US2040637A - Telephone system - Google Patents

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Publication number
US2040637A
US2040637A US751805A US75180534A US2040637A US 2040637 A US2040637 A US 2040637A US 751805 A US751805 A US 751805A US 75180534 A US75180534 A US 75180534A US 2040637 A US2040637 A US 2040637A
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Prior art keywords
relay
impulse
circuit
exchange
armature
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US751805A
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Wicks John
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Associated Electric Laboratories Inc
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Associated Electric Laboratories Inc
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Priority to US751805A priority Critical patent/US2040637A/en
Priority to GB12981/37A priority patent/GB466953A/en
Priority to GB27662/35A priority patent/GB463874A/en
Priority to FR803168D priority patent/FR803168A/fr
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04Q—SELECTING
    • H04Q3/00—Selecting arrangements
    • H04Q3/0016—Arrangements providing connection between exchanges

Definitions

  • the present invention relates to telephone systems in general, but is concerned more particularly with telephone systems in which automatic switches are employed in setting up connections.
  • the broad general object of the invention may be stated to be the provision of new and improved controlling or dialling arrangements for use in a telephone system wherein automatic switching apparatus is controlled over an inter-exchange trunk line or talking circuit.
  • Inter-exchange trunk lines as referred to herein shoud not be confused with inter-ofiice trunk lines used in multi-oflice telephone systems to interconnect the various ofi'ices into which an exchange may be divided.
  • the inter-exchange trunk lines referred to herein are those which connect the exchange of one city or village with the exchange of another city or village, which exchanges may therefore be many miles apart.
  • a trunk line that interconnects two exchanges separated by a considerable distance represents a sizeable financial outlay, as is well known. It has long been a practice, therefore, to economize as much as possible in the use of the conductors interconnecting two exchanges, one widely used measure of economy involving the use of a socalled phantom circuit by means of which a third talking circuit is obtained by the proper association of two physical circuits. In addition, the return on the investment has been increased substantially in many cases by using the conductors of the physical circuits separately, as single conductor telegraph lines or other lines over which telegraphic or similar signals are to be transmitted. Telephone lines so arranged are "sometimes referred to as composited lines, and the conductors leading therefrom over which the telegraphic impulses pass are referred to as the composite legs.
  • the automatic switching apparatus in the distant exchange is made ready for operation responsive to a seizing impulse transmitted over the talking circuit when the trunk line is seized;
  • the series of setting impulses (the impulses which bring about the desired positioning of the automatic switches) are transmitted as series of impulses of alternating current;
  • the supervisory signals which are necessary to indicate the removal of the receiver of the called line and the subsequent replacement of the receiver on the called line after conversation, are controlled by a single impulse of alternating current transmitted from the called exchange back over the inter-exchange talking circuit to the calling exchange when the receiver is removed and another single impulse of alternating current when the receiver is subsequently replaced; and the release of the automatic switches in the called exchange is brought about responsive to the prolonged impulse of alternating current transmitted over the talking circuit from the calling exchange to the called exchange.
  • voice-current repeaters in a talking circuit between two exchanges, being determined generally according to the length or transmission qualities of the circuit, must be taken into consideration, for example in the selection of a frequency of alternating current to be used in the transmission of the necessary impulses.
  • the frequency and voltage limitations of the voice-current repeaters commonly used are such that a higher freproblem is met by transmitting a carrier current of a frequency (IOOO-cycles for example) well within the voice range and by modulating this carrier current by means of a lower frequency (GO-cycles for example), and by arranging the signal receiving apparatus so that it will respond only to a current at the carrier frequency modulated by the determined modulating frequency.
  • the receiving arrangement is such that it will not respond to the two frequencies when one is merely superimposed on the other, but the carrier frequency must'be actually modulated by the lower frequency current, which condition does not obtain during conversation, as will be understood.
  • the arrangements of the receiving apparatus have been devised for responding to the carrier current when received, in impulses for switch setting purposes, and to respond selectively to the carrier current when modulated for signal purposes.
  • a combination of relays is employed which, by virtue of their operating and releasing characteristics, will respond one way when the carrier current is being received in impulses corresponding to the frequency of impulses used to position the automatic switches, and will respond in another way when carrier current modulated at the signal frequency is received.
  • the other arrangement which has been devised for separating the signal impulses from the switch setting impulses makes use of a receiving circuit tuned to the modulating signalling current.
  • This tuned circuit includes a signal relay which is not affected by voice currents during conversation and which is not affected by the switch-setting impulses, but which responds reliably each time the carrier current modulated at the signal frequency is received.
  • Fig. 1 is an inter-exchange trunking diagram showing how calls may be completed between three interconnected exchanges, A, B, and C.
  • Fig. 2 shows the circuit equipment associated with one end of an inter-exchange trunk line or talking circuit on which no voice-current repeaters are used, being adaptable for -cyc1e operation (used when the trunk line is not composited) and 120-cycle operation (used when the trunk line is composited)
  • Fig. 3 shows the equipment associated with one end of an inter-exchange trunk line supplied with a voice-current repeater.
  • the apparatus for responding selectively to the signal impulses includes a group of relays which respond selectively by virtue of their operating and release characteristics.
  • Fig. 4 shows a modification of the arrangement of Fig. 3, wherein the incoming-signal relay is included in a circuit tuned to the signal frequency.
