US2269462A - Telephone system - Google Patents

Description

Jan. '13, 1942.

B. F. LEWIS ETAL TELEPHONE SYSTEM Filed June 21, 1940 5 Sheets-Sheet l QUE NGQ

#vvmroks E LEW/5 H A-LEW/S ATTORNEY 3 Sheets-Sheet 2 B. F. LEWIS-ETAL TELEPHONE SYSTEM Filed June 21, 1940 Jan. '13, 1942.

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Jan. 13, 1942.

B. F. LEWIS .ETAL

TELEPHONE SYSTEM Filed June 21, 1940 3 Sheets-Sheet 5 FIG 3 a. LEW/S INVENTORS ATTORNEY menaa Jan. 13, 1942 2,269,462 TELEPHONE SYSTEM Benjamin F. Lewis and Herbert A. Lewis, Bayside, N. Y., assignors to Bell Telephone Laboratories, Incorporated, New York, N. Y., a corporation of New York Application June 21, 1940, Serial No. 341,631

14 Claims.

This invention relates to telephone systems and particularly to systems in which automatic utilized immediately to control the automatic switches to extend the connection, either to switching devices are used in the establishment other automatic switches in the same ofilce if of connections. I

The objects of the invention are to facilitate the transmission and utilization of telephone designations; to increase the speed with which these designations may be transmitted from one station and recorded at another; to simplify the process of retransmitting recorded designations for further recording; and in other respects to effect improvements in systems of the character above noted.

It has already been proposed to facilitate the acts of a subscriber in sending the wanted telephone numbers by providing his station with push buttons instead of a dial. These push buttons pluck vibratory reeds which send alternating currents to the central oflice, each digital character usually being represented by a code of two or more frequencies transmitted simultaneously. At the central oflice the component frequencies of each digit are separated by selective filters and utilized to operate digit registers. The registration thus established on the digit registers is then used to control the selective the call is a local one, or over an outgoing trunk if the call is intended for a distant omce. When the call is a local one, the numerical part of the designation recorded on the tape is transferred to switch-controlling registers in the local omce which serve to control the remaining automatic switches therein to complete the connection. However, if the call is for a distant ofllce, the numerical designation recorded on the magnetic tape is reproduced and transmitted over the interofiice trunk to the distant oflice as alternat-v ing current signals in codes of frequencies corresponding to those originally transmitted from the subscriber's station. At the distant ofice they are received by switch-controlling registers, utilized to control the switches therein to.complete the desired connection.

A particular advantage of the invention is that the senders in both originating and terminating omces may be designed to receive the same kind operation of the automatic switches to set up initiated by a calling subscriber must be extended to distant oillces for completion to the called lines. And in these prior systems, in which frequency codes are sent from the subscriber's station and registered in the originating office, usually on registers of the relay or stepping switch type, the selective operation of the switches in the distant called oifice is controlled by direct-current impulses transmitted from one ofiic to the other in accordance with the setting of said registers.

According to the present invention the ad'- vantage of using codes of alternating current frequencies for sending telephone designations is applied not only to the transmission from the subscriber's station to the central ofiice but also to the transfer of the designation from one office to another when interoflice connections-are required. More specifically the office code and numerical digits of a wanted line designation are transmitted in succession from the calling station to .the central ofllce by frequecy codes, and the alternating currents comprising these codes are recorded directly upon a magnetic tape or wire. The oflice code recorded on the tape isof designation signals for controlling the switches in their respective offices. Also, as above noted, the advantage inherent in the use of alternating currents for signal transmission is extended to the transfer of the designation from one oflice to another, the trunks interconnecting them oftentimes being of considerable length.

Another feature of the invention is a designation recording system in which the movement of the recording tape or similar medium is utilized to detect the presence of a permanent signal on a subscriber's line and to route the line automatically to a. service operator's posi tion.

A furthernand related feature is a recording system in which the movement of the recording tape is utilized to cause the automatic routing 1 of a line to an operator's position in the event the subscriber fails to complete his transmitting operation. These and other features of the invention will be discussed more fully in the following detailed specification.

