Patent GB-261481-A (GB)
Title: Improvements relating to switching devices for automatic and semi-automatic telephone systems
IPC: H01H67/12
Filed: 1925-08-20
Abstract: 261,481. Siemens Bros. & Co., Ltd., and Lambert, C. Aug. 20, 1925. Automatic exchange selectors.-In a selector in which the terminals are arranged in a straight line and a shaft carrying helically-arranged cams or wipers is first moved one or more steps longitudinally to select a group and then rotated step by step to bring the cams &c. successively into operation, the rotary movement is accompanied by a small longitudinal movement so that during successive revolutions of the shaft different sets of terminals are encountered. The arrangement of the terminals is such that the first choices in all groups occur first and are followed bv the second choices of all groups and so on. Thus in a 100-point selector, the lines are arranged in the order 11, 21, 31, - 01; 12, 22, 32, - - 02, &c. In a 200-point group selector, in which ten rotary steps perform a complete revolution of the shaft, the eleventh choices of all groups are arranged with the first choices, the twelfth with the second, &c. A 200-point private branch exchange connector is similarly arranged and will thus hunt automatically over groups of any size. In a 200-point ordinary connector, lines in the even and odd hundreds are arranged alternatively, lines in the latter being selected by the last two digits only, whilst if a number in the even hundreds is required an additional ten rotary steps are first given to the switch shaft. The selector may also be used as a line switch, when either all the lines in the bank may be tested in turn by rotation only or group-testing arrangements may be provided, the shaft being given one or more preliminary longitudinal steps to select a group containing an idle line. Fig. 5 shows a selector having twin shafts f each provided with cams g which act on teeth a - d d of continuous comb-members, the terminal bank with which the teeth a - - d are moved into contact consisting of bare wires A - - D interlaced through insulating members h, h<1>, as shown. An alternative arrangement of terminal bank, Fig. 1, for singleshaft selectors having four-nosed cams comprises zig-zag interlacing of the wires A - - D over insulating members of different sizes. In another arrangement, the wires A - - Dare replaced by zig-zag strips of varying width, and in a further modification, four spaced wipers engage projecting tongues on zig-zag terminal strips. Figs. 8 and 9 shows the operating means for a twin-shaft selector as shown in Fig. 5, the two shafts being coupled both as regards longitudinal and rotary motion. Longitudinal movement is produced by a ratchet 31 which engages a pinion 30 and operates the shafts 10 through gearing 29, 14. Rotary movement is produced by the ratchet 21, the engagement of the pinion 29 with the screw collar 14 causing the shafts also to move longitudinally. When the shafts reach the extreme right-hand position, pin 33 engages a pin 34 on a sliding frame 28 so that further rotation of the shaft causes pinion 29 to move from engagement with screw 14 into engagement with screw 13 and continued rotation restores the selector to normal. Alternatively, a quick restoration may be obtained through the gearing 31, 30, 29, 13 by further operation of the longitudinal magnet. Fig. 11 shows an arrangement for driving a single-shaft selector, the shaft having two oppositely-directed screw-threads which engage alternately with pinions 69, 70 according to the position of a sliding frame 65. One of the Provisional Specifications states also that the longitudinal and rotary movement may be produced by coupling the selector shaft to a continuously-rotating member, and that the longitudinal selection may take place in long and short steps first to select a group and then a sub-group, the selection of a sub-group also being possible by longitudinal movement of the contact comb-member.