now take place over the established connection and when it is finished both subscribers replace their receivers, The release of the equipment is brought about by the replacement of the receiver at the calling substation A which opens the circuit for the line relay 1.00 of connector H. The falling back of relay 100 followed by the deenergization of release relay 101 which removes ground from the release trunkconductor 68 allowing the selector D to release in the well known manner and the switching relay of line switch C to deenergize. The falling back ot release relay 101 also completes the following release circuit for connector H and frequency'selector F: from ground through armature 120 and its resting contact, armature 122 and its resting contact, conductor 171, resting contact of armature 226 and said arm-a ture, conduct-or 172, and in multiple through oil normal springs 208 and 207 and release magnet 221 oi frequency selector F to battery, and oil? normal springs 107 and 108 and release magnet 190 of connector H to battery. The release magnets 190 and 221 energize over the above traced circuit and restore their respective switches to normal.

In the foregoing it is shown how a connection with party line 123 is established and the code call 45 is sent out. We will assume that the same subscriber calls another subscriber (for example) A on the same party line and whose code number we will assume is 22.

In this case the calling subscriber will remove his receiver and dial 123 as before. At the end of the third digit the inn pulsing circuit is switched to the frequency selector as in the preceding call. In the same manner as before described the vertical magnet 201 raises the shaft and wipers in response to the fourth digit which in this case is 2. Likewise the rotary magnet 203 operates before and rotates the wipers in response to final digit which: in this case is 2 also. Vi e now have the wipers of the connector switch on the terminals of the party line X as in the preceding example and we also have the wipers or" the frequency selector F on the second set of contacts in the second level of the banks of said selector. After the end of the last digit the slow acting relay 20d falls baclr and completes the circuit from interrupted ground to the stepping magnet 21% of the code switch E as before.

The ringing relay 217 is now operated while the wipers 230 and 237 are on the first two contact sets or on the thirteenth. and fourteenth, depending upon whether the code ringing switch E started this time from the 12th or the 25th set of contacts, however, we will assume that it started from the twenty-fifth set in which case the bells on party line X will, as stated, he rung 0 while the wipers are on the first two sets ct contacts, but when the wipers 236 and 237 reach the third contact set current flows from grounded conductor 206 through wiper 236 and the third contact in its associated bank, conductor 242, bank contact 245, wiper 234, and relay 232 to battery. Relay 232 energizes and remains energized until the wiper 236 passes off the third contact. llelay 232, while energized, holds open the circuit to ringing relay 217 and, there-- fore, no ringing takes place while wiper 236 is on the third contact and a space is produced between the first and second digits of the code. The bells on party line X will be rung again when the fourth contact set is reached and also on the fifth but when the sixth contact set is reached wiper 236 allows current to pass from grounded conductor 206, through wiper 236 and the sixth contact in its associated bank, conductor 247, bank contact wiper 235, and re sistance to battery. This circuit shunts relay 231 and allows it to fall back and open the circuit tor ringing relay 217 at armature 216. It the called subscriber does not answer, the further rotation of switch l3] will reenergize relay 231 when the wiper 236 reaches the thirteenth contact in its associated bank, and the code will be repeated over and over until the called subscriber answers or the calling subscriber hangs up. If the called subscriber answers the ringing is stopped at the end of the code the' connection is completed, communication takes place and release is eifected all in the same way as in the previous example.

t could be shown how every one of the twenty code combinations is sent out, but it is thought that with the explanation already giyen, an examination of the drawing (Fig will clearly show how any code be sent out on any party line that ap pears in thebanks of connector H. In case smaller number of codes are required, con- Ill] tactsets in the bankof the code selecting switch F which are not used are not wired to thebank oi the ringing switch E, but are left dead except for the upper contacts of such contact sets, which are connected to ground as shown in the case of the contact sets in the fifth level and the last five con tactsets in levels 1 to 4. With this arrangement, if a subscriber should call an unused code number, by accident or otherwise, relay 232 will energize at once and no signaling will take place.