In the drawings accompanying the speciflcation, Figs. 1, 2 and 3, when arranged in the order illustrated in Fig. 4, disclose an automatic teletions. This figure also shows the switches and equipment in a distant ofiice over which calls from the local ofiice may be completed to subscribers lines in said distant office.

Figs. 2 and 3 show a common recording sender and a common switch-controlling marker in the local automatic office. Fig. 2 illustrates the signal receiving equipment in the sender including a magnetic signal recording device, and Fig. 3-

trated at the substation of line I00. A transmitter of this type is disclosed and described in the patent to R. F. Mallina, No. 2,147,710 of February 21, 1939.

At the central oflice the recording sender is arranged to receive and record the alternating current signals transmitted over the subscribers line and to utilize the recorded signals either for completing the connection to a subscribers line in the local oifice or for extending the line over an interofiice trunk to a distant office and then transmitting over the extended connection that part of the recorded designation which is necessary for controlling the operation of the switches in the distant oflice to further extend the connection toward the desired line. The alternating selectors S3 for completing calls in the same oifice. Also the office selectors S--I have access to trunks I09 extending to distant oflices for completing interofiice calls. The particular trunk I09 illustrated in the drawings terminates in an incoming selector switch 8-4 in the distant ofiice, which has access through a final selector switch S-5 to a called line IOI. Furthermore,

the ofiice selector switch S--I in the local officehas access to operators positions, such as the position I02. The link circuit I06 interconnecting the line switch LS and selector S appears in a sender selector 8-6 which serves to select and make connection with an idle recording sender. The local trunks I01 extending to the incoming selectors S2 also have access through sender selector switches S-8 to terminating senders in the local office, such as the sender I08.

At the distant office the incoming end of the trunk I09 also appears in a sender selector switch S1 which serves to associate the trunk with an idle incoming recording sender I03. The distant ofiice will also be provided with markers which cooperate with the recording senders for controlling the incoming and final switches S-4 and S5 to complete the connection to the called subscribers line.

Although the invention is not so limited it has been assumed for the purpose of the present disclosure that switches of the cross-bar type are used and that the operation of theseswitches is controlled by recording senders and common markers.

It is also assumed that the system disclosed herein is arranged for the transmission of telephone designations in the form of alternating currents of different frequencies, each of the several digital characters of a designation being represented by a particular combination oi! frequencies. For example, if five different irequencies are employed, each digital character may be represented by a combination of two of the five frequencies. In order that these designation signals may be transmitted over a subscribers line to the central oflice, the substation is equipped with a transmitter of any suitable type which the subscriber may manipulate to send the successive signals, two frequencies at a time, characterizing the wanted designation. A reed type of sender in which the manipulation of izeys by the subscriber plucks the reeds to generate alternating currents is suitable for this purpose, and one of these transmitters I04 is illusthe feed mechanism 2H.

current signals incoming from the subscriber's line pass through the sender selector switch S-6 and over the signaling circuit to the sender where they are selected by a band-pass filter 20I. After passing through the filter 20I the signal currents are amplified by an amplifier 202 and delivered to the output circuit 206. Some of the output energy from the amplifier is applied to an enabling device 205. The enabler 205 serves to extend the output circuit 206 to the recording unit 201 of a magnetic recording mechanism 240. Generally speaking, the function of the enabling device 205 is to respond to the incoming signals and to prepare a circuit at the proper time for delivering these signals to the recorder and to maintain the prepared circuit for the necessary period of time. Since the specific structure of the enabler is not necessary to an understanding of the present invention, it has been shown in diagrammatic form. For a complete description of the manner in which apparatus of this kind functions, reference may be had to the patent to A. A. Lundstrom, 2,237,742 of April 8, 1941.

