US2211020A - Telephone system - Google Patents

Description

W. A. MARRISON TELEPHONE SYSTEM Aug. 13, 1940.

4 Sheets-Sheet l Filed-Jan. 21, 1939 5 v at m ul N at at k wt 7 //v VEN TOR PKAMARR/SON *MWM A TTORNE V 1940 w. A. MARRISON 2,211,020

TELEPHONE SYSTEM Filed Jan. 21, 1959 4 Sheets-Sheet 2 lNl/ENTOR n. A. MARE/SON BYWWIM A TTORNEV 13, 1940- w. A. MARRISON 2,211,020

TELEPHONE SYSTEM Filed Jan. 21, 1939 4 Sheets-Sheet 3 INVENTOR VWAMARRISON Y ATTORNEY w. A. MARRISON 2,211,020

TELEPHONE SYSTEM Aug. 13, 1940.

Filed Jan. 21, 1939 4 Sheets-Sheet 4 INVEN TOR WAMARR/SON ATTORNEY Patented Aug. 13, 1940 UNITED STATES PATENT: OFFICE Y TELEPHONE SYSTEM Warren A. lvlarrison, Maplewood, N. .L, assignor "'to Bell Telephone Laboratories, Incorporated,

New York, N. Y.,"a corporation'of'lilew York" Application January 21, 1939,. Serial No. 252,117.

' 19 Claims. (Cli179 f1 6 This invention relates totelephone systems and particularly to those in whichautomatic switching equipment is used in the. establishment of telephone connections.

The objects of the invention. areto obtain greater efficiency and increased speedxin .the transmission'of telephone designations; to simplify the operations involved; to reduce the hold:- ing time of the equipment at the central ofiice; and otherwise to secure improvements "and-advantages in systems of this kind. 1 1- Systems have been proposed in the past for transmitting telephone designations, such as the numbers of subscribers? lines or the numbers of trunk circuits, from one point to another by means of currents ofidiiferent frequencies, the

frequencies singly or'in combination serving to identifythe different numerals or other characters of the designation. Where, however,

each character or numeral of a digitaltplace' in the designation is representedby a single frequency it has been necessary to 'transmit in succession the characters of the successive digital places, since any given frequency might be used for two or more places in the same designation. Also where the currents-representing,

all of the digital places 'are: sent simultaneously it has been necessary in these prior systems to utilize combinations of different frequency groups for each digital place, the frequencies of a group serving one digital place differing from those" of the groups serving other places.

The present invention secures advantages over these prior arrangements in that it is possible to transmit within the same brief. period of time the characters of all digital places? in a subscribers designation by using only one frequency for each of the several places, I

According to 'a feature of the invention; this advantage is achieved by a transmission system in which the successive digital places of the designation are represented by different frequencies, one for each such digital place, and inwhich current of the frequency representing each place is transmitted for a brief interval of time, the relative position of this interval in the total transmission period serving to identify 'the'character of the digital place; If,'for example,v a subscribers designation has seven digital. or character places, seven different frequencies of alternating current are provided, one-for each of the seven digital places" in the designation. The total period of transmission is then-divided into as many successive intervals as there are variationsin the character or numeral of. each digital place. Usually, ofcourse,a digital place will have ten different characters corresponding to the numerals. 1 to 0. .To send the numeral character I, therefore, current of the frequency the period. V. I

In order that the different frequencies representing the different digital places and the relativepositionsof the currentintervals during the total, transmission period lmay be: identified at the central ,ofiice the system is arranged for synchronousoperation of the 'substation transmitter and the central office receiving mechanism.

One of the advantages achieved by the present invention, is the ability of. the calling sub scriber toset up the entire designation on a preset type of transmitter before anyof the des-' ignation currents are transmitted over the line. Another, advantage is a distinct reduction in-the holding time, of. the common central office equip ment, such, as ,the register sender, which receives the transmitted designation and utilizes the same for the purpose of controlling the selective operation of the switches.

