US2383541A - Telephone or like system - Google Patents

Telephone or like system Download PDF

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US2383541A
US2383541A US516322A US51632243A US2383541A US 2383541 A US2383541 A US 2383541A US 516322 A US516322 A US 516322A US 51632243 A US51632243 A US 51632243A US 2383541 A US2383541 A US 2383541A
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relay
switch
frequency
relays
exchange
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Gillings Charles
Beale Charles Edmund
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Automatic Electric Laboratories Inc
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Automatic Electric Laboratories Inc
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04Q—SELECTING
    • H04Q3/00—Selecting arrangements
    • H04Q3/0016—Arrangements providing connection between exchanges

Definitions

  • the present invention relates to telephone or like signalling systems and is more particularly concerned with the setting and control of automatic telephone switching apparatus over long trunk routes involving mixed systems of voice frequency and direct current dialling and supervision.
  • the invention may be considered as a development of the arrangements disclosed in applications Serial Nos. 502,884 and 502,885 filed Sept. 18, 1943, and its general object is to improve the operation of systems of this type by cutting out unnecessary repetitions of impulses in the direct current portions of the connection so that operation may be effected at higher speeds and with less liability of error due to distortion.
  • connection which is to be set up includes a direct current link following a voice frequency link
  • avoidance of two repetitions in the same exchange may be effected by giving access to the outgoing auto-to-auto repeater on the line side so that this repeater is in effect by-passed for connections of this type.
  • Such an arrangement is not altogether desirable since it involves conditions representing a departure from standard practice and moreover it cannot be applied satisfactorily if a direct current signalling portion is involved at a further exchange in which case impulse repetition is unavoidable.
  • an incoming repeater for converting incoming voice frequency signals into direct current signals is arranged to transmit a voice frequency testing signal forward at the end of each train of direct current impulses and to respond to a characteristic signal sent back from an outgoing repeater if the succeeding inter-exchange trunk is operated on a voice frequency basis and thereupon to disable the converting equipment and condition the repeater for straight-through transmission of the voice frequency currents.
  • a repeater at the outgoing end thereof is arranged to test for a signal transmitted from a preceding stage of the connection and in response to such signal to transmit a characteristic signal quency currents.
  • a telephone system employing voice frequency currents for supervisory signalling and for controlling the selective setting of automatic switches
  • said system including in tandem at least three exchanges and two inter-exchange trunk lines over which signalling is efiected by voice frequency currents, signalling is initially efi'ected from exchange to exchange in cascade by way of repeaters for converting voice frequency signals into direct current signals and vice versa and in response to the reply of the wanted party the converting equipment is disabled to permit the straight-through transmission of voice frequency currents constituting subsequent supervisory signals.
  • Fig. 1 is a trunking diagram showing a typical connection to which the invention may be applied.
  • Figs. 2-5 when arranged in the manner shown in Fig; 6 show a circuit diagram of an outgoing voice frequency (V. F.) relay set which may be seized either from an operator's position or from a selector level, while Figs. 7 and 8 when arranged with Fig. 7 on the left show a circuit diagram of an'incoming relay set which terminates an inter-exchange V. F. trunk line and which has associated therewith an incoming selector.
  • the outgoing relay set is assumed to operate on the known sleeve-controlled basis.
  • Figs. 9 and 10 show circuit modifications which when applied respectively to the outgoing and incoming V. F. relay sets enable end-to-end signalling to be introduced for certain supervisory signals on connections involving direct current (D. C.) impulse regenerators.
  • D. C. direct current
  • a connection is to be set up from the manual board MB in exchange A to a subscriber in exchange D.
  • a. V. F. seizing signal is sent over the V. F. trunk VFII to exchange 3 to prepare the incoming V. F. relay setlRSl for operation.
  • the impulses are converted at relay set ORSI into suitable V. F. coded signals which are received by the incoming relay set IRS! and are there converted back into D. C. loop impulses which operate the incoming selector ISI. This then seizes a D. C. trunk line DCT to exchange C by way of the auto-to-auto repeater A-A REP since it is as- 7 sumed that direct current signalling is employed between exchanges B and C.
  • the second digit dialled by the operator is transmitted in coded V. F. form from exchange A to exchange B where it is converted into D. C. impulses which are repeated by the auto-to-auto repeater over the trunk line DCT to incoming selector IS! in exchange C.
  • the trunk line VFI'I from exchange C to ex change D is arranged for V. F. operation and it is therefore no longer essential for the exchange B incoming relay set IRSI to convert the third and any subsequent digital V. F. codes into trains of D. C. impulses as these V. F. codes could satisfactorily be transmitted straight through from the originating relay set ORSI to the exchange D terminating relay set IRS2.
  • the determination of when the second V. F. portion is reached is eil'ected by arranging for the incoming relay set IRSI to transmit a comparatively long V. F. signal, of the order of 800 milli-seconds (m. s.) after each train of direct current impulses. This V. F. signal pulse is without effect until the subsequent outgoing V. F.
  • relay set ORS2 is reached and this relay set on receiving the pulse returns a battery reversal signal back over the line which signal on being received at the relay set IRSI initiates through switching conditions thereat.
