BE412135A - - Google Patents

Description

       

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  Improvements to telephone systems.



  International Convention: Patent application in the United States of America N 751,805 filed on November 1934 by John WICKS of which the applicant is the beneficiary.

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   The present invention relates to telephone systems and more particularly relates to telephone systems in which automatic switches are used for establishing connections.



   When there are junctions connecting two offices located at a great distance from each other, for example in two different cities, a saving of conductors is usually achieved between the two offices by using phantom circuits obtained by the appropriate combination of two real circuits.



  In addition, the wires of real circuits can be used as simple conductors on which to carry out telegraphic transmission or signaling.



  Under these conditions the sending of the pulses on the loop of the conversation wires of the junction can no longer be done as usual and the pulses as well as the other signals are transmitted in alternating current.



     The object of the present invention is to provide improved devices for the transmission and reception of alternating current pulses.



   According to one of the characteristics of the invention in a telephone system comprising a junction connecting two offices and provided with two branches which are normally disconnected, and one or the other of which must be connected to the junction when the latter is put into service, for an outgoing call one of these branches is seized and connects to the junction while for an incoming call the fact that the junction is seized at the remote office causes the connection of the junction to the second branch.



   According to another feature of the invention in a telephone system using repeaters of im-

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 pulses intended to respond to the sending of an incoming pulse train and to transmit a regenerated pulse train, the repeated pulse is emitted a specified time after receipt of the incoming pulse and ends upon receipt of the next pulse or a certain time after sending the repeated pulse, as the case may be.



   According to another feature of the invention, in a telephone system using voice frequency pulses for establishing and supervising a connection, a thermionic amplifier located in an office and associated with the junction leading to the second office is provided. so that the potential which is applied to it varies according to the direction of the sending of the pulses on the junction so that the incoming pulses are amplified and repeated to the local equipment while for outgoing communications are current at frequency voice amplified / transmitted on the junction to the second office.



   The characteristics mentioned above and others will be better understood by the following description of three of its applications for which reference will be made to the appended plans, in which: FIG. 1 represents a junction diagram between offices showing how the calls can be established between three interconnected offices A, B and C, figs. 2 and 3 show the circuit of the equipment installed at the end of a trunk or conversation circuit in which no voice-frequency repeaters are used and designed to operate at 60 pps (when the junction is not ghosted) and to operate at 120 pps (when the junction is ghosted).

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 figs.

   4 and 5 show the equipment installed at the end of a trunk trunk and including a repeater for voice frequency current. In these figures the organs must respond selectively to the action of the impulses, so they include a group of relays which respond selectively by virtue of their attractiveness and release characteristics. figs. 6 and 7 show a modification of FIGS.



  4 and 5 in which an incoming signal relay is included in a circuit tuned to the frequency of the signal.



   Referring more particularly to fig. 1, it will be assumed that offices A and B are located far enough from each other for the use of a voice-frequency current repeater to be necessary, while office B is located a little closer to office C so that the transmission qualities of the junctions between offices B and C are such that voice-frequency current repeaters are not required. Office B is the tandem switching office with respect to offices A and C, that is, all calls from one of these offices to the other go through B.



   The group of junctions interconnecting desktops A and B is represented by junction TL1 from desk A to the via pulse repeater IR2 of desk B, / of a repeater station, while an identical group of junctions in - connecting the offices A and C is represented by the TL2 junction. It will in fact be understood that a sufficient number of junctions has been provided in each group to meet the traffic conditions.

   Each of these junctions is set up to work in both directions and the voice-frequency current repeater VCR through which the TLI junction passes into the repeater station is assumed to be.

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 a repeater of current manufacture, in which a vacuum tube or the like is used to bring the attenuated voice frequency currents to satisfactory values.



   We will assume that each of the offices A, B and C serves a few hundred lines. Therefore for a connection between two local subscribers a hundred selector and a connector will be used, while for a long distance call a junction such as TLI of office A will be entered in a particular level of the hundreds selector, such as S2, through the repeater
IR1. In an identical way - the TL1 junction is associated with the office A to an incoming selector S1. Identical devices are provided for offices B and C.



   The establishment of a local call to office B will now be explained. For this purpose, it will be assumed that the subscriber SS2 wishes to be placed in communication with the station SS3. For this purpose the subscriber SS2 goes off hook, the switch LS2 operates in the well-known manner to select a free selector, the selector S3, for example.



  Selector S3 is therefore ready to operate; it responds to the pulses of the first digit of the requested number (number 3 in this case) to select a free junction leading to the third level of its contact banks, the C3 junction, for example.



   When it is entered, connector C3 is ready to operate in the usual way, it responds to the action of the pulses of the last two digits of the number (digits 2 and 0 for example) to extend the connection to the requested line, the line from the SS3 post.



   The established connection is released in the usual way when subscriber SS2 hangs up.



   Suppose now that the SS2 subscriber of office B

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 wishes to converse with subscriber SS1 from office To. To do this, the SS2 subscriber picks up and sends the number of the SS1 subscriber preceded by the number 0 which is the indicative number of office A when called from office B. Assuming that the selector S is the one that was seized by the switch LS2 when the receiver was picked up at the SS2 station this selector under the action of the pulses of the digit 0 selects a free junction leading to the tenth level of its banks of contacts, the junction is extended by the intermediary from the pulse repeater IR2 to the trunk junction TL1, for example.

   When this junction is entered, the pulse repeaters IR2 and IR1 are ready to operate and under the action of the repeater IR2, the incoming selector Si at office A is ready to operate.



  The connection is then established by sending the desired subscriber number SS1, the subsequent operations follow normal practice.



   Identical operations are carried out when it is desired to establish a communication between offices A and B or between offices B and G or vice versa.



   A call from office A to office C is established through office B as follows: If the caller is subscriber SS1 and called subscriber SS4, the connection includes switch LS1 and may include the local selector S2 in position on the tenth level, the repeaters IR1 and IR2, interconnected by the TL1 junction, the incoming selector S4 in position on its ninth level, the pulse repeaters IR3 and IR4, interconnected by the TL2 junction and the incoming selector S7 as well as connector C5.



   To establish this connection, the subscriber SS1 sends the local number of the line of the subscriber SS4 preceded by the number 0 which is the code for office B and the number 9 which is the code for office C.



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If it is assumed that the SS4 subscriber wishes to converse with the SSI subscriber, the connection established must pass through office B to end at office A. The connection includes switch LS4 and may include local selector S6, repeaters IR4 and IR3 interconnected by the TL2 junction, the incoming selector S5, the S4 selector, the repeaters IR2 and IRI interconnected by the TL1 junction and the incoming selector SI as well as the C2 connector.

   To establish this communication, the SS4 subscriber sends the local number of the desired SSI subscriber preceded by the number 0 which is the area code for the office B and a second figure 0 which is the area code for the office.
The system having been described with regard to the junction diagram of fig.l further considerations will now be given relating to the circuits of figs. 2, 3, 4.5, 6 and 7.



   Figs. 2 and 3 show the IR3 pulse repeater located at office B and placed at one end of the TL2 junction connecting offices B and C. A relatively simple pulse and signaling circuit is used between the pulse repeaters IR3 and IR4. As the repeater IR4 can be identical, from a circuit point of view, to the repeater IR3, shown in fig. 2 and 5, the repeater IR4 is not shown in detail. The equipment shown in the upper right corner of fig. 3, and intended to be connected as indicated by the dotted lines, is used in place of relay 226 when the signaling current at 120 pps is used instead of the current at 60 pps when the talking circuit includes a
 EMI7.1
 fant8mized line.



   The detailed discussion will first include a description of Figs. 2 and 3 in relation to the junction diagram shown in fig. 1. For this purpose we will first assume

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 place that the subscriber SS2, fig. 2 and 1, the line of which ends at office B wishes to converse with subscriber SS4, fig. 1, whose line is connected to office C.



   As previously said the subscriber SS2, to establish the communication picks up his receiver and transmits the local number of the subscriber SS4 of the office C preceded by the number 9, indicative of the office C. The number 9 leads. selector S3 at the ninth level, this selector then searches for a free junction to office G.



   If it is assumed that the junction comprising the wires 261, 262 and 263 is the first which has been found free, it will have been entered and the connection to the wires 261, 262 and 263 is carried out in the usual way. The positive therefore extends through the release wire from junction 262 to the pulse repeater IR3, closing the circuit of relay 213 through the upper armatures of relays 218 and 220, through wire 264 and through the wires. contacts of relay 212. Relay 213 is provided to control the short-circuiting of the windings of the translator coils.

   In order to slightly delay the operation of the relay 213, the second winding of this relay is normally short-circuited by the lower contacts of this relay, thus forming the delay winding.



   By pulling relay 213, at its upper and lower armatures, short circuits the left windings of the translator coil and bypass resistor 270 to remove it from the conversation circuit.



   Relay 203 draws into the calling line circuit when the pulse repeater is seized. Line relay 203 closes the attraction circuit of slow relay 204 on its internal armature. Relay 204 attracts and through its upper armature places a

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 positive on wire 262 to maintain the connection made by selector S3 and switch LS2 and to keep relay 213 engaged. At its lower armature, relay 204 opens the circuit of relay 210 at one point and at its upper inner armature it closes the circuit for attracting relay 205 through armature 243 of relay 208.



   Relay 205 attracts and connects incoming conversation wires 261 and 263 to the left windings of the translator coil; at its upper inner armature it disconnects the armature of relay 205 from the circuit of relay 208 and transfers it to relay 202; it prepares the circuit of relay 218 to its lower internal frame and to its lower frame it closes the circuit of relay 214 through the intermediary of the upper internal frame of relay 217 and its contact at rest and through of wire 266 to switch on the relay devices necessary to transmit a commissioning pulse on the TL2 junction and to trigger the commissioning of the remote IR4 pulse repeater, fig. l.



   By attracting relay 214 disconnects the conversation wires coming out through junction TL2 from the windings of the translating coil which are associated with them and connects them through the upper and lower windings of the delay coil 215 to the armatures of the sending relay 216; it earths the free terminals of filter capacitors 256 and 257; and at its bottom armature it grounds wire 267, thereby closing the attraction circuit of relay 216 through the contacts of relay 217 and wire 368. Relay 216 therefore attracts and connects the circuit to 60 pps through the windings of the delay coil 215 to the talk leads of the TL2 junction.