The magnetic recording mechanism 240 of the sender includes a movable wire or tape 208, a substantial portion of which is normally stored in the container 209. When the recorder is taken in use, the driving motor 2I0 is started, and the feed mechanism 2 drives' the tape in the direction indicated by the arrows, withdrawing it from the supply container 209 and advancing it through the recording unit 201 to the second storage container 2 I 2. As the tape passes through the recording unit 201 it is magnetized in accordance with the incoming signals to record both the ofiice and numerical designations, and the magnetized tape is then stored in the container 2| 2. The areas of permanent magnetism thus produced in the tape are retained until they have served their purpose and have been erased as will be described hereinafter.

During the time the incoming signals are being received a second driving motor 2I3 is operated to drive a second tape feed mechanism 2. This second mechanism operates the tape at a speed somewhat slower than the operating speed of The function of the feed mechanism 2 I4 is to withdraw the prepared tape from the container 2 I2, move it through the reproducing unit 2 I 5, and return it to the storage container 200. i As the magnetized tape passes through the reproducing unit 2I5 the recorded signals are reproduced in their original form, whereupon alternating current signals representing the oflice code designation are transmitted over the circuit 2I6 to the signal receiver 300 of the sender. The ofiice. code signals flowing in the common input circuit 302 are applied to the channel filters 304, 305, 306, 301 and 308. Since transmission characteristics of the line.

the speed of the feed device 2M is somewhat slower than that of feed device 2, the frequencies of the reproduced signals are correspondingly lower than the frequencies of the original signals sent from the substation. The filters 304, 305, 306, 301 and 308 are, therefore, tunedto select the five reproduced frequencies; respectively. The output circuits of these filters lead to signal detectors 309, 3I0, 3H, 3l2 and 3I3, and the currents passing these detectors are utilized to operate the office code registers 3M, 3I5 and SIB.

As soon as the oflice code is registered on the registers 3, 3|?) and BIG, the sender seizes an idle marker 32I through the marker connector 322, and the office code is transferred to the marker. Thereupon the marker associates itself in the well-known manner with the district and office switches S and SI and operates these switches to seize either a local trunk I01 extending to the local incoming selector 8-2 or an interofiice trunk I09 extending to the distant office, depending uponthe nature of the ofllce code. If the call is a local one, the seizure of trunk I01 causes the operation of sender selector S8 to associate an idle terminating sender I08. Sim-' ilarly if the call is destined for the distant oifice illustrated, the seizure of trunk I09 causes the operation of sender selector 8-! in the distant nism 2I I drives the tape 208 at a greater speed than the feed mechanism 2I4. This speed differential may be selected with respect to the amount of tape normally stored in the container 209 such that the supply in said container is always suflicient for the normal holding time of the sender. In other words, if the call proceeds normally, the sender will have completed its functions and released before the supply of tape in the container 209 is exhausted. However, if the feed mechanism 2 is set in motion and the mechanism 2 fails to start thereafter or if both mechanisms are permitted to run simultaneously for a period of time in excess of the predetermined holding time of the sender, the supply'of tape in the container 209 becomes exhausted.

incoming sender I03 in the event of an interofiice call.

The advantages of this system of recording and utilizing designations for switch-controlling purposes will now be understood more clearly from the foregoing discussion. These designations are transmitted over the subscribers line in the form of alternating currents. The frequencies of these currents are selected within the voice frequency range in order to take full advantage, of the They are recorded directly on a magnetic medium in the originating sender, andthe ofllce code portion of the designation is immediately translated into oflice code registrations on registers of the usual type, such as relay registers, to extend the connection 'to a terminating sender either in the local oflice or in a distant ofilce. Thereupon the recorded alternating current signals representing the numerical designation are reproduced and transmitted directly from the originating sender to the terminating sender. Here they are received and translated into registrations on registers of the usual type for the purpose of completing the desired connection. By using a magnetic recording medium from which the recorded signals may be readily reproduced in their original form it is possible toobtain'the advantages incident to the the same type of receiving circuit may be used in t both local and interoflice incoming senders.