  • the V. F. signal pulse also initiates through switching conditions at the outgoing relay set ORSZ so that the third and any subsequent digits which are converted into coded V. F. form for transmission from exchange A to exchange B are transmitted without conversion into D. C. form through exchanges'B and C to the terminating exchange D where they operate the incoming relay set IRBI. This converts them into D. C. pulses for operating the appropriate switch or switch train therein to gain access to the required subscriber.
  • the coded prepare pulse is assumed to have a duration of 160 m. s. and the following coded digit pulse a duration of 100 m. s.
  • V. F. supervisory code to be employed is Considering now the circuit operations, the
  • Relay FXY brings brings up relay CS and causes switch TS to self-drive to position 3, whereupon relay SR releases and relays FXY and CS releases in turn. During this time contacts CSI and CS2 and FXYl, Fig. 3, will have caused a 100 m. s. pulse of X frequency to be transmitted forward over the trunk line to the incoming relay set IRS! at exchange B to bring about seizure of the associated incoming selector ISI.
  • Relay FXY on releasing brings up relay FC which locks up and causes switch TS to advance to position 4 from where it advances to position 6 under control of the interrupted earth source connected to lead it which connects with the switch magnet over bank and wiper TS5.
  • relay CNA At the end of the first series of impulses relay A holds and relay C releases after its slow period thus operating relays CNA and CNR in series over cwiper DSAI If the digit dialled is 5 orless, relay CNA operates over its left-hand winding and as will appear subsequently an interdigital pause is provided between successive re-transmitted digits which is shorter than that provided for digits 6-0.
  • Relay CNA in operating at contacts CNAI and CNA2 extends earth over wiper and bank DSAI and bank and wiper S03 to advance the sending control switch SC from its home osition to position 1 where relay ST is operated.
  • Relay ST connects up its low resistance right-hand winding to self-drive switch SC to position 4, maintains relay CS and at contacts ST!
  • Fig. 3 causes a prepare pulse of WY frequency to be connected to the trunk line extending to exchange B.
  • switch SC reaches position 4
  • relay ST releases after its slow period to disconnect'the WY prepare pulse and to operate relay S.
  • the duration of the prepare pulse is measured by the time taken for switch SC to step to position 4 plus the slow release period of relay ST which gives a total figure of 160 m. s.
  • Relay 8 holds relay CS and connects the digit code pulse to line, this pulse being dependent for its composition on the setting of the digit switch Wiper DSA3 or DSAl, Fig. 3, and is thus characteristic of the digit dialled.
  • Relay S short-circuits its left-hand high resistance winding to self drive switch-SC to position 8 where relay Z operates over its lower high resistance winding (magnet SCM being non-operative in this condition) and at contacts Z3, Fig. 3, disconnects the digit code pulse from the trunk line.
  • Relay S also releases but relay Z holds relay CS. 1
  • the duration of the code pulse is measured by the time taken for switch SC to step from position 4 to position 8 which time, together with the operating time of relay Z approximates to 100 m. s.
  • Relay Z at contacts Z2 holds relays CNA and CNR and at contacts Zl extends earth forward via its upper low resistance winding to home switch DSA whereupon relay Z releases and releases relay CS and. causes switch SC also to drive to its home position.
  • relay CNR will be maintained operated in series with relay CNB (not shown), relay CNA having released on the release of relay Z. Accordingly,-when switch SC arrives at its home position it will again selfdrive to position 1 where relay ST will re-operate to send out the prepare pulse of WY frequency iollowed by the code pulse WX for digit 4 which is picked up from the setting of switch DSB.
  • the interdigital pause between the two code digits transmitted to line will be measured by the heming time of switch DSA plus the homing time of the 50-point switch SC giving a total of not less than 1200 m. 5.
  • live or less machine-generated impulses are delivered by the distant incoming relay set to the incoming selector, then hunting takes place to select an idle trunk in the level selected, after which an 800 In, a. pulse of Y frequency is transmitted forward from the relay set as will be later described.
  • the selector is hunting, the incoming relay set decoding relays are released and reset to receive the second prepare and code signals which will require a time period of 160 plus m. s. giving a total of 260 m. s. which addd to the pause period of the order of 1200 m. s. already mentioned, gives a total the complete interdigital pause.
  • relay CNA will be operated over its right-hand winding in series with relay CNR and at contacts CNA3 brings about the operation 01' relay HS which locks over contacts HSI.
  • Relay HS at contacts HS'I, Fig. 3 changes over the connections of the prepare pulse circuit so that when relay ST operates on the first step of switch S0, a WZ pulse is connected to line. This is followed by the coded digit pulse and when relay Z operates to terminate the pulse,
  • switch DSA drives to its home position thus measuring oilv part of the interdigital pause
  • Relay HS is then disconnected at wiper and bank DSAI but holds for a short period due t its slug and at contacts HS3 causes switch DSA to make another half revolution.
  • relay HS is released but relay Z remains held over its upper winding and thus brings about a substantial increase in the interdigital pause. This extra pause ensures that the distant equipment has sufilcient time to perform the operations already mentioned before the next decoded digit is transmitted.
