Patent GB-223258-A (GB)
Title: Improvements in and relating to switching for multi circuit radio receivers
IPC: H03J5/00
Filed: 1923-04-17
Abstract: 223,258. Taylor, L. E., Taylor, E. A., Parkinson, W., and Bunting, R. S. April 17, 1923. Thermionic amplifiers and detectors tuning- apparatus, control of.-The tuning of the highfrequency circuits of a multi-valve set is simultaneously advanced step-by-step by switching-devices controlled by a single handle. When in the positions corresponding to the longer wavelengths, the switching-devices also serve to change over from tuned anode inter-valve couplings to resistance-capacity couplings. The switch may also vary the point of application of the reaction coil, and may serve to connect the low tension battery, and to connect and vary the high tension battery. A barrel, cylindrical, or like switch is preferably employed provided with a number of stepped metallic contacts engaged by rubbing springs When tapped inductance coils are used for tuning, the switch short-circuits the un-used portion. Fig. 3 is a diagram of a set embodying the invention, comprising two H.F. valves, a detector and two L.F. valves. The barrel switch is controlled by a graduated knob g, and carries a number of stepped contacts a - f (shown developed on the diagram) engaged by contact brushes, the numbers 1 - - 6 on the contacts indicating the six positions of the switch. The contacts a control the aerial tuning, the first position cf the switch putting a condenser K<1> in series with the aerial coils L<1>, L<2>. Position 2 cuts out the series condenser K<1>, and positions 3 - - 6 put the condenser K<1> - - K<4> in parallel with the coils L<1>, L<2>. Contacts b control the tuning of the secondary circuit, which is connected across the grid and filament of the first H.F. valve, the action of the switch being to insert at each step a portion of the coil L<4> in series with the coupling coil L<3>, and to short-circuit the portion not in use.. The circuit between the first and second H.F. valves is controlled by contacts c. For positions 1-4 this circuit is a tuned anode circuit L<5>, L<6>, C<5> of increasing wave-length. For positions 5. 6, the tuned anode circuit is cut out. and a resistance R<1> is connected between the valve anode and the H.T. positive. A condenser BC<1> passes on the anode impulses of the first valve to the grid of the second valve. The circuit between this valve and the detector valve G is identical with that alread described, and is controlled in the same way by contacts d. The detector plate circuit includes the primary coil of a L.F. transformer, and one or other of two reaction coils X<1>, X<2>, the circuits of the latter being controlled by the contacts e. In position 1, the coil X<1> is connected so as to react on the circuit between the first and second valves. For the positions 2-6, the coil X<2> is in circuit and reacts on the aerial. The contacts f complete the filament circuits, and connect the filaments to the H.T. negative terminal. These contacts may be stepped and arranged to vary the high tension applied to the valves. By subdividing the steps of the contacts c, d, and providing insulated portions, one or more of the valves may be cut out. Similar arrangements may be employed for controlling a number of associated circuits in a wireless transmitter.