. quency during the corresponding intervals of I The foregoing and other features of this inparts, of a telephone exchange system toillustrate the presentjinvention, g Fig. .1 shows the equipmentv at a subscribers station, including the designation transmitter;

Fig. 2 illustrates :the automatic switches in the central office together with ,a portion of one of the common register senders. This figure also illustrates a called subscribers line; i Figs. 3 and 4 disclosejjtheremainder of .thecentral oflice sender partially shown in Fig; 2;

Fig. 5 shows an alternative-form of driving mechanism for the substation transmitter; and Fig.6 shows a detail of the driving'mechanism for the receiving device at the central office.

The inventionis applicable particularly to systems in which the digitalzinformation .for a call is registered in a common register sender in the central office, the registered information being utilized to control the switches in the central office to establish the desired telephone connection. To this end the system chosen to illustrate the invention is one in which the central offices are equipped with automatic switches of the wellknown panel type. It will be understood, however, that other forms of switches, such as stepby-step switches and cross-bar switches, could be used to establish the connections. In the system shown in the drawings many details have been omitted, such as the structure and circuits of the selective switches, the manner in which the sender selectors seize idle senders in response to incoming calls, the manner in which the registers function to control the operation of the selector switches, and numerous other details of operation. For a better understanding of these details reference may be had to many patents in the prior art relating to systems of this general character and in particular to the following patents: Stearn et al. No. 1,395,977 of November 1, 1921; Stearn No.'1,505,l71 of August 19, 1924; and Raymond et al. No. 1,862,549 of June 14, 1932.

Referring to the drawings, the subscribers line F is equipped at the substation with the usual transmission elements, including the talking transmitter WI and the receiver I02. The designation transmitter, which is also provided at the substation in lieu of the usual dial, includes a rotary distributor shaft I03 driven by a synchronous motor I 04 to move a plurality of brushes over corresponding rows of fixed segments. The designation transmitter also includes a plurality of manually-operable devices by means of which the subscriber sets the transmitter in accordance with the several digital characters of the designation he desires to transmit. These manuallyoperable devices are illustrated as rotary contact keys I to ill, inclusive, although they may be push buttons or levers, or in any other desired form. These digit keys serve to connect corresponding sources of alternating current to the contacts in the corresponding rows of fixed segments in the rotary distributor.

The sources of alternating current are illustrated in the drawings as a series of generators or oscillators II2 to I I8, inclusive. Each one of these generators corresponds to a digital place in a subscribers designation and produces a current of a single frequency characteristic of such digital place. For example, generator II2 produces frequency f1 which corresponds to and identifies the first digital place in all designations that may be transmitted from the substation. Generator .I I3 produces frequency f2 corresponding to the second digital place, generator H4 produces frequency f3 corresponding to the third place, and, in like manner, generators H5 to IE8 produce frequencies ]4 to f7, inclusive. The digit key I05 associated with the generator H2 is capable of engaging any one of ten positional contacts which are connected respectively to the ten successive segments of the first distributor group H9. These ten segments correspond to the ten transmission intervals which make up the full transmission period. If key I05 engages the first contact, connected to the first segment in the group 'I IS, the frequency ii is transmitted during the first interval of the period and characterizes the digital character I. Similarly if key I05 is in engagement with any one of the successive nine positional contacts corresponding to any one of successive digital places of a designation.

the successive nine segments of the group I I9, the frequency i1 is transmitted during the corresponding interval in the period and identifies the corresponding numeral 2 to 0. The same is true with respect to each of the remaining digital keys I06 to III and the corresponding groups of segments I to I25, inclusive.

As will be explained more fully hereinafter, the synchronous motor I04 is set in motion by cmrent supplied from the central office to rotate the distributor shaft I03 through a single revolution, corresponding to the total transmission period, during which the brushes of the shaft I03 wipe over the corresponding groups of fixed segments to which the generators have been connected by the selective positioning of the digital keys.

The subscribers line I00 appears in the bank of a line finder switch F at the central ofiice, and the finder F is connected to a first or district selector switch SI. The switch S-I, together with the second or incoming selector S-2 and the final selector S-3, serves to complete the connection to-a called subscribers line 200 in the event of a local call. In case the calling subscriber wishes to converse with a subscriber in a distant office the'selector switch S-..I seizes a trunk extending to the distant office where incoming and final selectors are positioned under the control of the register sender to complete the connection to .the desired line.