  • Relay LR Fig. 2
  • Relay B in releasing homes the distributor switch DD (Fig. 4) to its mid-position ready for the operation of relay AA at a. later period, while relay BR in releasing connects the low resistance lower winding of relay RR into the sleeve circuit, relay RR being non-operative but causing the operator's supervisory lamp to glow.
  • Relays M, MM, CO, BS, FC and LR remain operated and the line condition is such that the operator is able to receive tones corresponding to the condition of the wanted party's line and, if necessary, speak without the necessity for a called party answer signal.
  • an answer signal comprising 140 m. s. pulses of Y frequency at spacings of 360 m. s. is transmitted back from the incoming relay set, this signal being repeated until acknowledged signal from the outgoing relay set.
  • relay Y in the VF receiver VFR, Fig. 3 operates and opens the circuit for relay BS.
  • relay BS On the release of relay BS after aperlod of the order of 100 m. s. relays MS and MT are operated in turn and hold for the remainder of the Y pulse.
  • relay BS re-operates and further opens the circuit for relay MS which has a release lag of the order of 350 m. s. If the interval between received pulses is of the correct duration, namely 01 the order of 1460 m. s. for
  • relay MS will release but not relay MT, since a period of 360 m. s. plus the m. s. release time of relay BS will elapse before any further circuit can be completed to relay MS so that on reception of the next Y pulse, relay SA will be operatedand at the end of this pulse relay SB will operate in series with relay SA.
  • Relay SA in operating gives local and through supervision at the outgoing operators position.
  • Relay SB brings up relay AA, Fig. 4, in series with the DD switch magnet DDM which proceeds to self-drive, while relay AA re-operates relay CS, Fig. 5, and at contacts AAI, Fig. 3, applies X frequency to the outgoing trunk.
  • the duration of the X frequency acknowledgment signal is measured by the homing time of switch DD plus the release time of relay AA. when the X pulse is received at the incoming relay set, transmission of the Y pulse is stopped. Relay BS therefore remains operated, while relay MT releases.
  • the incoming relay set transmits Y pulses of the same type as for the called party answer signal.
  • switch TS is in position 6 so that the first m. s. pulse of Y frequency releases relay BS and operates relays MS and M71- as before.
  • the following 360 m. s. break period operates relay BS and releases relay MS but not MT so that when the next Y pulse is received relay BS again releases and during the slow release period of relay MT relay SY now operates.
  • Relay SY which has a release lag of 400-450 m. s. lock up to the Y pulses, operates relay SZ and releases relay SA which gives the necessary clearing supervision at the outgoing operator's position.
  • Relay CS now re-operates via bank TSI, whereupon X frequency is applied to the trunk line.
  • relay SB operated the switch TS self-drives via bank TS3 from position 7 .to position 15 and then steps by means of interrupted earth on lead II and via bank TSS to position l8.
  • Relay m is then operated via bank TSl to disconnect the X frequency, the period of application being of the order of two seconds, while it also connects up Y frequency to the trunk line.
  • Wiper 184 on being stepped on to position 19 causes relays SR and BR to release after their and on release of relay BR earth is extended over bank T83 to step the switch from position 19 so that relay FXY releases and after its slow release its home position where relays CO, FC, and SB release.
  • relay BS will have released and relays MS and MT operated but without usefollows:
  • Seizur oflthe relay set is in this instance effected by earth extended forward over the private conductor P and relay SR thereupon operates andmoves the switch TS off normal as previously described and locks up over its upper winding to contacts] and 2 of bank TSfi.
  • the TS switch in advancing to position I operates relays 00, BS,
  • Relay SR in operating at contacts SR6 andSBI, F 3, connects the V. F. receiver responsive to-Y frequency to the line conductors fromthe selector level by way of. con en s- QC. nd eifect in this: instance. tended forwardvia the selector and this operates This operation is without A loop will also be exrelay A which in turn brings up relays B and BR, BB2 a guard earth is extended back over the P lead to hold the selector.
  • Relay FXY extends a 100 m. s. X frequency seizing pulse forwardly over the trunk to the distant incoming relay set and at the same time causes the switch TS to self-drive to position 3 where relaysSR and FXY are disconnected and relay FXY after itsslow release period terminates the X pulse and releases relay CS.
  • Relay FC, Fig. 5 is then operated over bank TSl and locks up and serves toj step switch TS to position 4 from which it slow steps frominterrupted earth on lead I l to position, 6.
  • relay A responds to the dialled impulses which are stored via the distributor switch DD on switches f DSA .DSD and are subsequently sent out under control of the sending'switch SC in codedV.
  • relay SA in operating reverses the A relay connections towards the calling party for supervision, while relay SB causes an x pulse acknowledgment .signal to be transmitted forweraly tothe distant exchange to terminate the backward Y answer signal and so enable conversational conditions to be set up.
  • the relay set is seizedfrom a circult including a V. F. link but not including a regenerator, for example if the relay set concernedis 01252 at exchange C, Fig. l, and assuming that A- A REP in exchange B is an ordinary impulse repeater then on seizure from the selector, earth will be extended forward over the P switch TS of! normal as previously described and locks up over its upper winding to contacts I and 2 of bank TS.
