US1864082A - Telephone exchange system - Google Patents

Description

June 21, 1932. R. F. MASSONNEAU I TELEPHONE EXCHANGE SYSTEM wFiled Sept. 25, 1931 a o mm \b n booo INVEN-TOR REMASSONNEA U By ATTORNEY 5 TI on iii 7 w l fl i Lmn E Patented June 21, 1932 ATENT OFFICE ROBERT FgMAssonNnA or 'SCA'RSDALE, NEW YORK, AssIeNon. To innn firem n -LABORATORIES, INCORPORATED, osnnw YORK, N. .Y., A conronmxon or NEW YORK - TELEPHONE EXCHANGESYSTEM Application filed September 25, 1931. Serial No. 565,053.

charges are made automatically.

The objects are to facilitate. the establishment of connections by subscribers on a party li'ne,to i sure the p roperassessment of service charges against calling parties, to render 1. it'impossible for aflcallingsubscriber to evade the service charge, and to otherwiseimprove systems of thischar'acter.

= Systems have been proposed heretofore in which-tests are made by the application of sources of alternating current of "different frequencies to identify the calling station in order to enable the selection and operation of the [corresponding message register. It has also-been suggestedto employ alteriv 2 nating current impulses for the purpose of controllingthe selective'operation of automatic switches; Moreovenfit' is old for a calling subscriber on a party line to send a special code individually characteristic" of his stationto effect the selectionand operation'of his service meter. According to, the present invention, advantages are secured ,over arrangementsof the foregoing character by means of a party line'telephone'system in which a calling party, by first dialing'his own party designation," selects one of a number'of sources of alternating current. This selected source is individual to the calling station and may be used only by that station fordialing alternating-current impulses to cause the selective operati'on'of thece'ntral oflice switches to complete the connection to the" called line. These results are secured by equipping the several stations on a party line with circuits tuned respectively to different frequency sources of alternating current so that any particular party will be able to send switch operating impulses only if he'has first dialed the code identifying his station. The act of dialing the. identifying code of the calling station infaddition to causing the selection of the proper source to enable further dialing also causes the selection and operation ofthe calling subscribers message register. Should a calling party attempt toevade the service charge by dialing the code of another station, the frequency'thus 'selected will not correspondwith the tuned circuit at his station and any further operation of his dial will an to smbns t e desired connection. Not only will'he fail to secure'a connection, but none of the service meters associated"with his line will be operated.

Thedrawing shows the invention applied to a'founparty line in'an automatic telephone'system. V v I The drawing shows, diagrammatically, four subscribers stations J M, Rand WJ'a line-finder switch LF and an associated selec- -tor SWltCh'S,'aI1d aregister 'sender RS for recording the ofiice and numerical digits of a called subscribers number'and' for controlling the operation of the various switches used'in extending a connection between" a calling and a called'station. 1 i 1 The telephone equipment at each of the sub: 'scribers stations J, M, R and W is of the usual type, providedwitha dialing device for use in directing the extension ofthe'callin'g line to any other line with which a' co'nnection' is desired; the ringing equipmenthas been omitted since it is not involved in this invention. Each of these stations is also provided with an alternating-current filter; the filter at station' jJ comprises the condenser 1 and coil'2 ;'the*filter at station M comprises the condenser 3 and coil 4; the filter at station R comprises the condenser 5 and coil 6 and the filter at station W comprises the condenser 7 and coil 8. Each of these filters, or networks, is connected in series with the transmitter a'n'd interrupter contacts of the dialing device but is normally 0011 2, and through'the interrupter contacts 10 of the dial to the lower conductor of line 11. The filter at station J is designed to pass current of one frequency; the filter at station M is designed to pass current of a second frequency; the filter at station R is designed to pass current of a third frequency; and the filter at station W is designed to pass current of a fourth frequency.