It was mentioned above that the feed mecha- The depletion of the tape supply in container 209 may indicate either that the subscribers line has a permanent signal condition thereon or that the subscriber has failed to complete the sending operation. To detect this condition the. container 209 is provided with any suitable mechanism for closing the circuit contacts 2". As illustrated the tape engages a plunger 2I8 when the tape supply runs low, and the upward movement of the plunger closes the contacts. The closure of these contacts may be utilized to operate a routing relay, the function of which is to cause the sender and marker to extend the subscribers line over the district and oifice switches and over a service trunk IIO to an operators position I02.

The container 2I2 is also provided with a set of contacts'2l9 and an operating plunger 220. 1

The purpose of these contacts is to stop the drive mechanism 2 I4 when the tape has all been transferred from the storage container 2 I2 to the container 209 following the use of the recorder.

It was noted above that the switches are assumed to be of the cross-bar type. Since these switches are well known in the art it is not considered necessary to disclose them in detail. Likewise the common controlling senders and the common markers are illustrated largely in diagrammatic manner, many of their details being omitted for the sake of clearness. For a better understanding of the principles of the cross-bar system and the details of operation, reference is made to the following: Carpenter Patent No. 2,089,921 of August 10, 1937.; Carpenter Patent No. 2,093,117 of September 14, 1937;- and Carpenter Patent No. 2,235,803 of March 18, 1941. 'Also reference is made to the patent to Lundstrom et al. No. 2,201,296 of May 21, 1940, for an understanding of the manner in which the incoming code signals of alternatingcurrents are received by the filter-detector circuits of the senders, such as receiver circuit 300, and transferred to the registers, such as the ofllce code registers 3H, 3I5, and SIB.

While the magneticrecorder illustrated herein uses a tape or wire of magnetic material itwill be understood that any suitable form of magnetic medium may be employed, such as magnetic discs and cylinders. a

The detailed operation of the system will now be described. when a call is initiated on one of the subscribers lines, such as line I00, the line switch LS and the sender selector switch 8-6 are operated to extend the calling line over the junctor I06 to the district selector S and also to theidle sender'disclosed in Figs. 2 and 3. The

seizure of the idle sender results in-the establishment of a signaling and controllingcircuit I05 which may be, traced from battery through the winding of control relay 22I, over conductor 222, through the sender selector S8 and the line switch LS over the loop of the line I and returning through the line switch and sender selector connector 223 through the winding of reactance coil 224 to ground. Seizure of the sender also results in the closure of a circuit from the tone source 225 through the filter 228 to the signaling circuit I05. 'The current passed by the filter 226 flows over the subscriber's line and produces a tone in his receiver which he recognizes as a Signal that the equipment is now ready to receive the wanted designation. Furthermore, the seizure of the sender results in the operation of a control relay 221 and the closure of a circuit from ground through the contacts of said relay over conductor 228 through the motor 2! 0 to battery. The motor 2I0 operates feed mechanism 2!! and the tape 200 is drawn from the supply container 209 through the eraser 229, which neutralizes all previously magnetized areas, and through the recording unit 20'! into the container 2I2.

The subscriber transmits the wanted designation by manipulating the reed transmitter I04 to send the three successive characters of the office code followed by the four successive characters representing the number of the called line. The alternating current signals representing these designation characters are passed by the filter 20!, amplified by the amplifier 202 and delivered to the output circuit 206. Each signal passing through the amplifier 202 is applied to the enabling device 205. The enabling device may'serve to introduce a preliminary delay between the arrival of a signal and the operation of a control relay 230. When the relay 230 operates at the end of this delay period, relay 23! is energized, and the output circuit 206 is connected through to the magnetizing element 201 of the recorder. The arrival of the first signal also causes the operation of relay 24! associated with the enabler and this relay looks over a control conductor 232. Relay 24! closes a circuit from ground through its armature and contact, conductor 233 through the contacts of an operated control relay 234, conductor 235 through the motor 2I3 to battery. The motor 2I3 drives the feed mechanism 2I4, and the tape 208 is withdrawn from the container 2I2 and passed through the reproducing unit 2!5. As the subscriber continues to transmit the alternating current signals the recording unit 201 responds to them and magnetizes the moving tape 208 to record them, representingfirst the three office code characters and then the four numerical digits of the designation.