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Relay 216 extends the ground wire 268 through wire 269 and the contacts of relay 218 to the coil of relay 217. Relay 217 is slow to pull such that a time sufficient is allocated for the transmission of the pulse on the TL2 junction.



   After a while, relay 217 attracts and closes its blocking circuit to its inner armature via the positive taken at the lower armature of the attracted relay 205, it simultaneously opens the circuit of relay 214 and its original circuit detraction. Relay 217 also opens the circuit of relay 216 at its bottom frame. As a result, relays 214 and 216 release and the 60 pps pulse transmitted on the TL2 junction is terminated.



   Subscriber SS2 then sends the first digit of the assigned local number, in office C to subscriber SS4, fig.l. When this number is emitted, each interruption produced in the circuit of the calling line by the usual calling device corresponds to a momentary release of relay 203, which momentarily opens the blocking circuit of relay 204 and closes the attraction circuit. from slow relay to release 218 through the contacts of the attracted relay 205. The relay 218 attracts immediately and remains attracted while sending the pulse train.



  By pulling relay 218 disconnects wire 262 from the coil of relay 213 and connects it to positive at an additional point, thus ensuring the blocking of the connection established through the repeater even if slow relay 204 vibrates or tends to release momentarily while sending pulses. The relay 213 is therefore released during the reception of the pulse train. Since relay 213 is released the upper left winding

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 of the translator coil is directly shunted and a shunt is placed on the lower left winding of the translator coil which includes resistor 271 and the upper coil of relay 212.

   The relay 213 being released, the capacitor associated with the left windings of the translator coil is in fact connected directly to the conversation wires entering in series with the resistor 270; this arrangement has been found to be very effective in helping line relay 203 to follow the movement of the disk through calling lines of various characteristics.



   Relay 218 places a positive on wire 266, to operate relay 214 while sending the pulse train. Since relay 217 is pulled and blocked as described, pulling relay 214 does not affect relay 216 at this time.



   With relay 218 being operated, each momentary release of relay 203 closes the circuit of relay 219 at the lower armature of the line relay and through the lower inner armature of relay 218. Therefore, relay 219 responds momentarily to each of the pulses of the line relay. train.



   The final result of the operations which will be described resides in that at each operation of the repeater relay 219 a corrected pulse is transmitted under the control of the relays and the delay coils 221-225 to the transmission relay 216.



   In the description of the operation of the pulse corrector composed of relays 221, 223 and 225, it will first be assumed that the calling device of the calling line is adjusted to operate at normal speed (usually 10 pulses per second) and that the line of subscriber SS2 has average characteristics of such

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 so that the relay 203 correctly follows the work of the therefore contacts of the calling device and delivers / pulses at the same ratio as that fixed for the calling device (preferably 60% for breaking and for closing the contacts between two periods of successive cuts).



   Under the admitted conditions, operation stops as follows: relay 219 operates, locks to its lower armature through the contacts of relay 221, and closes the circuit of relay 223 through the intermediary of its lower winding, to its upper inner armature and through the delay coil 222. The pull of the relay 223 is delayed in two ways: first by inserting a delay coil 322 into the circuit of its lower winding and then by bypassing it. 'upper winding via a normally closed contaat of the relay itself.

   The adjustment of the relay is preferably carried out so that it draws about four tenths of the time of a pulse cycle after the closing of its circuit, that is to say two tenths of a cycle (under the admitted conditions) before the relay 219 does not release following the opening of its circuit by the relay 203 when the latter re-attracts. In addition, the retraction time of relay 223 is six tenths of a pulse cycle before relay 219 re-draws.



   Pulling relay 223 to its lower frame and through the lower inner frame of the released relay 220 closes the pull circuit of relay 216 through wire 268. Relay 216 therefore attracts and sends the first repeated pulse to the junction. TL2 by means of the current at 60 pps and through the delay coil 215 and the contacts of the drawn relay 214.



   At its upper intermediate armature, relay 223 closes the circuit of the slow pull relay 221, that

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 ci attracts two tenths of a pulse cycle later to prepare its blocking circuit at its upper inner armature, while at its lower inner armature it closes the circuit of relay 225 through delay coil 224, it also unlocks time relay 219 to allow it to release as soon as the pulse sent to it has ended.



   Relay 225 has the same operating delay characteristics as relay 223 and has an identical setting for stop time.



   At its bottom armature relay 221 closes a parallel circuit for pulling relay 216 through contacts of relay 220 to keep relay 216 drawn through wire 268 after relay 223 has released.



   When relay 219 releases (six tenths of the time of a pulse cycle after it has operated, under permitted conditions) as a result of the re-attraction of relay 203, it opens the circuit of relay 223 and closes the blocking circuit of the relay 221 through the upper middle armature of relay 225 and the upper inner armature of the attracted relay 221. Relay 223 immediately releases (two tenths of the time of a pulse cycle after it has drawn) and opens the the original relay 221 attraction circuit as well as the original relay 216 attraction circuit. The relay 221 does not release at this time because it remains attracted through its blocking circuit described above, the relay 216 remains attracted via the lower contacts of relay 221.



   At the start of the second pulse cycle two things happen simultaneously: relay 219 re-attracts following the second release of relay 203 and (2) relay 225 attracts because four tenths of the time of a cycle

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 have elapsed since its circuit was closed by relay 221. The blocking circuit of relay 221 is therefore open at two points, it releases and opens the circuit of relay 216 to its lower armature and at the same time opens the circuit of the relay. relay 225 to its lower inner frame and re-establishes the blocking circuit of relay 219 which has re-drawn.



   The relay 216 which drew under the action of the pulse corrector for a period corresponding to six tenths of the normal time of a pulse cycle now releases to terminate the first pulse at 60 pps transmitted on the TL2 junction.



   The relay 219 is attracted and the operations described above are repeated.



   When the final train impulse has been transmitted the felais 219 does not re-attract, but the relay 221 releases and the end of the impulse as described takes place when the relay 225 attracts, this occurs at the moment that corresponds to the re-attraction of relay 219 in the event that the train comprises yet another pulse.



   Suppose now that the calling station's paging device is operating at normal speed and therefore pulses at normal speed and ratio, but the characteristics of the calling line are such that relay 203 does not release quickly enough at circuit breaking.

   Under these conditions the pulses given to relay 219 are shorter than normal, although the time measured between the start of one pulse and the start of the next pulse is the normal time of a pulse cycle. The operation of the pulse corrector / this case is the same as before, except that the relay 219 does not immediately release due to the faster re-attraction of the relay 203, but it remains activated.

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 d until the blocking circuit is opened as a result of the attraction of relay 221, which occurs just as the initial circuit of relay 219 is normally open.



   It will be assumed for a moment that the subscriber line SS4, although it is equipped with a call device correctly adjusted to work at normal speed, has characteristics which cause an abnormal pull delay of relay 203. after its release due to the interruption of the line circuit. Each pulse given to relay 219 is therefore longer than normal.



  The pulse corrector in this case operates as described previously since relay 219 remains attracted for a very short period of time through its initial circuit after its blocking circuit has been opened by relay 221.



   While it is assumed that the paging devices are set to pulse at the rate of ten per second, it is practically assumed that the operating speeds are between 8 and 12 per second.



  It will now be assumed that the call device of station SS2 is slightly out of adjustment so that it emits twelve pulses per second instead of ten. Under these conditions the re-attraction of relay 219 occurs earlier with respect to the second pulse than when the pulses are received at the rate of 10 per second. Therefore, relay 225 has not re-attracted when relay 219 re-attracts to the start of the second pulse received from the calling line. Either way, relay 221 releases when its blocking circuit is opened as a result of the retraction of relay 219 and the corresponding shorter repeated pulse is terminated when relay 221 releases.



   It will now be assumed that the calling device

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 of the calling line is slightly out of adjustment so that it pulses at the minimum allowable frequency (usually about 8 pulses per second). Under these conditions, relay 219 is not re-attracted by Inaction of the second pulse when relay 225 attracts following the closing of its circuit by relay 221, under the control of relay 223.

   The end of the first repeated pulse therefore takes place (six tenths of the time of a normal pulse cycle a) after it has started) under the control of relay 225, since relay 225 opens the control circuit. blocking of relay 221 and releases relay 221 although relay 219 has not yet been drawn.



   It will be noted that the capacitors 256 and 257 and the delay coil 215 constitute a filter intended to suppress the undesirable harmonic frequencies which generally accompany the current at 60 pps of the distribution networks.



   When the pulse train has been emitted the relay does not re-attract and the repeated final pulse ends as previously described by the attraction of the relay 225.



  At the end of the pulse train, the relay 218 releases allowing the relay 213 to re-attract via the grounded wire 262 and following its circuit described previously, including the wire 264. The relay 214 releases when its circuit including wire 266 is opened at the upper inner frame of relay 218.



   The operations described above are repeated for each of the following pulse trains corresponding to one of the digits of the desired number.



   When the number has been completely transmitted and when the calling subscriber is waiting for a response the relays 203, 204, 205, 213 and 217 are drawn while the

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 other relays of the IR3 pulse repeater are in the normal position. The repeater being in this state receives, via the TL2 junction, a 60 pps pulse from the called office, when the called subscriber answers.



   When the response supervision pulse is received from the remote office via the TL2 junction, relay 226 pulls. 'This relay is connected to the terminals of the conversation capacitor inserted in the straight windings of the translator coil and in series with the capacitor 272. The relay 226 is an alternating current relay having a partially split core, one of whose branches is split. - ches is fitted with a delay ring as shown in the drawing. Therefore the relay does not vibrate in synchronism with the alternating current, but it attracts and remains attracted during a complete pulse comprising several cycles.



   Pulling relay 226 closes the attraction circuit of relay 202 through the contacts of relay 208 and the upper inner armature of the attracted relay 205. Relay 202 is a two-stroke relay and currently operates. at the first time to close its blocking circuit at the contact marked X, the blocking circuit borrows the lower armature of relay 201 and the earthed wire. No current is flowing through the lower winding at this time because the initial circuit of the upper coil of the relay is still closed at the contacts of the pulse repeater relay 226.



