Patent GB-854612-A (GB)
Title: Improvements relating to telephone systems
Inventor: WORTHY FRANK ALLEN STALL
IPC: H04Q1/446
Filed: 1956-04-24
Abstract: 854,612. Automatic exchange systems. SIEMENS EDISON SWAN Ltd. May 10, 1957 [April 24, 1956], No. 12528/56. Class 40 (4). A single voice frequency is used for signalling over a both-way junction between an automatic subsidiary exchange and a main exchange with both automatic and manual facilities. When a subscriber at the subsidiary exchange clears from a call to a manual board at the main exchange, a " calling subscriber clears " signal (100-150 millisecs. pulses) is transmitted to the main exchange and a " clear forward " signal (2 sec. pulses) to the main exchange is delayed until the operator clears and a " calling subscriber clears acknowledgment " signal (80 millisecs.) is received at the subsidiary exchange. When the junction is taken into use at the subsidiary exchange a pick-up signal is transmitted over the junction to the main exchange, the duration of the signal signifying the type of call. A pick-up signal of 25-40 millisecs signifies an automatic call and signals of 100-150 millisecs and of over 350 millisecs signify calls to the manual board from an ordinary subscriber and from a call-box, respectively. The line circuits of Specification 827,174 are modified to provide these additional features. Corresponding parts of the circuits in the two Specifications bear the same references. Leg signalling is used between the exchange and the junction lines circuits. Outgoing circuit. Figs. 1A to 1D.-Line relays LA, LB, individual to the positive and negative wires, detect leg signals from the exchange. When a call is to be handled automatically in the main exchange, both LA, LB pull up. When the call is for a manual board, LA pulls up if the call is from an ordinary subscriber and LB pulls up if it is from a call-box. The duration of the pick-up signal transmitted over the junction connected to terminals 86, 87, is determined by relays WA, WB, WC, WS under the control of LA, LB. Relays SS, DC are used to delay the clear forward signal and relays DF, DG time the " calling subscriber cleared " signals. An incoming circuit is normally connected to the junction and to a common voice-frequency receiver over contacts of relays SA, SB. The receiver (not shown) is linked to the line 81, 82 by a transformer TR1 in compartment GH1. The receiver relay XX (not shown) is normally up but contacts xx1, xx2 are shown back in compartments GH2, GH3. Line splitting relay SP controlled by dialling relay CD and interval control relay CR, is not mentioned in the description below. Dialling relay CD pulls up in response to impulses from the exchange and voice-frequency signals received over the junction. Call to main exchange, automatic; outgoing circuit.-The line 75, 76 is looped and relays LA, LB, A, AB, SB, B, BA, WS, TX, SR, BB, SA pull up in sequence. Line relays LA, LB drop out when WS extends the line 75, 76 to relay A and the call is set up substantially as in Specification 827,174. Relays TX, SR both depend upon B and TX transmits a voicefrequency (2280 c/s.) pick-up signal of 25-40 millisecs terminated when slow-to-operate relay SR comes up. Relay TX follows A at contact a2 and repeats dialled impulses as voice-frequency pulses. Timing circuit AU4 starts to measure off a 2 seconds dial-pulse guard period when BB comes up but dialling relay CD pulls up with the first impulse and discharges condenser C2 to return to timing circuit to zero. On reply, relays XX, SR fall back during the answer signal (100-150 millisecs., repeated if necessary) and the answer relay D pulls up overwinding (I) and b4. Battery is reversed at d3, d5 to signal the exchange. When SR pulls up again after the pulse, TX transmits a voicefrequency " answer acknowledged " signal during the delay (80 millisecs.) before DD pulls up in series with D. Clearance of call to main exchange, automatic; outgoing circuit.-During a clear back signal of 100-150 millisecs (not repeated), relays XX, SR fall back as for an answer signal but in this case D falls back and DD is held until SR pulls up again at the end of the signal. Battery is reversed again at d3, d5, to signal the exchange. The circuit at this stage can respond to a further sequence of answer and clear back signals. If the calling line now clears, A falls back followed by AB, CR, B, WS, BA and relay DB pulls up. Relays CR, CF and timing circuit AU4 interact and TX transmits clear forward signals of 2 sees. with intervals of 1 sec. Relays XX and SR fall back in response to an acknowledgment signal of 100-150 millisecs. (not repeated). Relay XX pulls up again at the end of the signal and the circuit returns to normal with SA, SB back to connect the incoming circuit to the junction. If the calling line clears first the operation is modified in that relays D, DD fall back with B. Call to manual board from ordinary subscriber; outgoing circuit.