As the magnetized tape passes through the recording unit 201 and into the container 2I2 it is immediately withdrawn therefrom and driven through the reproducing unit 2!5. When the magnetized areas of the tape representing the ofifice code reaches the reproducer 2!5, alternating current signals are produced in the circuit 2I6 of somewhat lower frequencies and of the same combinations as those transmitted over the subscriber's line. These signals. representing the ofiice code, flow over circuit 2I6 through the normal contacts of relay 30! to'the c rcuit 302 and are applied to the five selective filters 304, 305, 305, 301 and 308. Since each signal may be assumed to comprise two different frequenc es the currents of these frequencies are selected by the corresponding filters, detected by the corresponding detectors 309, 3I0, 3II, 3I2 and 3I3,

' meantime.

and utilized to operate the registers 3I4, 3I5 and 3I6 to register the office code. The receipt of the code designation by the registers 3I4, 3I5 and 3I6 may serve in any well-known manner to operate a control relay 323 to release relay 234 to open the circuit of the motor 2I3. The withdrawal of the tape from the container 2I2 is thus stopped until the ofiice selections have been performed.

At the, proper time following the receipt of the office code designation the sender seizes an idle marker 32! through the connector 322, and the office code designation is transferred from the registers 3I4, 3I5 and 3! 6 to registers in the marker. The marker translates the office code information and in the well-known manner associates itself with the frames containing the district and office selector switches S and S! and operates these switches to extend the calling line and junctor I06 to an idle trunk in the required group. Following the selection of the idle trunk outgoing from the oifice switch 8-! the marker 32! releases and becomes available for the use of other senders. If the call is for a local subscriber, the office selector switch SI makes connection with a local trunk, such as the trunk I01, and the sender selector switch S-8 seizes a local incoming sender I08.

As' soon as the incoming sender I08 has been seized and is ready to receive thenumerical information, relay 234 in the originating sender is reoperated to again start the tape feed mechanism 2I4. Also relay 30! operates in a circuit closed through the contacts of relay 324 to ground, the latter relay having operated in the The tape 208 is drawn through the reproducer 2!5, and the recorded alternating current signals representing the numerical designation of the called line are reproduced in the circuit. 2I6 which now extends through the operated contacts of relay 30!, over circuit 303, through the contacts of sender selector SS, through the contacts of selector switches S and S!, over the conductors of trunk I01, through the contacts of sender selector S-8 to the input circuit I II of the signal receiver H2 in the incoming'sender I08. The signal receiver II2, like the receiver 300, is provided with five selecting channels including the filters H3, H4, H5, H6 and H1 and associated detectors H8, H9, I20, I2! and I22. The successive alternating current signals are selected by the receiver H2 and utilized to cause the registration of the numerical designation on the registers I23 in the incoming sender. Thereupon the sender I08 seizes a marker (not shown), and the numerical registration is utilized to operate the incoming and final switches S--2 and S-3 to complete the connection to the local called line I24.

The originating sender, having completed its functions, now proceeds to release. Ground potential having been removed from conductor 228 the tape feed mechanism 2! I comes to rest. The tape feed 2I4 continues to operate, however, to withdraw any tape that may remain in the container 2I2 and to return it to the container 209. When all tape has been withdrawn from the container 2I2 the plunger 220 closes the contacts.

2I9, and a circuit is closed through the winding of relay 236 to the contact of a control relay 231 which has operated in the meantime. Relay 23B removes ground potential from conductor 235, all other sources of ground potential having previously been disconnected from this conductor, and motor 2I3 and the feed mechanism 2! 4 come to rest. All other operated relays in the originating sender are released, the sender selector 8-6 is released, the sender I08 and sender selector 8-8 are released, and the conversational connection is now held under the control of the subscribers lines.