   When the response supervision pulse is terminated, relay 226 releases and opens the original circuit of the upper coil of relay 202, thereby this relay
2 attracts completely as it is powered by its series / windings. At its lower armature it prepares the blocking circuit of relay 201; to its upper armature it transfers the supervision circuit from its upper winding

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 to the winding of relay 201; and at its upper inner and upper intermediate reinforcements it reverses the connections of the windings of the relay 203 and of the incoming conversation wires 261 and 263 thus giving a reversal of the direction of the current in the wires of the calling line.



  This current reversal is used to provide response supervision in the event that the calling line passes through a manual table and to operate the meter or a similar device either in the office itself or in the subscriber equipment in the event that the calling line is part of a per-call pricing system.



   The IR3 pulse repeater circuits remain in the state they are presently throughout the conversation.



   Suppose that the subscriber of the remote office hangs up first at the end of the communication, a disconnection supervision signal is received from the remote office via the TL2 junction. When this signal is received (it consists of a 60 pps pulse) relay 226 attracts and relay 201 also attracts at the first time, the attraction circuit comprising the upper winding of the attracted relay 202. The lower inner armature alone of relay 201 closes its contacts at this time and closes the blocking circuit to the grounded wire 262 through the lower armature of the operated relay 202.



   When the relay 226 releases, the blocking circuit becomes effective and the 2 windings of the relay 201 are supplied in series, the relay draws completely. Relay 201 opens the circuit of relay 202 to its lower armature, the latter releases and restores the original direction of current in the calling line. This operation is used to give a supervisory signal if the call was established through an attendant position and

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 can also be used in other cases as is known.



   When subscriber SS2 hangs up, relay 203 releases, and a pulse is transmitted on junction TL2 in the manner described above and under the control of relays 219, 221, 223 and 225. At this moment however, relay 219 does not release. immediately as in the case where a pulse is transmitted because the line relay 203 does not re-attract after the receiver has been hung up. As a result, relay 219 remains attracted and maintains relay 223 attracted to block relay 216 which transmits an extended release pulse on the junction.



  It must be taken into account, in fact, that the relay 218 is attracted at this moment and that it keeps the relay 214 operated. via its lower inner frame.



   At the end of the delay period for which it has been adjusted, relay 204 releases and removes the positive at one point of wire 262, but this wire remains earthed to the upper armature of relay 218, to its inner armature upper relay 204 opens the circuit of relay 205 which releases after a certain time and opens the circuit of relay 218 at its lower inner frame and the blocking circuit of relay 217 at its lower frame. Relays 217 and 218 release and relay 218 opens the circuit from relay 214 to its upper inner frame; and its inner frame disconnects relay 219 which releases and allows relay 223 to release and open the circuit of relay 216.

   Relays 214 and 216 are therefore released to complete the extended release pulse which is transmitted to the remote office through the TL2 junction.



   At its upper armature, relay 218 eliminates

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 finally the positive of wire 262 to allow switch 152 and selector LS3 to release and make receiver IR3 available for further calls.



   The release of the connection established through the IR4 receiver of fig. 1 at remote office B occurs under the action of the release pulse as will be described below.



   In order to describe the operation of IR3 in the case of a call coming from the opposite direction, it will be assumed that the subscriber SS4, fig.l, wishes to be put in communication with the subscriber SS2. Let us suppose that the switch LS4, fig.l, seizes the selector S6 when one goes off hook at the station SS4 and that the selector S6 seizes the junction TL2 by the intermediary of the repeater of pulses IR4 when one emits the number 0. In these conditions the IR4 receiver operates as described previously for IR3 receiver, fig. 2 and 3, to transmit a commissioning pulse, on the TL2 junction.



   The pulse receiving relay 226 of the IR3 repeater attracts under the action of the start-up pulse and closes the attraction circuit of the two-stroke relay 208 through the contacts of the relays 208 and 205 and the lower winding of the relay 208, this attracts at the first time and closes its blocking circuit.



   It should be noted that relay 207 is normally connected in parallel to the lower winding of relay 208 through armature 245 but, although it is slow to pull, it does not pull in case present because the switch-on pulse is short compared to the release pulse.



   At the end of the start up pulse, relay 226 releases and relay 208 draws completely through the grounded wire 262 to its armature

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 upper and upper armature of the occupancy relay 206, in this way it prevents the TL2 junction and the IR3 receiver from being seized at the office B which would attract the relay 213.



   At armature 241 and its lower middle armature, relay 208 connects the conversation wires extending to the left of the left windings of the translator coil to conversation wires 281 and 282 which terminate at the incoming selector S5 while at its armature lower it completes a control circuit between conversation wires 281 and 282 of the upper conversation wire through the left winding of the translating coil, wire 273, the contacts of relays 223 and 221, the lower armature of relay 208 , resistor 271, the upper winding of polarized relay 212 and through the lower left winding of the translator coil to the lower talk wire.



   The line relay (not shown) of the selector 85 attracts in the circuit described above to prepare the selector for its usual operation but the relay 212 does not attract because it is intended to attract only in the case where the current flows in the same. direction in the 2 windings.



   Pulling relay 208 fully places a positive on wire 275 at its lower inner armature thereby preparing the blocking circuit of relays 209, 210 and 211 and closing the circuit of the polarizing coil of relay 212 through resistor 274 It disconnects the link of its own winding to relay 207 to armature 245; to armature 244 it connects the common pulse wire 276 for a reason which will be explained later; to armature 242 it transfers the control wire, coming from the contacts of relay 226 and connected to its winding-

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 own upper ment, to the repeater relay 219, thus preparing the transmission of pulses to the selector S5 by the relay 219 and the pulse corrector which is associated with it.



   When the calling subscriber SS4 operates his disk an alternating current pulse train is transmitted in the manner previously described by the pulse repeater IR3 over the trunk junction TL2 terminating at the pulse repeater IR3. The relay 226 momentarily attracts under Inaction each of the received pulses closes and. each pull the repeater relay circuit 219 / through the operated armature 242 of the relay 208. Each time the relay 219 pulls it closes the circuit of the relay 220 since the relay 218 is not operated at this time. By the combined action of the repeater relay 219 and the relay 225, the relay 220 is operated and kept attracted during the reception of the incoming pulse trains.

   The relay 220 disconnects the lower armatures of the relays 221 and 223 from the wire 268 and prepares the circuit of the release relay 207, this circuit only becomes effective when the established connection is to be released.



   Relays 219, 221, 223 and 225 cooperate with the previously described Strap to ensure correct pulse repetition. In the current example, the elective pulses constitute cuts in the loop circuit leading to the seized selector S5, they are elective at the upper contacts of the relays 221 and 223 instead of at the lower contacts. When the relay 220 attracts, it cuts at its upper armature the circuit of the relay 213 which releases and bypasses the upper left winding of the associated transfer coil, II its upper armature. At its lower armature, relay 213 shunts the internal winding.

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 lower left of the translating coil through the upper winding of relay 212 and resistor 271.

   The control circuit connected to the terminals of the conversation wires now includes the closed contact and the upper armature of relay 213, wire 273, the upper contacts of relays 223 and 221, the lower armature of relay 208 and the idle contact and the lower armature of relay 213. The pulse bridge is bypassed by a circuit which comprises the lower left winding of the translator coil, the associated talk capacitor and resistor 270 and given. a control of the line relay of the selector S5 found, this arrangement has been / very good in experience.



   At the end of the pulse train, relay 220 releases and again connects relay 213 which re-attracts and places the circuits associated with the windings of the translator coil in the talk condition.



   The selector S5 attracts under the action of the first train of repeated pulses and selects a free connector in the desired group, namely the connector C4, which attracts in the usual manner to establish the connection with the line of the called subscriber SS2.



   When the called party answers the direction of the current is reversed in the conversation circuits of the connector in the usual way. The connector line relay blocking circuit includes the top winding of the polarized relay 212 such that when the current direction is reversed, the 2 windings of the relay 212 are energized in the same direction and the relay attracts.



   Relay 212 shunts resistor 274 to increase the value of the current flowing in its lower winding momentarily and to keep the relay attracted regardless of the direction of the current flowing in the winding.

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 superior. At the same time, relay 212 cuts the circuit of relay 213 at its upper armature to momentarily remove power from this relay and bypass the control winding (upper winding) of relay 212 so that it is entirely under control. its lower winding.



   When relay 212 is drawn the positive of wire 275 extends from the lower armature of relay 212, through armature 255 and its idle contact, the lower armature of relay 205, the upper inner armature and the contact. at rest of relay 217, wire 266 to relay 214. The preparation relay 214 attracts and prepares the transmission circuit on junction TL2 with an alternating current pulse, which constitutes a response supervision pulse. As before the relay 214 attracts the relay 216 which sends the pulse in alternating current and to its lower armature closes the circuit of the relay 217 by means of the wire 269 and the contacts of the relay 218.



   After a while the relay 217 attracts and closes its blocking circuit to its lower inner armature, it cuts at the same time the attraction circuit of the relay 214. It also connects the relay 216 to its lower armature so that the relays 214 and 216 release to terminate the response supervision pulse.



   In addition, the relay 217 closes the attraction circuit of the relay 210 via its upper armature and the positive which extends through the lower armatures of the relays 203 and 204 via the wire 265 and the armature lower interior and the contact at rest of relay 211, relay 210 attracts and locks to its lower interior armature to wire 275; he opens

  <Desc / Clms Page number 25>

 shorting resistor 274 to armature 251; it causes relay 213 to be drawn back to its upper armature in order to place the circuit in the conversation position; it prepares the blocking circuit of the relay 211 to the armature 252; at armature 255 it opens the blocking circuit of relay 217 which releases.

   Relay 214 is not re-attracting now because its circuit is open at armature 255.



   The effect of the IR4 repeater response supervision pulse is the same as that described for the IR3 repeater.



   Note that relay 212 is made temporarily inoperative as already described, while the response supervision pulse is returned to the trunk.



