US2153129A - Telephone system - Google Patents

Description

H. M. BASCOM 2,153,129

TELEPHONE SYSTEM 3 Sheets-Sheet l Filed Aug. 51, 1957 INVEN TOR H M BASCOM MWW ATTORNEY April 4, 1939. H. M. BASCOM 2,153,129

TELEPHONE SYSTEM Filed Aug. 51, 1957' 3 Sheets-Sheet 2 V I W. J: 5 h5g8 2/4 INVENTOR h; M BASCOM WW my.

. April 4, 1939-.

\ Filed Aug. 31, 1937 H. M. BASCOM TELEPHONE SYSTEM- FIG. 3

3 Sheets-Sheet 3 FIG. 5

30 ,.2 aozB II II I! II //v l/E/V TOR h. M BASCOM wmvww ATTORNEY Patented Apr. 4, 1939 UNITED STATES PATENT OFFICE TELEPHONE SYSTEM Henry M. Bascom, Brooklyn, N. Y., assignor to Bell Telephone Laboratories, Incorporated, New York, N. Y., a corporation of New York Application August 31, 1937, Serial No. 161,749 g 7 Claims; (01. 179-18) 7 This invention relates to telephone systems and the following specification andwill also be set particularly to systems in which automatic forth in the appended claims.) switches are used for establishing connections. In the drawings accompanyingth s specifica- The objects of the invention are to simplify the tion: r 1.

acts necessary on the part of subscribers and Figs. 1 and 2 taken togetherillustrate an autooperators in transmitting and in recording telematic telephonesystem inuwhich some lines are phone designations; to improve the efiiciency equipped with impul'se'dials and. others with and to increase the speed of operation ofthe tone transmitting dials and inwhich a central equipment, and otherwise to improve systems of office is equip'pe'd'lwith register senders arranged this kind. to cooperate with lines of either kind to control 10 Systems have been proposed heretofore in which the selective operation- .oi the switches in the the designations of called lines or trunk circuits central officeto complete'telephone connections; are transmitted from one point to another by Fig; 3'shows amodified form of the tone remeans of currents of different frequencies, the ceiving equipment in the central ofiice register 7 frequencies singly or in combination serving to mechanism in which photoelectric devices are characterize the difierent numerals or other employed for. selectively recording the numbers characters of the designation. And it is, of transmitted; and course, the general practice to transmit telephone Figs. 4 and 5 are detailed illustrations of the designations by direct current impulses, the photoelectric receiving mechanism.

:0 number of impulses in the several series being The system shown in the drawings is abbrevirepresentative of the corresponding numerals ated to 'a large extent, all parts not essential or other characters of the designation, to an understanding of the invention being According to the present invention advantages omitted for the salge of clearness and brevity. s are secured in these prior systems by arranging The invention relates particularly to the transthe same central oifice mechanism to respond mission of wanted designations over a telephone to designation impulses sent over' a line by line -or circuit for the purpose of controlling the means of the usual direct current impulse trans selective operations necessary to complete the mitter at the subscriber's station and also to recorresponding connections to subscribers lines, spond to designation currents of different freto operators positions or to other stations; and

30 quencies transmitted-over a subscribers line or it is therefore applicable to a wide variety of types 30 trunk by means of a. transmitter designed to of communication systems and particularly to send alternating currents of different frequencies those of the kind in which register mechanisms I representative of the wanted designation. By are employed at the central oflice for registering this provision some of the lines may be equipped the designations transmitted and for controlling '35 with ordinary impulse dials and other lines with the selective operation of automatic switches tone transmitting devices, and the central office to complete the connections. Accordingly, the register mechanism is capable of functioning with system chosen to illustrate the invention is'one both kinds of lines. in which the central office is equipped with auto- Another feature of the invention is a system in matic switches of the panel type and with com- 0 which the central oflice is equipped with a frmon register senders for registering the designaquencyselective. mechanism comprising electrotions transmitted to the central office from submagnetic devices and tuned vibrating reeds carryscribers stations. Ahd it will be obvious that ing mirrors for directing beams of light to the other forms of switches may be .u'sed-ior ,estab sensitive elements of photoelectric cells. These lishing the connections such asthe well-known tuned reeds are set in vibration in accordance step by-step switches, or switches of the 'cross- 45 with the frequencies of the currents received, bar type. which represent the different parts of the wanted Referring to the. drawings, two subscribers designation, and the photoelectric cells are corlines; are shown. appearing i'n. the contact bank re'spondingly excited to v cause the operation, of of the'line-finder switch F. The subscribers line the relays of the usual designation registers. lflflis equipped withan ordinary impulsedial ll, 50 These registers in turn serve to control the seiecwhich sends series of direct current impulses tive operation of the switches to establish the representative of the letters and numbers in a desired connection called designation, and these impulses are re- The foregoing and other features of the inceived and registered at the central ofiice. The