Assuming that the call from the subscriber's line I is intended for subscribers line Ilil in a distant ofiice, the office code designation received by the marker 32I in the manner above described determines this fact, and the marker operates the district and oflice selectors S and SI to extend the calling line over the interofilce trunk I09 to the distant office. The seizure of trunk I09 causes the operation of sender selector 8-1 in the distant office and the seizure of an idle incoming sender I03. Following the seizure of the sender I03 the originating sender in the calling office proceeds as above described to extend the signaling circuit 216 through the front contacts of relay 30I, over circuit 303, through the contacts of sender selector S-B,

through the district and oflice selectors S and 8-4, over the interomce trunk I09, through sender selector S-1 to the input circuit I25 of the signal receiver I 26 in the incoming sender I03. The signal receiver I26, like the receivers 300 and H2, is provided with flve channels each having a filter and a detector and with registers I21 for registering the four digits of the numerical designation. The signaling circuit having thus been established betweenthe originating sender and the receiving circuit in the incoming sender at the distant 'oflice, the tape 201 is again started and driven through the reproducer 2 I5 to reproduce the alternating current signals representing the called subscribers number. These signals are transmitted over the interoflice trunk and are received by the signal receiver I25'and utilized to register the designation on the registers I21. Thereafter the sender I03 seizes an idle marker (not shown) and the incoming and final switches 8-4 and 8-5 are operated to complete the connection to the called line I M. When the connection has been completed, the markers and senders are released, and the connection is held under the control oi the subscribers lines. I

A description will now be given of the manner in which the system operates when a permanent signal condition occurs on a subscriber's line and when a subscriber initiates a call and fails to complete the sending operation.

Assume first that the loop of.subscribers line I00 is inadvertently closed either at the substation or elsewhere. This closure, known as a permanent signal condition, has the appearance of an actual call. It initiates the operation of the line switch LS and sender selector switch S6, and an idle sender is seized.' The seizure of the sender results in the operation of the relay 221 and the starting of the tape feeding mechanism 2| I. The feed mechanism 2, however, remains at rest since no signals are received from the subscriber's line, and the supply of tape in the container 209 becomes exhausted after a predetel-mined interval 'of time. When all of the tape has been withdrawn from the container 209,

' contacts 2" close, and a circuit is established from battery through these contacts, conductor 230, normal contact of relay 325, through the winding of relay 326 to ground. The operation of relay 326 is an indication to the sender that a permanent signal condition exists. Thereupon the sender seizes the marker 32I,a special code, determined by the operation of relay 326, is transmitted from the sender to the marker, and the marker proceeds to operate the district and oflice selector switches S and S I to seize a trunk IIII extending to an operator's position I02. The operator challenges on the subscriber's line and takes the'necessary steps to have the trouble remedied.

Assume next that the subscriber of line I00 initiates a call and transmits one or more digits and then fails to complete the sending operation. Since one or more of the ofiice code digits is received in the originating sender, one or more of the registers 3I4, 3I5 and 3I6 are operated resulting in the operation of relay 325. In this case both of the tape feed mechanisms 2 and 2 are set in operation. As previously ex.- plained, the mechanism 2 is started when the sender is seized, and the mechanism 2M is started when the first designation signals are received in the sender. Although both mechanisms are running, the supply of tape in container 209 eventually becomes exhausted since the feed device 2I I withdraws the tape faster than it can be returned by the feed device 2. Hence after the necessary time has expired, the contacts 2 are closed, and the circuit over conductor 238 extendsthrough the front contact of relay 325 and the winding of relay 321 to ground. The operation of relay 321 is an indication that the subscriber has failed to complete the sending operation. The marker is seized, and the switches are operated to extend the calling line to an operators position. She converses with the calling subscriber and instructs him to replace his receiver and initiate the call again.

What is claimed is:

1. In a telephone system, a central oflice a line terminating in said central oflice, a trunk outgoing from said central oilice, means for transmittingover said line alternating current signals of difierent frequencies representing a telephone designation, a magnetizable medium in the central oflice, means responsive to said signals for producing permanent magnetizations in said medium to record said designation thereon,

means for establishing a connection to said trunk, means for reproducing the alternating current signals recorded on said medium and transmitting them over said trunk,'and means responsive to the signals transmitted over said trunk for further extending said connection.