The line 11 connects to terminals in the banks of a group of line-finders in the central ofiice including the line-finder switch LF which is represented by the brushes designated 21 to 26, inclusive. The usual line and line cut-off relays are provided but are not shown in the drawing as they are not necessary to a clear understanding of the invention. The message registers 13, 14, 15 and 16 are provided forseparately registering the calls originated and completed from each of the four stations of line 11. The linefinder LF is permanently associated with a first selector switch S which is represented schematically by thebrushes 27 28 and 29. The line-finder LF and selector S may be of the panel type and of substantially the same construction and operation as is shown and described in the patent to O. H. Kopp No. 1,589,402, issued June 22, 1926. The linefinder selector unit includes a sender-selector switch SS which is represented by the brushes 41 to'46, inclusive, for extending a callin line to an idle register sender such as RS; the patent to Stearn et al. 1,395,977 issued November 1, 1921, discloses a system in whicha sender selector of the rotary type is used for this purpose. The line-finder selectorunit includes a sequence switch represented by the magnet 30 and the cams 31, 32 and 33, for controlling the operating circuits of this unit. The sequence switch may be similar to that illustrated in the aforementioned Kopp and Stearn et al. patents. The line-finder selector unit also includes the usual supervisory relay 35 which is operated in consequence of the answer of the called subscriber, and the charging relays 36 and 37 which control the operation ofthe calling subscribers message register. The control relay 39 is provided for transferring the calling line from connection with the register sender to the brushes of selector S to establish the talking circuit.

The register sender IRS is in general of the same character as-the register senders shown and described in the above mentioned patents to Kopp and Stearn et al. The switches for recording the digits dialed by the calling subscriber include a party-designation register in addtion to the usual office code and numerical registers. The party-designation register. PTY is represented by the stepping magnet 97 and brushes 98 and 99 together with the associated terminal banks; the ofiice code and numerical registers are represented by the registers A and B, comprising the stepping magnets 100 and 200 with the banks and brushes 101 and 102 and 201 and 202; the remaining register switches are omitted in their entirety. The usual register-control switch is provided for successively directing the dial impulses to the proper register switches; this control switch RC comprises the stepping magnet 94, the brushes 95 and 96'and their associated terminal banks. All of the registers and the register-control switches are of the type in which the brushes are advanced one step by each'release of the stepping magnet.

Since alternating current is used for transmitting dial impulses the register sender RC includes the transformer 51 which has four primary windings 53, 54, 55 and 56 and a secondary winding 52 which inductively cooperates with each of the primary windings to impose alternating potentials of four different frequencies across the calling line at the time that the first letter or digit. is dialed. The potentials of the four frequencies are supplied to the primary windings of the transformer by the sources 63, 64, 65 and 66 under the control of relays 73, 74, 75 and 76. The first digit dialed indicates which of the stations on a party line is the calling station; and during the dialing of this digit relays 73, 74, 75 and 76 are all operated to simultaneously impose the four dialing-frequency potentials on the line. During the dialing of the subsequent digits, only that one of relays 73, 74, 75 or 76 is operated which is eifective to impose the dialing-frequency potential which corresponds to the first digit dialed. Consequently, if a callingsubscriber falsely dials a party designation other than his own, the filter at his station will not pass the current from the potential source corresponding to the filter at his station, and the further dialing by the calling subscriber will not be registered at the central oflice. Avacuum-tube receiver, comprising the tubes 84 and 89, is provided for responding to the alternatingcurrent impulses created by the operation of the dial. The vacuum tubes 84' and 89 are of the usual three element type comprising a filament, a plate and a grid. The battery 85 supplies current for the filaments of both tubes. and supplies the grid potential for tube 84, the battery 86 supplies current for the plate circuits of both tubes, and they battery 87 supplies the grid potential for tube 89. The grid of tube 84 is connected through condenser 82 to conductor 50 which is included in the dialingcircuit as hereinafter described. Changes in the potential of conductor 50 are transmitted to the grid of tube 84, thereby causing variations of current in the plate circuit of this tube. The plate circuit of tube 84 is inductively coupled by transformer 88 to the grid of tube 89 which acts .as an amplifier. An impulse relay 91 is connected in the plate circuit of tube 89. When the filament circuits are closed by the ECO operation of the relay-81 upon seizure of the register sender, the plate circuit current through the winding of relay 91 is effective to operate this relay- Each time thedia'lcircuit -isopened, the current in the-plate'circuit'oftube-89 is reduced sufficiently to cause theu elease er relay91. The trains of dial 'imp'u'lses received by relay '91:a=re successively directed to the various registers by the-regseleotor SS tothe register sender BS. The