In code ringing party line systems known heretofore, the called subscriber can, by answering during the time that the code is being sent out, cause the code to stop before it is finished, thereby signalling the wrong subscriber. However, in the present invention this difficulty is done away with in a very simple manner. As previously pointed out, during the time that the relay 231 of frequency selector F is energized, the re turn path 01 the generator is connected to ground at armature 233. Ring cut-off relay 125 of the connector I-I, included in the circuit for ringing current, can energize only when direct current flows through it and, since relay 231 does not deenergize until the end of the code, no direct current can flow through the circuit during the code and the ring'c-ut-otf relay cannot energize to break the ringing circuit. As before pointed out, the d'eenergization of relay 231'ends the last digit of the code and upon deener-- gizing', it connects battery at armature 233 through resistance R to thecircuit so that should the called subscriber have his receiver ofi the hook or it he removes it before relay 231 energizes again to repeat the code, direct current flows over the circuit previously traced for relay 125 which. energizes and completes the talking'circuit in a manner already explained. The code ringing switch E, however, does not stop as soon as the called party answers but continues to advance step by step until. the wipers reach one of their normal positions. In actual practice, however, most if not all of the bells on the party line are stopped "from ringing or f are caused to give only a low buzz, due to being shunt-ed, whenever a called subscriber takes off his receiver during the code series. To overcome this, each and eve y subscriber on the party line is definitely instructed not to answer during the code and in case one of them forgets,

the unpleasant ring in the ear is a reminder that he has committed an error. Accordingly, very soon all of the subscribers form the habit of not answering until the code is'finished.

If the called subscriber does not respond, the calling subscriber will hang up and he is like-ly'to do so whilethe code is being sent out.

ately when the calling subscriber hangs up. many times the last code would be that oi some other subscriber and not the one that is wanted. In the present disclosure, however, the code will be ceni 'ileted even though the calling subscriber docs hang up his receiver before its completion. Upon reterrin 5.1 to the drawings, it will be seen that neither the connector H nor the frequency selector T can release and that code sending switcn l cannot stop until relay 205 of selector b) deenergizes. Now when the calling subscriber hangs up and allows relays MK) and 101 to deenergize ground is removed from conductor 173 at armature 123, but ground is kept on conductor 173-3 from wiper 23. over conductor 206, working contact of armature 228 and said armature. This ground holds relays 125, 117, and 205 energized un til the wipers of switch E reach the twelfth or twenty-fifth contact set. When they do so the code has been finished, ground is no longer present on them, relay 205 dccn rgizes, and svitches F and II release in the usual manner.

Having described our invention, what we consider to be new and desire to have protected by Letters Patent will be pointed out in the appended claims.

Whatwe claim as our invention is:

1. In a telephone system, a party line, a plurality of signals on said line, a source of ringing current, means for connecting said source of current to the line so as to operate said signals according to predetermined codes, means for disconnecting said source of current from said line, and means for ren dering said disconnecting means inoperative except at the end of the code.

2. In a telephone system, a party line, a plurality of signals on said line, a source 0t ringing current, means including subscriber controlled automatic switches for connecting said current source to said line so as to oper ate said signals according to a n'cdetcrniined code,means tor disconnecting said source o't current from the line, and means for rendering said last means ineffective until the code is finished.

3. In a telephone system, a calling and a called line, a plurality oi? stations on the called line, an automatic connector switch for connecting said lines, a code sclcctii'ig switch and cooperating mechanism associated with said connector for signalling any station on said called. line according to a pre-assigned code ring, and means for pro-- venting the release of said connector in (also the callin subscriber hangs up his receiver before the code ring is completed.

4. In a telephone system, a calling and a called line, a plurality of stations on the called line, an automatic connector switch for connecting said lines, a code selecting If the code should be stopped inunediswitch and cooperating =f-(l11I]lSlll associat- I with said connector for signalling any station on said called line according to pre-assi nod code ri in, means for releasing said conncctm' controlled by calling subscriber, and means for prevention the calli subscriber from producii Y a false signal releasing said connector i rore the code rin is completed.

5. ln a telephone system, a calling and a called line, a pluralnzy ot stations on the called line, an automatic connector swi ch for connecting said lines, a code selecting switch and. cooperating mechanism associated with said connector for signalling any station on said called line according to a pre assigned code ring, means in said con-- nector for releasing the same when the calling man hangs up his receiver, and means in said code selecting switch for preventing the operation of said releasing; means before the code ring is completed.

6. In a telephone system, a calling and a called line, a plurality of stations on the called line, an automatic connector switch for connecting said lines, a code selecting switch and cooperating mechanism associated with. said connector for signalling any station on said called line according to a pro-assigned code ring, means in said connector for releasing the same when the calling man hangs up his receiver, a third switch included in the said mechanism cooperating with said code selector, and means for preventing the operation of said releasinp; means when the said third switch is out of its normal position.

7. In a telephone system, a calling and a called line, a plurality ott stations on the called line, an automatic connector switch for connecting said lines, a code selecting; switch and cooperating mechanism associated with said connector for signalling any station on said called line according to a pro-assigned code ring, and means for pre venting the called subscriber from stopping the signalling operation before the code ring is completed.