-The circuit is seized by a leg signal consisting of negative battery on the positive wire 76. Relay LA comes up, followed by A in a local circuit and the connection is built up as before. Timing relays WB, WA follow B and energization of SR over wb3 is delayed until WB is back after a slow release, thereby extending the pick-up signal to 100-150 millisecs. Call to manual board from call-box; outgoing circuit.-The leg signal in this case is earth on negative wire 75. Relay LB comes up, followed by A &c. Timing relays WC, WB, WA pull up in turn and WB, WC fall back slowly. Operation of SR is delayed sufficiently to extend the pick-up pulse to 350 millisecs. Operator answers; outgoing circuit.-When relays D, DD come up, as before, to transmit an " answer acknowledged " signal, relays SS, DC, follow, WS being back. Relay SS completes the speech circuit over condensers C22, C23 and opens the leg signalling circuits to signal the exchange, where the negative wire is earthed if the call is from an ordinary subscriber or negative battery is connected to the positive wire if the call is from a call-box. Relay CH follows SS and connects both relays LA, LB to the line wires again to transmit the " answer " signal to the exchange. Caller clears call to manual board; outgoing circuit.-Relay DC which pulled up an answer, holds up clear forward pulses. In accordance with the type of calling station, relay LA or LB falls back on clearing and A, AB, B, BA, BB follow, the operating circuit of TX being opened at dc6. Negative battery applied to wire 76 over resistor R56 provides a holding condition for the preceding circuit. Relay TX transmits a voice-frequency " calling subscriber cleared " signal under the control of relays DF, DG which interact to measure off pulses of 100-150 millisecs., contacts df3, dg4 being connected across dc6. Pulses continue to be transmitted as long as BA, AC are both back. Relay MH enables the caller to recall at this stage by earthing the negative wire 75. Relays A, AB, B, BA pull up again in sequence and the circuit is then as it was before the caller cleared. When the operator clears in response to the " calling subscriber cleared" signal, an acknowledgment signal sends back XX and brings up AC over winding (I) and xx2, both DF, DG being up immediately after a " calling subscriber cleared " signal. When DC falls back with a delay after AC, the " clear forward signals (2 second pulses) are transmitted as before. Pick-up signal discrimination at incoming circuit, Figs. 2A to 2C.-If the signal calls for connection to automatic equipment (25-40 millisecs.) relay WE pulls up on winding (I) and holds on winding (II). Relay WD cannot operate in the time available. The automatic equipment is seized on completion of the loop at wel, we2 and the connection is built up as described in Specification 827,174. Relays DR, DA interact and SX transmits answer signals (2 sec. pulses) when DP responds to battery reversal on reply. If the signal is for a manual board and comes from an ordinary subscriber both WE and WD come up during the 100- 150 millisecs. but WE cannot fall back before the signal ends and both relays lock to BC over windings II. When CC falls back after the pick-up signal, negative battery is connected over R59 and winding of relay DE to the positive wire to give the appropriate lamp signal on -the board. Relay DE comes up and is followed by DZ. When the operator answers, the positive wirecircuit is opened to release DE and negative battery is connected to the negative wire. As DE goes back, DY comes up and both DY, DZ lock to BC. With DE back, ground is connected to the negative wire over we6 with the effect that the positive wire circuit is completed again in the succeeding circuit and DE pulls up. Relay DP follows in a circuit between wd3 and the negative wire and the answer signals are transmitted as before. If a signal for a manual board comes from a call-box, both WE, WD come up and WE falls back before BC comes up as a short-circuit is removed from BR at the end of the signal. Each is connected to the negative wire over wd3 and the winding of relay DE to give a lamp signal on the board. Relay DE comes up but falls back when the operator replies by opening the negative wire circuit and grounding the positive wire. Relay DY comes up and connects negative battery to the positive wire over resistor R58 and thereby brings about closure of the negative wire circuit again. Relay DE comes up again and DP follows in a circuit connected to battery over R59. The answer signals are transmitted as before. Release of call to manual board; incoming circuit.-As in Specification 827,174, relay AK came up in response to the " answer acknowledgment " signal (80 millisecs.) from the-outgoing circuit. In this case, AK was followed by manual board relay MB. When CC responds to a " calling subscriber cleared " signal (100-150 millisecs.) it is followed by SC. The consequent disconnection of the negative wire and connection of the positive wire to ground through relay OH, which comes up, is a signal to the operator. Relays