2. In a telephone system. a central ofiice, a subscribers line terminating in said omce, means at the subscribers station for transmitting alternating current signals in codes of diiferent frequencies representing the characters of a wanted telephone designation. a movable'magnetic tape in the central omce, means responsive to said signals for magnetizin said tape to record the wanted designation thereon, a distant central oflice. a trunk-outgoing from said first central ofllce to said distant oflice, means for extending a connection from said subscribers line over said I in said distant oflice responsive to said signals for further extending the connection established over said trunk.

3. In a telephone system, a central ofllce, a subscribers line terminating'therein, means at the subscriber's station for transmitting over said line alternating current signals of different frequencies representing the ofilce code and numerical designations of a wanted line, a switch controlling sender in said office including a movablemagnetic medium, means responsive to said alternating current signals for magnetizing said medium to record said oflice and numerical designations thereon, automatic switches in said oflice, a trunk accessible to said switches, means controlled in accordance with the office code recorded on said medium for operating said automatic switches to extend said line to said trunk,

means for reproducing and transmitting over said trunk alternating current signals of frequencies corresponding to those recorded on said medium, and means responsive to the signals transmitted over said trunk for further extending the connection toward the wanted line.

4. In a telephone system, a local office, a subscribers line terminating therein, a distant oifice, a sender in said local oilice including a magnetizable medium, means responsive to the initiation of a call on said line for associating the line with said sender; means at the subscriber's station on said line for transmitting alternating current signals in codes of difierent frequencies representing the 'oflice code and numerical designations of a wanted line, means responsive to said signals for magnetizing said medium to record said designations thereon, automatic switches in said local oflice, trunks accessible to said switches, certain of said trunks extending to said distant office, means controlled in accordance with the oifice code designation recorded on said medium for operating said automatic switches to extend the subscribers line to one of said trunks, means efiective if the connection is extended to one of said interofiice trunks under the control of the office code designation for reproducing and transmitting over saidinterofflce trunk the alternating current signals representing the numerical designation recorded on said medium, frequency selective means in said distant oflice responsive to the alternating current signals transmitted over the interoflice trunk, and automatic switches controlled by .said frequency selective means for further extending the connection toward the wanted line.

5. In a telephone system, a local oflice, a subscribers line terminating therein, a distant office, called lines appearing in said oflices, a sender in said local oflice including a magnetizable medium, means responsive to the initiation of a call on said subscribers line for associating the line with said sender, means at the subscriber's station on said line for transmitting alternating current signals in codes of different frequencies representing the oflice code and numerical designations of a called line, means responsive tosaid signals for magnetizing sa'id medium to record said designations thereon, automatic switches in said local ofllce, local trunks accessible to said switches for completing connections to called lines in the local ofllce, outgoing trunks accessi ble to said switches and extending to said distant ofilce, means controlled in accordance with the oflice code designation recorded on said medium for operating said automatic switches. to extend the subscribers' line either to one of said local trunks or one of said interoflice trunks according to the destination of the call, means controlled in accordance with the numerical designation recorded on said medium for operating the automatic switches in said local oflice to complete the connection extended over saidv local trunk to the called line in the event the called line appears in said local office, means effective if the connection is extended over one of said interofiice trunks to the distant office for reproducing and transmitting over said interofilce trunk the alternating current signals representing the numerical designation recorded on said medium, and means in the distant oflice responsive to said alternating current signals for completing the extended connection to the called line therein.