  • the group of trunk lines or talking circuits interconnecting exchanges A and B is represented by the trunk line or talking circuit 'I'Ll, extending from the impulse repeater IRI in exchange A to impulse repeater 1R2 in exchange B, by way of a repeater station, while the group of trunk lines or talking circuits interconnecting exchanges B and C is represented by the trunk lines or talking circuit TL2, extending from impulse repeater IRS in exchange B to impulse repeater ml in exchange C. It will be understood, of course, that a sufficient number of trunk lines in either interexchange group is provided to meet the traffic requirements. Each of these trunk lines is equipped for two-way telephonic operation; that is, each of the impulse repeaters IRI to LR4 is a two-way repeater.
  • the trunk line TLI passes through the voice-current repeater VCR in the repeater station.
  • This voicecurrent repeater is assumed to be of the usual construction, wherein a vacuum-tube or similar apparatus is employed to restore attenuated voice currents to satisfactory values.
  • Each of the exchanges A, B, and C is assumed to be serving at present a few hundred lines. Therefore, a local connection from one subscribers line to another passes through a hundreds selector and a connector.
  • exchange A one substation, 88!, is shown associated with a line terminating at the exchange in the line switch LSI.
  • the lineswitch LSI has access to a group of hundreds selectors, of which the selector S2 is one.
  • the selector S2 has access to a number of groups of connectors, the connector CI of the second group being indicated, as is the connector C2 in the third group.
  • the interexchange trunk lines such as the trunk line TLI are reached through the tenth level of the selectors such as S2, by way of the impulse repeaters such as IRI.
  • Each of the trunk lines, such as 'ILl has an incoming selector, such as SI, associated therewith through the impulse repeater, such as IRI.
  • the arrangement in exchange B is similar to that described in exchange A, local substations SS2 and SS3 being shown in association with lines terminating respectively in the line switches LS2 and LS3.
  • the line switches have common access to a group of selectors, such as the selector S3, and the selectors have access through their various levels to groups of connectors, such as the connectors C3 and C4, representing the thirdand second-level groups, respectively.
  • the connector C3 has access to the line'of substation SS3,
  • Incoming selector S4 is individual to the trunk line 'I'Ll interconnecting exchanges A and B, while the incoming selector S5 is individual to the trunk line TL2, interconnecting the exchanges B and C.
  • trunk lines extending to exchange A are reached by way of the tenth level of the selectors, while the trunk lines extending from exchange B to exchange C are reached by way of the ninth level of the selectors.
  • selector S6 accessible to the line switch LS4 of the local substation SS4, is representative of the group of local selectors
  • the connectors C5 and CB represent the third and hundreds groups, respectively, the connector 05 having access to the line of substation SS4.
  • the connector C3 Upon seizure, the connector C3 is prepared for operation in the usual manner, and it responds to the two'final digits in the number (the digits 2 and O, for example) to extend the connection to the desired line, the line of substation SS3.
  • the established connection is released in the usual manner when the subscriber at substation SS2 replaces his receiver.
  • exchange B desires to converse with the subscriber at SSI, exchange A.
  • the subscriber at substation SS2 removes his receiver and dials the listed number of the subscriber at substation SSI, preceded by the digit 0, assigned to exchange A when called from .exchange B.
  • the selector S3 is the one seized by the lineswitch LS2 when the receiver is removed at substation SS2
  • this selector responds to the digit 0 by selecting an idle trunk line extending from the tenth level of its bank contacts, the trunk line extending by way of the impulse repeater 1R2 to the inter-exchange trunk line TLI, for example.
  • the impulse repeaters 1R2 and IRI are prepared for operation, and, through the respcnse of the repeater 1R2, the incoming selector SI in exchange A is prepared for operation.
  • the selector SI When the first digit in the listed number of the subscriber at substation SSI is now called, the selector SI responds by selecting an idle trunk line extending to a connector, such as the connector C2, having access to the line of substation SSE. The connector C2 may then respond to the two final digits of the number and extend the connection to the line of substation SSi.
  • the established connection is released when the calling subscriber at substation SS2 replaces his receiver.
  • connection is extended by way of the line switch LSI to a selector such as S2, and may be further extended by way of the tenth 1eve1 of the selector S2 and the impulse repeater IRI to the inter-exchange trunk line 'I'Ll, whence it extends by way of the impulse repeater 1R2 and the voice-current repeater VCR to the incoming selector S4.
  • Inter-exchange calls between exchanges B and C Inter-exchange calls may be completed between subscribers in exchange B and subscribers f" in exchange C in a manner similar to that described.
  • a connection set up from the line of substation SS2 of exchange B to the line of substation SS4 in exchange C includes the line switch LS2, and may include the selector I S3, operated to the ninth level, the impulse repeater 1R3, trunk line TL2, impulse repeater IRA. incoming selector S! and the connector C5.
  • the listed number of the subscriber at substation SS4 is dialled, preceded by the dlgit 9.
  • Tandem calls between exchanges A and C A call from exchange A to exchange C is switched through exchange B, and it may be set up in a manner now to be described:
  • the connection includes the line switch LSI, and may include the local selector S2, operated to the tenth level, the repeaters ml and IE2, interconnected by the trunk line 'ILl the incoming selector S4, operated to its ninth level, impulse repeaters IE3 and IR4, interconnected by the trunk line TL2, and the incoming selector S1, as well as the connector C5.
  • the subscriber at substation SSI dials the listed local number of the line of the subscriber at substation SS4, preceded by the digit 0, indicating the exchange C, and the digit 9, indicating the exchange B.
  • the connection includes the line switch LS4 and may include the local selector S6, the repeaters IR4 and 1R3, interconnected by the trunk line TL2, the incoming selector S5, the repeaters IE2 and IRI, interconnected by the trunk line TM, and the incoming selector Si, as well as the connector C2.
  • the subscriber at substation S4 dials the local listed number of the line of substation SSI, preceded by the digit 0, indicating the exchange B, and the further digit 0, indicating the exchange A.