The central office is provided with a plurality of common register senders, one of which is illustrated in Figs. 2, 3 and 4. These register senders are selected by means of sender selector switches, oneof which, such as the sender selector S--4, is provided for each link circuit comprising a line finder F and adistrict selector SI. The sender selector 8-4 is set in motion in response to the act of the. finder F in finding the calling line. Selector S--4 hunts for and seizes the first idle register sender and associates it with the calling subscribers line through the link circuit and the brushes of the line finder F.

- .The register sender in the central ofiice comprises numerous circuit controlling relays, a receiving synchronous distributor similar to the one provided at the substation, receiving relays and sets'of register relays corresponding to the The rece'ivingdistributor comprises a rotary shaft 300 operated by a motor L which is driven in synchronism with the motor. IM at the substation, and groups of stationary segments corresponding to the successive digital places. For example, the

group of stationary segments 20I corresponds to the first digital place of the designation and serves to bring about the operation of one of a series of receiving relays 202 depending upon the value of the digit. Similarly the succeeding groups of segments 203, 204, 205, 205, 20? and 208 correspond to the successive digital places and serve to operate the relays of the correspond ing groups of digit receiving relays 209 to 2 I 4, re spectively.

The currents of the several frequencies characterizing the digits of a complete designation are received in the central oflice sender by the common receiving circuit 2 I5. After passing through the filter 2I 6, and after being amplified by a suitable amplifier 2, these currents are applied to I the successive filters 2I8 to 22 3, inclusive. These filters are designed to pass selectively the respective frequencies corresponding to the generators H2 to H8. Filter 2| 8 passes the frequency 11 and no other frequencies, filter 2I9 passes frequency f2, filter, 2'20 passes frequency is, and, similarly, filters 22I to 224 pass frequencies f4 to f7, respectively.

The currents passing the filters 2I8 to 224 cause the operation of certain relays in each of the groups 202 to 2I4, and these relays in turn cause the selective Operation of the corresponding sets of register relays shown in Fig. 4. There are seven sets of these registers 400'to 406, inclusive, representing in that order the seven successive digital places of a subscribers designation. After the designation has been registered on the registers of, Fig. 4, these registers then serve, through the agency of controlling circuits not shown in the drawing, to control the selective operation of the automatic switches S-I,

S2 and 8-3 to extend the calling subscribers line I through to the called line 200.v

The operation of the system will now be described in detail, assuming, for this purpose, that the subscriber of line I00 desires to call the subscriber of line 200 and that the designation of the line 200 is CH 3-5000. It will be noted that the first two digital places in this designation are occupied by letters instead of numerals. This practice makes for ease in remembering the designation, since the letters are usually the first letters of the office name. They are, however, (the equivalent of numerals with regard to the effect they have on the central office mechanism.

First the calling subscriber sets up the desired designation on his transmitter. To do this he moves the digital key I to its second position contact I26 and the key I06 to the fourth position contact I21, corresponding respectively to the letters C and H of the called designation. He then positions the key I01 on the third contact I26, which corresponds to the character 3 in the ofice code part of the designation CH 3. Finally he positions the key I08 on its fifth'position contact I29, and the keys I09, H0 and III on their 0 position contacts I30, I3I and I32, corresponding to the numerical portion 5000 of the designation. The subscriber then depresses the button I 33, which latches and closes the contact springs I34 and I35 to prepare the circuit for the synchronous motor I04. Finally he removes his receiver I02 from the switchhook, closing the loop of the line I00 and initiating the operation of the line finder F at the central office.

When the finder F finds the calling line I00 and the selector S4 extends this line through to the idle register sender, a circuit is completed from battery to the left winding of relay 225, sender selector brush 226, through the contacts of sequence'switch spring 221, thence over the brush of line finder F over the lower sideof the line I00, through the substation circuit and returning over the upper side of the line through the brush of finder F, contacts of sequence switch spring 228, brush 229 thence to ground in the register sender. The relay 225 operates and closes a circuit from battery through thewinding of relay 230, contact of relay 225 to ground at the left back contact of relay 23I. Relay 230 operates and connects the source of alternating current 232 to the synchronous motor 30I associated with the receiving distributor of the sender and simultaneously to the synchronous motor I04 associated with the transmitter at the subscribers station. The circuit for motor 30I may be traced from the generator 232, through the outer contacts of relay 230, right contacts of relay 23I and thenceover .thecircuit 233 to the motor 30I. The circuit for motor I 04.: at the substation may be traced from generator 232 through the inner ,contactsof relay 230 through filter 234 thence over circuit 2I5 through the brushes 226 and 229 and thence over the subscribers line I00 through the filter I36 to the windings of the motor I04.