  This is for the purpose of making operation safer and to ensure that the signal is sent correctly in the event that the fork does not operate properly when the hook is released and to ensure correct transmission of the signal in the event that the subscriber shakes the pitchfork of his post.



   The circuits of the repeater IR3 remain in this state throughout the conversation, the relays 208, 210, 212 and 213 being drawn.



   Suppose that at the end of the call the calling subscriber SS2 hangs up first. The connector C4 operates in the usual way to restore the direction of the current in the conversation wires according to the normal, therefore the relay 212 releases and closes the circuit of the relay 211 to its lower armature through the wire put to the ground. earth 275 and through the lower armature of relay 210. By attracting relay 211, it closes its blocking circuit to its lower intermediate armature through wire 275 and the operated armature 252 of relay 210, thereby in fact it remains attracted at present regardless of any subsequent action of relay 212.



    @

  <Desc / Clms Page number 26>

 
In its internal frame, relay 211 extends the positive of its blocking winding to the winding of relay 214. Relay 214 again attracts and prepares the sending of an alternating current disconnection pulse on junction TL2 in conjunction with the relay 216, the length of the pulse is controlled as before by the relay 217. when the relay 217 attracts to terminate the pulse and to cut its original circuit of attraction it does not block on itself because its circuit The blocking is cut at the armature 253 of the relay 210 and at the lower armature of the relay 212. The relay 217 being slow to release (just as to the pull) remains attracted for a certain time.

   To its upper armature it applies the positive taken through the lower armatures of relays 203 and 204 by means of wire 265 and the lower internal armatures of the operated relay 211 at the junction point of the coil of relay 210 and of the associated resistance.



  The relay 210 is therefore shunted, it releases to disconnect its own winding from the wire 275 at its lower inner frame; at armature 252 it opens the blocking circuit of relay 211, in addition to opening the original circuit of this relay at its lower armature.



   Relays 211 and 214 are now also releasing. The slow running relay 217 finally releases.



   At this point we can mention that the relay 212 attracts again to perform the functions described above in the case where the receiver is off hook again at the called party's station before the connection is released as occurs in the case where the The subscriber shakes his fork to remind the operator when communication has been established through the intervention of a manual position. We reinar-

  <Desc / Clms Page number 27>

 Therefore, the transmission of the response and disconnection signals can be repeated as many times as the relay 212 is attracted and released.



   When the caller SS4 hangs up the release of the established connection follows the same course as that described for the repeater IR3. When the extended release pulse is received at office B, relay 226 remains attracted for a longer period of time than when it attracts under the action of position pulses. When it pulls at this moment it causes repeater relay 219 to pull in the operation of relays 220, 223, 221 and 225. Relay 225 closes the circuit of relay 207 to its lower armature through the armatures of the at- relays. drawn 221 and 220.

   The relay 207, because of the relatively large length of the release pulse has its circuit closed for a sufficient time to make it attract, it then extends the positive which made it operate up to the blocked air. relay 208 and iV connects the local positive relay 208 blocking circuit.



   When the release pulse is complete relay 226 releases followed by relays 219, 223, 221 and 225 as well as relay 220 after a short interval.



  The release of the relay 225 comes from the fact that the circuit of the relay 207 has been opened, it is the same for the blocking circuit of the relay 208 which releases. The relay 207 being somewhat slow on release just as it is slow on pulling only releases after a certain time.



   Relay 208 removes the positive from wire 262 at its top armature to make repeater IR3 and junction TL2 free again for selectors such as selector S3; at the reinforcements 241 and 242 it disconnects the wires 281 and 282 which lead to the incoming selector S5, thereby causing the release of the established connection

  <Desc / Clms Page number 28>

 via selector S5. All parts of the IR3 pulse repeater have now returned to their normal position.



   Special devices have been provided, which include the two-stroke relay 209, to bring about the release of the repeater IR3 under certain conditions without receiving a release pulse from the remote office via the TL2 junction.



   This arrangement is useful in the event that the remote repeater IR4 is at fault and does not correctly transmit the release pulse or in the event that the relay 266 is inadvertently actuated, for example, under the action of an atmospheric discharge. Anyway when the relay 208 attracts under Inaction of the activation pulse and causes the seizure of the selector S5 and its activation, the common wire 276 coming from the common pulse device 283 is connected to. Armature 244 through contacts of relays 210 and 209 to the top winding of relay 209. Common pulse device 283 may be provided to transmit a pulse on wire 276 once in every 30 second period or once per 30 second period. minute for example.



   The first pulse received on wire 276 as a result of operation of armature 244 has the effect of partially attracting relay 209 through its upper coil, so that only its contact marked "X" operates.



   When the pulse is over, relay 209 draws completely and reception of the next pulse causes the circuit of relay 207 to close through the operated upper armature of relay 209 unless relay 210 has been operated during this time. time to release relay 209. If relay 209 is still attracted

  <Desc / Clms Page number 29>

 relay 207 attracts under the action of the pulse and opens the initial blocking circuit of relay 208, keeping this relay drawn in parallel with its own winding at the time considered. When the pulse is over relay 208 releases and releases the repeater as described.

   In normal operation of the repeater, the call is extended to the requested line and the answer normally given or the call is cut off in the usual way if the called subscriber is busy, before the forced disconnection has had the effect. time to become effective.



   It should be noted that the relay 210 which is attracted, as it was previously deorit, when the called subscriber answers, opens the blocking circuit of the relay 209 to the armature 252 to release the latter and prevent any release. forced during the course of the conversation. It will be noted however that the forced release can still take place in the event that. the regular release does not take place after the release of the answer supervisory relay 210, as already described, when the called subscriber hangs up.



   For the purpose of explaining an additional special feature it will be assumed that the TL2 junction is seized at the same time in both offices 0 and B. When the repeater IR3 is seized at office B, the fact that a positive is placed on the wire release of the junction 262 by the seized selector, causes the operation of the relay 213 via the wire 264, the attraction of the relay is accompanied by the operation of the relays 203, 204 and 205.



  By attracting, the relay 205, at its lower frame, operates the relays 214, 215 and 217 which send a commissioning pulse to the remote office.



   It will be noted that identical operations are carried out

  <Desc / Clms Page number 30>

 kill at the same time in the remote office and the transmission of the two commissioning pulses which takes place at both ends has no result if the seizure of the junction takes place at both ends at the same time, which occurs very rarely. If the seizure at office B for example occurs a little later, the relay 205 can no longer attract after the operation of the relay 204, since the relay 208 has attracted under the action of the pulse received from the far end.

   In this case relay 206 operates through the operated armature 243 of relay 208 to disconnect the release wire from incoming junction 262 of the upper armature of relay 208, leaving wire 262 grounded only to the armature. top of relay 204. Relay 206 also connects the common BT busy tone wire through the usual small capacitor to the top talk wire, thereby sending the busy tone to the calling station.



   When the caller hangs up under these conditions relays 203 and 204 successively release and relay 204 opens the circuit of relay 206. Relay 204 also disconnects the positive taken at its upper armature from wire 262 to allow local switches inserted into the connection. to release. A little later the relay 206 releases and at its upper frame again places a positive on the jumper wire 262 through the operated upper frame of the relay 208, thereby keeping the junction against any further seizure in the office B.



   Special precautions have been taken to release repeaters at both ends of the line when a call is abandoned before the called line has been selected. We will remember that an impulse

  <Desc / Clms Page number 31>

 release is sent by the repeater IR3 on the TL2 trunk when an outgoing communication through the repeater 1R3 of the TL2 trunk is to be released but it is obvious that the release pulse will be transmitted by the IR3 repeater on the TL2 trunk to a any moment of the connection after the repeater IR3 has been seized since the relays 203-205 operate successively when the repeater is seized and they establish the circuits for transmitting the release pulse.



   A special condition which must be taken into consideration is that which occurs when the calling subscriber abandons the call some time after the selector, such as S3, has operated to establish the connection to the pulse repeater IR3. At this moment the relays 214 and 215 attract to transmit on the junction TL2 a relatively short commissioning pulse.



   If the caller hangs up and causes the release of relay 203 while the seizure pulse is transmitted, relay 218 is operated by relay 203 through the contacts of relay 205 to close a new attraction circuit for relay 214 and for connect relay 219. Relay 219 attracts and pulls relay 223 to close a new circuit, through wire 268, to keep relay 216 attracted. The circuit of relay 217 is open at the lower contaets of relay 218 and pulling of relay 217 is not possible at this time.



   The relays 214 and 216 are kept attracted to prolong the pulse transmitted over the TL2 junction until the relays 204, 205 and 218 release.



   When relay 218 releases relays 214 and 216 also release to complete the pulse.



   As we will show later this impulse

  <Desc / Clms Page number 32>

 prolonged prevents the associated incoming selector from being seized and released at the end of the pulse.



   Now consider the case where junction TL2 is seized at office B by repeater IR4 and where. The call is dropped immediately. Under these conditions the pulse received by the repeater IR3 is an extended release pulse instead of the shorter switch-on pulse normally received, the relay 216 attracts and closes the circuit of the lower winding of the relay 208 through contacts of relay 208 and the upper inner armature and the idle contact of relay 205. Relay 208 draws as before to close a slightly adjusted blocking contact. At the same instant a circuit is established in parallel on the lower winding of relay 208 through the armature 245 of relay 207 and its contact at rest.

   Relay 207 attracts and removes the positive from the upper inner armature of relay 208 and substitutes for it the positive applied by the armature of relay 226. As a result, when relay 226 releases at the end of the extended pulse it does not There is no blocking polarity existing to feed the upper coil of relay 208 in series with the lower coil. The relay 208 therefore does not operate completely but releases and opens its blocking contacts. A moment later, the relay 207 releases and abandons the repeater IR3 in the idle state.



   The above description of the IR3 repeater operating mode, fig. 1 and 2, has been given on the assumption that the TL2 junction does not include an actual circuit arranged for telegraphic or other transmission through its conductors. In the case of a combined circuit line, the current at 60 pps is considered to be of too low a frequency owing to the interference which may occur between the transmitted pulses and the remote signals.

