Patent GB-828787-A (GB)
Title: Improvements relating to automatic telephone and like signalling systems
Inventor: WARMAN BLOOMFIELD JAMES
IPC: H04Q3/00
Filed: 1956-08-02
Abstract: 828,787. Automatic exchange systems. SIEMENS EDISON SWAN Ltd. July 31, 1957 [Aug. 2, 19561, No. 23883/56. Class 40 (4). An automatic exchange is provided with a digit receiving circuit comprising A, B and C, elements to which are applied trains of pulses produced by interruptions of a calling condition; the A element producing an output for each pulse received; the B element being held operated when subject to the calling condition and producing an output by passing to an unoperated condition after a time delay when the calling condition is removed for a period greater than the time delay; the C element being unoperated when subject to the calling condition but operating in response to the first pulse of a train and relapsing to an unoperated condition and producing an output if a sufficiently long period of uninterrupted calling condition occurs; an artificial calling condition being normally applied so that when the elements are taken into use the artificial calling condition can be replaced by an actual calling condition with the elements in instant readiness to respond to pulse trains. The elements are the transistor trigger circuits A, B and C, of Fig. 2D. General description.-The invention is applied to an exchange using motor uniselectors controlled by reverting impulses to the register controller. Figs. 1A and 1B show an incoming selector having access to the intermediate and final selectors shown in Fig. 3. Each selector has upper and lower sets of outlets accessible under control of wiper-switching relays. At an incoming selector register controllers, such as that shown in Figs. 2A to 2F, are marked in the upper outlets available to wiper SW7. Digits are sent over wiper SW5, or SW6, as soon as a register controller is seized, it being possible that part only of the first impulse survives before connection is made. While the register controller is receiving digits it connects itself to the incoming selector by means of a coupling switch with wipers CW1 to CW8. Incoming selectors may be of two sorts depending on whether four or five digits are necessary to set up a call. In either case the first digit is registered on both of two scaling tubes SD1 and SD2. If five digits are necessary, which becomes evident at the end of the first digit when the coupling switch has found the selector, scaling tube SD2 is restored and used to register the second digit. Remaining digits are registered on tubes SD3, SD4 and SD5. By marking rectifier gates, a scaling tube RD controls the distribution of pulse trains to the tubes SD1 to SD5 and is stepped itself by the end of train circuit C. The circuit A repeats the incoming pulses while the circuit B produces a pulse output to release the register controller if the calling loop is broken long enough to indicate release. A circuit BE repeats pulses reverted from selectors without being sensitive to wiper bounce and counts out the complement to 10 of the digits in SD1 or SD2, and the complement to 100 of the tens digit in SD4 and the units digit in SD5, distribution of pulses to the scaling tubes being effected by sequence relays AA and BB which mark rectifier gates. Tube SD3 marks one or more of the wires 33, 34 and 35 to determine which of relays WSA, WSB and WSC respond in order to control wiper switching at the selectors, this feature being the subject - matter of Specification 828,788. Digit receiving circuits at register controller.- Transistor trigger circuits A, B and C, Fig. 2D, perform the functions of the normal A, B and C relays and are controlled from a lead 25 which when the register controller is idle is connected to negative battery so that an input transistor TSR2 is normally conducting and in consequence its collector and the point 43 are relatively positive. In this condition the trigger circuit A is operated (TSR3 is cut off while TSR4 conducts) and trigger circuit B is also operated (TSR7 cut off while TSR8 conducts), the bases of TSR3 and TSR7 being clamped to - 25V over MR19 due to the relative positive potential at point 43. In this condition furthermore, trigger circuit C is unoperated (TSR5 conducts while TSR6 is cut off) since the base of TSR5 is connected over a point 44 to the collector of TSR3 which is cut off and consequently cuts off the clamp rectifier MR20. Each of the circuits A, B and C, produces an output in a transformer only when triggered from operated to inoperated. Circuits B and C due to capacitor rectifier combinations C3, MR17 and C4, MR18, and high base resistances to TSR5 and TSR7, are fast to trigger to an operated condition but are slow to become unoperated. When lead 25 is connected to the incoming selector the calling condition is negative battery which, as it is the same as the idle condition of lead 25, finds the trigger circuits already conditioned to receive impulses. Lead 25 may in fact be connected part way