Patent GB-695497-A (GB)
Title: Improvements in or relating to automatic telecommunication exchange system
Inventor: BRAY FREDERICK HARRY
IPC: H04Q3/42
Filed: 1951-04-06
Abstract: 695,497. Automatic exchange systems. STANDARD TELEPHONES & CABLES, Ltd. April 6, 1951, No. 8035/51. Class 40 (iv). An automatic exchange comprises a plurality of registers and a common translator, means for continuously scanning said registers in search of a register requiring the services of a translator, and means responsive to the detection of such a register to disable the said scanning means and to interconnect the translator and that register to the exclusion of said other registers. The system is described first with reference to the schematic, Fig. 1. Each digit is received by a multi-cathode tube 1, which is then driven to home position by pulses which also drive the appropriate tube of the code and numerical storage circuits 2, 3 which thus register the complements of the dialled digits. When the three code digits have been received, the request tube 5 fires to signal the common translator which energizes a register ring counter 8 to hunt for the calling register. When the register is found the coincidence trigger pair 9 reverses to stop the counter and cause a tube 9A to send a 12 millisec. pulse to the register to step the first code storage tube through one complete cycle. This pulse also drives the first tube of the translation code acceptor 10, which is marked by the code storage tube when the latter passes zero position so that the code acceptor 10 registers the actual code digit. The process is repeated for the other code digits under the control of translation distributer 11. The acceptor 10 then fires a route tube 13 corresponding to the required exchange to set up the first translation digit in storage circuit 14, which is controlled by distributer 11 to send the complement of the translation to circuit 15 in the register. Circuit 15 then steps on to enter the true digit into circuit 16, after which the translator is released. Circuit 16 pulses out the first routing digit at dialling speed and is controlled by interdigital pause circuit 17. The translation distributer 18 in the register steps on to call the translator again, this time for the second translation digit and so on. Means are provided to indicate to the register when the translation is complete, whereupon the numerical storage tubes are driven in turn to home position to send out their digits. Use is made of multi-cathode tubes such as are described in Specification 692,415, [Group XL (a)]. Register, Figs. 2-7.-Entry of digits. Operation of relay A, Fig. 8, energizes B to connect H.T.+ to all multi-cathode tubes, which fire on their home cathodes. A follows the dialled impulses, C operating at the first break to operate BA, which locks up, connects all remaining H.T. supplies, connects earth to all points marked E and starts the translator circuit. Tube T9, Fig. 2, fires to fire T8 which then extinguishes T9. T8 biases gate tube G1 which fires at the next pulse on its cathode to step input tube MCT1 from its home to its second cathode. G1 also extinguishes T8. Subsequent dialled impulses repeat the process so that finally MCT 1 registers the first digit. Release of C at the end of the digit causes T6 to fire at its next cathode pulse to cause G1 to fire at succeeding cathode pulses to step on MCT1 to its final cathode, where MCT1 pulses G1 to step MCT1 to home position and fire T7 to extinguish T6. The output of T6 is also fed over lead L1 to the trigger circuits of gate tubes G3-G9, Figs. 4, 5. Since for the first code digit, the input distributer tube MCT2 is discharging on its first cathode, G3 is biased to respond to pulses from T6 so that the complement of the first digit is entered into storage tube MCT3. When MCT1 reached its final cathode it opened gate G2 to step distributer MCT2 to second position so that the second digit is entered into MCT4 and so on for MCT5- MCT9. Signalling translator. - When distributer MCT2 steps to its fourth cathode, it sends a pulse over lead L2 to fire translator request tube T10, Fig. 2, which signals the common translator, described in detail later, over lead L3. When the ring counter in the translator finds the register it returns a 12 millisec. pulse over lead L4 to gates G10-G12, G17, to drive tubes MCT3-MCT5, MCT10 through one complete ycle. As each tube reaches its last cathode it applies a pulse to the translator over leads L5-L7, L12, the time with respect to the beginning of the 12 millisec. pulse indicating the code digits and the number of the translation digit requested. As described later, the translator returns a D.C. pulse over lead L8, Fig. 7, the duration corresponding to the complement of the translation digit requested. This pulse, together with a +ve potential from the ring counter on terminal ACTRC opens the gate G18 long enough to enter the complement of the translation digit into translation tube MCT11. The translator then pulses lead L9 to fire release tube T11, so extinguishing request tube T10. Sending impulses to line. Tube T16 of interdigital pause trigger pair T15, T16, Fig. 6, is normally discharging, so that when T11 conducts and MCT11 is discharging over one of its cathodes 3-12, +ve potential is applied to T18, Fig. 7, which fires at the next coincidence of impulses on its anode and grid (10 i.p.s. with a make of 70 per cent on the anode and 1 millisec. 