The-filters I36 and 234 pass current of the frequency produced by the generator 232 and exclude currents of other frequencies. Similarly the filter 2I 6 prevents current from source 232 from passing to the common receiving circuit When relay 225 operates, it also closes an obvious circuit for relay 244. Relay 244 closes a circuit from battery through the windings of all of the relays 401, 4, M2, M3, M4, M5 and M6 in parallel, thence over common conductor 4I1, outer contacts of relay 244, thence over conductor 245 to ground over the contacts of each of the relays M0, M8, M9, 420, 42I, 422 and 423. The relays 401, 4, M2, M3, M4, M5 and M6 serve respectively to connect the successive registers 400 to 406 through to the contacts of the digit receiving relays 202, 209, 2I0,- 2II, 2I2, 2I3 and2l4.

The distributor shafts I03 and 300 rotate in synchronism with each other through a complete cycle, which corresponds to the transmission period. Since these shafts are in synchronism with each other, their brushes engage simultaneously the segments corresponding to the ten successive positions 1 to 0. When theshaft 300 'moves out of its normal position, a circuit is closed from battery through the winding of relay 262, segment 263 and thence through the When the shafts I03 and 300 reach the sec- 0nd position segments, the first impulse is sent for the assumed designation. The circuit for this purpose is closed from the right pole of generator I I2 through the key I05, contact I26, segment I31 of the group II9, distributor shaft I03, common segment I38, conductor I39, thence over the lower conductor of line I00 through the finder F, spring 221, brush 226, conductor 235 to the filter 2I6. The other side-of the circuit may be traced from the other pole of the filter 2I6, back over conductor 236 through the brush 229, spring 228 through the finder switch F, thence over the upper side of the line through conductor I40 and finally to the left pole of the generator II2. Current of the frequency ii is transmitted to the, central oifice, where it passes the filter 2I6 and is amplified by the amplifier 2" and delivered to the circuit 231, which is common to all of the filters 2 I8 to 224, inclusive. Since the current thus transmitted is of the frequency f1, it is passed selectively byv the filter 2I8 and current is caused to flow in the output circuit of the filter, which may be traced by way of conductor 238 through the winding of the receiving relay 239 of, the group 202, thence to the second position segment 240, with which the brush shaft 300 is now in engagement, over said brush shaft through the common segment 24I, conductor 242 to the other terminal of the output circuit of filter 2I8. Relay 239 operates in this circuit and closes a circuit from ground through its. contact, conductor .243 through the .closed lcontact'of relay 401, left winding of register relay 458 to battery. Relay 458 operates and locks in acircuit from battery through its right winding and contact, conductor 409 through the winding of relay 4Ifl to ground. Relay 4 Ill operates in series with the register relay and removes its ground connection from the common conductor 245. Relay 491, however, remains operated as long as ground is present on the common conductor 245.

When the distributors reach their third position contacts, a circuit is closed from the right terminal of generator II4, digit key I01, terminal I28, segment I4l, shaft I03 common segment I38 thence over the line circuit to the filter 2IB and returning over the line by way of conductor I40 to the other pole of generator II 4. A current of frequency is is transmitted over this circuit and thence to the common circuit 231. Since the filter 220 is tuned to frequency f3, current flows in the output circuit of filter 226 over conductor 245 through a relay in the group 259 corresponding to relay 247, over conductor 248, segment 249, shaft 380, common segment 24I, conductor 242 to the other terminal of the filter 220. The operated relay of the group 2I0 applies ground potential to conductors 25B and 25I, which extend through the contacts of relay M2 to the windings of register relays 424 and 425. Relays 424 and 425 operate and look through their right windings and contacts over conductor 432 to the winding of relay M9 to ground, operating relay 4I9.