8. ln a telephone system, a calling and a called line, a plurality of stations on the called line, an automatic connector switch for connecting said lines, a code selecting switch and cooperating mechanism associated with said connector for signalling any station on said called line according; to a pre-assigned code ring, means tor terminating the signalling operation when the called subscribed answers, and means for preventing the called subscriber from producing a false signal by answering before the code ring is completed.

9. In a telephone system, a calling and a called line, a plurality of stations on the called line, an automatic connector switch for connecting-said lines, a cone selecting switch and cooperating mechanism assoelated with said connector for signalling any station on called line according, to a pre-assin'ned code ring, means tor repeating the rode ring at intervals, means for ten mnmtinp' the signalling operation when the called sul scriber answers, and means for insuring that any code ring which is starter will be completed. whether the called subscriber answers or not.

10. in a telephone system, a calling and a called line, a plurality of stations on the called line. an automatic connector switch for connecting said lines a code selecting switch and cooperating mechanism asse eluted with said connector for signalling any station on said called l' 1e according to pro-assigned code ring, a ring; cut-elf relay in said connector connected in series with the called line during the signalling operation and adapted to stop the ringing when the caller subscriber answers, and means whereby said relay is rendered in effective until after the code ring has been completed.

11. The combination, with an automatic progi as -vely moi able connector switch :tor completing connections to called subscribers lines, oit progressively movable code rin icy; switch, and a release magnet for said connector switch controlled by said ringing switch.

12. The combination, with an automatic progressively movable connector switch for com iletinp; connections to called subscribers lines, of a progressively movable code ringing switch, a line relay for said connector, and a release magnet for said connector controlled jointly by said line relay and said ringing; switch.

13. The combination, with an automatic projn'essively movable connector switch il'ior completing connections to called subscribers lines, of a. progressively movable code ring; inp; switch, a. line relay for said connector swi *h, a second relay energized while said ringrinog switch is operating to transmit a code ring, and a release magnet for said connector controlled joi. .tly by said relays.

14-. The combination. with an automatic connector switch for completing; connections to sul scribers lines, olcode ringing equip ment for gnalinp; on a connected line, said equipment comprising; a code selecting switch and a code sending device, means tor restoring said connector, and means for preventing the restoration oil said; connector while said sending; device is transmitting;' a code.

15. The con'ibination. with an automatic connector switch tor completing connections to subscribers lines, ct code ringing; equipment for signalii 'r on a connected line, said equipment comprising a code selecting switch and a code sending; device, rino' cutotl means in connector adapted to be controlled. by a called subscriber for stepping the transmission of code signals over his line, and means for rendering said ring .cut oil means ineffective while said sending device is transmitting a code.

16. The combination, with an automatic progressively movable switch for completing connections to subscribers lines, of a progressively movable code ringing switch for signaling over a connected line, a ring out-oil relay in said connector, and means for preventing the operation of said relay while said ringing switch is operating to transmit a code ring.

17. The combination, with an automatic progressively movable connector switch for completing connections to subscribers lines, of a progressively movable code ringing switch for signaling over a connected line a relay energized during the operating of said ringing switch, a ring cut-ofi' relay in said connector, and an energizing circuit for said ring cut oil relay completed only when said first relay is deenergized.

18. In a telephone system, a calling and a called line, a plurality of stations on the called line, an automatic connector switch for connecting said lines, code ringing mechanism associated with said connector for signalling any station on the said called line according to a pre-assigned code ring,

and means for preventing the release o i? said connector in case the calling subscriber hangs up his receiver before the code ring is completed.

19. In a telephone system, a calling and a called line, a plurality of" stations on the called line, an automatic connector switch for connecting said lines, codc ringing mechanism associated with said conucmor for signaling any station on the said called line according to a pro-assigned code ring, means for releasing said connector con trolled by the calling subscriber, and means for preventing the calling subscriber from producin a false signal by releasing said connector before the code ring is ()OlllPlOl'Gd.

20. In a telephone system, a calling and a called; line, a plurality of stations on the called line, an automatic connector switch for connecting said lines, code ringing mechanism associated with said connector for signalling any station on said called line according to a pie-assigned code ring, and means for preventing the called subscriber from stopping the signalling operation liefore the code ring is completed.

Signed by us at Chicago, Cook County, Illinois, this 22d day of Nov., 1920.

BERNARD D. WILLIS. ARTHUR J. RAY.