6. In a telephone system, a local central 0ffice, a subscribers line terminating in said office, a distant central office, a trunk interconnecting said offices, means at the subscribers station for transmitting over said line to the local central office currents in codes of different frequencies representing a telephone designation, a magnetizable medium in the local central oiilce, means responsive to said designation currents for producing areas of permanent magnetism in said medium to record the designation thereon, means for extending a connection from the local central ofiice over said trunk to said distant oflice, means controlled by said medium for reproducing and transmitting over the extended connection currents of frequency codes corresponding to those transmitted over the subscriber's line, frequency selective means in said distant omce for separating the frequencies of said codes, and means in the distant office controlled in accordance with the designation codes received by said frequency selective means for further extending said connection.

7. In a telephone system, a central ofiice, a calling subscribers line terminating in said office, a trunk line outgoing from said oflice, called lines terminating in said oflice, means at the calling subscriber's station for transmitting over said calling line alternating currents representing a telephone designation, a movable magnetizable medium in the central oflice, means responsive to said designation signals for recording them on said magnetizable medium, andmeans effective either to reproduce said signals and utilize them for establishing a connection to one of said called lines or for reproducing said signals and transmitting them over said trunk line.

8. In a telephone system, a telephone line, means for transmitting current signals over said line representing a telephone designation, a recording mechanism including a movable magnetizable medium, means for starting said medium in operation, means responsive to said currentsignals for magnetizing said medium to record the telephone designation, a conversational circuit, and means dependent upon the extent of movement of said magnetizable medium for automatically establishing a connection with said conversational circuit.

9. In a telephone system, a telephone line, means for'transmitting current signals over said line representing a telephone designation, a recording mechanism including a movable magnetic tape, means for starting said tape in operation when said mechanism is taken in use, a trunk circuit, and means effective in response to the movement of said tape through a predetermined distance for establishing a, connection to said trunk circuit.

10. In a telephone system, a subscribers line, means for transmitting current signals over said line representing a telephone designation, a recording mechanism including a movable magnetic tape, means responsive to a calling condition on said line for seizing said mechanism and starting said tape in operation, means responsive and utilized, and means responsive to the continued movement of said tape if the designation signals are not received within a predetermined time for establishing a connection to said trunk circuit.

11. In a telephone system, a central ofllce. a subscriber's line terminating therein, a recording mechanism including a movable magnetic tape, means responsive to a calling condition on said line for seizing said mechanism and start ting said movable tape in operation, a trunk circuit in said central oflice, means for transmitting signals over said line representing a telephone designation, means responsive to said signals for magnetizing said tape to record the same thereon, means for releasing said recording mechanism after the designation has been received and utilized, and means controlled by said tape after it has moved through a predetermined distance if no designation signals are received for establishing a connection to said trunk circuit.

12. In a telephone system, means for transmitting signal currents representing a telephone designation, a movable magnetic tape, means responsive to said signals for magnetizing said tape to record the telephone designation thereon, a storage reservoir for said tape, driving means for said tape, means for starting said driving means in operation to withdraw the tape from said reservoir, a conversational circuit, and means controlled by said tape when the supply thereof in said reservoir is reduced to a predetermined amount for establishing a connection to said conversational circuit. 4

13. In a telephone .system, a line, a recording mechanism including a magnetizable movable tape, means responsive to a call on said line for seizing said mechanism, means for transmitting signals over said line representing a telephone designation, means responsive to 'said signals for magnetizing said tape to record the telephone designation thereon, a storage container normally having a supply of said tape therein, a driving device for said tape, means efiective when the recording mechanism is seized for starting said driving mechanism to withdraw the tape from said container, a second driving mechanism operable in response to said signals 'for returning the tape to said container, a telephone circuit, and means effective when the supply of tape in said container is reduced to a predetermined amount for automatically establishing a connection to said telephone circuit. 4

14. In a telephone system, a line, a recording mechanism including a movable magnetic medium, means for transmitting signals over said line, means responsive to said signals for magnetiz'ing said medium to record a telephone designation thereon, a container for said medium normally having a supply of the medium therein, a second container for said medium, driving means controlled over said line for moving said medium out of the first container. and into said second container, a second driving means for withdrawing said medium from the second container and returning it to said first container, a

telephone circuit, and means effective if the supply of medium in said first container is reduced

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