Patent GB-603789-A (GB)
Title: Improvements in or relating to telephone systems
IPC: H04M15/38
Filed: 1945-06-13
Abstract: 603,789. Automatic exchange systems. AUTOMATIC TELEPHONE & ELECTRIC' CO., Ltd., and BAKER, G. T. June 13, 1945, No. 14949. [Class 40 (iv)] In a multi-exchange system having automatic ticketing facilities at a central exchange, in response to the reception at an originating exchange of the called party answer signal, calling line identification is initiated and the speaking path between the calling and called parties is temporarily interrupted to provide a signalling path for the transmission of the calling line identification signals from the originating exchange to the exchange at which ticketing is to take place. Preferably the transmission takes place during the interval between the called party lifting his receiver and commencing conversation, and VF signalling currents are employed. As shown in Fig. 1 the ticketing equipment for both of the exchanges St. Mary's (SM) and Penrith (P) is centralized at Penrith, where all the information required is stored on a toll line relay set TRS-A, or TRS-B, according as the call originates at St. Mary's or Penrith. The calling lines are marked by connecting characterising signals to the metering wires via discs of non-linear resistance material which allow passage of the signals only. to engaged lines of which the metering wire is earthed. Two discs are used on each line, one being commoned for all the subscribers' lines in the 100- group having the same units digit, and the other for all subscribers' lines in the group having the same tens digit. Each digit is sent in the form of a 4-unit code, in which a pulse of 750 c/s. current represents a mark and absence of current a space, thus:- 1 2 3 4 5 6 7 8 9 0 W X Y Z WX WY WZ XY XZ YZ and a synchronizing pulse of 600 c/s. current is sent between units and between digits. Line marking equipment for 3-digit exchange, SM.LE, Figs. 2, 3. The tens marking wires are 1-0 in Fig. 2 and the wires for the first hundred group are 1-0 in Fig. 3. Since no thousands digit is involved, the marking wires in Fig. 2 are connected directly to contacts of the marking relays MW-MZ. A similar arrangement of wires to that of Fig. 3 is provided for the lines in each of the other hundreds groups. Considering a toll call originating at St. Mary's, battery reversal, on the reply of the called party, causes the auto/auto repeater AARS, Fig. 1, to test for battery on the S wire of the subscribers' line marking equipment. If this equipment is idle, wiper M1 in position 1 supplies the battery and AARS extends earth over the ST wire to bring up the start relay ST, 'followed by IG when the impulse springs 3IS next open; the latter relay connecting up the impulse springs 1IS, 2IS and 3IS, and connecting 750 c/s current to transformers TR 1-4. The next operation of 3IS steps M to position 2, brings up HM followed by IMA, IMB and corresponding relays in the other hundreds groups, so that all lines having the same hundreds digit are connected together and extended to the appropriate contacts of relays CW-CZ over strappings from terminals L. Operation of 2IS brings up CW and 750 c/s. current goes out to the resistance discs of all lines having the hundreds digits 1, 5, 6 and 7. The uni-selector M steps to positions 3, 4 and 5 to operate CX, CY and CZ in turn to complete transmission of the hundreds digit. When M steps to position 6, HM, IMA and IMB fall away changing over the circuits associated with the contacts of CW-CZ to common all lines having the same units digit and extend them to the appropriate relay contacts. Further stepping of M determines the tens digit in positions 6-9 by operation of MW-MZ and the units digit in positions 10-13 by re-operation of CW-CZ. In position 14 M removes the earth applied to the Z wire over M2, causing AARS to remove' earth from the ST wire, whereupon ST and IG fall away and M homes. Auto /auto repeater, AARS, Figs. 11, 12. On seizure IA pulls up to the loop, followed by IB, and IBB to complete the loop over the outgoing leads, and to busy the repeater. The release of IA to the first impulse brings up IC and CA, while IA repeats the impulses to the toll line relay relay set TRS-A. Battery reversal on the called party's reply brings up ID which extends earth over SI and lead S to SLME, and battery from an idle SLME operates SI, which connects up leads Z, PU and ST, extends earth over ST to start the line marking equipment, and disconnects the calling end of the connection from the outgoing leads, to which it connects the secondary of transformer LT, the primary of which is connected over a change-over contact of HS to a source of 600 c /s. current or to the metering wire of the calling line. Moreover, a separating pulse of 600 c/s current is sent to prepare the receiving equipment and HS operates to earth on PU from 1IS of SMLE to test the first marking position. The subsequent positions are then tested in turn and the identity signals