line re'lay 81 -of the register sender operates in a circuit which maybe traced from battery through its right winding, winding of retard coil *80, conductor 50, terminal and brush42 of the sender-selector, lower back contact of relay 39, brush 22 and terminal of line-finder LF, over the lower conductor of line 11, through the lowest and the middle ib'ack contacts of the dial at station J, through the transmitter, the left receiverswit'chcontact, the left winding of induction coil'9, back over the upper conductor of line 1 1, terminal and brush 21 0f line-finder L'F, upper back contact of relay 39, brush 41 and "terminal of sender-selector SS, through the secondary winding 52 of transformer 51, to ground. Relay 81 closes'a locking circuit through its left-"winding and inner'le'ft front Contact, through the secondary winding of tone 'transformer 79, through the normal ter- :minal and brush 95 of the register-control 'switch, to'ground. A dialtone is induced in thiscircuit through the windings of tone transforn1er79-as a signal to the calling subscriber that the dial maybe effectively operated. Relay'81 also closes a circuit through its "right front contact for operating relays 73, 74, 75 and 76; and, with "each ofyrelays 73, 7 4,75 and 76 operated,the various sources :of dialing potentials63, 64, 'and'66are respectivelyconnected to the primary windings 5'3',f54,-55;and 56 of thetransformerfil. fRelay 81' also closes the circuit for-energizing ithe=filaments of tubes 84 and 8'5,"thereby rendering these' tubes effective to respond to dial impulses. The-current in the plate circuit of tube 89 operates the impulse relay 91, and -relay91 in turn closes a circuit for operating zrelay92.

[The calling subscriber first'dials a letter or numericaldigit which corresponds to the-pariticular party designation of the station. To iIIustr'ate, at station J, the letter-J (or'digit '5 should be dialed; at station M',the letter (oridigit 6 shou'ldbe dialed; :at station R','"the letter (fordi'git 7) should beldialed; and'at station W,; the letterW' (or digit.9 should be dialed. Since thecallfin question is from station J, the lettertJ (or digit 5)' is dialed to indicate to the central oflicea pparat-us that station J is thecallin'g station. When the dial'is moved oif. normal, and :as long asthe dia'l is out of its normal position, the middle and upper back contacts of i the dial are opened and the front'contactsare closed; the lowest back contacts of the dial (that is, the interrupter contacts 'of'the dial) remaincloseduntilthe dialbegins its return movement. Thus, the direct current circuit through the right winding of relay 80 is opened at the off-normal contacts of the dial,

8% and 89 sothat the corresponding ivariations in the current through-the winding 'of relay-91 are effective to -oausethealternate release and reoperation of this relay.

The first release of relay.91,'upon receipt of the impulses created by the dialing of the,

party-designation digit, closes axcircuit from ground at its back contact,through the front contact of relay 92, windingof relay 9.3, brush 96 andtnormal'terminal, through the winding of stepping magnet 97, to battery. Relay 93 and magnet-97 both operate in this circuit. Relay .93 closes a circuit-for operating the stepping -magnet 94' of the register-control switch; When relay 91- reoperatesat the end.

of the first impulse, magnet 97 releases there- "by advancing the brushes .98 and 99 onestep,

that is, from their normaltoi-their first offnormal position. The alternate release and reoperation of relay 91 in response to each of the succeeding impulses. created by the dialing of the party-designation digit, causes the alternate operation and release of magnet .97 thus advancing: the brushes 9.8- and .99 "to :the fifth;;off-normal' terminal of their banks Relay-92 remains operated during thereceipt of impulses since this'relay isslow in releasing- Relay93 is also slowiin releasing so; that it. remains operated until all of the impulses, corresponding to a; single'digit have been, received. Then'relay '93 releases-,magnet 94 releases therebyadvancingathe brushes '95 and 96 of'the registencontrol switch one step-to the first off-normal position.'