  • the TS switch in advancing to position 1 operates relays C0, BS, CS and FXY.
  • Relay SR in operating connects the V. F. receiver VFR to the line conductors from the selector level, contacts FXY5 and FXYG serving for contact wetting purposes.
  • a loop will also be extended forward via the selector and this operates relays A, B and BR in turn.
  • Relay FXY extends a m. s. X frequency seizing pulse forwardly over the trunk to the distant incoming relay set IRS! at exchange D, and at the same time causes the switch TS to self-drive to position 3 where relays SR, FXY and CS are in turn released, relay FXY after its slow release period terminating the X pulse.
  • a prolonged pulse of Y frequency of the order of 800 m. s. will be projected forward from the incoming relay set IRS! in exchange B, such a Y frequency pulse following each direct current impulse train from relay set IRS! but being ineffective until an outgoing relay set is reached.
  • Relay Y in the V. F. receiver VFR- therefore operates and hence relays MS and MT are energised.
  • Relay RB, Fig. 5, now operates and in turn brings up relay AC, Fig. 4,.from the earthed contacts Bl.
  • Relay RB in operating at its contacts BB2 and R33, Fig. 2, reverses the connection of relay A to the incoming line and, as will be subsequently described in connection with Figs. '7 and 8, sets up through switching conditions in the exchange B incoming relay set IRSi so that subsequent V. F. digital information received by this relay set will not be converted to D. C. loop impulse form but will be extended straight through to exchange C.
  • Relay AG in operating locks up at contacts AC i, at contacts AC3, Fig.
  • this is suitable for use as relay set conductor to operate relay SR which moves the 7 looks and brings up relay PY and at the same time extends a forward earth over the P conductor to the incoming selector ISI conductor to the selector, operates relay IL over the negative line in series with the selector impulse accepting relay and also operates relay Gx, whereupon relay PY is locked. Relays L, PY, NN, IL and GK are therefore held operated at this stage.
  • Y or IW and IZ operate in receiver IVFR. of the incoming relay set and bring up their relief relays WR and YR or WR. and ZR.
  • relay CL alone is operated or relays CL and CH. In either case the line termination, normally comprising resistances YM and YN in parallel, Y?
  • the impedance of the repeating coil RPCI being sufficiently high to be neglected at this time, is converted into a loss pad with considerable attenuation which prevents the passage of V. F. signals beyond the incoming relay set.
  • the prepare pulse of 160 m. s. is followed by the code digit pulse of 100 m. s. duration, relay CL and relay CH if energised holding operated during the short interval between pulses due to their slugs.
  • relay CL will be operated in response to prepare pulse WY over contacts YR2, WRf, 1R2, Ii and NNI to earth and prepares a circuit for relay CB which is at present short-circuited.
  • the prepare pulse is replacedby the code W for digit 1, relay- WR holds and relay YR releases, and relay CB therefore operates in series with relay CL which now holds.
  • Relay CB in operating locks relay WR to store the digit and this relay over contacts WRA, Fig. 8, of a suitable pyramid of contacts prepares to connect earth to the contact 2 in the bank SS2 of the sending switch as in order to pear subsequently.
  • the contact pyramid of the code relays WR-ZR prepares to connect earth markings to the sender switch bank 832 to control the sending out of the digit concerned.
  • the particular part of bank $32 which is to be effective at any time is determined in accordance with the digit concerned by the operated or normal condition of relay CH. If the digit concerned is .in the 1-6 group, relayCH will be normal and an earth marking will b prepared to one of the five contacts 26 via contacts SZI and CH2 and when the SS switch is set in motion the marking will be completed via bank, SS3 when wiper 88! reaches position 2, this wiper being earthed via contacts MA! and RN! to earth.
  • relay CH will be operated
  • the earth marking will be prepared to contacts 7-11 of bank 882 via contacts 82 I, and will subsequently be completed via when wiper 88! reaches position '7.
  • relay WR will be operated and relay CH will be normal so that an earth marking will be prepared to contact 2 of bank 882.
  • relay CB in series with relay CL, on the operation of relay CB earth will be extended to operate relay CY over contacts 0L5, CBI, NR! and LI, while relay P will also be operated and will lock.
  • Relay P at contacts P4 prepares a circuit for the line supervisory relay I, while relay CY in operating short-circuits its lower winding to render itself slow to release, at contacts CYI prepares a circuit for transmitting Y frequency forward and at contacts CY2 operates relay CC.
  • relay IG Fig. 8
  • Relay IG at contacts 163 drops relay 1L and transfers to the springs 33% M the forward selector seizing circuit previously closed by relay NR at contacts NNS.
  • the springs 33% M are closed at this time since they are operated in the opposite manner to the magnet impulse springs 66% M which have just opened to bring about the operation of relay 16.
  • the impulse springs 33% M are normally short-circuited over wiper S8! in its home position so that when the magnet springs 66% M next close to energise magnet SSMpf switch 88 the opening of springs 33% M is without effect.
  • magnet 88M is de-energised and the SS switch wipers are thereupon advanced 'to position 1 where the springs 33% M now become eflective but are closed at this particular instant.
