Patent GB-806069-A (GB)
Title: Improvements relating to automatic telephone exchanges and like selective systems
Inventor: WARMAN BLOOMFIELD JAMES
IPC: H04Q3/42
Filed: 1956-02-27
Abstract: 806,069. Automatic - exchange systems. SIEMENS EDISON SWAN Ltd. Feb. 6, 1957 [Feb. 27, 1956], No. 6011/56. Class 40 (4). In an arrangement for coupling registersenders as required to a common translator, a register-sender is coupled to a translator during two of a succession of " transfer periods," during the first of which the register-sender feeds an exchange code to the translator and during the second of which the translator feeds the translation to the register-sender, and the intervals between the transfer periods are used to scan the register-senders to find one which requires the use of the translator. Such a register-sender is thus detected during a scanning period, connected during the immediately succeeding transfer period for exchangecode transfer and connected again during the following transfer period for transfer of the translation. The same transfer period may be used for reception of an exchange code from one register-sender and the emission of the translation of an exchange code received from another register-sender during a preceding transfer period. Fig. 2 illustrates a pulse P1 occupying the transfer periods, a pulse P2 occupying the scanning periods and a pulse P3 coincident with P1 and the latter half of P2. Each register-sender has associated therewith a circuit, as shown in Fig. 3. When a registersender requires to be coupled to the translator it applies potential to lead x to fire V10. The resulting rise in potential on lead y is applied to one of 30 leads L1 ... L30, Fig. 1, each associated with a different register sender. Scanning is effected by means of three multicathode discharge tubes VI, V4, V7 whose auxiliary grids g1, g2 are driven during P2 pulses for effecting the stepping of the glow along the cathodes. It is arranged however that the left-hand half of one of the tubes V2, V5, V8 is always conducting to restrict the stepping of the glow to one tube. Thus with V2 conducting, its rise in cathode potential inhibits the stepping of V1, V7, so that only V4 steps. When the glow reaches the last cathode of V4, this strikes tube V5 which extinguishes V2. Tubes V1, V4 are now prevented from stepping and V7 steps to its end cathode, whereupon V8 strikes to allow V1 to step and so on. Preferably at least a complete scan is completed during a P2 pulse. Stepping ceases in any case at the end of the P2 pulse and is resumed at the beginning of the next P2 pulse. If a request potential exists on one of leads L1 ... L30, e.g. L1, when the glow reaches the first cathode, the resulting pulse over condenser C101 superimposed on the potential of L1 causes rectifier Rf 101 to conduct to fire the left-hand side of tube V3. The resulting rise of its cathode potential inhibits the stepping of all the tubes. The combination of the rise of cathode potential of tube V3, and the rise of potential of the first cathode of tube V1, causes the output of a gate comprising rectifier Rf 201 and resistance R201 to rise in potential, to cause the striking of a tube OV1 corresponding to the register-sender in question. The anode of tube OV1 is energized during the P3 pulse, the trigger of OV1 being arranged to hold its striking potential at least until the beginning of that pulse. The anode of V3 is energized by a P2 pulse so that when this terminates, V3 is extinguished and scanning is resumed as previously described. Striking of OV1 raises the potential of lead OL1 which is connected to lead z, Fig. 3, corresponding to the registersender in question. This fires tube V12 for the duration of the P1 pulse, the cathode output on lead 01 being arranged to open an electronic gate (not shown) connecting the registersender to the input of the translator. The output from the cathode of V12, slightly delayed, is also used to cause V13 to strike for the duration of the succeeding P2 pulse; and the cathode output of V13, slightly delayed causes V14 to strike for the duration of the succeeding P1 pulse. The cathode output of V14, on lead 02, opens an electronic gate (not shown) for connecting the output of the translator to the register-sender.