  • Fig, 2 illustrates the impulse repeater IE3 which is located in exchange B and associated with one end of the trunk line TL2 extending between exchanges B and C. Since the trunk line TL2, according to the previous assumption, is not of suificient length or of sufficient voiceattenuating characteristics to require the use of a voice-current repeater, a relatively simple impulse and signal circuit can be used betweenthe impulse repeaters IE3 and IE3. Since the repeater IR4 may be identical in circuit arrangement with the repeater 1R3, illustrated in Fig. 2, the repeater IR4 is not illustrated in detail. The equipment shown in the upper right-hand corner of Fig.
  • part 2 is to be used in place of the impulse repeating relay 226 when 120-cycle signalling current, in place of 60-cycle signalling current, is used on account of the associated talking circuit including a composited line.
  • the subscriber at substation SS2 in order to complete the connection removes his receiver and dials the local listed number of the subscriber at substation SS4, exchange C, preceded -by the digit 9, assigned to exchange B.
  • the line switch LS2 When the receiver (not shown) is removed at substation SS2, the line switch LS2 is caused to operate in the usual manner in search of an idle line. It will be assumed that the trunk line extending to the selector S3 is the first one found to be idle and is therefore seized. Under this condition, the selector S3 is separated for operation in the usual manner, and it responds to the exchange digit 9 by raising its wipers opposite the ninth level of bank contacts and searching for an idle trunk line extending to exchange C.
  • trunk line comprising conductors 26l, 262, and 263, and extending to exchange C by way of the impulse repeater IE3 and trunk line TL2
  • this trunk line is seized and connection to conductors 26l, 262, and 263 is made in the usual manner.
  • a standard automatic selector is arranged to place a ground potential momentarily upon the test wiper thereof upon seizing an idle trunk line. This ground potential is extended over the release-trunk conductor or test conductor 262 to the impulse repeater 1R3, closing a circuit through the upper armatures of relays 2l8 and 220, by way of conductor 264, and through contacts of supervision-control relay 2l2 to the upper winding of shunt-control relay 2l3.
  • 3 is provided for the purpose of controlling the shunt connections around the associated repeating-coil windings. In order to prevent delay slightly the operation of relay M3, the second winding of the relay is normally closed through the inner-lower contacts of the relay,
  • line relay 203 closes a circuit for the slow-acting release relay 204.
  • Relay 204 operates and places ground potential at its upper armature on the release trunk conductor 262 so as to maintain the connection established through the selector S3 and the line switch LS2, and to maintain the shunt-control relay 2l3'in operated condition.
  • release relay 204 opens a point in the circuit of the incoming answeringsupervisory relay 2
  • Cut-through relay 205 now operates and extends the incoming talking conductors 26i and 263 through to the left-hand repeating coil windings; at its inner upper armature it disconnects the armature of the impulse-receiving relay 226 from the selector-seizing relay 208 and transfers ltto the outgoing answering-supervisory relay 202; it prepares a circuit at its inner lower armature for the outgoing series relay M8; and at its lower armature it closes a circuit by way of the inner upper armature and resting contact of pulse-timer relay 2
  • preparing relay 2 disconnects the talking conductors outgoing to the trunk line TL2 from the associated repeating-coil windings and extends them through the upper and lower windings of the retard coil 2l5 to the armatures of the dial-out relay 2l6; it grounds the free terminals of the filter condensers 256 and 259; and at its lower armature it grounds conductor 261, thereby closing a circuit through contacts, of the pulse timer relay 2
  • 6 thereupon operates and closes the associated 60-cycle leads through the windings of the retard coil 2
  • the dial-out relay 2l6 also extends the now grounded conductor 268 by way of conductor 209 and contacts of the outgoing series relay 2l8 to the winding of the pulse-timer relay 211.
  • Relay 2 being provided with a copper collar on the armature end of its core, as indicated by the solid-black upper portion of the relay, is slow to operate so as to allow time for the impulse to be transmitted over the trunk line TLZ.
  • pulse-timer relay 2I'l operates and closes a locking circuit for itself at its inner armature to ground through the lower armature of the operated cut-through relay 205, at the same time opening the circuit of the preparing relay 2! and opening its own initial circuit.
  • Relay 2 also opens the circuits of dial-out relay 2l6 at its lower armature.
  • 8 immediately operates and remains operated throughout the series of impulses, because of its slow releasing characteristics. Upon operating, relay 2
  • relay 2l8 places a ground potential on conductor 206, so as to bring about an operation of the impulse preparing relay 2 M for the duration of the series of impulses. become operated and locked as described, the operation of preparing relay 2 does not affect the dial-out relay 2
  • each momentary deenergization of line relay 203 results in the closure of a circuit at the lower armature of the line relay and through the inner lower armature of relay 2l8 for the two-way repeating relay 2l2.
  • 2 therefore responds momentarily to each of the impulses in the series.
  • pulse timer relay 223 The operation of pulse timer relay 223 is delayed in two ways; (1) the building up of current through the lower winding of relay 223 is delayed by the inclusion of the retard coil 322 in its circuit, and (2) the upper winding of relay 223 is included in a closed circuit through contacts of the relay, having therefore a retarding efiect upon the building up of the flux the relay operates about four-tenths of an impulse cycle aiter its circuit is closed, which is two-tenths of an impulse cycle (under the assumed condition) before the repeating relay Elli restores responsive to the opening of its circuit by line relay when the latter relay reoperates. Moreover, the time of operation of pulse-timer relay 223 is six-tenths of an impulse cycle before the next reoperate time of the repeating relay 2E9.
