Patent GB-1099842-A (GB)
Abstract: 1,099,842. Tuning arrangements. INTERNATIONAL STANDARD ELECTRIC CORPORATION. Dec. 9, 1965 [Dec. 12, 1964], No. 52286/65. Heading H3Q. In a remote tuning arrangement for a receiver the tuning motor is controlled by light-modulating means which affect the illumination of a photo-electric element. In the simplest arrangement (Fig. 1) a motor-driven disc 1 carries adjustable marks or pointers 3 which pass between a photo-cell 4 and an illuminated slit 5. When a mark comes opposite the photo-cell the motor stops, but can be restarted by optically deflecting the light source in 5 or by momentarily switching on an auxiliary light source, e.g. by a push-button or by a charged capacitor (Figs. 2, 3, 3a, not shown). By suitably shaping the marks the speed of the motor can be reduced in advance of the actual tuning point. The marks can be reflecting instead of opaque, and the motor is then restarted by momentarily dimming the light (Fig. 4, not shown), using a relay or electronic switch to control the motor. To achieve automatic return from the last mark to the first the disc 1 (Fig. 6) carries a reflecting stripe 20 which illuminates an auxiliary photo-cell 18 from a separate light source 19. The last mark 21 has a reflecting piece 22 which reflects light from the lamp 5 on to the photo-cell 18, whose change in resistance initiates backward drive of the motor. The stripe 20 maintains this condition until the first mark 23 is reached, as this mark has an extension which interrupts the stripe 20. The lamp 5 is switched off during this backward running so that it will not produce an interfering voltage from the main photo-cell (not shown) between the marks 3. The arrangement of Fig. 9 can be used for tuning to a definite position without stopping at intermediate positions. A cylindrical reflector 32 is divided into separate light-proof compartments 33 which can be covered by light-impermeable strips 34. A lamp is provided in each compartment so that bright-dark horizontal transitions 37 can be produced at any desired vertical position by adjusting the strips 34. A continuous band 35 with horizontal slots 36 is driven synchronously with the tuning drive. When one of the lamps is lit, e.g. by a pushbutton, the band 35 runs until a slot 36 coincides with a transition 37 and allows light to fall on the photo-cell 24 thus stopping the motor. The rear side of the housing can have an indication of the tuning setting. If the direction of the motor depends on the sequence light-dark or vice versa, any overshoot will produce reversal of the motor back to the correct position. This can be achieved by including the motor in the diagonal of a bridge circuit (Fig. 7, not shown) of which the photocell forms one arm. The bridge will be balanced, and the motor will stop, at medium illumination of the photocell, i.e. when the illumination is partly bright and partly dark. The balance point can be made sharper by including transistors in the bridge (Fig. 8, not shown). The lamps can be operated via remote control lines or a radio link. The light and dark marks can be along a linear scale. The lamp and photo-cell may move along the scale or be fixed. The light and dark marks can be replaced by polarizing filters or colour filters