When the distributors reach their fourth position'contacts the generator H3 at the substation is connected by way of digit key I06 and segment I42 to the line, and a current of frequency f2 is transmitted. Current of this frequency passes the selective filter 2I9 and operates the fourth receiving relay of the group 209 by way of a circuit including conductor 252, conductor 253 and segment 254. The operated relay of the group 2553 applies ground potential to conductor 255 which extends through a closed contact of relay 4II to the left winding of register relay 425. Register relay 426 operates and locks through its right winding and the winding of relay 4I8. Relay 4l8 also operates and removes its ground connection from the common conductor 245.

When the synchronous distributors reach their fifth position segments, the generator IE5 is connected to the line by way of digit key I68 and segment I43. Current of the frequency f4 flows over the line and is passed by the filter 22! in the sender. Current flowing in the output circuit of the filter 22I causes the operation of the fifth relay of the group 2I I by way ofa circuit including conductor 256, conductor 25! and the fifth segment 205 of the distributor. The operated relay of the group 2 applies ground potential to conductor 258, which extends through the operated contacts of relay M3 to the left winding of register relay 427. Relay 421 operates and locks in series with relay 420, the latter relay also operating.

Since the numeral occurs in each of the last three places of the designation, no more currents are transmitted until the synchronous distributors reach their last or 0 position segments. On reaching the last segments in the distributor groups, circuits are closed for connecting the three generators IIG, Ill and H8 simultaneously to the line. The generator H6 is connected by Way of digital key I09 and distributor segment I44, generator II! is connected by way. of key Ill] and distributor segments I45, and generator I I8 is connected by way of key I I I and distributor segment I46. i Currents of frequencies f5, f5, and J? are transmitted over the line and are selected respectively by filters 222, 223and 224. In the manner already described I currents flowing in the output circuits of these filters cause the operation of the tenth relay in the relay groups 2I2, 2I3 and 2I4. These relays apply ground potential to conductors 259, 260 and 25!, which extend respectively through the contacts of relays 4 I 4, 4| and 4 I 5 to the windings ofrelays 428, 429 and 430. These register relays operate and lock, respectively, through the windings of relays 42!, 422 and 423. Relays 42I, 422 and 423 operate, and, since all of these relays are now energized, ground potential is removed from the common conductor 245 to permit the release of 1'elays4fil', 4H, 4I2, M3, M4, M5 and M5. These relays disconnect the receiving relays shown in Figs. 2 and 3 from the register relays shown in Fig. 4.

The entire designation has now been transmitted to the central oflice and registered on the register relays in the sender. It will be noted that the order in which the short current impulses are transmitted over the line does not bear any definite relation to the sequence of the digital places in the designation. Instead the order of transmitting the impulses representing the different digital places depends upon the value of the digit. These current impulses may be transmitted in succession if the digit values occur in that manner or two or more of them may be transmitted simultaneously, as in the case of the last three digits in the assumed designation. Or the impulses in some cases may be sent in the inverse order of the sequence of digital places.

As the distributor shaft I03 at the substation approaches its normal position the uppermost end thereof engages the dog I41, causing it to tilt and release the switch springs I34 and I35. This opens the circuit of the motor I54, bringing the distributor to rest in its normal position. Also as the distributor shaft 300 of the distributor at the central office approaches its normal position, a circuit is closed for the relay 23I extending from battery through the winding of said relay, closed contacts of relay 2B2, segment 26! thence through brushes of the distributor to the grounded segment 264. Relay 23I opens its right contacts and also releases relay 236. Thus the source of current 232 is disconnected from the subscribers line and also from the synchronous motor 3M and the distributor shaft 309 comes to rest in its normal position.

The register sender now proceeds to control the selective operation of the switches SI, S2 and S-3 in accordance with the designation registered on the register relays of Fig. 4 to extend the calling subscribers line Hill through to the called line 2053. Thereafter the register sender restores to normal and is ready for use in connection with another call.,