10 i.p.s. on the grid) to operate sensitive relay IR, which impulses the line at ir2, Fig. 8, and operates ID to open gate G19, so stepping MCT11 on at the rate of 10 i.p.s., T18 firing in synchronism therewith. When MCT11 reaches home position, T15 fires to extinguish T16, which cannot refire until slow-release relay ID restores. This fires the interdigital pause and T18 and IR cannot operate again until MCT11 receives another translation digit. Firing of T15 also energizes translation distributer control tube T5 which fires G17 to extinguish T5 and step MCT10 once. This fires tube T10 to request the use of the translator again. Controlled by the different positions of MCT10, the process repeats for the remaining routing digits. Digit cut-off. After the last routing digit has been sent, the register seizes the translator again but the translation pulse returned over lead L8 is of such a length as to step MCT11 once only to the second cathode to fire digit cut-off tube T17 which applies a pulse to the seventh cathode of MCT10 so that the discharge shifts to that position and pulses are sent to line from the numerical storage tubes in a similar manner, proof that the 2nd-4th digits have been received being given respectively by tubes T3, T4 conducting and by MCT2 conducting on its eighth cathode. When all digits have been sent, MCT10 steps to its eleventh cathode from which there is no output. When MCT9 reaches its 12th cathode to complete sending the last digit, it pulses tube T13 which energizes relay R to release the register. Calls to operator. Dialling "O" causes the input distributer MCT2 and the first code storage tube MCT3 to conduct at their second cathodes, to fire the O level tube T2, which pulses those cathodes of tubes MCT6-MCT10 appropriate to the O level translation and numerical distribution. The translation is then sent out in the manner of numerical digits without the use of the common translator. Dead code. If there is no translation for the code digits the register receives back the digit cut-off signal which steps MCT11 to its second cathode to fire T14, which operates FR to cause forced release. Digit absorption. Digit 1 is not used in first digital position and if it occurs there it is absorbed. If MCT2, MCT3 are in positions 2, 11 respectively, digit absorbing tube T1 fires to operate relay DA, Fig. 3, which releases BA, Fig. 8, to reapply dial tone. Code only translations. Code only tube T12, Fig. 3, is fired from the translator as described later so that as soon as the routing digits have issued, tube T13 fires to release the register. Translator, Figs. 9-14.-Ring counter. In the example the translator serves 33 registers- Tube T51 of ring counter trigger pair T51, T52 is normally conducting and causes the sequential opening of gate tubes G51-G53 which fire at cathode impulses under control of ring counter distributer T53-T55, which steps to a new position each time one of the ring counter tubes MCT51-MCT53 reaches home position. When the ring counter encounters a calling register, T52 fires, due to coincidence of calling potential on lead L3 and a +ve potential on lead L30 extending to the ring counter cathode for that register. T52 extinguishes T51 to halt the distributer and counter. Translation. T52 also fires T56, Fig. 10, T59, T61, T63, Fig. 11, and T71, Fig. 12. T56 extinguishes T57 and starts a 12 millisec. pulse on lead L4. T56 also causes gate tube G54 to step on tube MCT54 for a complete cycle, the end of the cycle extinguishing T56 to end the 12 millisec. pulse. Tubes T59, T61, T63 extinguish T58, T60, T62 to open gates G55- G57 until timed impulses on leads L5-L7 refire tubes T58, T60, T62 to enter the code digits on tubes MCT55-MCT57, and the remaining tubes are set to discharge on their 11th cathodes. Tube T71, Fig. 12, opens gate T64 to step on the translation distributer MCT64, Fig. 14, until the translation distributer in the register reaches its last cathode when an impulse over lead L12 fires T70 to extinguish T71 and step MCT64. According, therefore, to whether the register is asking for the 1st-6th routing digit, the tube MCT64 is stopped on the 12th-7th cathode. Coincidence of +ve potentials on the three leads connected to its trigger electrode from the cathodes of code acceptor tubes MCT55-MCT57, selects a route tube such as T73, Fig. 12, corresponding to the code digits. T73 fires then at receipt of a pulse when T65 is fired at the end of the 12 millisec. pulse. T73 sets up the translation on some or all of translation storage tubes MCT58-MCT63, the remaining tubes being left at 11th position for the purpose of digit cut-of