5 vention will be'described more fully in detail in other subscribers line, line I02, is equipped at u the substation with a designation'transmitter I03, which is designed to produce in the line alternating currents of different frequencies, the frequency or combination of frequencies bein chosen to represent the different letters and numbers constituting the wanted designations. These alternating currents are received at the central omce and, as will be explained presently, utilized to register the corresponding parts of the designations on the same registering equip-,

ment as is used to register the numbers of the designations received on other calls from lines equipped with impulse dials. I

.- The line finder F is joined to a first or district selector switch S--I, and these two switches together constitute a link for extending subscribers lines to trunks I04 leading to incoming selectors, such as the selector 8-2, which may be located in Q the same omce with the finder-district link or in a distant machine switching oflice. The, incoming selector 3-2 in turn has access to a final selector 3-3 which serves to complete the connections to called subscribers lines. One of these lines, line 200, is shown appearing in the terminals of the final selector S3.

The line finder and'district link has access through a sender-selector switch S4 to any one of a number of common register-sender mechanisms. The remainder of Figs. 1 and 2 of the drawings discloses in detail some of the essential parts of one of these register senders. The number of registers employed in these senders will, of course, vary with the requirements of the exchange area. In some of the larger areas oflice codes require two or three code registers, and the numerical part of the designation usually re-- quires four registers. In the present system two office code registers A and B are shown. Also the thousands numerical register Th and the units numerical register U are shown, it being understood that the hundreds and tens registers would be provided and inserted between these two as illustrated by the broken lines. These registers, each of which comprises five register relays, are operated to register the corresponding parts of a designation either by means of a counting relay set 20I or by means of the frequency selective equipment I05. The counting relay set MI is effective to receive dial pulses'when the sender is serving a subscriber's line equipped with a dial I I, and the frequency selecting mechanism I05 is effective to receive the designation currents when the sender is serving a subscriber's line provided with a tone-designation transmitter I03.

The frequency selecting mechanism I05 includes an amplifier I06 for amplifying the alternating currents incoming from the subscriber's line and a plurality of selective circuits I01, I08, I09 and I I0. These selective circuits may include any suitable resonant devices such as filters which are: tuned to select currents of particular frequencies and to exclude currents of other frequencies. They may also include any suitable demuch of the equipment for performing the nu-- merous other functions of the sender has been omitted. For an understanding of the details of the omitted parts reference may be had to the many prior-art patents showing them in full. In

arsarao particular reference is made to the patent to Raymond et al. 1,862,549 of June 14, 1932, and to the patent to Steam and Scudder 1,395,977 of November 1, 1921. The finder and selector switches, which are illustrated diagrammatically in the drawings, may be of any suitable and well-known type, such as the switches disclosed in the Raymond et al. and Steam et al. patents above noted. The designation transmitter I03 at the subscribers station may be of any suitable construction. As illustrated herein, it comprises a plurality of vibratory reeds III, which are tuned to vibrate at different natural frequencies, and a microphone transmitter I I2 sensitive to the vibration of the reeds III to produce in the line I02 currents having frequencies corresponding to the particular reed or combination of reeds set in vibration. The transmitter also is provided with a set of contacts II3 normally short-circuiting the transmitter II2. When the transmitter is manipulatedg'to set the reeds in vibration, the contacts H3; are opened in any suitable way to render the r'nicrophone transmitter II2 effective. Any suitable mechanical means may be used for plucking the reeds II I to cause their vibration. Referencejis made, for example, to the structure and operation of the transmitter disclosed and described in my copending application Serial No. l61,75I};" "filed Aug. 31, 1937.