  • the pulse timer relay When the pulse timer relay operates, it closes a circuit at its lower armature through the inner lower armature of the unoperated incoming series relay and over conductor 268 for the dial-out relay 2&8.
  • Relay 2th thereupon operates and starts the first repeated dial impulse over the trunk line Th2 "from the GQ-eycle supply through the retard coil 2i?) and contacts of the operated preparing relay 2 it.
  • relay 223 closes a cirsuit for the p 11 e-loelr relay 22 i, whereupon relay 22! operates and prepares a locking circuit for itself at its upper armature, while at its inner lower armature it closes a circuit for the pulsetirner relay 225 through the retard coil 226, at the same time unlocking the repeating relay 2li so as to permit this relay to restore now as soon as the dial impulse being delivered to it is termihated.
  • the pulse-timer relay 225 has delay provisions similar to those set forth in connection with the pulse timer relay 223 and it has a similar adjust ment as regards its operating time. Relay 225 therefore does not operate immediately.
  • the pulse lock relay 22i closes a parallel circuit for dial-out relay 2H5 through contacts of relay 220, so as to maintain relay 2l6 operated over conductor 268 after the pulse timer relay 223 has restored.
  • 9 restores (sixtenths of an impulse cycle after it operated, under the asumed conditions) upon the reoperation of line relay 293, it opens the circuit of pulsetimer relay 222 and closes a. lockingcircuit for pulse-lock relay 22! through the middle upper armature of pulse-timer relay 225 and the inner upper armature of the operated pulse-lock relay 22L
  • the pulse-timer relay 223 immediately restores (two-tenths of an impulse cycle after it operated) and opens the initial circuit of the pulse lock relay 22! as well as the initial circuit of the dial-out relay 2 l6.
  • Relay 22! does not restore, however, for the time being because of the before-mentioned locking circuit, and dial-out relay 2l6 remains operated throughthe lower contacts of relay 22 I.
  • pulsetimer relay 225 operates because four-tenths of an impulse cycle have elapsed since its circuit was closed by the pulse-lock relay 22i responsive to the operation of the pulse-timer relay 223.
  • the locking circuit of the pulse-lock relay MI is therefore opened at two points, and relay 22i restores as a result and opens the circuit of dialout relay M6 at its lower armature, at the same time opening the circuit of pulse-timer relay 225 at its inner lower armature and reestablishing the locking circuit of ,the now reoperated repeating relay H9.
  • the dial-out relay 2l6 having been operated aoaaear under the control of the impulse corrector for a period of time corresponding to six-tenths of.
  • repeating relay 26% does not reoperate, but the restoration of the pulse lock relay 22i and the described termination of the impulse takes place when the pulse timer relay 225 operates, which takes place at the same time that the reoperation of relay 2i?) would have taken place had the series contained another impulse.
  • the impulse corrector in this case operates as previously described, as the repeating relay 2l9 merely remains operated for a very slight interval over its initial circuit after its locking circuit is opened upon the operation of pulse lock relay 22L Correcting impulses from a fast calling device
  • calling devices are intended to be adjusted so that they deliver impulses at a rate of ten a second
  • the operating speeds normally tolerated in practice range from eight impulses a second to twelve impulses a second.
  • the calling device at substation SS2 is slightly out of adjustment so that it sends impulses at a rate of twelve 21. second instead of ten 2. second.
  • the pulse-timer relay 225 is adjusted so as to permit the repeated impulses to be of maximum length when the calling device is operating more slowly than normal, while the termination of the repeated impulse is brought about by the reoperation of the repeating relay pursuant to the next received impulse when the calling device is operating at the maximum allowable speed, it being kept in mind that the starting of the repeated impulse is delayed for a predetermined time (usually four-tenths of a normal im pulse cycle) after the repeating relay has operated responsive to the incoming impulse. It is to be understood, however, that the timing described for the corrector is given by way of example only.
  • dial-out relay 2I6 responds to each repeated impulse and applies GO-cycle current to the conductors of the trunk line TL2 each time it responds, for the purpose of controlling the switchingoperation in the distant exchange C in a manner to be subsequently made clear.
  • the resistor connected in circuit adjacent relay 2I5 is introduced for the purpose of improving the operation of the dial-out relay.
  • condensers 256 and 257 operate in conjunction with the retard coil 2l5 to act as a filter to suppress undesirable harmonic frequencies, commonly present in commercial 60-cycle current.
  • 9 does not reoperate, and the final repeated impulse is terminated upon the previously described operation of the pulse-timer relay 225.
  • the outgoing series relay 2 l8 restores, permitting the shunt-control relay 213 to become reoperated from the grounded release trunk conductor 262 over its previously traced circuit, including conductor 264.
  • 4 restores when its circuit over conductor 266 is opened at the inner upper armature of the outgoing series relay 2
  • ! are in operated position because of operations described heretofore, while the remaining relays of the impulse repeater 1R3 are in normal condition.
  • an impulse of 60-cycle current is received over the trunk line TL2 from the called exchange when the called subscriber responds.
  • This impulse of current is sent back from the impulse repeater 1R4, Fig. 1, in exchange C, in a manner which will be subsequently explained in connection with a call in the reverse direction over the trunk line TL2.
  • the impulse receiving relay 226 When the answering-supervision impulse is received over the trunk line TL2 from the distant exchange, the impulse receiving relay 226 responds. This relay is shunted around the talking condenser associated with the right-hand repeating coil windings, in series with condenser 212.
  • the relay 226 is an alternating-current relay having a partially split core with one sectlon shaded or retarded, as indicated in the drawings. Accordingly, the relay does not vibrate in unison with the alternating current, but it operates and remains operated throughout an entire impulse of several cycles.