passed to the main exchange, ID being released by SI which then holds over the Z lead, until the end of transmission, whereupon ID re-operates and, since ZI is now up, brings up IDD to reverse the battery connections over the incoming speak leads. Identification control relay set ICRS, Figs. 13, 14. The toll line relay set TRS-A is arranged so that the incoming +ve and - ve wires are extended through it over the hunting switch H to 2VFR, while in TRS-B the incoming +ve wire is earthed and the ve wire is connected to the metering lead from the calling line. In both cases relays AX and AY of 2VFR respond to the 750 c/s. and 600 c/s. signals respectively and the resultant earths are distributed over the storage relays in the toll relay sets and to the relays ACWACZ of ICRS. Connection of earth to the start lead ST (Fig. 13) by TRS-A on a St. Mary's call brings up AST and starts the switch H, AK pulling up to stop the hunting, followed by AKR which switches the line through to 2VFR and operates ACW. Relays AY, AB and ABR respond to the first 600 c/s. pulse, after which ACX pulls up, AB holding up for the duration of signalling due to the parallelconnected rectifier AMRA. If the first digit is 1, 5, 6 or 7 a 750 c/s. pulse is received to which AX responds, and extends earth over the W lead to operate the W storing relay of TRS-A. Relay AY responds to the next 600 c/s. pulse, releases ACW, and then falls away bringing up ACY. Relays ACW-Z continue to operate in pairs under control of AY, circuits being prepared successively over the W-Z leads, the operation or non-operation of AX to 750 c/s. pulses determining whether these circuits are closed. After operation of ACZ, the next release of AY re-operates ACW to repeat the cycle and on the next operation of AY ACZ falls away and removes the earth it had extended over the pulsing lead PU, thus stepping a distributer switch in the toll relay set to connect up the next group of storage relays. The cycle is repeated as long as signals are received, after which AB and ABR fall away. If ICRS is taken into use by a Penrith subscriber, TRS-B extends earth over the PU lead to bring up ALC which locks and tests for battery in SLME ; ASI pulls up, locks to the Z wire, releases ALC, earths the ST lead, connects up AHS, and connects 600 c/s. current to the - ve lead to 2VFR, after which operation is similar to that for St. Mary's calls. If the calling party's number includes the full number of digits, the toll relay set removes battery from the T wire to release AK and AKR. However, AOS is energized during the release time of ABR after AB has fallen away and if AKR is still up, AOS locks, and re-operates AB after ABR has fallen away. Relays AB and ABR then interact and pulses, are sent over the PU lead, during the release time of AB, to step the toll relay set distributer over the idle contacts, after which battery is removed from the T wire and pulsing stops. Toll line relay set TRS-A, Figs. 4-9. This set from which TRS-B differs only as noted above, comprises four-unit multiple relays of the type disclosed in Specification 591,655, [Group XXXVII], the components of which operate and lock individually to store the X, Y, and Z units of the code. On seizure, A, B and BB pull up to busy the set and A repeats the incoming pulses to the distant exchange and to CNM to step CN. Relays C, and CR operate to the first impulse and the release of C at the end of the first train applies earth tu wipers CN3 and CN4, the position of which determines which windings of the first storage relay DA will be energized over wipers D2-5. The release of CR steps the distributer D to position 2 and advances CN to position 13, the second digit then being registered in a similar manner. The relay set caters for a called number of eight digits and when D steps tu position 9, MD pulls up. If the calling party hangs up before completing dialling, MD maintains the busy earth, while the set is restored to normal. On the reply of the called party relay D operates and steps the distributor D to position 11, releasing MD and bringing up C1 which earths the start lead ST to associate ICRS. Relay H then pulls up to earth on the T lead, bringing up DD to reverse the .battery connections and open the speaking connection. The coded identity of the calling party is then received over leads W-Z and is stored on relays IAW-IAZ and corresponding relays. Stepping of D to position 14 releases C1 and H, and the set ICRS ; after which D self-drives to position 17. Operation of DD also starts the timing relay set TIMS (Fig. 1) by applying earth to the ST and D leads, these earths being removed by re-operation of MD when BB is released by the called party hanging up. The duration of the call is recorded in minutes and tenths of minutes on the three sets of relays TAW-Z, TBW-Z and TCW-Z. The timing relay set, which is described in Specification 593,61.9, tests the digit stored on these relays and controls their operation at appropriate intervals to increase that di