Patent GB-399500-A (GB)
Title: Improvements in or relating to wireless receiving apparatus
IPC: H03J1/16
Filed: 1932-04-04
Abstract: 399,500. Condensers. BRITISH RADIO CORPORATION, Ltd. and BUNTING, R. S., 15, New Burlington Place, London. April 4, 1932, No. 9617. [Class 38 (ii).] A wireless receiver is provided with a control member which is capable of a step-by-step rotary movement in one direction, whereby it can be set to switch in selectively, fixed tuning condenser elements having predetermined capacities, by means of which the input circuit or circuits of the receiver may be tuned to known wave-lengths, and which when rotated in the other direction can control the volume of the output without affecting the tuning. Fig. 1 shows a switch-tuning device adapted for the aerial and two intervalve circuits of a receiver as in Fig. 8. There are three similar sets of stationary condensers 1, 2, 3 corresponding with the number of input circuits to be simultaneously tuned, and a fourth set 4 (the aerial condenser), all the condensers being insulated in a frame 5. One set of alternate plates in each similar set of condensers are connected together and to the tuning inductances, while the other alternate plates are connected either singly or in groups of two or more plates to insulated contact brushes 6. With each brush is associated a metal spider 8, having a number of radial arms corresponding to the number of wave-lengths to which the apparatus can be tuned, and, in addition, a pair of " dummy" arms. The spiders are mounted on a spindle 10, supported in bearings 12, 13. The arms 9 of each spider, which each have a contact adapted to engage a brush 6, are staggered so that according to the angle of rotation of the spindle 10 from its inoperative position, one plate only or a predetermined group of plates in each set of condensers,'is connected in circuit. The end of the spindle 10 adjacent to the control panel has one or more toothed wheels 15, 16 geared by chains to an indicating device or another switching mechanism as subsequently described. The wheel 16 has a projecting pin 17, adapted to coact with a pin 22 projecting from a sleeve fixed to a spindle 19. This is supported on a panel 20, and has an operating knob 18. A contact brush 23 is carried by a collar 23a, mounted on and frictionally connected to the spindle 19, the brush engaging with a resistance coil 24. Pawl and ratchet mechanism 25 is provided at the opposite end of the spindle 10, to allow it to rotate in one direction only. Thus, when the knob 18 is turned in one direction, the pin 22 engages the pin 17 and rotates the spindle 10 for the purpose of tuning by switching-in the condenser plates as described. -Rotation of the knob in the other direction leaves the spindle 10 stationary, and effects movement of the contact brush 23, for volume control. Two separately insulated spiders are associated with the condenser set 4, which is divided into two groups having small and large values of capacity respectively. The spiders enable either of these to be connected directly to the aerial as required. A vernier condenser 39 is also arranged as shown in Fig. 8. Specification 295,849, [Class 38 (ii), Electric currents, Converting &c.], is referred to