Patent GB-190815470-A (GB)
Title: Improvements in Electric Selective Systems.
Inventor: PEARNE FRANK DILLAYE
Filed: 1908-07-21
Granted: 1909-02-25
Abstract: 15,470. Pearne, F. D. July 21. Selectors. -Relates to an electric selective system of the type in which a succession of line impulses is received by a combination of relays or switches and energizes one of a number of fical circuits, which may for example be the actuating-circuits of an electromechanical typewriter. The first impulse passes through one member of a group of main conductors and energizes a selective switch or set of switches in circuit with the corresponding member of a branch group of conductors, which are normally connected to the main conductors. At the cessation of the impulse, a transfer switch is actuated which transfers the connexions of the main group of conductors from the first branch group to a second branch group. The second impulse passes through one of the main conductors, which may or may not be the same as that which carried the first impulse, and energizes one of the. selective switches controlled by the second branch group of conductors. When this impulse dies away, a second transfer switch comes into action and transfers the main conductor connexions to a third branch group in readiness for the third impulse, and so on. The selective switches energized by the line impulses are maintained in their energized condition by self-holding circuits which are closed through secondary coils in their magnets, and their contacts are connected so as to control the final circuits which are to be selected from. For this purpose, each final circuit contains a number of breaks or gaps, and _each line impulse closes one of the breaks in certain of the final circuits. The number of breaks in each circuit is equal to the number of line impulses in a complete combination, and, when the full combination has been received, there is one circuit in which all the breaks have been closed and which is accordingly energized. The identity of this circuit is determined by the particular distribution of the successive line impulses among the members of the group of main conductors. The energization of the selected circuit actuates a typewriter key or other device, and also controls means by which all the switches and circuits are returned to normal. In the arrangement shown, in which sixty-four characters or signals may be selectively operated, each signal is made by three line impulses which are distributed successively to four main conductors 10. The latter may for this purpose extend to a distant transmitting station ; or, as shown in Fig. 1, they may be selectively energized through the agency of four polarized relays 15, which are connected in series in the line wire 14 and are constructed and combined so as to respond respectively to strong positive, strong negative, weak positive, and weak negative currents. These relays operate as follows :-A weak positive current attracts only the armature of the third relay, and a circuit is closed from one of the lines 10 through the armature and front contact of this relay and the armature and back contact of the first relay to a line 17 leading to a source of power 16. A strong positive current attracts the armature of the first relay, which through its front contact connects another of the conductors 10 to the power line 17 ; the armature of the third relay is also attracted as before, but this relay is now inoperative, its local circuit being interrupted by the separation of the armature of the first relay from its back contact. The fourth and second relays respectively energize the remaining two conductors 10 in the same way by connecting them to the power line 17, when weak and strong negative currents are received over the line 14. The first line impulse causes the following circuit to be energized : power line 17, combination of relays 15, one of the main conductors 10, through one of the back contacts of a differentially-wound transfer switch 19 to one of four branch conductors 11, thence through one of four locking-magnets 24 and four selective switches 39 in the same horizontal row to the return wire 26, and through one of the differential windings of the transfer switch 19 to the return power line 28. A locking-magnet 24 is thus energized and closes the following locking or self-holding circuit: power line 17, contacts 25 of locking-magnet 24, through secondary coils in the magnet 24 and in the corresponding horizontal row of selective switches 39 to the return wire 30, and through the second differential winding of the transfer switch 19 to the return power line 28. The double windings of the magnets 24, 39 are not differential, but are for the purpose of keeping a proper balance of resistance in the differential circuits of the transfer switch 19. The action of the locking-magnet 24 energizes the second differential winding of the transfer switch 19 before the previous energizing of the first winding has had time to take effect, so that the switch is not actuated as long as the line impulse continues, but. as soon as that impulse ceases, current is cut off from the first of the differential windings by the return of the relays 15 to normal, and the switch is actuated and held in position by the current which has been permanently closed through its second winding. The contacts of the switch are thereby moved so as to transfer the connexi ons of the main conductors 10 from the branches 11 to lines 10<a>, which lead to a second and similar transfer switch 22, through which connexions are normally made to a second branch group of conductors. These branches are connected to four locking-magnets 31, which are related to the transfer switch 22 in the same way that the locking magnets 24 are related to the switch 19, so that the second line impulse energizes one of the magnets 31 and a corresponding selective switch 47, but does not actuate the switch 22 until it ceases, whereupon the switch transfers the connexions of the conductors 10<a> from the second branches to a third branch group 13 connected to four magnets 61. The third line impulse energizes one of these magnets and thereby completes the selection of the final circuit. The selection takes place as follows :-Each of the sixteen selective switches 39 has four contacts controlling four of the final circuits. The first line impulse, as explained above, permanently energizes a particular horizontal row of four of these switches, while the second line impulse energizes one of the four selective switches 47. Each of the switches 47 has its four contacts connected in series with the corresponding contacts of the four switches 39, which are situated in a vertical row above it in the diagram. Thus the first and second line impulses limit the selection to the four final circuits controlled by one of the switches 39. The final selection is made by the third impulse which energizes one of the magnets 61, each of which has a single contact connected in series with the first, second, third, or fourth contacts of all the switches 39. The circuit closed by the energized magnet 61 passes through the magnet itself, so that the selected final circuit is maintained closed independently of the continuation of the line impulse. As soon as current flows in the selected circuit, the power circuit is broken by means of an electromagnetic switch 70, which is connected in the common return wire of all the selectable circuits, so that all the switches are de-energized and the circuits returned to normal. Or the switch 70 may effect the same purpose by breaking the self-holding circuits. The switch 70 may be mechanically opened by the operation of the typewriter or other controlled mechanism. Each locking-magnet 24 and its horizontal row of four switches 39 might be combined in a single instrument, but the arrangement shown allows greater speed of operation. A modification is described in which five successive impulses are distributed to two main conductors, enabling a choice of thirty-two final circuits to be made. The combination of line relays 15, described above, may be used with this arrangement, the contacts being connected so that a strong positive or weak negative impulse in the line wire energizes one of the two conductors, while a strong negative or weak positive impulse energizes the other, whereby positive and negative impulses may always alternate on the line to assist in clearing the static charge.