  • impulse receiving relay 226 closes a circuit through contacts of the selector-seizing relay 208 and the inner upper armature of the operated cut-through relay 205 for answering-supervisory relay 202.
  • Relay 202 is a "two-step relay, so designed and adjusted that an energization of its upper winding alone results in its operation through its first step only,
  • the two-step answering-supervisory relay 202 Upon operating through its first step only, the two-step answering-supervisory relay 202 closes a locking circuit for itself at its inner lower armature (the locking contact) through the lower armature of relay 20l to the grounded releasetrunk conductor 262. No current flows through the lower winding of relay 202 for the time being, because the initial circuit of the upper winding of the relay is still established at the contacts of the impulse receiving relay 226.
  • impulse receiving relay 226 restores and opens the initial circuit of the upper winding of relay 202, whereupon the relay becomes fully energized through the two windings in series and operates completely.
  • relay 202 prepares a locking circuit for the disconnectsupervisory relay 20l at its upper armature it transfers the supervisory-control circuit from its own upper winding to the winding of the disconnect-supervisory relay 20! and at its inner upper and middle upper armatures it reverses the connections between the windings of line relay 203 and the incoming talking conductors 26! and 263, thereby bringing about a reversal of ourrent-flow in the conductors of the calling line.
  • This reversal of current-flow is used for the purpose of giving answering supervision in case the calling line is a line extending from an operators switchboard, and it is used to operate a meter or call register either in the exchange or on the subscriber's premises in case the calling line is a measured service line.
  • Th circuits of the impulse repeater 1R3 remain in the present condition throughout conversation.
  • a disconnect-supervisory signal is received over the trunk line TL2 from the distant exchange being transmitted therefrom in a manner to be brought out hereinafter.
  • impulse-receiving relay 225 responds and operates the disconnect supervisory relay 201! through its first step, the circuit including the upper armature of the operated answering-supervisory'relay 252.
  • the disconnect-supervisory relay 2M 15' magnetized only to an extent that permits the op eration of its lightly adjusted locking armature (the inner lower armature).
  • the operation of th inner lower armature of relay 20l results in the closure of the locking circuit from grounded release conductor 252 through the lower armature of the operating answering-supervisory relay 202.
  • relay 20E opens the circuit of answering-supervisory relay 222 at its lower armature, whereupon supervisory relay 2G2 releases and restores the current flow in the calling line to its normal direction by reversing the connections between line relay 203 and incoming talking conductors '26l and 263 to normal.
  • This operation is used to give disconnect supervision in case the call is from an operator's switchboard and it may also be of utility in many other situations, as is well known.
  • release relay 204 restores, as its circuit is not again closed by line relay 203.
  • relay 204 removes ground potential at one point from release-trunk conductor 252, but conductor 262 is maintained grounded for the time being at the upper armature of the outgoing series relay 2l8.
  • release relay 204 also opens the circuit of cutthrough relay 205, permitting slow-acting cutthrough relay 205 to restore after a slight interval.
  • cut-through relay 205 opens the circuit of the outgoing series relay 210 at its inner lower armature and opens the locking cirand permits impulse timer relay 223 to restoreand open the circuit of the dial-out relay 215.
  • outgoing series relay 2H3 finally removes ground potential from the release trunk conductor 262 so as to permit the lineswitch LS2 and the selector LS3 to release and clear out and to tree the repeater IRB for further use.
  • connection set up through the repeater ERG, Fig. l, in the distant exchange B takes place responsive to the release impulse in a manner which will become clear upon a further perusal of the specification.
  • this impulse is received at the repeater ITS, Figs. 1 and 2, from the impulse repeater 1R4, Fig. 1.
  • Impulsing receiving relay 226, Fig. 2 responds to the receiving impulse and closes a circuit through contacts of relays 208 and 205 for the lower winding of the two-step selecd tor-seizing relay 208. Responsive to the closure of the circuit through its lower winding, relay 208 is energized only sufliciently to operate its lightly adjusted inner upper armature to close the locking circuit.
  • incoming-release relay 201 is normally connected in parallel with the lower winding of relay 200, by way of armature; 245.
  • Incoming-release relay 201 having a slaw-operating characteristic, is not operated at t. is time, as the seizing impulse is short, relative to the releasing impulse.
  • relay 208 When the seizing impulse is terminated and the impulse receiving relay 226 restores, the looking circuit for relay 208 becomes effective and current flows through the two windings of the relay in series. As a result, relay 208 now operates fully. Upon operating fully, relay 208 grounds the release trunk conductor 262 at its upper armature by way of the upper armature of busy relay 205, thereby guarding the trunk line TL2 and the repeater IRS against seizure in exchange B, and bringing about the operation of shunt-control relay 213. At armature 2H and its middle lower armature, relay 208 connects the talking conductors extending to the left from the left-hand repeating coil windings to the talking conductors 281 and 282 extending to the incoming selector S5, Fig.
  • the line relay (not shown) of selector S5 is operated over the bridge circuit above traced to prepare the selector for its usual operation, but the electro-polarized supervision control relay 212 is not operated at this time, as it is designed and adjusted so as to operate only in case the current is flowing through both windings in the same direction.
  • selector seizing relay 208 places a ground potential on conductor 215 at its inner lower armature thereby preparing a locking circuit for relays 208, 210, and 211 and closing a circuit through resistance element 210 for the polarizing winding of the electro-polarized relay 212.
  • impulse receiving relay 228 closes a circuit through the operated armature 242 of relay 208 for the repeating relay 219.