'I'he' operation of the system will now be described in detail, and for this purpose it will be "assumed, first, that the subscriber of line I00,

which is equipped with an ordinary impulse dial, wishesto converse with the subscriber of line 200. When the subscriber of line I00 initiates the call, the line finder F isstarted in operation in the well-known manner and advances its brushes into engagement with the terminals of the line I00. Also the operation of the sender-selector switch 5-4 is initiated automatically, and this switch seizes the terminals individual to anidle register sender for the purpose of associating the sender with the subscriber's line to receive the register the wanted designation. When these automatic operations have been completed, an impulse transmitting circuit is established and may be traced from battery through the right winding of impulse relay Ill, conductor II5, brush III of the sender selector, closed contacts of sequence switch spring IIO, thence through the middle brush of the line finder F, over the subscriber's line I00, and returning through the uppermost brush of line finder F, closed contacts of sequence switch spring II9, sender-selector brush I20, conductor Hi, to ground. The impulse relay Ill operates in this circuit and closes an obvious circuit for the slow-release relay I2I. Relay I2I closes the circuit from battery through the winding of relay I22, outermost contact of relay I2I, to ground at the back contact of relay I23. Relay I22 operates and associates the counting relay set 20I with the first code register A by extending the group of leads I24 through to the windings of the relays of said register. Tone current from the source I25 flowing in the left winding of relay Ill induces in the right winding of said relay a current which flows over the subscriber's line, giving him a characteristic tone in his receiver. The equipment isnow in readiness for dialing, and the tone received by the subscriber apprises him of this fact.

The calling subscriber manipulates his dial IOI to transmit six series of impulses. The first two of these series represent code letters designating the name of the office in which the called line 200 appears, and the remaining four series represent the numerals in the four digital places of the subscribers line number. The impulses of each of these series operate the pulse relay H4, and this relay causesthe successive operation of the counting relays 20I, the number of pairs of countin relays being operated depending upon the number of impulses in the series. In order to describe the operation of the counting relays 20l, it will be assumed that a series of ten impulses are transmitted. When the subscriber's line is opened for the first impulse, relay II4 releases and closes a circuit from ground through its left armature and back contact, closed contactof relay I2I, through the winding of slow-release relay I25, to'battery. Relay I26 operates and closes an obvious circuit for relay I21. Relay I21 operates and looks through its contacts to ground through a closed contact of relay I2I. The purpose of operating relay I21 is to sever the impulse receiving leads H5 and H6 from the frequency selective equipment I05, this latter equipment not being used on a call-from a line provided with an impulse'dial.

The release of relay II4 on the first opening of the subscriber's line also closes a circuit from ground through its right contact, closed contact of relay I2I, conductor I28, right back contacts of relays 2I I, 209, 201, 205 and 208 in series, winding of relay 202 to battery. Relay 202 operates and closes a circuit from battery through its winding and the winding of relay 203, contact of relay 202, conductor 2I4, back contact of relay 205, conductor 2I5 to ground at the front contact of relay I26. Relay 203 is shunted by the circuit abdve traced for relay 202 and does not operate. As soon as the subscribers line is closed to complete the first impulse, relay II4 reoperates and opens the energizing circuit of relay 202. Relay 203 now operates in series with relay 202 in the circuit traced by way of conductors 2I4 and 2I5. Thus at the end of a single impulse representing the digit I, relays 202 and 203 are operated, and relay 203 at its left contact applies ground potential to the conductor 2I5.

When relay II4 releases on the opening of the line for the second impulse, the grounded conductor I28 is extended through the front contact of relay 203 and the winding of relay 204 to battery. Relay 204 operates and prepares a series operating circuit for relay 205, but the. latter relay being short-circuited does not operate at this time. At the end of the second impulse the short circuit is removed on the operation of relay H4, and relay 205 operates in series with relay 204. The holding circuit for relays 204 and 205 extends through the back contact of relay 200 to grounded conductor 2I5. Relay 205 in ;.operating opens the circuit of relays 202 and 203, and these relays release. Thus at the end of two impulses relays 204 and '205 are operated, and relay 205 applies ground potential to the conductor 2".

When relay II4 releases for the third impulse, the grounded conductor I28 is extended through the front contact of relay 205 and the winding of relay 206 to battery. Relay 206 operates, and, when relay II4 reoperates, relay 201 operates in series with relay 206 in a circuit traceable through the back contact of relay 208 to the grounded conductor 2I5. Thus at the end of the third impulse both relays 205 and 201 are operated, and ground potential is applied to conductors 2l6 and 2".