If it is desired to dispense with the synchronous motor for operating the distributor at the substation, this may be accomplished by providing a driving mechanism the power for which is stored up by an act of the subscriber and which is controlled by a governing device to operate the distributor at a speed which corresponds substantially to the speed of the distributor in the central office sender. A driving mechanism for the substation distributor is illustrated in Fig. 5. To set the device for operation the subscriber seizes the knob I48 and pulls the bar I49 outwardly against the tension of the spring I50. The rack on the bar I49 rotates the shaft I5I through an angle corresponding to a rotation of the distributor shaft I03. The subscriber then releases the bar I49, and the spring I50, being under tension, tends to drive the shaft I52 through the pawl I 54 and ratchet I55. However, shaft I52, to which the ratchet I55 is attached, is held in its position by the latch magnet I53". When the system is ready for the transmission of impulses, current flowing from the central ofiice over the line causes the operation of the latch magnet I53, which attracts its armature and releases the driving mechanism. The spring I50 thereupon rotates the shaft I5 I, and, through the pawl and ratchet connection, the shaft I52, which in turn drives the distributor shaft. The speed of the distributor shaft is closely regulated by a governor device I56. At the same time the distributor in the central office sender is set in rotation and operates in synchronism with the distributor at the substation.

An alternative form of driving mechanism for the distributor at the central office is illustrated in Fig, 6. Here the synchronous motor I51 is connected through a friction clutch I58 to the shaft I59 which drives the distributor. To rerelease the distributor for operation following the application of current to the motor I51, an impulseis transmitted to operate the trip magnet I60. The magnet I60withdraws the latch and allows the motor I51 to drive the shaft I59 through the friction clutch I58.

What is claimed is:

1. In a telephone system, a telephone line having a subscribers station thereon, means for producing currents of a plurality'of different frequencies, each frequency representing a different digital place in a telephone designation, a transmitting device at said station having a period of operation comprising a plurality of successive intervals of time, said transmitting device including means for applying to said line current of each of said frequencies for a time equal to one of said intervals, and means for selecting any one of the successive intervals of said period for application to designate the value of the character in the digital place represented by the frequency applied.

2. In a telephone system, a telephone line having a substation thereon, means for producing alternating currents of a plurality of different frequencies, a single frequency serving to identify a particular one of the several digital places in a telephone designation, a transmitting device at the substation having a definite cycle of operation which is divided into a plurality of short successive intervals of time, said transmitting device including means for applying to the-line each one of said frequency currents for a time equal to one of said intervals within a single cycle" of operation of said transmitting device, and manually operable means under control of the subscriber at the substation for varying in said cycle the relative position of the interval of application of each of said frequency currents to designate the value of the digital character in each of the digital places of the designation.

3. In a telephone system, a telephone line having a subscribers station thereon, means for producing currents of a plurality of different frequencies, each frequency representing a different digital place in a telephone designation, a transmitting device at said station having a period of operation comprising a plurality of successive intervals of. time, said transmitting device includingr'neans for applying to said ,line current of each of said frequencies for a time equal to one of said intervals, means capable of being positioned inadvance by the subscriber for selectingany one of the successive intervals in said period for the application of each of said frequency currents to designate the value of the characters in each of the digital places, and means for operating said transmitting device, after the selections for all digital places have been made.

4.- In a telephone system, a telephone line having a subscribers station thereon, means for producing currents of a plurality of different frequencies, each frequency representing a different digital place in a telephone designation, a transmitting device at said station having a period of operation comprising a plurality of successive intervals of time corresponding to the different characters in a digital place, a plurality. of. digit keys capable of being preset by the subscriber in accordance with a wanted designation, each key representing a different frequency and serving toselect any one of said successive intervals, and means for operating said transmitting device to send over the line current of all of said frequencies during the particular intervals ofsaid period determined by the settings of the corsponding'digital place, means at the central ofiicefor selecting said impulses in accordancewith' their frequencies, and means for utilizing the selected impulses to control the operation of said automatic switches. I Y

6. In a telephone system, a central office, a subscribers line, automatic switches in the central office for extending said line, a transmitting device at the substation of said line having a period of operation, means for operating said device to send over the line a plurality of current impulses of different frequencies, each frequency serving to identifya digital place in a telephone designation, means for varying the chronological position of each impulse in said period to identify the character in the corresponding digital place, 'registers atthe central office for controlling-said automatic switches, said registers corresponding respectively to the digitalplaces of the designation, means for selecting each impulse transmitted in accordance with its frequency, and

means operable in accordance with the chrono' logical position of each selected impulse for setting the corresponding register.

tral office for extending said line, a transmitting device at the substation of said line having a" period of operation, means for driving said device through its period of operation to send over the line a plurality of current impulses of different frequencies, each frequency corresponding to a digital place in a telephone designation, means for varying the chronological position of each im- 65 7. In a' telephone system, a central office, a subscribers line,automatic switches in the cenpulse in said period to determine the value of the digit in the corresponding digital place, means at the central office for selecting said impulses according to their frequencies, registers for controlling said automatic switches, and means operating in synchronism with the transmitting device for determining the chronological position of the selected impulses and for causing the operation of said registers to register the transmitted designation.