  • springs 33% M open to send out the first impulse and on the next opening of springs 66% M which causes the S8 switch wipers to advance to position 2 springs 33% M reclose to terminate the break portion of the first impulse.
  • the digit concerned is 1 so that wiper 882 in position 2 will pick up an earth marking over operated contacts WRA and relay 82 will operate and at contacts 822 loops the outgoing line conductors to terminate the outgoing impulse train.
  • contacts SZI it completes a locking circuit for itself via bank and wiper S83 and at the same contacts removes the short-circuit from relay PR. which operates in series with relay 82 which holds.
  • Relay PR in operating at contacts PRI prepares for connecting the rectifier polarised relay DT across the outgoing line, at contacts PR2 completes an alternative holding circuit for relay CY, at contacts PR4, Fig. 7, releases relays CB and CL, whereupon relays WR and IG release, and at contacts PR8 connects up Y frequency to the transformer VFTI.
  • Relay CB on releasing at contacts CB8, Fig. 8 connects the polarised relay DI across the outgoing conductors, resistance YV obviating any tendency of the selector to release during the changeover. and at operate terminate transmission of Y frequency and effect the through switching is sent back to the incoming relay set. The polarised relay DT which would respond to such signal does not therefore under these conditions.
  • relay SR when the SS switch in performing its selfdriving operation reaches position 12, relay SR operates in series with the magnet SM which cannot now operate.
  • Relay SR short-circuits its high resistance left-hand winding and enables the switch to step to position 13.
  • relay SR releases and at contacts SRI completes a circuit for advancing the switch to position 14. This operation continues until the switch reaches position 22 in which position relay PR is disconnected and releases to transmission of the Y frequency after a period of application of the order of 800 m. s. n release of relay PR, contacts PR3 complete a circuit to home switch SS and relay SZ then releases, whereupon relay IL re-operates over the negative lead.
  • Relay PR in releasing also releases relay CY and this relay releases relay CC.
  • Relays L, PY, NN, IL, GK and P remain operated.
  • relays CL and CH are initially operated and subsequently locked up in series with relay CB, while relay WR is again energised.
  • Relay CB brings up relays CY and CC and relay IG then operates to initiate the sending out of the digit in D. C. impulse form.
  • no circuit is completed over contacts 2-6 of the switch SS and the earth marking is not therefore communicated to bank SS2 until the switch reaches position '7 when relay SZ operates and holds in series with relay PR which then operates.
  • relay PR in operating brings about the release of relays CB, CH, CL, WR and IG, connects relay DT across the outgoing leads, and applies the forward Y frequency pulse.
  • Relay SZ self-drives the SS switch to position 12 from which it operates by interaction with relay SR towards position 22 to time the forward Y frequency pulse.
  • the second series of impulses will be repeated by the auto-to-auto repeater A-A REP, Fig. l, and will operate the incoming selector 182 in exchange 0 which will seize an outgoing relay set ORS2 having circuits as illustrated in Figs. 2-5.
  • the relay set ORS2 willmomentarily reyerse battery back over the line to the auto-toauto repeater A-A REP at exchange B where it is repeated back to the incoming relay set and will bring ,up relay DT.
  • Relay DT in operating locks up over its contacts DTI, at contacts DT2 shortcircuits relay PR, at contacts DT3 short-circuits relay SR and provides a quick homing circuit for switch SS, at contacts DTl, Fig. 7, locally operates relay IL and at contacts DTS brings up relay IR.
  • Relay PR in releasing releases relays CY and CC in turn, whilerelay SZ also releases on the homing of the switch SS.
  • Relay IR in operating at contacts IRI disables the loss. pad, at contacts IR2 disables the code signal responding circuit including relays CL, CH and CB so as to prevent further coded V. F. signals from being effective on the incoming relay set and at contacts IRS releases relay L.
  • the relays WRZR will respond, the relays CL, CH and CB will be non-responsive and the loss pad will not be brought into circuit with the line so that the V. F. signals will be transmitted straight through via the repeating coil RPC2 to the outgoing side of the circuit whence they extend via the exchange B selector terminate the relay set IRSI a ISI and auto-to-auto repeater A-A REP and exchange 0 incoming selector 1S2 going relay set ORS2.
  • Relay set ORS2 will have responded to the Y frequency transmitted forward as already described in connection with Figs. 2-5 so that it oifers a straight-through path and hence the third and any subsequent coded V. F. signals are transmitted direct from the outgoing relay set ORSI in exchange A to the incomingrelay set IRS2 in exchange D.
  • This relay set may be assumed to be identical with that shown in Figs. 7 and 8, and when it has converted the received V. F. codedinformation into direct current impulse form to actuate the selector to gain access to the wanted subscriber on this exchange, it will send forward in the same manner as for long pulse of Y frequency which is clearly inefiective so that relay DT therein is not operated.
  • the relays L, PY, NN, IL, GK and P will therefore remain operated in relay set IRS2 while the required subscriber is being rung.
  • relay I in relay set IRSZ at exchange D When the wanted party replies, relay I in relay set IRSZ at exchange D is operated over the positive lead and relay IL releases.
  • Relay I in operating brings up relay IR which disconnects relay L and on the release of this relay relay MA operates.
