Patent GB-791855-A (GB)
Title: Improvements in or relating to electrical signalling systems particularly telephone or like systems
Inventor: MANN VICTOR EDMUND
IPC: H04Q3/42
Filed: 1954-11-19
Abstract: 791,855. Automatic exchange systems. BRITISH TELECOMMUNICATIONS RESEARCH, Ltd. Nov. 8, 1955 [Nov. 19, 1954], No. 33617/54. Class 40 (4). A high-speed register of the magnetic drum type is arranged to provide quick switching- through of special calls such as 0 and 999. If the first digit dialled involves a special code then an electronic relay is set up. If the subsequent digits are inconsistent with the special code the relay is restored. On the other hand if the relay is still operated when appropriate tests have been made the call is switched through without delay. Fig. 1 shows the reading head RH, writing head WH and associated circuit for one track of a magnetic drum. Six such tracks are associated in turn with the common equipment of Fig. 2, each track comprising 20 registers. Each register has 14 blocks TY1-TY14 with 6 unit areas TX1-TX6 each. Block TY1 is used for detecting an interdigital pause. Code digits are initially entered in blocks TY6-TY8 with the numerical digits in TY9-TY12 Translations are later stored in TY2-TY8. Block TY13 is used for call timing and forced release and TY14 for detecting a change in the condition of the calling line. Detection of dialled impulses. When a line is looped a signal on lead PIA coincides with time pulses TX3, TY14 to operate electronic relay MAN over coincidence circuit 1. MAN marks lead SBN to enter 1 in element TX4, TY14 over circuit 2. When the loop is open MAN is unoperated and its inverse output MAN marks lead SAN to enter O in this element over circuit 3. If a dialled impulse is being received MAN is unoperated at time TX4, TY14 and circuit 4 registers an impulse in TX5 or TX6 of TY14, the latter being used to store a second impulse if the dialling speed is unduly high. MAN is released at TX1, TY14, circuit 5, in each scan if it has not released earlier due to excessively high impulsing speed. Transfer of impulses to digit stores. The common equipment of Fig. 2 is switched sequentially to each of the tracks so that it is associated with each register one each 100 m.secs. The common equipment transfers impulses stored temporarily in TX5 and TX6 of TY14 to the appropriate digit store TY6-TY12 of the same register, and also detects the end of an impulse train. When an auxiliary reading head positioned one register ahead of the normal reading head detects 1 in element TX5 or TX6 of TY14 it energizes lead SLP and operates electronic relay MAB over circuit 7. If marks occur in both elements circuit 8 operates MBB also. The marks in the temporary store are removed at the same time by circuit 9. Circuit 10 operates MCB when the first store in the group TY6-TY12 is reached in which the " registration complete " element TX2 is unmarked. If MAB alone is operated 1 is added into the selected store over circuit 11 or 12 on the binary principle by reversing all markings until a 0 has been changed to 1, whereupon the first signal SLS releases MAB and MCB over siccuits 13 and 14. If MAB and MBB are both operated 2 is added, the circuits 11 and 12 being ineffective until circuit 15 has restored MBB at time TX3, i.e. when the first binary shift has been made. After the transfer has been effected MBB operates over circuit 16 and energizes circuit 17 to cancel any metering marks in section TY13. The above process repeats for subsequent impulses until the end of the digit when MAB remains unoperated during the passage of section TY1 of the following block. Thus if no impulse has been received for 100 m.secs. circuit 19 enters 1 in element TX5, TY1. If no impulse is received during the succeeding 100 m.secs. MCB is set up by this mark over circuit 20, enters 1 in TX6, TY1 over circuit 21, and enters a busy mark in the last completed digit store over circuit 22. Simultaneously circuit 23 restores MCB which remains thus in subsequent scans under the control of circuit 24. When the interdigital pause ends, so that MAB operates, circuit 25 cancels all markings in section TY1. Release. When the calling subscriber hangs up before completing the call the scan recognises the condition as a line break longer than a normal impulse. The auxiliary reading head enters 0 in TX4, TY14 to set up MBB over circuit 26. For a normal impulse MBB is reset by circuit 27 when 1 has been entered in the temporary store. If, however, MBB has not been reset MCB is operated by circuit 20 at the next scan and the operated relays MBB, MCB together with the unoperated relay MAB combine in circuit 28 to cancel all sections of the register later than TX5, TY1. When TY13 is being scanned circuit 29 signals over wire POF to disconnect the register from the calling line. The electronic relays are released before the scan of the next register on the track. If the full complement of digits has been received the register is retained until the translation has been sent as described in Specifications 717,688 and 717,690. Call to operator. When a subscriber dials 0 the resultant impulse train is stored in TX4 and TX6 of TY6. The mark in the TX4 element energizes MAA, Fig. 3, over circuit 32. If the TX6 element is 0 the number cannot be 10 and circuit 33 resets MAA. Therefore if MAA remains operated after section TY6 has passed then the first digit is 10 or, under fault conditions, more than 10. Confusion between a dialled digit 10 and a translated digit 10 is prevented by a " translation complete " mark in TX2, TY14 which resets MAA over circuit 34. As an alternative to the above system MAA is operated if 0 is found in TX1, TY6 and is reset if there is no registration in TX4 and TX6 of TY6. In either case MAA is reset before or at the end of the register, in the latter case over circuit 35. If MAA is operated at the end of the register, MBA is set up over circuit 36 to mark TX1, TY6 over circuit 37 whereby pulsing out takes place. If the digit 0 is translated into a number other than 10 the markings in TX (3-6), TY6 are erased by circuit 38 and the translation entered over circuits such as 39, 40. MBA enters a " translation complete " mark in TX2, TY14 over circuit 41 and resets itself over circuit 42. Absorption of a single impulse. If a first digit of 1 is received it is recorded in TX3, TY6 to operate MCA over circuit 43. If markings occur in any of the subsequent elements of TY6 circuit 44 resets MCA. MCA is also reset over circuit 45 in pulsing-out conditions or over circuit 46 if there is no busy mark in TX2, TY6. If MCA remains operated until TX3, TY6, the markings in TX2 and TX3 of TY6 are cancelled by circuits 47, 48. Circuit 49 then resets MCA to complete the absorption of the single impulse. Emergency dialling 999, Fig. 4. If 999 is dialled 1 is entered in elements TX3 and TX6 of each of the blocks TY6, TY7, TY8. The first mark operates MDA over circuit 50. If the mark does not appear in any one of the other elements concerned MDA is restored by circuit 51 or 52. The identity of the 9 in the last store is dependent also on the presence of a busy mark and the absence of this mark energizes circuit 53 to restore MDA. Similarly a " translation complete " mark energizes circuit 54 to restore MDA. Prior magnetic drum systems are represented by references to Specification 717,689; Specification 791,856 also is referred to.