When 'brush 95 is advanced from its norma'l position, the dial tone circuit through 'the left winding of relay 81 is opened and the circuit through the-right windings of relays 73, 74,75 and 76 is opened. Relays 74, 75 and 76 release but relay 73 remains operated since its left Winding is energized in a circuit which passes through the fifth olfnormal terminal and brush 98 of the partydesignation register. The dialing-frequency potential source 63 continues to .be inductively imposed on the line 11 through windings 53' and 52 of transformer 51, but the dialingfrequen'cy potential sources 64,65 and 66 are no. longer operatively associated .with the transformer. The dialing of each of the ofiice code and numerical digits is now effective to repeat thecycle of operations described above as being responsive to the dialing of the party-designation digit. The impulses createdby the dialing of the first office code digit are directed to magnet 1'00, those created by the dialing of the second oflice code digit are directed to magnet 200, and the succeeding trains of impulses are successively directed by the register-control switch BC to the remaining register switches in like man-- If the subscriber at station J has dialed any other party designation (or a digit other than 5) further dialing would be ineffective. To illustrate, the subscriber at station J dials M (or 6) as the firstdigit, brush 98 is advanced to the sixth off-normal terminal. Since relay 74 is now held operated, while relays 73, and 76 release, the dialing-fre quency potential source 64 remains opera- 'tively associated with transformer 51. But

the condenser land coil 2 do not permit current of this frequency to pass so -that the opening and closing ofthe interrupter con tacts of the dial'do not cause corresponding impulses to be received by relay 91. This condition would also result if either of dialing-frequency potential sources 75 or 76 were at this time operatively associated with transformer 51.

When the brushes of selector switch S and the other necessary switches have been directively advanced under the control of the register sender ES to extend the connection to the desired line, the sequence switch of selector S is advanced under the control of the register sender in the usual manner into the proper position for closing the talking path disconnected from the line-finder selector .unit after talking selection is completed, the ringing of the called station being automatically controlled by the penultimate selector of those used in completing the connection; but in the system here illustrated the register sender remains connected with theline-find'er selector unit until the connection is released by the calling subscriber. When the called subscriber answers, assuming that to be the case, the supervisory relay 35 is operated in the usual manner as is fully described in the aforementioned patents to Kopp and Steam et al. As soon as the upper contacts of interrupter 34 are closed, after relay 35has operated, a circuit is closed from ground through. the left springs of sequence-switch cam 31, front contact of relay 35, uppercontacts of interrupter 34, through the winding of relay 36, to battery. Relay 36 operates and locks through its right front contact and the front contact of relay 35, to the same ground. The interrupter 34 is designed to interrupter 34, front contact of relay 35, to

ground at sequence-switch cam 31. Relay 37 locks through its front contact to ground at sequence switch cam 32 until the sequence swltch has advanced beyond position-17. No further operation takes place until the calling subscriber replaces the receiver upon the receiver hook, at which time the sequence switch magnet 30 is energized-to advance the switch into position 17, in which position the meter 13 of the calling station J is operated. The circuit for operating meter 13 is traced from ground through the winding of this meter, brush 23 of line-finder LF, brush 43 of sender-selector SS, the fifth off-normal terminal and brush 99 of the party-designation register, over conductor 38, through the left front contact of relay 37, and through the upper right'and lower contacts of sequence-switch cam 33 to battery. The register sender RS is thereafter released, the line-finder switch LF and the selector S being restored to normal in the usual manner.