On the release of relay II4 for the fourth impulse the grounded conductor I28 is extended .pulses relays through the front contact of relay 201 and the winding of relay 208 to battery. Relay 208 operates, and, when relay II4 reoperates at the end of the impulse, relay 208 operates in series with relay 208 in a circuit through the back contact of relay 2 to the grounded conductor 2I5. Relay 209 in operating causes-the release of relays 204, 205, 286 and 201. "Thus at the end of four im- 208 and 200 are operated, and ground is applied from a front contact of relay 209 to conductor 2I8.

When relay- I I4 releases at the beginning of the fifth impulse, conductor I28 is extended through the front contact of relay 205 and the winding of relay 2I0 to battery. Relay 2! operates, and,

when relay II4 reoperates, relay 2 is energized in series with relay 2I.0 in a circuit traceable over conductor 2 through the back contact of relay 205 to the grounded conductor 2I5. Relay 2 in operating opens the holding circuit of relays 208 and 209. Thus at the end of five impulses relays 2I0 and 2 are operated, and relay 2 closes a circuit from ground through its inner left front contact, outer left back contact of relay 2I8, to conductor 2I9. Relay 2 also closes the circuit from the grounded conductor 215, outer left front contact of relay 2| I, inner bacl" contact of relay 2I3, winding of relay 2I2,'to battery. Relay 2I2 operates and closes the circuit from bat tery through its winding and the winding of relay 2I8, contact of relay 2 I2 to the grounded conductor 2I5. Relay 2I3, however, is short-circuited as long as relay 2I I remains energized.

When relay I I4 releases at the beginning of the sixth impulse, a conductor #28 is extended through the front contact of relay 2, thence through the back contacts of relays 201, 205 and 203 in series, winding of relay 202, to battery. Relay 202 operates, and, when relay H4 reoperates,- relay 203 operates in series with relay 202 in the circuit previously traced to. the grounded conductor 2 I5. Thus at the end of the sixth impulse relays 202, 203, 2l0, 2H and 2I2 are operated and ground potential is placed on conductors 2|5 and US.

At the beginning of the seventh impulse relay I I4 operates, and conductor I28 is extended through the front contact of relay 202 and the winding of relay 204 to battery. Relay 204 operates. When relay II4 reoperates, relay 205 energizes. Relay 205 opens the holding circuits of relays 202, 203, 2I0 and 2H and these relays re lease. Relay 2 removes the short circuit from relay 2I3. and the latter relay operates in series with relay 2I2 to the grounded conductor 2I5. Thus at the end of the seventh impulse relays 204, 205, 2I2 and 2I3 are operated. Relay 205 grounds the conductor 2" and relays 2H and M3 complete a circuit from ground through the back contact of relay 2, right front contact of relay 2I8 to conductor 2l8.

At the beginning of the eighth impulse relay II4 releases, and conductor I28 is extended through the back contact of relays 2H, 209 and 201 in series, front contact of relay 205, winding of relay 208 to battery. Relay 200 operates, and, at the end of the impulse, relay 201 operates in series therewith as above explained. Thus at the end of the eighth impulse relays 204, 205, 200, 201, 2I2 and 2l8 are operated, and ground is placed on conductors 2I1, 2I8 and H8.

When the relay II4 releases at the beginning of the ninth impulse, conductor I28 is extended through the front contact of relay 201 and the winding of relay 208 to battery. Relay 208 operates, and at the end of the impulse relay 20! operates in series therewith. Relay 200 releases relays 204, 20!, 208 and 201. At the end of the ninth impulse relays 203, 20.0, 2I2 and 2|! are operated, and conductors 2I8 and 2I8 are grounded. V

Finally, when relay II4 releases at the beginning of the tenth impulse, conductor I28 is extended through the right front contact of relay 209 and the winding of relay 2I0 to battery.

' Relay 2| operates, and, at the end of the impulse, relay 2II operates in series therewith. Relay 2" releases relays 208 and 209. Thus at the end of the tenth impulse relays 2I0, 2II, 2I2 and 2I3 are energized and the circuit is closed from ground through the inner left front contact of relay 2i I, outer left front contact of relay 2i 3, to conductor 220.

