Patent GB-565174-A (GB)
Title: Improvements relating to signalling apparatus
IPC: H04B10/11
Filed: 1940-09-30
Abstract: 565,174. Signalling by visible signals. ALDIS, A. C. W. Sept. 30, 1940, Nos. 14727 /40, 9835 /41 and 10118 /41. [Class 118 (ii)] [Also in Groups XXXIX and XL] A signalling apparatus is adapted both to observe a distant station and to project a beam of light to that station, and is provided with light-deflecting means which can be moved to either of two positions for enabling the station to be observed or the beam of light to be projected. The apparatus may be provided with a light-responsive device adapted to be actuated by light received from the distant station, and also with means for modulating the projected beam of light so that it can be converted into sound vibrations at the distant station. The apparatus comprises a tubular body a, Fig. 1, having at one end an object lens band at the other end a housing for an incandescent electric lamp d. At an intermediate point, the body a is provided with a tubular branch e fitted with an eyepiece g, erecting lenses i and a graticule m. A light-deflecting device, such as a prism j, is mounted within the body a in such a position that light received by the lens b can be deflected through the lenses i and the eyepiece g. The prism j is carried by a slide v which can be moved to either of two positions, one in which the lenses act as a telescope to view the distant station, and the other in which the prism is clear of the beam of light passing from the lamp d to the lens b. The light from the lamp is concentrated by a condensing lens p on to a small aperture o, in a stop n, at the focus of the object lens b, and in the side of the stop near the lamp a shutter is provided which is movable under the control of a manually-operated plunger, or an electromagnet controlled by a signalling key, to transmit signals to the distant station by interrupting the beam of light projected by the lens b. The slide v may be provided with a contact member that makes and breaks the circuit of the lamp d and prevents the lamp from being lighted when the prism j is in the observing position. Colour screens 25, mounted in a movable holder, may be arranged between the prism and the lens b, and means provided for bringing them into the path of the projected light when required to impart colour to the beam. The apparatus is supported at its ends in bearings 35 to enable it to be turned to bring the eyepiece to a position convenient for the observer. The apparatus may be adapted to receive signals without requiring the observer to remain on watch. For this purpose, a chamber containing a photo-electric cell is mounted on any convenient part of the body a and a lightreflecting member, such as a prism, is so mounted within the body that it can be moved to and from a service position on the optical axis of the telescope. When in the service position, light signals received by the lens b are deflected through a small aperture on to the photo-electric cell and are converted into audible signals or operate a visible indicator or recording device. The apparatus may be adapted to transmit oral communication. This is effected by means of a vibratory light - reflecting or refracting element capable of oscillating in response to a mechanism actuated by sound vibrations and modulating the beam of light that is projected through the object lens b, the variable beam thus produced being converted into sounds by the receiving instrument. The element may be actuated by a valve oscillator under the control of a signalling key. Preferably, the element 48, Fig. 15, is arranged close behind the small aperture o and is secured to a spindle 51. A steel bar 52 is secured at right angles to, and extending from opposite sides of, the spindle, and its ends are situated between polepieces 54 on a permanent horseshoe magnet 55. Rubber cushions 53 support the bar and spindle while permitting them to vibrate about the axis of the spindle. Bobbins 59 wound with fine wire surround the ends of the bar 52 and are connected to a microphone. With this construction, an electric lamp and a condensing lens are enclosed in a housing secured at one side of the tubular body a, and the light from the condenser passes through apertures and falls on the element 48 by which it is reflected through the aperture o to the object lens.