If the call originates at station ,M, the calling subscriber dials the letter M (or digit 6) as the first digit, the party-designation register being thereby advanced to the sixth offnormal position; in this case relay 74 is held operated, after the brushes of the registercontrol switch RC have advanced out of their normal position, to render the dialing-frequency potential source 64 continuously effective in cooperation withtransformer 51 to supply dialing current which is passed by the condenser 3 and coil 4. If the call originates at station R, the calling subscriber dials the letter-1R (ordigit ,7 aslthe first digit, the party-designation register beingi thereby ad- :vancedto the seventh ofi n'ormal position in gilhlSCfiSG relay .7 5 is held operated to render the 'dialing-frequency potential source 65 continuously cfiective in cooperation with transformer '51 to supply dialing current WihlClLlS passed'by the condenser 5 and coil 6. :If the-call originates at station W, the calling --l0"isubscriberdials the letter (or digit 9) as :the first digit, the party-designation *regis- -te'r :being thereby advanced tothe ninth olfrnormal position; in this case relay 76 is held -;operated to :render the dialing-frequency po- 1tential source 66 continuously effective in ,cooperation with transformer 51 to supply dialing current which is passed bythe condenser 7-=and coil 8.

-It-is,-of courseyunderstood that the appli- ..'-2 --cation of-the invention is not limited to the specificarrangement "disclosed. An advanrtageous modification of this arrangement would consist of providing-station designa- -tion relays in 'theiline-finder selector unit c which'would control theoperation-of the calling-subscribers meter. These relays could u be -operated :under control of brush 99' at the time that the sequence switch of the sedoctor-S is advanced to the talking position a and the register sender RS could then'bere- -leased as soon as'talking'selectionis completed in the usual manner.

*What'is claimed is:

1. The combination in a telephonesystem 3:35 of a line having a calling dial, a plurality of sources of current each of I a dilierent characvteristic, automatic switches, means respon- #sive to theoperation of said dial for selecting a particular one of said sources of current,

'i i ra-nd means responsive to other operations of I said dial for sending. impulses of current sup- ':-=plied fromysaid iselected source to "cause the: selectiveoperation of said automatic switches.

1 -7 2 2.- The combination in a telephone system of a l-ine-having a'number of stations thereon,

calling dialszfor-said stations, sourcesof aleternating current of-rdifi'erent frequencies, each sourcebeing individual to a particular 5 oneof said stations, automatic iselector --switches, means responsive 'to the operation lofithe dial-at a callingstationfor selecting 'thet'source of current individual-to said station, landvmeans controlled by vother opera- -tions of-said dial for sending-impulses of current 1 supplied from said selected source to eefliect .theloperation of said automatic selector switches. I p

. 3.: In a telephone system,vai line having a T5560 calling dial ata substation thereof,-a plurality ot sourcesof current, each of a different electricalcharacteristic, automatic switches, -means responsive to an intial-operation of said dial for choosing aparticular'one of said -sources:otcurrent, aandi means responsive to switches in response to t1on 'of'said device;

' other operations a of: said dial for transmitting impulses .su-pplied from said tchosen source of current tocause the selective operation of said switches, .saiddast-means-being rineffectiveto cause the operation of said' switches in case said dial in actuated" to select a source "of current otherthan: said particular source of current.

acteristic, filters one iat veach= of said stations for passing currentfrom a difi'erent' one of said sources, and means responsive to the 'operation of the-dialing deviceat any oneof said stations for rendering the corresponding one of said sources effective duringv thelfurther operationof said device. v

plurality of subscribers stations, a calling device at each of said stations,'apluralityiof sources of potential each ofadifl'erentcharacteristic, filtersr'one for each-of said stations for passingcurrent from a different one *OfSElld sources, means for imposmg allfof "said sources of potentlahon said line, and

means responsive to the operation of the dial at any one of said stationsforlmposing a 5. In a telephonesystem,a line serving a single one of said sourcessoni'said line: dur-i ingthe further operation of said dial.