  • relay 219 closes a circuit for the incoming series relay 220, as
  • the outgoing series relay 218 is not operated at this time.
  • incoming series relay 220 is operated and maintained operated throughout each incoming series of impulses.
  • incoming series relay 220 disconnects the lower armatures of pulse lock relay- 221 and pulse timer relay 223 from conductor 268 leading to the dial-out relay 218, and it prepares a circuit for operating the incoming release relay 201, which circuit is effective to operate the relay only when the established connection is to be released responsive to a prolonged releasing impulse.
  • Relays 219, 221, 223, and 225 cooperate in the manner hereinbefore explained to secure the repeating of corrected impulses.
  • the impulse repeating is performed by pulse timer relay 223 in conjunction with pulse lock relay 221, as in the described example of a call from exchange A to 5 exchange B.
  • the impulses delivered constitute breaks in the loop circuit extending to the seized selector S5, and are delivered at the upper contacts of relays 221 and 223 instead of at the lower contacts of these relays.
  • each impulse is repeated upon the operation of relay 223 and is terminated either by relay 221 or by relay 223, whichever one restores last.
  • incoming series relay 220 When incoming series relay 220 operates, it breaks the established circuit of the shunt control relay 213 at its upper armature, permitting relay 213 to restore and shunt the upper left-hand winding of the associated repeating coil at its upper armature. At its lower armature, shunt control relay 213 by-passes the lower left-hand winding of the associated repeating coil, the upper winding of supervision control relay 212, and resistance element 211.
  • the control bridge across the talking conductors includes the resting contact and upper armature of relay 213, conductor 213, upper contacts of the impulse-corrector relays 223 and 221, lower armature of selector-seizing relay 208, and the resting contact and lower armature of relay 213.
  • the impulsing bridge is shunted by a circuit which includes the lower left-hand repeating coil winding, associated talking condenser, and the resistance element 210, giving a control condition over the line relay (not shown) of the selector S5 which has been found by experiment to be very good.
  • incoming series relay 228 restores and again connects up shunt control relay 213 to permit the latter relay to reoperate and place the circuits associated with the repeating coil windings in talking condition.
  • the selector S5 is operated responsive to the first repeated series of impulses, and it selects an idle connector in the desired group, the connector C4, Fig. 1, for example.
  • the connector C4 is operated in the usual manner responsive to the two series of repeated impulses corresponding to the two final digits in the called number to extend connection to the line of the desired substation SS2.
  • the connector C4, Fig. 1 operates in the well known manner to reverse the current flow in its incoming talking conductors.
  • the holding circuit for the line relay (not shown) of the connector C4 60 includes the upper winding of the electro-polarized supervision-control relay 212, Fig. 2.
  • the two windings of relay 212 are energized in the same direction, and the operation of the relay is thus 65 secured.
  • relay 212 Upon operating, relay 212 places a shunt around the resistor 214 so as to increase the current flow through its lower winding momentarily to maintain the relay operated for the time being irre- 70 spective of the direction of current flow in the upper winding. At the same time, relay 212 breaks the circuit of the shunt control relay 213 at its upper armature, momentarily deenergizing the shunt-control relay to shunt out the control wind- 75 ing (the upper winding) of the supervision control relay 2
  • 2 At the lower armature, relay 2
  • 2 groundpotential on the grounded conductor 215 is extended at the lower armature of relay 2
  • Preparing relay 2 is operated to prepare the circuit for the transmission of an alternating current impulse over the trunk line TL2.
  • 4 closes a circuit over conductor 261, through contacts of relay 2
  • 6 is operated to start the alternating-current impulse, and at its lower armature it closes a branch circuit over conductor 269 and contacts of the outgoing-series relay 2
  • 1 After the interval for which it is adjusted, relay 2
  • 1 closes a circuit at its upper armature which extends ground potential from the serially related lower armatures of the line and release relays 203 and 204, by way of conductor 265 and the inner lower armature and resting contact of the disconnect-supervisory relay 2
  • 0 When relay 2
  • Relay 2 does not reoperate now because its circuit is open at armature 255.
  • 2 is temporarily rendered non-responsive in the manner described, while the answering supervisory impulse is retransmitted back over the trunk line. This is for the purpose of rendering the operation more reliable and to insure the completion of the signal in the event that the switchhook is not permitted to operate in normal manner upon its removal and to insure correct signal transmission in the event that the switchbook is subsequently moved up and down rapidly.
  • the circuits in the repeater 1R3 remain in this condition during conversation, relays 208, 2
  • 2 Upon restoring, relay 2
  • extends ground potential from its own locked winding to the winding of the preparing relay 2
  • Relay 2 is again operated to prepare for transmitting an alternating-current disconnect-supervisory impulse over the trunk line TL2.
  • 5 now operates and transmits the supervisory impulse over the trunk line TL2, at the same time closing a circuit over conductor 269 for pulse-timer relay 2
  • 1 When relay 2
  • 1 being slow-releasing (as well as slow-operating), remains operated for a slight interval.
  • 1 applies ground potential, obtained through the lower armatures of line and release relays 203 and 20l, by way of conductor 265 and the inner lower armatures of the operated relay 2
  • Relay 2 0 is thereupon shunted and caused to restore.
  • disconnects its own winding at its inner lower armature from conductor 215, and at armature 252 it opens the. locking circuit of relay 2
  • 4 now restore also.
  • 1 now finally restores.
  • 2 is again operated to bring about the results hereinbefore described in case the receiver is again removed or the hookswitch again raised at the called substation before the connection is released, as in the case of flashing the switchhook to signal the operator when the call has been extended through an operators switchboard. It will be observed,
  • Relay 225 closes a circuit for relay 201 at its lower armature through the lower armatures of the operated relays 221 and 220, relay 220 being operated at the upper armature of relay 219.
