Patent GB-776772-A (GB)
Title: Improvements in or relating to telephone systems
Inventor: BAKER GEORGE THOMAS
IPC: H04Q3/42
Filed: 1954-02-15
Abstract: 776,772. Automatic exchange systems. BRITISH TELECOMMUNICATIONS RESEARCH, Ltd. Feb. 3, 1955 [Feb. 15, 1954], No. 4408/54. Class 40 (4). When the code digits of a called party's number have been entered into a register of a magnetic drum-type they are compared with permanent registrations representing possible code digits corresponding to the different changing bases until identity is found when the corresponding charging base is returned to the register to control the operation of the calling party's meter. General lay-out. The drum rotates once every 16<SP>2</SP>/ 3  m.secs and carries 6 tracks, each track being associated with the common equipment in turn under the control of pulses TW1- TW6. Each track has 20 register positions, each sufficient to deal with one call. Each register position has 14 blocks TY1-TY14, and each block 6 unit areas TX1-TX6. An auxiliary reading head PRH is located one register position ahead of the regular reading head RH on each track to pulse lead SLP or SLP according to whether it reads 1 or 0. Similarly the regular reading head pulses leap SLS or SLS. Registration of impulses. When a register is taken into use it examines the calling line once in each cycle of 100 m.secs., so that gate 31 operates electronic relay MAN if the line is looped to enter 1 in element TX4, TY14 by pulsing lead SBS. If the line is open MAN is not operated and lead MAN pulses lead SAS to enter O in the same element. If MAN does not operate during TX4, TY14 it is assumed that an impulse is being received and gate 34 registers the impulses in area TX5 or TX6 of TY14. Normally the entry is made in TX5 and MAN is operated by gate 35 to prevent entry also in TX6 but if dialling speed is high a second impulse can be detected and entered in TX6. MAN is operated by gate 35 to prevent open loop condition detected in two successive scans being interpreted as two pulses. Gate 36 releases MAN towards the end of every scan. When the auxiliary reading head reads 1 in element TX5 or TX6 of TY14 during the appropriate TW pulse then gate 37 operates electronic relay MAB in the common control circuit. If both TX5 and TX6 are occupied then gate 38 operates MBB also. Gate 39 removes the marking in TX5 or TX6 by pulsing lead SAS. The busy element TX2 of a digit store is changed to 1 only when a complete digit is stored there. The outputs from operated relays MAB and MCB and from non-operated relay MBB use gates 41, 42 to add 1 to the first incomplete digit store on the principle of reversing readings in turn until a 0 has been changed to 1, whereupon gates 43, 44 release MAB, MCB. If both TX5 and TX6 of TY14 have an entry then 2 is to be added. In this case MBB is also operated and gates 41, 42 are ineffective until gate 45 restores MBB after one step of the digit store. Inter-digital pause. If MAB is unoperated at the scan of TY1 it is an indication that no dialled impulse has been received since the previous scan, and gate 48 enters 1 in TX5, TY1. If no dialled impulse is received before the next scan, MCB operates and gate 50 enters 1 in TX6, TY1. MCB opens gate 51 to enter a busy mark in the last completed digit store by tending the mark all the busy marking elements until one is encountered bearing 0, whereupon gate 52 restores MCB. The mark in TX6, TY1 maintains MCB released in subsequent scans over gate 53. When an impulse of the next digit is received the markings in TY1 are removed. Abandonment of call. When the loop opens again MBB operates over gate 55. If this is a normal dialled impulse gate 56 restores MBB. If, however, the loop is still open after 200 m.secs., then the calling party has hung up and gate 49 operates MCB so that gate 57 cancels the entries in those sections of the register after TX5, TY1. Gate 58 pulses lead POF to initiate forced release and MAB, MBB, MCB are restored by gates 59, 60, 61 to clear the register. Metering. General. If the full complement of digits is received the register is retained until translation, transmission, and metering have been completed and the called party has answered. If metering is repeated at timed intervals the register is retained throughout the connection. Translation may be effected as described in Specifications 717,690 and 717,688. Metering. Details. A ring counter, Fig. 4, comprises toggle circuits 1-30 and is stepped on by a pulse on lead PL every 100 m.secs. Toggle 1 provides a start pulse and toggles 7, 11, 15, 19, 23, 27 provide metering pulses feeding gates 68-72 to give an output on lead TMM. Various toggles also feed gates 79-81 to give an output on lead TMT. The charge appropriate to the code digits dialled is selected from a library track in the same manner as the routing digits, as described in Specification 717,690, and entered in block TY2. The routing digits are then sent, as described in Specification 717,689 and the pulsing out equipment enters 1's into the whole of block TY13 to indicate that metering is called for. Gate 62 then operates MCE which is re-set by gate 63 if TY13 includes a 0. If TY13 is full, however, MCE remains operated and gate 64 operates MAE. When the called party answers, potential on lead PID opens gate 66 to enter 1 into the metering start control position TX1, TY14 as soon as the ring counter of Fig. 4 starts a new cycle. Untimed call. For untimed calls the metering change is entered in TX4, TX5 of TY2. For a mark in TX4 gate 70 opens to pulse lead TMM, gate 73 operates MBE. At block TY13 relay MBE opens gate 74 to pulse wire POI leading to the subscriber's meter which may be of the type described in Specification 723,148. MBE also cancels the entry in TX3-TX6 of TY13. MBE is restored at block TY14. For a mark in TX5 of TY2, gate 71 opens twice to pulse wire POI twice, in a similar manner. When the ring counter cycle.restarts the start control marking is erased by gate 77. Repeat metering. Calls with differing basic charges are differentiated by varying the intervals at which a single repeat metering operation occurs. Repeat metering is indicated by a mark at TX3, TY2 and the entries in TX5, TX5 of TY2 determine the repetition interval of 15 or 30 secs., 1 or 3 minutes. The signal for timed metering is that the block TY13 has been filled either by setting up the call or by the expiry of a period of time. The markings in TX3, TX4, TX5 of TY2 control the pulsing of lead TMT over gates 79-81 and the operation and resetting of MDE over gates 78, 91 and 82, 83, 86. MDE is operated 12 times during any metering period, some of the pulses TM19-29 from the ring counter being rendered ineffective according to the metering period selected. If MDE remains operated long enough, it adds 1 to the count in block TY13 in known manner. When a full count is reached in TY13, either by the setting up of a call or by the elapse of a metering period, MCE remains operated and prevents further operation of MDE until the necessary pulse has been sent to the subscriber's meter. The count in TY13 is then deleted and a new count starts if the call is still in progress. Multi-fee pulses at defined time intervals requires merely the separation of the storage areas, e.g. if TX4-TX6 of TY2 are used for storing multi-fee information then TX1-TX3 can be used for storing the timing information. Forced release. If the subscriber delays for more than 15 seconds between the dialling of successive digits then forced release takes place. The timing block TY13 is cleared each time the loop is interrupted and if it builds up to a full count the forced release operation takes place. When the loop is closed the auxiliary reading head operates MEE through gate 88. MEE is restored by gate 89 at each impulse and the reading in block TY13 is erased by gate 47 as previously described. MEE is also restored at the completion of dialling by gate 90. If MEE is still operated at TX3, TY12 when a TMT pulse occurs then gate 91 operates MDE to add 1 to the count in TY13. As long as MCE is unoperated due to TY13 not being full MEE can be reset by gate 92. When TY13 is full, however, MCE remains operated and gate 93 pulses lead POF to initiate forced release. Gate 94 then restores MEE. Specification 776,773 also is referred to.