GB416435A - Improvements in or relating to means for controlling and indicating the setting of apparatus for modulated carrier wave reception - Google Patents

Abstract

416,435. Wireless receivers. ELECTRICAL & MUSICAL INDUSTRIES, Ltd., Blyth Road, Hayes, Middlesex, and MITCHELL, F. A., 18, Cornwall Gardens, South Kensington, London. March 14, 1933, No. 7776. [Class 40 (v).] In a system for tuning a modulated carrier wave receiver, such as a wireless receiver, from a remote point, the controlling means comprises a conducting drum, provided with an insulating strip running at an angle, to the axis of the drum, co-operating with brushes individual to the selection required, the brushes being adjustable in a direction at right angles to the axis of the drum. The brushes are connected to individual sockets on a plug board, which may be in the form of a map so that when a plug is inserted in a selected socket the drum rotates and tunes the receiver to the frequency of the selected station. If the selected station transmits on long waves the insertion of the plug controls the opening of contacts which norrr.ally short the longwave coils. An auxiliary control enables fine tuning to be effected and a volume control is fitted on the main panel. Additional sockets may be provided on the selecting panel for switching off the set and for changing over to gramophone reproduction and when the apparatus is in this last condition, the auxiliary fine tuning control can be used for record changing. The output is muted whilst selection is in progress. The description is identical with that in Specification 416,775, which is divided out of this application but claims other features. The general arrangement of the set panel is shown in Fig. 2. The tuning condenser 102 can be controlled by knob 103, the setting being indicated at 112. The condenser shaft 81 can also be driven by motor 70. The shaft 81 carries drum 119 which comprises two conducting surfaces 83, 84 and an insulating strip or groove 82 which runs at an angle to the axis of the drum as shown. Two sets of brushes cooperate with the drum and are mounted as shown in Fig. 5. The brushes can be adjusted by screws 1A, 2A, &c. which are staggered to facilitate adjustment, so that when the condensers are correctly set the appropriate brush is contacting with the insulating strip 82. The brushes are connected to appropriate studs 2S, 3S, &c. wiped over by wiper 94 controlled by knob 93 and to appropriate sockets 4E, 4B, &c. (Figs. 1, 7 or 12). When the wiper 94 engages a contact the motor 70 is started and drives the condenser shaft until the circuit is broken by the appropriate brush. If the station transmits on a long wave, wiper 95, which is coupled to 94 contacts with 34P (Fig. 1) and releases relay 104 to remove a short circuit from the long wave coils. If the remote indicator is to be used the knob 93 is turned to the remote position and then insertion of plug 63 in the appropriate socket selects the appropriate brush and controls the setting by connecting the plate 53 with the appropriate socket. The plug must be pressed down to start the motor so that the pin 62 (Figs. 10 and 11) is moved against spring 64 and contacts with plate 52 but once the motor has started the circuit is maintained by contacts 31S, 44S controlled by a friction clutch 76 on the motor shaft. Contacts 45S, 46S controlled also by this clutch serve to mute the receiver during tuning. When the motor stops the clutch is forced back by the contact springs to open the contacts. The motor is reversible and if it overrides the selected station the motor steps back. The insulating zone is provided with ample clearance for the brushes and consequently when the motor stops, the set may not be accurately tuned. If now the button 59 or if the control is local the button 99, is depressed the motor rotates until the brush reaches the edge of the insulating segment, in which position the station is correctly tuned. If the station is a long wave one, insertion of the selecting plug moves plate 51 (Fig. 1) to the left (the long wave stations having holes in this plate out of center with the holes in plate 54) opening contacts 34S, 36S to release relay 104 to cut in the long wave coils. Insertion of the plug in the off position drives the drum to an extreme position where contacts 40S, 41S and 43S are open to cut of the mains from the receiver, while, in the "GRAM" position, the drum is driven to the other extreme position in which cam 86 closes contacts 41 S1 and 43S to switch on the gramophone motor and connect up the pick up. In this position the control button 59 may control the record changing device. The muting switch may be mounted on the condenser shaft. A volume control 57 and a pilot lamp 56 are also provided on the panel. An alternative arrangement, in which an ordinary wander plug is used on the control panel, is also described. The Provisional Specification states that the wander plug may carry a lamp adapted to light up when the plug is inserted in a socket and that a press button type switch may be provided at each position on the map instead of a movable plug.