  • Relay MA prepares a circuit for connecting'up Y frequency to the line transformer VFW, Fig. 7, connects the secondary of this transformer to the incoming trunk line, connects relay CY up to bank SSi, Fig. 8, and at contacts MA'I completes a self-driving circuit for switch SS.
  • relay CY is operated from earth over wiper and bank SSI and therefore Y frequency is transmitted back over the connection set up, while during the remaining eighteen steps relay CY is not operated and hence with the normal adjustment of the switch to make fifty steps a second this will represent a Y frequency signal timing of m. s. on and 360 m. 5. off. So long as relay MA remains operated the switch continues to self-drive.
  • ORS2 in exchange C BS and A0 are held operated at this time and the'switch TS is in position 20, the V. F. receiver responds to the Y frequency but owing to the fact that relay AC in this relay set is operated the energisation of the Y frequency relay produces no effect and the signal is' passed straight through. It also passes straight through the auto-to-auto repeater and the incoming relay set IRSI at exchange B where relays PY, NN, IL, GX, P, DT and IR are held operated dependent upon the outgoing relay set ORSI at exchange A.
  • relay set relay AC In this relay set relay AC is not operated, relays M, MM, CO, BS, FC and LR being operated and the switch TS being in position 6, and switch DD occupying its midposition so that the first pulse of Y frequency energises relays MS and MT after BS releases. During the succeeding blank period relay MS releases so that on reception of the next pulse relay SA is operated and at the end of this pulse relay SB operates in series with relay SA.
  • relay SA gives the operator to the outof the connection.
  • Relay GX is accordingly released owing to the length of time its circuit is broken by contacts XR4 while the operation of relay GY provides a locking circuit for relay PY. Relay PY releases at the end of the X pulse and in turn releases relay MA which thereupon terminates the trans- .mission of the interrupted Y pulse.
  • connection is now completely set up and conversation may take place, and it may be as well at this stage to review the circuit conditions obtaining in the various relay sets, which are as follows:
  • relay DT in operating short-circuits and releases relay PR, provides a quick homing circuit for switch SS, holds relay IL independently of the outgoing line, and brings up relay IR.
  • Relay PR in re leasing releases relays CY and CC in turn while relay IR in operating sets up through switching conditions and releases relay L.
  • relay I On the release of relay SZ however, when the BS switch reaches its home position, relay I will be operated, since the battery reversal persists and relay I in operating opens the locking circuit of relay DT, whereupon relay IL is released and completes the circuit for relay MA to initiate the returning of the interrupted Y frequency subscriber answer. signal When the wanted connections to line tor are restored relay' IL is again operated, while relay I releases. Relay I in releasing at contacts II releases relay IR and recompletes an energising circuit for relay MA which was released in response to the acknowledgment signal from the originating end, and this relay in operating causes the transmission of interrupted Y frequency in the manner previously described, this signal now constituting a called sulbscriber clearing signal.
  • relay SY is now energised and releases relay SA to give the operator clearing supervision.
  • - Relay SY is sufliciently slow to remain operated the battery final selecparty hangs up.
  • this relay set in lays together bring about the release and the latter releases Relay SR CS and these reextension of an X frequency signal forward over the connection time relays SY and SZ release. Since relay SB is operated, the switch TS continues to self-drive from position 7 to position 15 via bank T33 rupted earth to position 19 via 'bank T85.
  • Relay P'X'Y is then operated over bank T84 and serves to disconnect the X frequency after a period of in operating re-operates relay the two second X pulse operates relays XR and circuit for relay N to the Y pulse and also connects earth to the P conductor extending forwardly to the automatic switch train in exchange D. relays YR and switch train whereupon the relay set is free for further calls.
  • the two seconds X, 300 m. s. Y release pulse in passing through the intermediate incoming relay set IRBI in exchange B operates the responding equipment to produce the release of the following manner.
  • YRand CR are operated and the latter translay DI and removes the earth from the P conductor extending to the 'auto-tc-auto repeater, the loop to this repeater having been opened on the release of relay NN.
  • This interruption is repeated by the auto-to-auto repeater to the outgoing relay set ORSi in exchange C wh'ere relays A, B, BR, C0, B8 and AC are held operated and switch TS is in position 20.
  • Relay A now releases and releases relays B and BR in turn.
  • Relay AC then falls away and the switch TS is stepped to normal via banks TS! and T85, no signals being transmitted to line during this time.
  • relays CO and BS release and th'e earth is removed from the incoming P lead to this relay set by bank and wiper T84, whereupon the preceding exchange C selector train is released and the whole connection is then completely broken down.
  • connection includes one or more D. 0. links involving regenerators, for instance where. in Fig. l, the auto-to-auto repeater A--A REP includes a regenerator so that end-to-end impulse sending is not possible and in this case it is important to ensure that supervisory signalling from the called party takes place in cascade.
  • a regenerator in the repeater A-A REP a connection has been set up as shown in Fig. i. this will mean that through signalling conditions will not have been set up in the relay sets IRS! and ORS2 so that in both the relay sets DB3! and ORSZ relay AC will'be normal and switch TS in position 6 and in both the relays sets IRSI and IRS2 relay DT will be normal:
  • relay I in operating brings up relay IR which disconnects relay L and on the releaseof this relay, relay MA opcrates to transmit interrupted Y frequency back to exchange A.