8. The method of transmitting designations in a telephone exchange system which comprises applying to a telephone line during the period of transmission a pattern of current impulses in which the digital places of a designation are distinguished from each other by differences in the frequencies of said impulses and the char acters of the digital places are identified by the chronological positions of the current impulses in said transmission period.

9'. The method of transmitting designations in a telephone system which comprises applying to a telephone line during a definite period of transmission a pattern of current impulses in which each digital place of a telephone designation is identified by a single impulse of a distinctive frequency and the characters of each digital place are identified by the relative position of the impulse in said transmission period.

10. The method of transmitting a digit of a multidigit telephone designation which comprises applying to a telephone line an impulse of alterhating current which identifies the character of the digit by the chronological position of the time interval in which the impulse occurs during the transmission period and distinguishes its dig-- ital place from other digital places in the designation by the frequency of the impulse.

11. The method of transmitting a multidigit telephone designation in a given time period, in which the several digital places are represented respectively by brief intervals of current of distinguishing frequencies applied to a telephone line, and in which the character value of each digital place is determined by the position in the transmission period of the brief interval of current representing such digital place.

12. The method of transmitting, within a period of time consisting of a plurality of successive r i brief intervals, 2. multidigit telephone designation which comprises identifying each of the digital places of the designation by transmitting a single impulse of current of distinguishing frequency over a telephone line during any one of said brief intervals, and identifying the characters of the digit of each place by transmitting the impulse of distinguishing frequency during the corresponding one of said intervals.

13. The method of transmitting designations in a communication system, in which a designation comprises a series of units, in which the several units are represented respectively by brief intervals of current of distinguishing frequencies applied within a given period of time to a transmission circuit, and in which the character of each unit is identified by the chronological position of the current interval in said period.

14. The method of transmitting in a given period of time a signal comprising a series of units, in which each of the signal units is represented by an interval of current of a distinguishing frequency, and in which the character of the signal unit is identified by the chronological position of the interval of current in the transmission period.

15. The method of transmitting information in a communication system which comprises applying to a transmission circuit within a given period of time a current pattern in which different portions of the information are represented by intervals of current of distinguishing frequencies, and in which the character of each portion of the information is identified by the chronological position of the current interval in said period of time.

16. In a telephone system, a telephone line having a subscribers station thereon, means for producing currents of a plurality of different characteristics, each characteristic representing a different digital place in a telephone designation, a transmitting device at said station having a period of operation comprising a plurality of successive intervals of time, said transmitting device including means for applying to said line current of each of said characteristics for a time equal to one of said intervals, and means for selecting any one of the successive intervals of said period for application to designate the value of the character in the digital place represented by the characteristic current applied,

1'? In a telephone system, a telephone line having a subscribers station thereon, means for producing currents of a plurality of different characteristics, each characteristic representing a different digital place in a telephone designation, a transmitting device at said station having a period of operation comprising a plurality of successive intervals of time corresponding to the different characters in a digital place, a plurality of digit keys capable of being preset by the subscriber in accordance with a wanted designation, each key representing a different characteristic current and serving to select any one of said successive intervals, and means for oper ating said transmitting device to send over the line currents of all of said characteristics during the particular intervals of said period determined by the settings of the corresponding keys.

18. The method of transmitting designations in a telephone exchange system which comprises applying to a telephone line during the period of transmission a pattern of current impulses in which the digital places of a designation are distinguished from each other by differences in the characteristics of said impulses and the characters of the digital places are identified by the chronological positions of the current impulses in said transmission period.

19. The method of transmitting a multidigit telephone designation in a given time period, in which the several digital places are represented respectively by brief intervals of current of distinguishing characteristics applied to a telephone line, and in which the character value of each digital place is determined by the position in the transmission period of the brief interval of current representing such digital place.

WARREN A. MARRISON.

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