  <Desc / Clms Page number 33>

 graphics. In this case the frequency of 120 pps which can be easily obtained from the network at 60 pps using a frequency doubler has been found to be very satisfactory.



  The pulse repeater device is modified when using the current at 120 pps by removing the jumper wire terminating at relay 226 and its armature and by connecting the jumper wires represented by the dotted lines to the circuit of relay 228 and to the armature of the relay 229. It will be noted that the coil 227 and the capacitor 254, in series, form a tuned circuit having a resonance of about 120 pps, a maximum voltage is therefore obtained at the terminals obtained / of the polarized relay 228. The armature of polarized relay 228 is normally in the neutral position and is attracted first in one direction and then in the other by the action of successive positive and negative alternations of current at 120 pps.



   Each time the armature of relay 228 is driven in one direction the circuit of relay 229 is closed. Relay 229 is shunted by a relatively high resistor which makes the relay slow enough to release that it remains attracted during a series of vibrations of the armature of relay 228, but relay 229 almost releases. instantly when the armature of relay 228 returns to idle.



   Relay 228 on each pulse of 120 pps current and relay 229 pull for the duration of the pulse and release immediately thereafter. As a result, relay 229 controls the pulse repeater circuits as described for relay 226.



   Note that the variable resistor 255 which bypasses relay 228 can be adjusted from time to time to improve the operation of relay 208 when

  <Desc / Clms Page number 34>

 temperature varies or to take into account other conditions that could affect its operation.



   It has been observed previously that the junctions passing from office A to office B, fig. l, pass through a repeater station voice-frequency currents, a separate two-way repeater being provided for each junction; and that the practical limits of application of the voice rate repeater require that the selection pulses be transmitted as current pulses at voice rate and at an intensity of the same order as that of the voice currents. It is therefore necessary to take certain precautions to prevent pulses produced by the voice currents from being taken for signaling pulses, which will be explained in the course of the description.



   Two modifications have been made to the device for sending current pulses at voice frequency, one is shown in fig. 4 and 5, the other in fig. 6 and 7. The main difference between the two constructions lies in that in figs 4 and 5 slow release relays have been provided to control the signaling operations separately from the selection pulses while in fig. 6 and 7 a relay tuned for the reception of the signals is provided to respond to modulations of the frequency of the carrier current at 1000 pps.



   We will now describe the repeater IR1 shown in fig. 4 and 5.



   Three vacuum lamps are associated with the repeater IR1, an amplifier 336, a grid-screen voltage amplifier 337 and a detector 338. The plate voltage and the bias voltage of the lamps 336, 337 and 338 are supplied by the rectifier lamp. 335 and the devices associated with it. The transformer 331

  <Desc / Clms Page number 35>

 has a winding for supplying the filament of the rectifier 335, another giving the current to be rectified, and a third winding for heating the filaments of the lamps 336, 337 and 338. The shock coils 332 and 333 and the capacitors mounted in parallel dampen the ripples of the rectified current.

   The multi-tap resistor typically marked 334 provides a positive 9 volt on wire 346 for grid bias, 100 volts positive on wire 347 for plate voltage and screen grid voltage, a voltage -plate of 115 volts on wire 348 and a plate voltage of 200 volts on wire 349.



   The transformer 361, common to a group of pulse repeaters, provides current at 1000 pps for signaling and sending the pulses. Transformer 364, also common to a group of repeaters, provides current at 60 pps which is used to modulate the current to 1000 pps for signaling purposes independent of the transmission of the selection pulses.



   The relays 321, 322 and 323 are provided with a resistor mounted in shunt on their windings, they are adjusted to remain attracted between pulses emitted at the rate of 60 per second, but none of the relays 321, 322 and 323 will remain attracted between successive pulses delivered at the frequency of the disc or at the frequency usually used for positioning the switches.



   Except for what has been said above, the repeater IR1 is identical to the repeater IR3. Suppose a subscriber such as SS1 wishes to place a call to a subscriber in office B or office C. The subscriber's line is extended as described above to wires 351-353 and the repeater of IR1 pulses. At the time of commissioning, relay 326 is normally drawn into the circuit of the

  <Desc / Clms Page number 36>

 plate of the detector 338 and it keeps normally on the time relay 321. In addition, the relay 309 is normally attracted in a local circuit through the associated resistors and it keeps the relay 307 on.



   When repeater IR1 is seized, relay 303 draws through the contacts of relay 302, wires 351 and 353, and the loop of the calling line. Attracting relay 303 causes relay 304 to attract which at its upper armature places a positive on the release wire of junction 352. Relay 304 attracts relay 305 through armature 375 and its idle contact.

   The relay 305 at its upper frame and the frame 372 extends the conversation wires to the translator coil; it prepares the attraction circuit of the relay 302 and at one point opens the circuit of the relay 308 to its lower internal frame; it prepares the attraction circuit of relay 315 to armature 371 and at its bottom armature it places a positive on wire 397, thereby closing the attraction circuit of relay 313 through armature 377 of relay 316 and its contact at rest to transmit a commissioning pulse on junction TL1 to the remote pulse repeater IR2.



   When the relay 313 attracts it disconnects the wires of the TL1 junction from the right windings of the translator coil to its upper armature and to its inner inner armature, at its lower armature it attracts the relay 320 to disconnect the relay 322 from the breaking contact of relay 326 and to open the circuit of relay 323 at one point. Relay 320 also gives an additional positive to wire 352.



   Relay 313 also removes the positive from its lower intermediate armature normally applied to wire 396 through the contacts of relay 315 and

  <Desc / Clms Page number 37>

 extends this positive to relay 314 via the contacts associated with armature 376 of relay 316. Relay 314 attracts to connect the outgoing wires from junction TL1 to wires 393 and 394, leading to the secondary winding of the transformer 363, preparing the transmission of a commissioning pulse on the wires of the TL1 junction.



   The normally attracted relay 325 releases as a result of the opening of its closed circuit previously by wire 396, at the lower intermediate armature of relay 313; it disconnects the amplifier plate 336 from the voltage amplifier gate circuit 337 as well as the DC connection of the plate resistor 343 and transfers it through the primary winding of the transformer and from the armature and the idle contact of relay 324 to the secondary winding of modulating transformer 364. As a result, the amplifier plate 336 is now supplied with alternating current at 60pps via the primary winding of the output transformer 363.

   At the same time the gate circuit of the amplifier 336 is transferred from the tuned secondary winding of the input transformer 362 to the secondary winding of the carrier current carrier at 1000 pps 361. The carrier current at 1000 pps is therefore continuously connected to the amplifier grid for the moment while the plate current comes from a 60 pps alternating current source.



   During the positive half-wave at transformer 364 current flows from the positive through the secondary winding of transformer 364 to amplifier plate 336 through the primary winding of transformer 363 and the contacts of relay 325 released.

  <Desc / Clms Page number 38>

 during each negative half-wave, no current flows in the plate circuit of the amplifier 336 so that successive trains of pulses at 1000 pps are emitted through the secondary winding of the output transformer 336 and on the junction TL1 at the rate of 60 pulse trains per second.



   The current transmitted over the TL1 junction at this time is a commissioning pulse which is used at the remote office to prepare the repeater IR2, fig.l, for inbound service.



   The transmitted start pulse ends under control of relay 316 which is powered in parallel with the winding of relay 314 through the lower intermediate armature of relay 314 and the contacts of relays 315 and 316. Relay 316 responds to closing this circuit after the time for which it has been adjusted has elapsed, it locks to the grounded wire 397 by its inner right winding, at the same time it opens its original circuit of attraction. At its outer armature, relay 316 closes the attraction circuit of relay 324 through resistor 379 and wire 395; at armature 376 it opens the circuit of relay 314 and transfers relay 314 under the control of the drawn relay 303; at armature 377 it opens the circuit of relay 313.



   Relays 313 and 314 therefore release and terminate the commissioning pulse transmitted on junction TL1, relay 325 immediately re-attracts via wire 396 when the positive is reapplied on this wire to the lower intermediate armature of relay 313.



   With relay 314 released relay 324 attracts through wire 395 and through resistor 379 and the outer contacts of relay 316. Pulling relay 324 sets the plate circuit to 100 volts of

  <Desc / Clms Page number 39>

 amplifier 336 through the primary winding of output transformer 363 and wire 347 preparing for transmission of the repeated pulse over the junction to the remote office.



   Relay 325 re-attracts through wire 596 and returns the associated circuits to the state shown in the plans. - when the caller emits the first digit, relay 303 momentarily releases a number of times depending on the value of the digit, on each release relay 303 closes the circuit for attracting slow relay 315 to its internal armature and through the armature 371 of relay 305. Relay 315 attracts under the action of the first pulse and remains attracted while the train is being sent. At its right outer armature, relay 315 disconnects the positive of wire 396 to release relay 325 and it causes relay 313 to re-attract to open the conversation circuit and to attract relay 320 again.



   With relay 324 pulled in and relay 325 released a voltage of 1000 pps is continuously connected to the grid of amplifier 336 and the plate is connected to wire 347 giving the voltage-plate of 100 volts, through the upper armature of the Relay released 325, the primary winding of the output transformer 363 and the armature of the transfer relay attracted 324. A voltage at 1000 pps is therefore generated in the secondary winding of the output transformer, it passes over wires 393 and 394 and leads to the contacts of the armatures of relay 314.



   The preceding preparatory operations take place almost instantaneously when the line relay 303 is released for the first time.



   Each time the line relay 303 releases it closes the circuit of attraction of the relay 314 by ltin-

  <Desc / Clms Page number 40>

 intermediary of the wire and the operated armature 376 of the relay 316. The relay 314 therefore attracts each time the line relay releases and by attracting it connects the wires 393 and 394 to the wires exiting from the TLI junction. As a result, a current pulse at 1000 pps is transmitted on the TL1 junction. To its lower armature, relay 314 applies the positive of wire 395 to bypass relay 524 but although it is bypassed it remains attracted throughout the train of pulses.



   At the end of the pulse train, relay 503 remains attracted and allows releasing of relay 315. By releasing relay 315 opens the circuit of relay 313 to its right armature, relay 313 releases and releases relay 320. Relay 313 also restores the attraction circuit of relay 325 which re-attracts via wire 397.