Having shown how the counting relays respond to the impulse dial IOI, it will now be assumed byway of specific example that the subscriber of line I00 dials the designation CH 5678, in which the letter C is represented by a series of two impulses: and the letter H is represented by a series of four impulses. In this case the first series of two impulses causes the grounding of conductor 2". Since the conductors I24 are at this time connected through the contacts of relay vening registers, thence through the contacts of relays 222 and 22I, winding of relay I23, conductor I3I, through the contact and right winding of register relay I30 to battery. Relay I30 looks, and relay I23 operates in this circuit before the holding circuit of the counting relays 20-4 and 205, which is opened by relay I20, is efiective in releasing these counting relays. When relay I23 operates it closes a substitute holding circuit for relay I30 and for itself through its front contact to ground. Relay I23-in operating also releases the cut-through relay I22. Relay I23 also closes the circuit for relay 22I of the second register This circuit may be traced, from-battery through the winding of relay 22I, normal contact of relay 225, through the contacts of relay I23 to ground. Relay 22I operates and extends the conductors I24 through to the windings of the relays of register B. At the end of the second digit, which comprises a series of four impulses, ground potential is placed on conductor 2I8 and register relay 226 operates in a circuit through its left winding and through a contact of relay 22I to said grounded conductor 2I8. When relay I 26 releases at the end of this second series of impulses, it grounds conductor 224 as above described and relay 225 is operated in a circuit from battery through the right winding and contact of relay 226, through the winding of relay 225, thence as traced to the grounded conductor 224. Relay 225 at its right' contact closes a locking circuit for itself and for the relay 226 independent of conductor 224. Relay 225 also releases relay 22I and closes an operating circuit for the next cut-in relay 222. The full release of relay I 26 at the end'of the series causes the release of all sands, hundreds, tens and units registers.

operated counting relays. In a similar manner the transmission of the next four series of im pulses representing the digits 5, 8, I and 0 of the called subscriber's number causes the operation of the corresponding relays of the th gtue thousands digit 5 causes relay 227 to operate and lock in series with relay 228, the hundreds digit 6' causes the operation of relays in the hundreds register corresponding to relays 229 and 221, the tens digit I causes the operation of relays in the tens register corresponding to relays 230 and 221, and the units digit 8 causes relays23l, 232 and 233 to operate and lock in series with relay 234.

The designation of the wanted line 200 having thus been registered on the registers of the sender, the sender now proceeds in the well-known manner to control the selective. operation of switch S-I in accordance with the office code recorded on registers A and B to choose'an idle trunk I04 extending to the incoming selector switch S2 either in the same or in a distant office. Thereafter the sender further controls the selective operation of switches S2 and 8-3 in accordance with the numerical part of the designation to complete the connection through to the called subscribers line 200. The sender is then released in any well-known manner, and, following the conversation between the subscribers, the established connection is also restored to normal.

Assume next that the subscriber of line I02 equipped with a tone dial I03 initiates acall for the purpose of conversing with the subscriber of line 200. The initiation of the call causes the line finder F to operate and seize the terminals ofthe calling line and also causes the sender-selector switch 8-4 to operate and associate the line finder district link circuit with an idle sender, such as the one illustrated in the drawings. The extension of the subscribers line through to the idle sendercloses the loop circuit previously traced from battery through the right winding of relay I I4, thence over conductor H5 and thence over the loop of the calling line and returning to ground by way of conductor I I0. Relay I I4 energizes and operates relay I2I. On a call of this type no impulses are sent over the line by opening and closing same, relay II4 remains energized, and relays I26 and I2! do not operate. Since relay I21 remains deenergized, the tip and ring conductors of the subscriber's line I03 are extended by way of conductors H5 and IIS through to the frequency selecting circuit I05.