  • relay set IRSI the interrupted Y frequency signals are prevented from extending forward due to the operation of relay MA, while at the originating outgoing relay set ORSI they are prevented from passing further backwards by .virtue of the operation of relay CS.
  • the outgoing relay set ORSI thereupon transmits forward the X frequency acknowledgment signal to terminate the sending out of the interrupted Y frequency from relay set IRSI.
  • relay I in releasing in relay set IRS2 recompletes an energising circuit for relay MA, and this relay causes the transmission of interrupted Y frequency back to relay set ORS2.
  • relay MS and MT operate, but since at this time relays SA and SB therein are already operated, relay SY is now energised and releases relay SA to restore the reversal extended to the incoming relay set IRSI when the called subscriber answered. Relay SY remains held to the interrupted Y frequencvy from relay set IRS2.
  • relay set IRSl Similar considerations apply to thatat relay set IRS2 and interrupted Y frequency is sent out to relay set ORSI, where relays MS, MT and SY are operated and relay SY is brought up and remains operated from the interrupted Y frequency signal from relay set IRSI.
  • a two-second X frequency signal and a 300 m. s. Y frequency signal are sent forward to relay set IRSI where relays XR and GY operate and the former release relay GX which thereupon brings up relay CC and releases relays MA and CY to terminate the interrupted Y frequency signal being transmitted from this relay set.
  • the remainder of the two-second X pulse goes forward to the relay set ORS2 where it is without effect and proceeds to extend through to the relay set IRS! where relays XR and GY are operated, relay GX, released, relay CC operated and relays MA and CY released to terminate the Y frequency being sent back to relay set ORSZ.
  • the clear-down signal from the operators position operates substantially simultaneously on a plurality of sections regardless of whether regenerators are involved in the connection or not, while when regenerators are involved in the connection the subscriber answer signal and subsequent supervisory signals suchas the subscriber clearing signal are transmitted on a cascade signalling basis.
  • regenerators are involved in the connection the subscriber answer signal and subsequent supervisory signals suchas the subscriber clearing signal are transmitted on a cascade signalling basis.
  • the outgoing relay set V. F. receiver is arranged to respond selectively to both X and Y frequencies instead of only to Y frequency as before, while an additional circuit is provided for the through switchingarelay AC over extra contacts SAT, BS2 and AA From Fig. 10 it will contacts XR1 and XRB a through transmission circuit independently of the operated or normal condition of relay MA.
  • relay set ORSI thereupon transmits forward the X frequency acknowledgment signal to terminate the sending out of the interrupted Y frequency from relay set 1178i.
  • relay se t ORSI modified in the manner shown in Fi 9 it will be seen that the associated V. F. receiver VFR can respond to the X frequency acknowledgment signal. but since relay AA is held operated during the homing of switch DD which times the x frequency acknowledgment signal, contacts AAI prevent the response of the V. F. receiver to the X frequency from being effective.
  • relay XR is efl'ective in normal manner to terminate the sending out of the interrupted Y frequency to relay set ORSI by releasing relay MA but it will be noted from Fig. 10 that in the present instance the additional contacts KR! and X38 provide an immediate through path for the X frequency acknowledgment s gnal from relay set ORSI so that this signal, as well as being received in the incoming relay set IRSI, will also extend forward over the connection to the exchange C outgoing relay set ORSI. At this relay set the x relay in the V. F.
  • the X frequency acknowledgment also extends forward to the incoming relay set IR82, but since this latter relay set will have already responded to an x frequency acknowledgment signal from relay set 0382 the receipt of a second acknowledgment signal will be without effect.
  • the interrupted Y frequency clearing signal is transmitted from relay set 11182. Since the V. 1". receiver of relay set 0R8! is disabled as far as Y frequency is concerned, this frequency will therefore extend right back over the connectionto the originating outgoing relay set ORSI where it functions as before described to give a clearins i nal to the operator. When the operator clears, the clear down of the equipment will be as already described for an end-to-end signalling connection.
  • a repeater responsive to incoming voice frequency signals for transmitting corresponding direct current signals forward to succeeding switches, said repeater being operative to at times transmit a voice frequency testing signal forward and being operative in response to a consequent return signal to condition itself for straight-through transmission of subsequent voice frequency signals.
  • a repeater for converting incoming voice frequency signals into corresponding outgoing direct current s gnals to control succeeding automatic switches. said repeater being operative to transmit a voice frequency testing signal forward after each direct current signal, a second repeater accessible to the succeeding automatic switches and operative said testing silnal to return a characteristic signal to said first repeater, said first repeater being operative in response to the return of said characteristic lilnal to condition itself for straight-through transmission of subsequent voice frequency signals.