   The same operations are carried out for the following digits and after the complete transmission of the number, the circuits of the repeater IR1 remain in position until the called subscriber has answered. A response supervision pulse is then transmitted back to the TL1 junction by the remote office to indicate that the called subscriber has answered. This pulse is a current pulse at 1000 pps modulated by a current at 60 pps. Note that the input transformer 562 is connected across wires 391 and 392 such that the incoming supervisory pulse is received on the primary winding of the input transformer 362. Blocking capacitors are connected in circuit. , one on each side of the primary winding of transformer 362, the whole constitutes a resonant circuit tuned to approximately 1000 pps.

   An additional resonant circuit bridged across wires 391 and 392 includes coil 365. This additional circuit which improves

  <Desc / Clms Page number 41>

 the circuit also has a resonance of around 1000 pps.



   The secondary winding of transformer 362 is more precisely tuned to 1000 pps by a variable capacitor. Current at 1000 pps is passed from the secondary winding of transformer 362 and through the contacts of the drawn relay 325 to the gate of amplifier 336. Amplifier plate 336 is connected through the contacts of the relay. attracted 325 to wire 349 providing current at 200 volts through common resistor 345 and individual plate resistor 343. Therefore the 1000 pps signal fed to the gate of amplifier 336 is amplified and transmitted to the voltage amplifier 337.

   The signal is greatly amplified by voltage amplifier 337 so that a high voltage is fed to the lamp plate which takes its plate current to wire 349 through common resistor 345 and plate resistor 344. This Amplified signaling voltage is fed through a low capacitance gate capacitor 342 to the gate of the detector 338. The gate of the detector is connected to earth through the leakage resistor 341, this resistor is particularly high to operate the lamp 338 as a gate leakage type detector and gate capacitor.

   The reception of each pulse of the 1000 pps amplified signal therefore causes a stop in the flow of the current-plate of the detector, the relay 326 releases consequently while on the reception of a succession of pulses the relay 326 releases and re-attracts 60 times per second.



   When the relay 326 releases for the first time it closes the circuit of attraction of the relay 332 through the contacts of the relay 320 and through the internal armature.

  <Desc / Clms Page number 42>

 ery of the attracted relay 321. The relay 322 attracts and connects the relay 323 in parallel with the relay 321 through the lower contacts of the relay 320. As a result of its release delay, the relay 324 can remain attracted during the rather short interruption. produced in its circuit by releasing relay 326 when it is working at 60 pps. Each time relay 526 re-attracts it causes relay 321 to re-attract and the first time it re-attracts it attracts relay 323 in parallel with relay 321.

   The relays 321, 322 and 323 remain energized while sending the 60 pps pulse trains.



   At the end of the response supervision pulse, relay 326 remains on permanently, relay 321 remains on and relays 322 and 523 release.



   When the relay 322 attracts it opens the bridge formed by the translator coil and the capacitor placed on the conversation wires entering from the TL1 junction, to reduce to a minimum the effect of the Shunt of the conversation circuit on the remaining portion of the pulse. . when relay 325 attracts, it bypasses relay 309 and causes its release. When he released relay 309 opens the circuit of the attracted relay 307 and closes the attracting circuit of the two-stroke relay 302 through the lower inner armature of the attracted relay 305, the upper armature of the 302 relay and the upper winding of relay 302. The duration of the pulse is not sufficient to cause the release of relay 307.



   As a result of the closing of this circuit, relay 302 attracts enough to operate its lightly adjusted armature. At this armature, the blocking circuit of the two series windings closes by means of the lower armature of the relay 301 and the earthed wire 352. The relay 311 connected to the contact at rest of

  <Desc / Clms Page number 43>

 the armature of the relay 326 through the contacts of the relay 317 attracts or does not attract under Inaction of the relay 326 working at 60 pps, this depends on its adjustment and does not matter.



   When relay 323 releases at the end of the response supervision pulse and pulls relay 309 which opens the initial pull circuit of relay 302 and re-establishes the blocking circuit of relay 307, relay 302 pulls fully and inverts the connections of conversation wires 351 and 352 to relay 505. Relay 302 also transfers its attraction circuit to its upper armature to relay 301, while at armature 559 it prepares the attraction circuit of relay 301 .



   The direction of the current has therefore been reversed in the calling line, this action can be used for various purposes, and the conversation between the two subscribers can be established.



   During the conversation the relay 325 being attracted the lamps 336, 357 and 338 are connected in tandem to repeat the signals received from the TL1 junction to the relay 326. However, only the current at 1000 pps can pass through the input circuit. amplifier 336. It may however happen that during the conversation a voltage of 1000 pps is applied between the conversation wires of the TL1 junction and causes the relay 326 to be momentarily attracted. The relay 321 will therefore release occasionally during the conversation as a result. release of relay 326 and relay 322 will be able to attract momentarily because it tends to operate through the idle contact of armature 326 before relay 321 has been able to release following the opening of its circuit by the relay 326.

   At this moment the untimely attraction of relay 322 has no unfortunate consequences since the conversation circuit passes

  <Desc / Clms Page number 44>

 by the lower right armature of relay 302 independently of the possible path through the armature; top of relay 322. The relay 323 can only attract if the relay 326 releases and re-attracts under Inaction, successive current pulses at 1000 pps received at a frequency of 60 per second approximately. This condition occurs rarely and may never be during conversation.



   It will be assumed that the called party hangs up first when the conversation is finished, under these conditions the repeater supervision at the remote office sends an end / pulse to the repeater IR1 through the TL1 junction. This pulse is identical to the response supervision pulse and operations similar to those described above are carried out.



   At this instant, the release of relay 309 under the control of relay 323 causes the closing of the attraction circuit of the two-stroke relay 301 through the lower internal armature of the attracted relay 305 and the upper armature of the relay. attracted 302; relay 301 attracts at the first time and closes its blocking circuit under the action of the pulse and it attracts completely by the effect of its two windings in series at the end of the pulse to open the blocking circuit of relay 302, which releases and restores the direction of the current to normal to provide disconnection supervision in the event that the calling line is a metered line or a line passing through a manual office. Relay 301 now releases since it is released at armature 359.



   When the caller SS1 hangs up at the end of the inversion, relay 303 releases and closes the attraction circuit of relay 315 to its internal armature and through the operated armature 371. as previously the relay 315 pulls to cut the circuit from relay 325 to wire 396

  <Desc / Clms Page number 45>

 and to close the circuit of relay 313 which attracts relay 320. At this point grounding of wire 362 by relay 320 is necessary to keep the junction occupied at that end until the pulse release has been fully transmitted, and the pulse repeater relays have had time to return to the rest position.



   With relay 303 released the positive of wire 397 extends through the lower armature of relay 303 and armature 376 from attracted relay 316 to relay 314. Relay 314 attracts and (for the purpose of transmitting an extended pulse release) connects the wires 593 and 394 to the wires of the TL1 junction. At this moment the relay 325 releases and the current at 1000 pps / is connected to the grid of the amplifier 536 whose plate is connected to the primary winding of the output transformer 363.



   Since relay 324 is operated through wire 395 the right terminal of the primary winding of transformer 363 is connected to supply wire 347. A current pulse at 1000 pps is therefore transmitted on junction TL1.



   Shortly after relay 324 releases since it is shunted to the lower armature of relay 314, it substitutes the plate current at 60 pps for direct current through wire 347. As a result, during the end of the pulse at 1000 pps carrier current is transmitted modulated at 60 pps by plate current.



   This sustained release pulse persists until relays 314, 305, and 315 successively release. Relay 315 eventually removes the positive from its left armature of wire 397 thereby opening the circuit of relay 314, marking the end of the pulse.

  <Desc / Clms Page number 46>

 release, and the circuit of relay 316 which releases, it is the same for relay 313, the circuit of which is open at the right armature of relay 315. A little later, relay 320 releases following the release of relay 313 and finally removes positive from wire 352 to make repeater IR1 free to selectors that have access to it.



   To explain the operation of the repeater IR1 in the case of an incoming call, it will be assumed that a subscriber either from office B or from office C wishes to be put in communication with a subscriber from office A. It will also be assumed that the junction is seized. via the pulse repeater IR2 of office B when the indicative number of office A is transmitted.



   When the TL1 junction is seized the repeater IR2 draws in the manner described for the repeater IR1 to transmit a turn-on pulse on the TL1 junction to office A. This incoming pulse is received on wires 391 and 392 connecting the wires from conversation of the TL1 junction to the primary winding of the input transformer 362, it is repeated through the lamps 336, 337 and 338 towards the relay 326. As it has already been explained the attraction of the relay 326 shunts the relay 309 which releases and closes the attraction circuit of the two-stroke relay 308 by its lower winding to the armature of the relay 309 and through the lower armature and the contact at rest of the relay 305 and through the contacts of the relays 507 and 308.

   Relay 308 therefore attracts at the first time and closes its blocking circuit to its upper inner armature through the upper armature of relay 309. Relay 307 is not attracting at this time because the pulses are too short. when the start-up pulse is finished, relay 326 remains engaged and relays 322 and 323 re-

  <Desc / Clms Page number 47>

 let go; relay 309 re-attracts and again closes the attraction circuit of relay 307; it opens the original pull circuit of relay 308 which pulls all the way in and places a positive on the release wire from incoming junction 352 to armature 373; it removes the control of the relay 308 by the relay 309 at its lower inner armature, it closes to the armature 374 a control circuit connected to the conversation wires ending in the left windings of the translatriae coil;

   at its lower armature it puts the wire 399 to the ground and closes the circuit through the resistor 398 of the polarizing winding of the electrically polarized relay 310; to its upper frame and to its lower intermediate frame, it connects the conversation wires going to the left of the left winding of the translator coil to the corresponding conversation wires ending in the selector S1 of FIG. 1.



   A control bridge therefore exists on the conversation wires leading to the selector Sl, it is established as follows: from the negative conversation wire of the selector Sl through the upper armature of the relay 508 attracted to the upper conversation wire of the repeater of IR1 pulses, the upper left winding of the translator coil, the upper armature of relay 311, armature 374 of relay 308; the upper winding of the electrically polarized relay 310, the lower left winding of the translator coil and the lower intermediate armature of the relay 308 to the positive conversation wire of the selector S1.