6. Ina telephonesystem, aline serving: a plurality of subscribers stations, acallingde- 'vice ateach of said stations, filters one-for each of said stations eachcof said filters de-- signedto pass current: of a different'characteristic, a pluralityof sourcesv ofcurrent each of a different characteristic, i automatic switches, means responsive to the operation of the dialing devicerat=anyfone ofsaid'sta tions for selecting a particularone "of said sources of current, and means responsive to other operations of saidl'dial for sending'rimpulses of current supplied fromzsaid selected sourceto causetthe operation of saidvauto matic switches.

7 In 'a telephone system, a line serving a plurality of subscribers stations, acalling device at each ofsaid stations, a plurality of sources ofpotentiaheachof a difii'erent characteristicyfilters one for: each of said stations r'or passing currenthfrom'a different one of said sources, :means' responsive to the operation of the dIa'lIIIg'dBVICQ, at 'fifballillllg one of said stations :for imposinga'isingleonw #of said sources" onresaid iline,"automatic switches, and meansefiective lonly if said single source is the source corresponding to said calling stationv for advancing said 8, In 'a'telepho'ne system, a line having a number of substations thereon, fcal'lin'g' dials forsaid substations, a .plura'lityf of sonrces- "of alternating current having different frethe further operaquencies each individual to a particular one of said stations, tuned circuits for said substationseach circuit exclusively tuned to the .frequency of the source individual thereto, :automatic switches, means for connecting all of said sources to the line to enable a calling party to dial a preliminary series of impulses to select the source of current individual to his station, meansfor disconnecting the remaining sources of current from said lme, and means responsive to subsequent operations of said dial for sending impulses thereon,- calling dials for said substations,

a plurality of sources of current, each of a different characteristic, selector switches, registers respectivelyindividual to said substations, means responsive to'the operation of the dial at a calling substation for selecting a particular one of said sources of current and for selecting the register individual to said substation, means responsive to other operations of-said calling dial for sending impulses of current supplied from said selected sourceto' cause the operation of said automatic switches, and means for operating the selected register- 1O. In a telephone system, a line having a number of substations thereon, calling dials for said substations, a plurality of sources of alternating current having, different frequencies each individual to a particular one of said substations, automatic switches, message registers individual respectively to said substations, a control switch, means'respon- 'sive to a preliminary operation of a calling dialfor' operating said control; switch to select the source of current individual to the calling substation and forselecting the message register individual to said substation, means responsive, to further operations of the calling dial for. operating said automatic switches by means of impulses furnished by said selected source of current, and means for actuating'the selected message register.

device at each of said stations,

11. In a telephone system, a line serving a plurality" of subscribers stations, a calling a message register for each of said stations, a plurality of sources of potential each of a difl'erent characteristic, filters one for each of said stations for passing current froma di'fierent one of saidsources, means responsive to the operation of the dialing device at a calling one of said stations for selecting a particular one of 'said sources of current, and means .efiectiveonly if said selected sourcelis the one corresponding to the filterat said calling station foroperating the message register of said 'calling'station. 1

12. In a telephone system, a line serving a plurality of subscribers, stations, a calling dial at each of said stations, a message register for each of said stations, a plurality of sources of current each of a difi'erent characteristic, filters one for each of said stations, each of said filters comprising a condenser and an induction coil designed to pass current from a different one of said sources, automatic switches,,control means responsive to the operation of the dial at a calling oneof saidstations for selecting a particular one of said sources of current, means responsive to other operations of said dial for sending impulses of current supplied from said selected source to operate said automatic switches, and'means cooperating with said control means for operating the message register of said calling station. V

13. The combination in a telephone system of a line serving a plurality of subscribers stations, a calling dial for each ofsaid sta-- tions,a message register for each of said stations, a plurality of sources of current each of a different characteristic, filters one for each of said stations, each of s'aidfilters designed to pass current from a different one of said sources, automatic swltches, means responsive to the operation of the dial at a calling one of said stations for selecting a particular one of said sources-of current and for selecting one of said message registers, means responsive to the operation of said dial for sending impulses of current supplied'from said selected source to operate said automatic switches, and means for operating said selected-message register. 7 I