  • Relay 201 because of the relatively great length of the releasing impulse has its circuit closed for a sufficient interval to bring about its operation.
  • Relay 201 it will be noted is slow to operate because of its construction and does not therefore operate during the repeating of switch setting impulses because of its slow operating characteristic.
  • Upon operating relay 201 extends its operating ground potential to the locking circuit of relay 298 and disconnects the locking circuit of relay 208 from the local supply of ground potential.
  • relay 226 restores and permits relays 219, 223, 221, and 225 to restore successively, and the incoming series relay 220 to restore after a short interval.
  • the restoration of relay 225 results in the opening of the circuit of the incoming release relay 201. Since relay 201 is operated when its circuit is opened, the locking circuit of the selector-seizing relay 208 is also opened and also 208 restores immediately. Relay 201, being somewhat slow in restoring as Well as slow in operating, does not restore until a short time later.
  • relay 208 Upon restoring, relay 208 removes ground potential from release-trunk conductor 262 at its upper armature so as to make the repeater 1T3 and the trunk line TL2 test idle again to selectors such as S3, and at armature 241 and 242 it disconnects the conductors 281 and 282 leading to the incoming selector S5, thereby bringing about the release of the connection set up by way of the selector S5. All of the circuit apparatus of the impulse repeater IE3 is in normal condition.
  • the common timer lead 2115 coming from the common impulse device 283 is connected at armature 244 through contacts of relays 210 and 209 to the upper winding of the two-step forcedin the partial energization of relay 209 through its upper winding.
  • relay 209 Only the lightly adjusted locking armature of relay 209 is operated at this time, and it closes a locking circuit for the two windings .in series from the grounded conductor 1., 215tby way of armature 252 and its resting con- When the impulse is terminated, relay 209 operates fully on account of its two windings being at that time energized in series. in
  • relay 209 With relay 209 operated fully, the receipt of the next impulse (say thirty seconds to one minute later) results in the closure of a circuit through the operated upper armature of relay 209 for the incoming release relay 201 unless the answering -13 supervisory relay 210 has been operated in the meantime to restore relay 209. If relay 209 is still operated, relay 201 responds to the impulse and opens the initial locking circuit of relay 208, holding this relay operated in parallel with its own winding for the time being. Then, when the impulse is terminated, relay 208 restores and clears out the repeater as described. In the normal operation of the repeater, the call is put through to the desired line and is ordinarily an- 33 swered, or else the connection is released in the normal way if the called line is busy, before the forced released described has had time to be effective.
  • the answering supervisory relay which is operated as previously described when the called subscriber responds, opens the locking circuit of relay 209 at armature 252. so as to restore relay 209 and thereby prevent the forced release operation from being performed during conversation. It will be understood, however, that' the forced release operation may be again initiated in casethe regular releasing operation does not take place following the restoration of answering supervisory relay 5 210, as described, when the receiver is replaced at the called substation. This will be readily apparent, as relay 210, upon releasing, again prepares the locking circuit of relay 209 and again connects the relay to the common impulse lead 55 216.
  • Figs. 1 and 2 is seized at about the same moment in exchanges C and B.
  • the repeater IE3 is seized in exchange B, the placing of ground potential on the release trunk conductor 262 by the seizing switch brings about the hereinbefore .65 described operation of shunt control relay 213 over conductor 264, accompanied by the described successive operation of the line, release, and cutthrough relays 203, 204, and 205.
  • the operation of the cut-through relay 205 as hereinbeiore described, at its lower armature sets in motion the operation involving relays 214, 215, and 211 to cause a. seizing impulse to be transmitted to the distant exchange.
  • relay 206 Upon operating, relay 206 disconnects the incoming relcase trunk conductor 262 from the upper armature of relay 208, leaving the incoming release trunk conductor 262 grounded only at the upper armature of release relay 204. Busy relay 206 also connects the associated common busy-tone lead through the usual small limiting condenser to the upper talking conductor, thereby transmitting busy-tone current to the calling substation to inform the subscriber thereat of the busycondition.
  • the line and release relays 203 and 204 restore successively, and release relay 204 opens the circuit of the slow releasing busy relay 205.
  • Release relay 204 also disconnects ground potential at its upper'armature from the incoming release trunk conductor 262 so as to permit the local switches involved in the connection to release.
  • a moment later busy relay 206 restores and at its upper armature again places ground potential on release trunk conductor 262 through the actuated upper armature of selector-seizing relay 208, thereby guarding the trunk line against further seizure in exchange B.
  • the releasing operations took place only after the call had been completed and conversation had taken place. It is evident that the releasing impulse will be transmitted from the repeater 1R3 over the trunk line 'I'L2 at any stage of the connection after the repeater m3 has been seized, as the relays 201-205 operate successively upon the seizure of the repeater and thereby make the necessary circuit preparations for the transmission of the releasing impulse.
  • a special condition which must be considered is the one arising when the calling subscriber abandons the call only a moment after a selector such as the selector S3 has been operated to extend a connection to the impulse repeater 1R3.
  • the preparing and dial-out relays 2 l4 and H5 are operated to transmit a relatively short seizing impulse over the trunk line 'I'L2, the length of which is determined by the slow-operating characteristic of pulse-timer relay 2.
  • outgoing series relay 2 is operated by line relay 203 through contacts of relay 205 to close a new circuit for preparing relay 256 and to connect up repeating relay 2l9.
  • Repeating relay 2i9 operates and brings about the operation of pulse-timer relay 223 to close a new circuit over conductor 268 to maintain dial-out relay operated.