   The line relay of the selector S1 is operated in the control circuit which has just been described in order to prepare the operation of the selector. when the calling subscriber, at the remote office, operates

  <Desc / Clms Page number 48>

 its calling device to send the first digit of the local number of 1 * subscriber called in office A, the repeater IR2 operates as described for the repeater IR1 to transmit pulses at 1000 pps at the normal frequency of the disk. When the first pulse of the train is received the relay 326 releases, it opens the circuit of the relay 321 and closes the circuit of the relay 522. The relay 322 attracts but its circuit is opened due to the release of the relay 321 and it releases, the relay 325 therefore does not attract when relay 326 re-attracts, it is therefore not affected by the operations described.



   Relay 311 attracts with each release of relay 526, through the left inner armature of relay 317.



  By attracting the relay 311 cuts at its upper armature the control bridge placed on the conversation wires and consequently the circuit of the line relay of the selector S1 while at its lower armature it closes the circuit of extraction of the relay 312 which comprises the The outer armature of the released relay 315. The relay 312 attracts and remains attracted while sending the train of incoming pulses.



   At its upper armature, relay 312 cuts the conversation bridge placed on the right windings of the translator coil to ensure better operation of the pulse receiving devices for the rest of the train, while at its inner armature it places a resistance in shunt on the lower left winding and the control winding of relay 310 and that at its intermediate armature it bypasses the upper left winding of the translating coil and incorporates the associated resistance in the circuit to improve the conditions of the pulse circuit to the selector to be operated.



   Each time relay 326 re-attracts at the end

  <Desc / Clms Page number 49>

 with an impulse from the train it opens the circuit of relay 311 which releases and closes the control circuit. The pulling of the relay 311 under the control of the relay 326 controls the line relay of the incoming selector S1 in the usual manner to put the latter in position.



   - It should be noted in particular that the relay 321 releases each time the relay 326 releases under the conditions present as a result of the relative slowness of the releases and re-withdrawals of the relay 326. The relay 322 therefore does not allow the relay 323 to respond as in the case considered previously when the relay 326 releases and attracts at the rate of 60 per second.



   At the end of the pulse train, relay 312 re-. loose to return the associated circuits to the talk position. The series of operations which have just been described is repeated for the following pulse trains which represent the remaining digits of the desired number. when communication has been established to the called party and the latter has responded in the usual way the direction of the current flowing in the outgoing wires to the local switches through the contacts of relay 308 is reversed, it follows that the relay 310 attracts since the direction of the current flowing in its upper winding is reversed. By attracting relay 310 bypassing resistor 398 to its inner armature through the idle contact and armature 380 of relay 317.

   The shunt of resistor 398 increases the value of the current flowing through the lower winding of the relay 310 in a sufficient manner to allow the relay to remain attracted regardless of the direction of the current flowing in the upper winding.



   At its lower armature, relay 310 closes the attraction circuit of relay 319 by means of the grounded wire 399 through the contact at rest and

  <Desc / Clms Page number 50>

 the left outer frame of the relay 317. The relay 319 attracts and closes the attraction circuit of the preparation relay 513 to its inner frame; it bypasses the contact at rest and the armature 380 to its intermediate armature; and at its outer frame it places a ground through the lower frame of relay 305 on wire 397 to prepare the blocking circuit of relay 316.



   When the relay 313 attracts at this moment it disconnects the conversation wires; it closes the circuit of relay 314 to its inner intermediate frame and to its lower frame it attracts relay 320.



   Relay 325 is released as previously described when its circuit is opened to wire 396 by relay 313. This results in no pulse at 1000 pps. Modulated 60 times per second is transmitted again on the wires of the TLa junction through 1 * ' through wires 593 and 394 and through the contacts of relay 314. This impulse operates the remote repeater IR2 at office B, it goes into the response supervision position as has been explained for the repeater IR1.



   After a while the relay 316 attracts and locks to wire 397, at armature 376 it closes a new attraction circuit for relay 314 through the lower armature of relay 303, the lower armature and the contacts at the rest of relay 305 and the left inner armature of relay 319. At armature 578, relay 316 closes the attraction circuit of relay 317 by means of wire 399 earthed and through the right armature and the idle contact of relay 518. Relay 317 attracts through the associated resistor and at its inner right armature it blocks directly to wire 399.

   At its right outer frame it completes a conver-

  <Desc / Clms Page number 51>

 station interrupted; at its left inner armature, it disconnects relay 311 from the rest contacts of the armature of relay 326 ′ so that the incoming pulses which can release relay 326 have no effect on relay 311; at armature 381 it prepares the attraction circuit of relay 318; at armature 380, it cuts the shunt established on the resistance associated with the polarizing winding of relay 310 at a point and prepares the blocking circuit of relay 318; on its left armature it opens the circuit of relay 319 and prepares a new circuit for this relay by means of the contacts of relay 318.



   Relay 319 releases and opens the circuit of relay 313 to its inner armature, finally it removes the shunt placed on resistor 398 to its intermediate armature; and, at its left armature, it removes the positive of wire 397; thereby opening the relay blocking circuit 316 and the relay blocking circuit 314. Therefore, the relays 313 and 314 release to complete the response supervision pulse and the relay 313 again applies the positive to its armature. lower intermediate to wire 396 to attract relay 325.



   Shortly thereafter, relay 316 releases and opens the original circuit of pulling relay 317 to armature 378 leaving relay 317 locked to its right armature by grounded wire 399. when the communication is terminated, the two subscribers hang up. If it is assumed that 1 ', called hangs up first, the connector in service causes the reestablishment of the direction of the current in the normal direction in the wires which terminate there and coming from the pulse repeater IR1 via the contacts of relay 308. at this moment the electrically polarized relay 310 releases and closes the

  <Desc / Clms Page number 52>

 circuit for attracting the relay 318 to its lower armature and through the operated armature 381.

   The relay 318 attracts and locks at its intermediate armature through the armature operated 380 on the grounded wire 599; it closes the circuit for attracting relay 319 to its left armature by means of the operated left armature of relay 317; at its left inner frame it closes the circuit of relay 313. The relay 319 attracts and at its inner frame closes an additional circuit for the attraction of the relay 313; at its intermediate armature it bypasses resistor 398 and at its left armature it places a positive on wire 397 to prepare the blocking circuit of relay 316.



   When the relay 313 attracts at this moment it causes the relay 320 to attract again to its lower armature, while at its lower intermediate armature it disconnects the positive of the wire 396 to release the transfer relay 325 and it closes at the same. armatures the attraction circuit of relay 314. As a result, the disconnection supervision pulse is transmitted back over the TL1 junction to the calling office as has been described for the transmission of the response supervision signal.



   Relay 316 attracts again when its circuit closes at the lower middle armature of the attracted relay 314. At this point it locks by its inner armature to grounded wire 397, while at armature 378 it extends the ground wire 399 through the right operated armature of relay 318 to the common point of the coil of relay 517 and the associated resistor carrying the supply current. The relay 317 being bypassed releases after a short time interval; it opens its blocking circuit to its right armature; he

  <Desc / Clms Page number 53>

 reconnect relay 311 to its left inner armature; to its extreme left armature it transfers relay S19 of wire 399 to the front contact of the lower armature of relay 310, thereby opening the circuit of relay 319.

   The S19 relay releases and allows the release of the relays 316, 313, 314 and 320 at the same time as the re-attraction of the relay 525.



   With the circuits in this state, response supervision may be given again in the event that the caller goes off hook again and it may be followed by disconnection supervision.



   The repeater at the sending end of the TL1 junction then transmits an extended pulse at 1000 pps modulated at a rate of 60 per second to ensure the release of the connection. When this release pulse is received, relay 326 of repeater IR1 releases and re-attracts at the rate of 60 per second.



   The relay 321 is kept attracted and the relay 322 attracts to connect the relay 323, the latter attracts and closes the shunt causing the release of the relay 309.



  At this moment, relay 309 remains released for a time long enough to cause the release of relay 307.



   When the relay 307 releases it opens at an additional point the circuit by which the relay 309 controls the relay 308 and it opens the blocking circuit of the relay 318. Consequently this one releases and releases the selector S1 at the same time as it removes the positive from wire 399 at its bottom armature. Relay 309 is not currently attracting through the idle contaat of the lower armature of relay 309 because it cannot re-attract while relay 307 is released.



   At the end of the release pulse, relay 326 remains in the attracted position shown in the plan, the

  <Desc / Clms Page number 54>

 relays 322 and 323 therefore release while the relay 321 remains attracted. The relay 309 attracts again following its local circuit following the release of the relay 323 and it causes the attraction of the relay 307 which finally at its upper armature removes the last positive of the release wire of the junction 352, the junction therefore becomes free when tested by a selector such as S2.



   In the case of a double test of the TL1 junction, the action of the IR1 pulse repeater is the same as that described for the IR3 repeater.



   As has already been said, Figs. 6 and 7 show the repeater IR1 'which is a modification of the pulse repeater IR1 of FIGS. 4 and 5. While in repeater IR1 a combination of slow running relays (321 to 323) is used to differentiate an incoming signaling pulse (such as a release pulse or supervisory pulse) from a selection or pulse at 1000 pps, in the modified repeater IR1 'a simple device is employed which makes use of a tuned circuit for the incoming signaling relay 404. The relay 404 can be operated under the control of the lamp 338 in a resonant circuit which includes a fixed tuning capacitor 405 and which at a resonant frequency of 60 pps.

   With this device it is not necessary that the incoming signaling relay be operated by anything other than a signal transmitted from the remote office on the TL1 junction, to operate this relay, the normal pulses of the disk transmitted by the line are transmitted. at a rate of 8 to 12 per second and no special current such as voice rate current or line discharge should have a carrier frequency of 1000 pps modulated at 60 pps.