through the first pulse of the first digit. During a digit pulse TSR2 is cut off and the potential at point 43 falls to cut off clamp rectifier MR19 and generate a pulse over rectifier MR17 to charge capacitor C3 which therefore holds circuit C operated. Capacitor C3 discharges slowly over R21 and permits TSR7 to conduct only if the calling condition has been disconnected sufficiently long to indicate release. Each time TSR2 cuts off, TSR3 conducts to cut off TSR4 and repeat the incoming pulse over transformer TR1. With TSR3 conducting during each dialled pulse the potential of point 44 rises to open clamp rectifier MR20 and cut off TSR5 so that TSR6 conducts and circuit C is operated. At the end of each dialled pulse TSR3 cuts off to increase the potential at point 44, disconnecting clamp rectifier MR20 and charging capacitor C4 by a pulse over MR18. Capacitor C4 discharges slowly over R22 and holds TSR5 cut off unless the calling condition on lead 25 persists long enough to indicate the end of a digit train. Seizure of incoming selector and register controller.-An incoming call causes LA to respond and connects up latch magnet LMA to drive the incoming selector and also connects up BH which ensures that drive continues even though LA relapses to the first dialled pulse. On finding negative battery marking a free register controller, relay STA operates to halt the motor. In the register controller where C5 is normally operated, HT responds in series with STA and connects wipers SW5 and SW6 over wires 23 and 25 to the transistor impulse repeating circuit A. CU operates connecting up LM to send the register controller coupling switch in search of the incoming selector, relay TS responding over wiper CW8 to negative battery on wiper SW1 to stop the switch. Registration of digits.-The scaling tubes in the register controller are set on the O cathodes with the exception of RD which is set on its 1 cathode to open gate MR8 to the input tube V11 of tube SD1. Gate MR11 to input tube V12 of tube SD2 is normally open as neither relay S nor F is operated. The first pulse train is repeated over wire 26 from circuit A and registered on tubes SD1 and SD2. At the end of the train, circuit C produces an output to step RD to its 2 cathode and by striking tube V1 operates BS. Relay BSS follows and connects up wipers CW1 to CW7. If the incoming selector is of the sort handling five digit calls it has negative battery connected over link 31 to the top of relay HA and when wiper CW1 is connected up relay F operates in circuit with HA which does not respond. When F operates direct earth on lead E2, Fig. 2C, is momentarily removed and causes tube SD2 to restore to its O cathode ; the normally open gate MR11 now being dependent on the 2 cathode of RD which permits registration of the second digit in SD2. The subsequent three digits go in turn to tubes SD3, SD4 and SD5. If the incoming selector is of the sort handling four digit calls positive battery is connected over a link 32 to the top of HA so that relay S and not F operates and produces a pulse on lead 42 to step RD to its 3 cathode while closing gate MR11. The second digit now goes to SD3 and the remaining digits go to SD4 and SD5. Revertive control of selectors.-At the end of the last pulse train RD steps to its 6 cathode and causes SR to respond to disconnect pulse lead 25 from the selector and hold the digit receiving A, B and C circuits inoperative. By bridging a winding of F or S, as the case may be, HA is allowed to respond and operation of relay WT is initiated. By applying a pulse to the leads 33, 34, 35, those ones of the relays WSA, WSB, WSC conditioned by tube SD3, respond. Relay HAS is operated by HA and causes STA, TS and HT, to fall back. Wiper switching relay WS responds over wiper CW2 if WSA is operated with F, or if WSB is operated with S. When WT finally responds DR operates over a loop including wipers CW4 and SW5 or SW6 and connects up magnet LMA to drive the incoming selector. The wire leading to circuit BE is connected over wiper CW5 to SW3 or SW4 from which a pulse is reverted each time the selector passes from one group of outlets to another. Pulses from BE are passed over a wire 28 and, assuming relay F is up, gates MR9 and MR10 are held open, since sequence relays AA and BB are back, so that SD1 is stepped back to its O cathode and the next additional pulse via MR10 fires valve V18 to operate AT and connect test relay TA over wiper CW7 to wiper SW7 or SW8. TA responds to an idle outlet and stops the selector by connecting relay AR in series with magnet LMA, which when de-energized disconnects itself and reconnects AR in series with the magnet LMB of the seized intermediate selector. A contact of AR connects up AA to open the input gates MR12, MR13 to tube SD2 but, during the time it takes AA to respond, if WSB is operated, wiper switching relay BWS at the intermediate selector operates over wipers CW5, SW1 or SW2. With AA up AR is released and magnet LMB is operated to drive the intermediate selector which sends back pul