  • the circuit for the pulse timer relay 211 is opened at the lower contacts of outgoing series relay 2i8, whereby the operation of pulse timer relay 2
  • Relays 2M and 216 are now maintained energized to prolong the impulse of current being transmitted over the trunk line TL2 until relays 204, 205, and H8 restore.
  • relays 2 l8 and 2 I are permitted to fall back as hereinbefore described, finally terminating the impulse.
  • this prolonged impulse instead of causing the distant repeater 1R4, Fig. 1, to seize the associated incoming selector, causes the said repeater ml to refrain from seizing the associated incoming selector and to become cleared out upon the termination of the impular.
  • impulse receiving relay 226 Upon the receipt of this impulse, impulse receiving relay 226 responds and closes a circuit through contacts of relay 208, and through the inner upper armature and resting contact of cut-through relay 205, for the lower winding of the two-step selector-seizing relay 208.
  • Relay 208 operates as before to close a lightly adjusted locking contact (the inner upper armature and associated contact).
  • a circuit extends in parallel with the lower winding of relay 208 through armature 245 and its resting contact for the incoming-release relay 201.
  • Relay 201 is a slow acting relay, being adjusted so that it does not operate in parallel with the lower winding of relay 208 when a relatively short selector-seizing impulse is being received.
  • the impulse being received is a prolonged releasing impulse and is of suflicient duration to bring about the operation of relay 201.
  • the relay 20! removes the local ground connection from the inner upper armature of relay 208 and substitutes the ground potential now being applied by the armture oi the impulse-receiving relay 226.
  • relay 226 restores, at the end of the prolonged impulse, there is no locking potential present to cause the upper winding of relay 208 to become energized in series with the lower winding of'the relay.
  • Relay 208 therefore, does not operate fully but restores and opens its looking contacts.
  • relay 201 restores and leaves the impulse repeater IR3 in a completely cleared-out condition.
  • the jumpers extending to relay 226 and its armature are removed and jumpers indicated by the dotted lines are connected up to the circuit of relay 22B and to the armature of relay 229.
  • the retard coil 221 and the condenser 254 in series, form a tuned couple designed to peak at about 120-cycles, whereby a maximum potential is impressed on the terminals of polarized relay 228, relay 228 being in shunt of condenser 254.
  • the armature of relay 228 normally stands in neutral position and is forced first in one direction and then in the other by the successive positive and negative surges of the 120-cycle current.
  • Relay 229 is shunted by a relatively high resistor, which arrangement makes the relay sufficiently slow to release that it remains operated throughouta series of vibrations of the armature of polarized relay 228, but relay 220 restores almost instantly when the armature of relay 228 comes to rest.
  • relay 228 responds to each received impulse of 120-cycle current by vibrating its armature, and that relay 220 operates for the duration of the impulse and then restores immediately. As a result, relay 228 operates to control the circuits in the impulse repeater 1R3 in the manner described in. connection with the armature of impulse receiving relay 226.
  • variable re- :istcr 255 shunted across the polarized relay 228, may be adjusted from time to time in order to improve the response of relay 228 under, for example, varylng temperature or other conditions I which may affect the operation.
  • Three vacuum tubes are associated with the repeater IRI, a power amplifier 332, a screen-grid voltage amplifier 331, and a detector tube 338. Plate current and biasing potential for the tubes 336, 331, and 338 are furnished by the rectifier tube'335 and associated apparatus.
  • the transformer 33! it will be noted, has one winding for lighting the filament of the rectifier tube 335, another winding for furnishing the current to the rectifier for use by the vacuum tubes, and a third winding for heating the filaments of the heater-type tubes 336, 331, and 338.
  • the multi-tap resistor indicated generally by the reference character 334 provides nine volts posi tive potential over lead 346 for grid biasing purposes, 100-volt positive plate and screen-grid current over lead 341, one 115-volt current over lead 348 and 200-volt current over lead 349.
  • Each of the tubes 336, 331, and 338 is of the usual heater type; each includes the heater element, a cathode element, a control grid, and a plate.
  • the voltage-amplifier tube 331 has in addition a screen grid interposed between the usual control grid and the plate element of the tube.
  • the transformer 36! common to a group of impulse repeaters, furnishes 1000-cycle current for signalling and dialling purposes.
  • the relays 32l, 322, and'232 are each provided with a resistor in shunt of its winding, the resistance of which is relatively high but low enough 7 the rate of sixty a second, but neither of the re-

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  • Engineering & Computer Science (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Interface Circuits In Exchanges (AREA)
US751805A 1934-11-07 1934-11-07 Telephone system Expired - Lifetime US2040637A (en)

Priority Applications (4)

Application Number Priority Date Filing Date Title
US751805A US2040637A (en) 1934-11-07 1934-11-07 Telephone system
GB12981/37A GB466953A (en) 1934-11-07 1935-10-07 Improvements in or relating to telephone systems
GB27662/35A GB463874A (en) 1934-11-07 1935-10-07 Improvements in or relating to telephone systems
FR803168D FR803168A (fr) 1934-11-07 1935-11-07 Perfectionnements aux systèmes téléphoniques

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
US751805A US2040637A (en) 1934-11-07 1934-11-07 Telephone system

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US2040637A true US2040637A (en) 1936-05-12

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US751805A Expired - Lifetime US2040637A (en) 1934-11-07 1934-11-07 Telephone system

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FR (1) FR803168A (fr)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2707211A (en) * 1951-03-30 1955-04-26 Itt Adapter circuit

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2707211A (en) * 1951-03-30 1955-04-26 Itt Adapter circuit

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