The calling subscriber receiving dial tone from the source I25 proceeds to transmit the wanted designation by manipulating his sender I03 in accordance with the letters and numerals of said designation. Each manipulation of the sender causes one or more of the tuned reeds III to be set in motion. The microphone H2 is sensitive to the vibrating reeds and modulates the direct current flowing in the line from the central ofilce'tio produce in said line alternating currents of frequencies. corresponding to the vibrating reeds II I. Themicrophone I I2, which is normally shortgcircuited by the contacts I I 3, is rendered effective on each manipulation of the sender by the opening o'fsaid contacts. These alternating currents are received by any suitable amplifying mechanism I 06, which increases their amplitudes and delivers them to the frequency selecting filters I01, I08, I09 andIIO. Whileany suitable frequencies may be used, it "will be assumed by 2,153,129 way or eiramplethat there are four reeds III in the substation sender which vibrateatirequencies H2, 120, H48 and I628, and it will, be further assumed that the tour filters I01, I08, I09 and H are tuned to these frequencies respectively. It will be noted that the frequency selecting mechanisms or filters I01, I08, I09 and H0 are provided with relays I33, I34, I35 and I36, respectively, in their output circuits. These relays operate in response to currents of the corresponding frequencies passed by the filter circuits. Relays I33,

' I34, I35 and I36 in operating cause the operation of the respective locking relays I31, I38, I39 and I40, Therefore, each digit transmitted by the calling subscriber is represented by one' or two frequencies causing the operation of either one or two of the relays connected to the output circuits of the selective filters. These relays in turn cause the operation or the common relay I32 and the operation of the corresponding locking relays I31, I36, I39 and I40. Any one of these locking relays in operating locks in ,a circuit from battery through its winding and left contact, through the common conductor I4I thence through the closed contact of relay I32, to ground at the normal contact of relay I26. The relays I31, I38, I39and I40 in operating place ground potential on the conductors I24 in the same manner as described in connection with the operation of the counting relays 20I. The following table shows the tone responsive relays operated for the several digital numbers:

' closed by the relay I2I.

Digit 137 and 138 l 137 and 139 137 and 140 13s and 139 138 and 140 It will be noticed from inspectlon lthat relays I31, I38, I39 and I40, when operated in the combinations above listed, cause the conductors I24 tobe grounded in the same combinations as was true of the operated counting relays 20I tor the same digits.

When the calling subscriber at the substation of line I02 initiated the call as above explained, the cut-through relay I22 operated in a circuit Accordingly, when the first digit is received on relays I31, I30, I39 and I40, the correspondingly grounded conductors I24 cause the operation of one or two or three of the relays of theregister A. When the alternating currents representing this first digit cease to flow,

in the line, the relays in the output circuits of the filters release'and open the circuit of relay I32. As the continuity contacts of relay I32 close,

a circuit may be traced from ground through the contact of relay I26, through said contacts, of relay I32, conductor 224 and thence as traced through'back contacts of the different registers, through the winding of relay I23, conductor I3I through the holdingv windings of the operated relays of register A, to battery. The operated register relays hold and relay I23 operates and closes the locking circuit above described. Relay I23 releases relay I22 and prepares the next register by operating relay 22I. On the complete release of relay I32, ground is removed from conductor MI, and the particular one or more of the locking relays I31, I38, I39 and I40 that were 139 and 14 0 1 operated are released to remove ground potential from conductors I24. In a similar manner the transmission 01 tone currents for the remaining digits of the wanted designation causes the registration of these digits on the corresponding registers at the central oflice.

Thereafter the sender controls the selective operation of the switches to complete the establishment of the connection from the calling line I02 to..the called line 200. Following the completion of its functions, the sender is restored to normal in the well-known manner, and, when the subscribers have completed their conversation, the automatic switches are also restored to normal.

A description -:will now be given of the alternative tone receiving mechanism illustrated in Figs. 3, 4 and 5. This alternative mechanism, the circuits for which are illustrated in Fig. 3, may be substituted for the frequency selective mechanism I05 shown in Fig. 1. It consists essentially of an electromagnetic device 300 comprising an electromagnet and four tuned reeds SM, 302, 303 and 304, mounted to vibrate in response to currents flowing through the winding of the magnet. These reeds are provided, respectively, with small mirrors 305, 306, 301 and 308, which serve to reflect beams of light froni a common source 309 to corresponding photoelectric cells 3I0, 3I I, 3I2 and 3I3. When no current of a frequency to which the reeds are responsive is flowing in the magnet 300, the mirrors are at rest and the beams of light from the source 309 do not enter the windows 3I4, 3I5, 3I6 and 3I1 of the photoelectric cells. This is illustrated best in Fig. 5 of the drawings. When, however, currents of the proper frequencies fiow,in the magnet 300, one or more of the reeds are set in vibration and the beams of light are directed through the windows of the photoelectric cells to cause their excitation. For