14:. Ina telephone system, a line serving a plurality of subscribers stations, a calling dial for each of said stations, a message register for each of said stations, a plurality of sources of current each of a different characteristic, filters one at each of said stations for passing current from a different one of said sources, means responsive to the operation of the dial at any one of said stations for rendering the corresponding one of said sources effective during the further operation of said "dial and for selecting the corresponding one of said message registers, and'means for operating the selected message register.

15. In a telephone system, a line serving a plurality of subscribers stations, a calling dial for each of said stations, a message register for each of said stations, a plurality of sources of potential each of a different characteristic, filters one for each of said stations- 7 operation of said dial and for selecting. one of saidmessage registers. and means for operating said selected register. 16. In a telephone system, a line serving a plurality of subscribers stations, a calling dial for each of said stations, a message register for each of said stations, a plurality of sources of potential each of a different characteristic, filters one for each of said stations tuned to pass current from a different one of said sources, means for imposing all of said sources of potential on said line, means responsive to the operation of the dial at any one of said stations for imposing a single one of said sources on said line during the further operation of said dial and for selecting one of said message registers, automatic switches responsive to said further operation of said dial, and means for operating said selected register.

17. In a telephone system, subscribers lines, each of said lines having a plurality of stations, a calling dial for each subscribers station, a message register individual to each of said stations, a plurality of sources alternating current for use in transmitting dial impulses, the current from each source being of a different frequency. an induction coil and a condenser at each of said stations tuned to pass current from a different one of said sources and a meter control switch operative in response to the dialing of a first digit at a calling one of said stations for selecting the message register which corresponds to the digit dialed and for rendering that one of said sources which corresponds to the digit dialed effective to thereafter supply the dialing current.

18. In a telephone system, subscribers lines, each of said lines having a plurality of stations, a calling dial for each subscribers stations, a message register individual to each of said stations, a plurality of sources alternating current for use in transmitting dial impulses, the current from each source being of a different frequency, an induction coil and a condenser at each of said stations tuned to pass current from a different one of said sources, a meter control switch operative in response to the dialing of a first digit at a calling one of said stations for selecting the message register which corresponds to the digit dialed and for rendering that one of said sources which corresponds to the digit dialed effective to thereafter supply the dialing current, and means for operating the selected register.

19. In a telephone system, subscribers lines, each of said lines having a plurality of stations, a calling dial for each subscribers station, a message register individual to each of said stations, a plurality of sources of alternating current for use in transmitting dial impulses. the current from each source being of a different frequency,an induction coil and a condenser at each of said stations tuned to pass current from a different one of said sources, a meter control switch operative in response to the dialing of a first digit at a calling one of said stations for selecting the message register which corresponds to the digit dialed and for rendering that one of said sources which corresponds to the digit dialed effective to thereafter supply the dialing current, automatic register switches, means effective to operate said register switches in response to the further operation of said dial, and means for operating the selected message register.

20. In a telephone system, subscribers lines each of said lines having a plurality of stations, a calling dial for each subscribers station, a message register individual to each of said stations, a plurality of sources alternating current for userin transmitting dial impulses, the current from each source being of a difierent frequency, an induction coil and a condenser at each of said stations tuned to pass current from a differentone of said sources, a meter control switch operative in response to the dialing of a first digit at a calling one of said stations for selecting one of said message registers and for rendering one of said sources efiective to supply the dialing current during the further operation of said dial, means efi'ective only if the source thus rendered effective corresponds to said calling station for responding to the further operation of said dial, and means effective only if the selected message register is the register of said calling station for operating said selected message register.

In witness whereof, I hereunto subscribe my name, this 22d day of September, 1931. ROBERT F. MASSQNNEAU.

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