   It should be noted that the detector plate 338 of FIG. 6 includes either a 403 delay coil

  <Desc / Clms Page number 55>

 or a relay 402 depending on whether the relay 401 is attracted or released. The relay 401 is normally released and the delay coil 403 is normally on, this state being maintained for the duration of an outgoing call; relay 401 is attracted, however, for an incoming call to disconnect delay coil 403 and replace it with relay 402. to explain the operation of the modified repeater IR1 ', it will be assumed that this repeater is used for an outgoing call on the TL1 junction connecting the offices A and B. The identical organs of FIGS. 6 and 7 and fig. 4 and 5 the same reference numbers.



     When seized the repeater IR1 'operates exactly as described for the pulse repeater IR1 to issue a commissioning pulse on the TL1 junction to the remote office and to repeat the selection pulses on the causing junction positioning of switches at the remote office.



   After the establishment of the requested communication and after the response of the called subscriber, the response supervision pulse is transmitted back from the called office to the calling office through the TL1 junction, it is amplified through lamps 336, 337 and detected by detector 338 causing the application of a current at 60 pps superimposed on the plate current of detector 338 and passing through the split-core relay 404, this relay attracts and closes the attraction circuit of the relay 406. Relay 406 is slightly slow to pull so that it is not affected in the very rare cases where relay 404 momentarily pulls under the action of a current with characteristics identical to those of the current. normally employed.

   Attracting relay 406 causes relay 302 to attract first and second beat

  <Desc / Clms Page number 56>

 time when this same relay 406 releases, thus giving answer supervision to the calling line. when the disconnection supervision signal is transmitted back on the TL1 junction when the called party hangs up the relay 404 attracts again to attract the relay 406, the relay 301 momentarily attracts as described above to bring about the release relay 302 and to give disconnection supervision to the calling line.



   The release of the outgoing communication is carried out as described for FIGS. 4 and 5. For an incoming call, the activation pulse is transmitted on the TL1 junction of the remote office to the pulse repeater IR1 '. On reception of this pulse, the current at 60 pps is transmitted by the action of the lamp 338 to the relay 404 which attracts. Relay 404 attracting relays 406 attracts, thereby two-stroke relay 308 pulls at the first step to close its blocking circuit and is then operated at the second step to grab the associated selector. when wire 399 is grounded to the lower armature of relay 308 when this relay fully draws the transfer relay circuit 401 closes through the right armature and the closed contact of relay 317.

   Relay 401 attracts and closes the circuit of relay 311 to its upper armature; at the same time substituting relay 402 for the delay coil.



  Relay 402 immediately draws into the detector plate circuit and opens the circuit of relay 311 before it has had time to draw.



   It should be noted that the delay coil 403 should preferably have the same electrical characteristics as the relay 402, so that the frequency at which the incoming signaling relay circuit 404

  <Desc / Clms Page number 57>

 has been tuned is not altered by the substitution of relay 402 for delay coil 403.



   When the 1000 pps pulses corresponding to the first digit of the requested number are transmitted from the remote office on the TL1 junction to the repeater IR1 'the plate current of the detector 338 momentarily ceases a corresponding number of times. Each time the plate current ceases, the relay 402 releases and closes the attraction circuit of the relay 311. The relay 311 therefore attracts a number of times corresponding to the number emitted in order to exercise the desired control on the selector in service.



   This operation is repeated for each of the following digits of the requested number.



   It should be mentioned in passing that the repeater IR1 'transmits answer and disconnect signals back over the TL1 junction to the originating office in the manner explained for the repeater IR1.



   During the conversation, the relay 401 is released by the relay 317 to replace the relay 402 by the delay coil 403 thereby preventing any attraction of the relay 311 under the action of the currents at voice frequency.



  Relay 311 is more or less put out of service by relay 401. Relay 401 re-attracts when relay 317 is released under the action of the disconnection pulse.



   When the caller is hung up, the release pulse is transmitted from the calling office via the TL1 junction to the repeater IR1 '. As this signal consists of a pulse extended to 1000 pps and interrupted at a rate of 60 per second the relay 404 attracts again for a sufficient time to allow the release of the relay 307 which in turn causes the release of the relay 308 which causes the release of automatic switches from the local office.

  <Desc / Clms Page number 58>

 



   Relay 401 releases when positive is removed from wire 399 at the lower armature of relay 308.
 EMI58.1



    

Claims (1)

CLAIMS. A telephone system comprising a junction connecting two offices and provided in an office with two normally disconnected branches, one or the other being intended to be connected to the junction when it is put into service, in which for an outgoing call one of these branches is seized to be connected to the junction while for an incoming call the seizure of the junction at the remote office is used to cause the connection of the junction to the second branch. A telephony system using pulse repeaters designed to operate under the action of an incoming pulse train and to transmit a regenerated pulse train, in which the transmission of a repeated pulse takes place for a specified time after receipt of the incoming pulse and ends upon receipt of the next pulse or a specified time after the start of the repeated pulse, regardless of the order in which these events occur. A telephone system using voice frequency pulses for establishing and supervising a communication in which a thermionic amplifier located in an office and associated with the junction leading to a second office is arranged for the operating voltage to operate - the amount applied to it varies according to the direction of the transmission of the pulse on the junction so that the incoming pulses are amplified and repeated to the localized equipment <Desc / Clms Page number 60> in the office while for outgoing communication amplified voice-frequency currents are transmitted over the junction to the second office. A telephone system using voice-frequency signals for establishing communications between two offices, in which the signals consist of currents at a single frequency modulated at other frequencies which are determined by the function to be performed by the signal, at Receiving office signals are detected and sent over a circuit that includes several receiving devices, one or more of which are tuned for particular modulation frequencies while the others are normally disconnected from the circuit and are connected when the signals to which they correspond enter the office. A telephone system as claimed in claim 1 in which the second office is also provided with two disconnected branches and in which the junction is connected to one branch when a call is made in that office and to the second branch when the call is made. in, the second office. A telephony system as claimed in claim 1 or 5 wherein the first branch is associated with automatic switches for setting up outgoing calls from the office and the second branch with automatic switches for setting up incoming calls in the office. . A telephony system as claimed in claim 1 or 5 wherein upon an incoming call to an office a signal is transmitted from the remote office to cause the connection of the second branch <Desc / Clms Page number 61> at the junction and also to close a control bridge on the conversation wires of the junction, the control bridge being interrupted by the incoming selection pulses to allow the automatic switches of the office to be placed on the requested line. A telephone system as claimed in claims 6 or 7 in which the signaling and selection pulses transmitted over the junction consist of alternating current pulses. A telephony system as claimed in claim 8 wherein the selection pulses and signals, which include turn on and off pulses and supervisory signals, consist of alternating current pulses of the same frequency. A telephony system as claimed in claim 8 wherein the selection pulses and signals, which include turn on and off pulses and supervisory signals, are a carrier current modulated at different frequencies. A telephony system as claimed in claim 2 in which the regenerated pulse is independent of the length of the incoming pulse up to a certain limit value while when the length of the incoming pulse exceeds the limit value the transmitted pulse is increased by a corresponding amount. A telephony system as claimed in claim 2 wherein the pulses enter the repeater at a determined frequency, the repeater is set to transmit regenerated pulses of a <Desc / Clms Page number 62> length determined while when the pulses enter at a lower frequency means have been provided to control the length of the repeated pulses. A telephone system as claimed in claim 2, 11 or 12 in which a timing circuit closes on receipt of a pulse and after a certain time causes the transmission of the repeated pulse which is controlled by a another circuit on time or by the operation of a pulse repeater relay on receipt of the next pulse. A telephony system as claimed in claim 13 in which operation of a relay in the first time circuit transfers control of the end of the repeated pulse to the second time circuit. A telephony system as claimed in claim 3 in which the pulses received and transmitted consist of a certain modulated carrier current at a / frequency for the selection pulses and at a different frequency for the pulses comprising the signals. of.supervision. A telephony system as claimed in claim 15 in which the selection pulses are modulated at a lower frequency than the pulses constituting the supervisory signals. A telephone system as claimed in claim 5 in which the variation of the voltage applied to the electrodes of the thermionic amplifier is dependent on the state of a relay which is controlled by the direction of the transmission of a pulse. on the junction. A telephone system as claimed in claim- <Desc / Clms Page number 63> cations 15, 16 or 17 in which pulses are amplified and applied to a detector lamp provided to normally pass the current necessary to maintain a relay in the circuit of the plate thereof while for the incoming pulses the current which circulates in the lamp decreases and increases the releases and retractions of the relay in synchronism with the variations of the current. A telephone system as claimed in claim. 18 in which the plate circuit relay is tuned to the highest modulation frequency. A telephony system as claimed in claim 19 in which a parallel branch of the circuit board is turned on when pulses at the lowest modulating frequency are received, which branch comprises a relay adapted to operate at the frequency of lowest modulation. A telephony system as claimed in claim 18 in which the relay also operates under Pulse Inaction at the lowest modulation frequency. A telephony system as claimed in claim 21 in which this relay is provided to control two circuits, one of them is always closed regardless of the frequency at which the relay attracts while the other becomes effective only when the relay operates at the highest frequency. A telephony system as claimed in claim 22 wherein the first circuit is provided. <Desc / Clms Page number 64> of the workforce by a device controlled by the direction of the transmission of the impulses on the junction and by the frequency at which it is formed by the relay. A telephony system as claimed in claim 22 in which the second circuit is effected by a time-regulated device such that it operates only when the relay is operating at the highest frequency. A telephone system as claimed in claims 15, 16 or 17 in which when the transmission of the pulses is to the junction the type of pulse transmitted depends on the state of one which EMI64.1 relaiaT 'when it is released causes the sending of carrier current modulated by a current at low frequency and which when it is attracted causes the sending of carrier current alone. A telephony system as claimed in claim 25 in which the modulated current is transmitted as a single pulse under the control of a device in time for the purpose of giving supervisory signals. A telephony system as claimed in claim 25 in which the carrier current is modulated under the control of a relay which operates under the action of pulses transmitted by the sending device of the calling subscriber. A telephone system in principle as described and EMI64.2 illustrated in the attached plans. 14rvev-B- / 4tek 1tu! I8I1 .. le (1, .t.-nJ M, (4J g, a4 <oeaam- iip + - Lx - J-rma- t.