  • a plurality of exchanges trunk lines connected therebetween, means in one of the exchanges for transmitting voice frequency signals over a trunk line to a second exchange, means in the second exchange responsive to said voice frequency signals for operating an automatic switch therein into association with a trunk line extending to a third exchange and for repeating subsequently received voice frequency signals as corresponding direct current signals to the third exchange, said second means being adapted to transmit a voice frequency testing signal forward following each direct current signal, an automatic switch in the third exchange operated in response to the direct current signals for further extending the connection, means in a succeeding stage of the connection responsive to said testing signal for as new and desire to secure by returning a characteristic signal to said second means, said second means being responsive to said characteristic signal to condition itself for straight-through transmission of voice frequency signals.
  • a telephone system employing mixed systems of voice frequency and direct current signaling for controlling the setting of automatic switches comprising means for transmitting voice frequency signals from a first exchange to a second exchange, and means in the second exchange for either extending said voice frequency signals directly to further exchanges or converting them into corresponding dir at current signals before they are extended depending upon the condition of the connection thus far built up in the further exchanges.
  • a telephone system includingat least three exchanges and two inter-exchange trunk lines over which voice frequency signaling currents are transmitted for supervision and for controlling the setting of automatic switches, repeaters associated with the incoming ends of said trunk lines for initially converting voice frequency signaling currents into corresponding direct current signals, repeaters associated with the outgoing ends of said trunk lines for initially converting direct current signals into corresponding voice frequency signaling currents, means for completing a connection to a called party through said trunk lines and associated repeaters in cascade, and means in said repeaters responsive to an answer by the called party for conditioning intermediate ones of said repeaters for straightthrough transmission of subsequent voice frequency signaling currents.
  • a repeater responsive to incoming direct current signals for transmitting corresponding voice frequency signals forward, said repeater being operative to test for an incoming voice frequency signal when seized and being operative in response to the presence of said voice frequency signal to condition itself for straight-through transmission.
  • a repeater for converting incoming voice frequency signals into corresponding outgoing direct current signals to control succeeding auto-' matic switches-said repeater being operative to transmit a voice frequency testing signal forward after each direct current signal, a second repeater accessible to the succeeding automatic switches and operative to convert incoming direct current signals into corresponding outgoing voice frequency signals, said second repeater being operative in response to the reception of said testing signal to condition itself for straight-through transmission of voice frequency signals and to return a characteristic signal to said first repeater, and said first repeater being operative in response to said characteristic signal to condition itself for straight-through transmission of subsequent voice frequency signals.
  • said consequent return signal comprises a momentary reversal of the direct current flowing over the speaking leads of the succeeding switches.
  • testing signal has the same frequency as a voice frequency supervisory signal and operates the same signal receiver in the sec ond repeater as said supervisory signal.
  • a telephone system as claimed in claim 1 in which said repeater is adapted to transmit the voice frequency testing signal for a predetermined minimum time interval after each direct current signal transmission.
  • a telephone system as claimed in claim 1 in which said repeater is adapted to terminate the transmission of the testing signal in response to reception of the consequent return signal.
  • a telephone system as claimed in claim 5 in which the operation of said last means is brought about by the forward transmission of an acknowledgment signal by the repeater at the originating end of the cascaded trunk lines in response to the reception of the called party answer signal.

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  • Engineering & Computer Science (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Interface Circuits In Exchanges (AREA)
US516322A 1943-02-13 1943-12-31 Telephone or like system Expired - Lifetime US2383541A (en)

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Application Number Priority Date Filing Date Title
GB2401/43A GB563504A (en) 1943-02-13 1943-02-13 Improvements in telephone or like systems

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US2383541A true US2383541A (en) 1945-08-28

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US516322A Expired - Lifetime US2383541A (en) 1943-02-13 1943-12-31 Telephone or like system

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US (1) US2383541A (fr)
FR (1) FR932910A (fr)
GB (1) GB563504A (fr)
NL (1) NL64785C (fr)

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2468299A (en) * 1945-07-07 1949-04-26 Bell Telephone Labor Inc Supervisory signaling in telephone or like switching systems
US2486100A (en) * 1944-05-05 1949-10-25 Automatic Elect Lab Voice frequency signaling circuits for telephone systems
US2557388A (en) * 1947-05-28 1951-06-19 Automatic Elect Lab Automatic telephone system employing finder switches for connecting calling lines tonumerical switches
US2594719A (en) * 1945-05-19 1952-04-29 Automatic Elect Lab Voice-frequency telephone signaling system
US2655652A (en) * 1948-06-28 1953-10-13 John H Homrighous Multiplex time division telephone systems

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2486100A (en) * 1944-05-05 1949-10-25 Automatic Elect Lab Voice frequency signaling circuits for telephone systems
US2594719A (en) * 1945-05-19 1952-04-29 Automatic Elect Lab Voice-frequency telephone signaling system
US2468299A (en) * 1945-07-07 1949-04-26 Bell Telephone Labor Inc Supervisory signaling in telephone or like switching systems
US2557388A (en) * 1947-05-28 1951-06-19 Automatic Elect Lab Automatic telephone system employing finder switches for connecting calling lines tonumerical switches
US2655652A (en) * 1948-06-28 1953-10-13 John H Homrighous Multiplex time division telephone systems

Also Published As

Publication number Publication date
FR932910A (fr) 1948-04-06
NL64785C (fr)
GB563504A (en) 1944-08-17

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