example, when the mirror 301 is set in vibration;

the window 3I6 of cell 3I2, as indicated by ,the

line 323, during half-of the vibratory cycle of the reed, and is reflected indirectly by way of a stationary mirror 324 through the window 3I6, as indicated by the 1ine'325, during the other half of the vibratory cycle of the reed. Thus the photoelectric cell receives a substantial amount of light when the mirror is vibrated. The currents resulting from the excitation of the photoelectric cells are amplified in any suitable way by amplifiers 3I8, 3I9, 320 and 32I and the currents from these amplifiers cause the operation of relays 326, 321,328 and 329. These relays, which correspond to relays I33, I34, I35 and I36 of the mechanism I05, cause the operation, respectively, of the lockmg relays I31, I38, I39 and I40.

With the central oflice register sender equipped with the frequency selective register sender of Figs. 3, 4 and 5, the tone currents transmitted by the calling subscribers sender I03 pass over conductors I I5 and I I6, through the contacts of relay I21, thence to the amplifier 335 and to the frequency responsive electromagnetic device 300. The reeds and mirrors are set in vibration and the corresponding photoelectric cells are energized to cause the operation of the proper combination of the relays 326, 321, 328 and 329. The manner in which the several digits are registered on the registers of the sender is substantially the same as that already described and no further detailed explanation is believed to be necessary.

What is claimed is:

1. In a telephone system, a telephone line, a transmitter for said line for sending series of direct current impulses representing telephone designations, a. second telephone line and a transmitter therefor .forsending over the line alternating currents of different frequencies replines for establishing telephone connections.

2. In a telephone system, a telephone line, a

transmitter for said line for sending series of current impulses representing telephone designations, a second telephone line and a transmitter therefor for sending alternating currents or different frequencies representing telephone designations, a receiving mechanism having a series of counting relays for receiving the series of impulses transmitted over said first mentioned line, frequency selective devices in said receiving mechanism responsive to the alternating currents transmitted over said second line, and registering mechanism controlled either by said counting relays or by said frequency selective devices for registering the designations received over said lines and for establishing telephone connections.

3. In a telephone system, a telephone line having an impulse. dial for sending direct current impulses over the line, a second telephone line having a transmitter for sending alternating cur-' devices ineffective when direct current impulsesv rents -of difierent frequencies over said second mentioned line in accordance with wanted'desiginations, means, for rendering said tuned selective are being transmitted to said sender, and register means responsive either to said counting parts of a telephone designation, registers for recording designationa photoelectric means selectively energized in accordance with the'frequenciesof the currents transmitted over a telephone line,-

different frequencies transmitted over said line,

photoelectric mechanism selectively operated by said frequency selecting devices in accordance with the different parts of a telephone designation, and switch controlling registers responsive said photoelectric mechanism for registering he desired designations. I

6. In avtelephone system, atelephone line, a transmitter for said line for sending direct current impulses on a decimal basis to represent wanted telephone designations, a second telephone line and a transmitter therefor for sending alternating currents of different frequencies to represent the wanted telephone designations, a line finder switch for extending either one of said lines when calling, automatic selector switches, a number of register senders, each common to all of said switches, means associated with said finder for selecting an idle one of said registersenders and for extending either of said lines when calling to the selected sender, countsaid first-mentioned line, frequency selective devices in the sender for receiving the alternating currents when transmitted over said second line, and registers in the sender controlled either by said counting relays or by said frequency selective devices for registering the designations received over said,l ines and for controlling the selective operation of said automatic switches.

, 7. In a telephone system, a telephone line,. a transmitter for said line for sending series of direct current impulses representing telephone designations, a second telephone line having a transmitter for sending alternating currents of different frequencies representing telephone designationa'a central ofllce register sender having a series of counting relays for receiving the direct current impulses when transmitted over said first line, frequency selective devices in said register sender-I; responsive to the alternating currents when transmitted over said second line, a pluralityj'ofdigit registers in said center for registeringthedesignations received by said counting relays; f51a'nd photoelectric means responsive to said frequency selective devices for operating said registers to register thereon the designations trans 'riitted over said second line.

HENRY M. BASCOM.

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