Patent GB-770617-A (GB)
Title: Improvements in or relating to electrical selecting systems
Inventor: HARRIS LIONEL ROY FRANK
IPC: H04Q11/04
Filed: 1950-12-21
Abstract: 770,617. Automatic exchange systems. POSTMASTER GENERAL. Dec. 8, 1952 [Dec. 21, 1950], No. 31140/50. Addition to 722,179. Class 40 (4). A registering device for use in a selecting circuit as described in the parent Specification comprises a closed circuit comprising a gate operative to emit pulses when it receives pulses from two sources, the output pulses being lengthened to form a D.C. signal which enables a second gate to pass pulses from a source, one of the pulse sources for the first gate being derived from the pulse output of the second gate. Setting of master register. On reception of marking pulses, control equipment, Fig. 2 (not shown), operates as described in the parent Specification to place enabling potential on lead 26 and to repeat the marking pulses to lead 28. The circuits of valves v48, v47, v43, v42 operate as described in the above Specification to produce an output pulse delayed by 1 Ás. (which equals the multiplex channel spacing) compared with the incoming pulse. Thus if the incoming pulse is coincident with the 9- and 11- phase pulses P1/9, P1/11 then the output pulse is coincident with pulses P2/9, P2/11. All the capacitors K4, K5 ... are normally charged over diodes v6, v7 ... by negative pulses P2/9, P3/9 ... to keep their upper plate at potential - V. When the condensers receive a positive pulse from v42 coincident with P2/9, capacitor K4 becomes charged to a potential - 2V which permits diode v4 to conduct and transmit the succeeding P1/9 pulses to the amplifiers v8, v9. The pulses then pass through a delay line d1 which delays them to coincide with P2/9 whence they are fed to condenser K4 to maintain the circulation. An 11-phase register operates similarly and the outputs of the two registers are combined in a coincidence circuit w7, w10 whose output is fed via amplifiers v16, v17 to the output lead 30. The output is also fed via transformer t1 and diode v18 to charge condenser K14 to a potential which disables v43 thereby preventing the register from being affected by any subsequent marking pulses. Since the master register is required to be operated by a single pulse the capacitor values are kept small and thermionic diodes having extremely high back-resistances are used so that the capacitor charges are readily maintained. Operation of slave register. The slave register is enabled by A.C. on leads 13a or 16a (as described in the parent Specification), which is rectified to charge condenser K29, thereby removing the back-biasing potential on rectifier w27. The pulse train on lead 30 is thus applied to the amplifier v17, v18 whence it is applied to the 9- and 11-phase registers. Coincidence between these pulses and the P1/9 pulses charges capacitor K16 and part of this charge is transferred to condenser K14 in the interval between the pulses to permit rectifier w15 to pass P1/9 pulses to the coincidence circuit w44, w45. The 11-phase circuit also operates similarly to pass a P1/11 pulse to the coincidence circuit and when the two pulses coincide a pulse is passed to the amplifier v17, v18 whence it is passed back to the registers to maintain the capacitor charges. In this case the use of dry rectifiers, whose back resistance is not as high, entails the use of larger capacitors so that several pulses incoming over lead 30 are necessary to establish the charge. After the required number of pulses have been transmitted to lead 11 condenser K28 charges positively to back-bias rectifier w28 to render the circuit independent of further pulses received over lead 30. Release. The pulses on lead 11, are used inter alia to suppress the marking pulse, so lowering the potential of lead 26. Rectifier w5 is thereby back-biased to cut off v8 and interrupt the pulse circulation in the 9-phase register. The 11-phase register releases similarly. The slave register is released at the end of the connection by the disappearance of the A.C. on leads 13a or 16a. Specifications 694,092; 707,379, 707,384, [both in Group XL (c)], and 770,616 also are referred to.