Visual signalling systems utilising modulated light

Abstract

Abstract 1,018,921. Signalling by light. ASSOCIATED ELECTRICAL INDUSTRIES Ltd. Feb. 1, 1963 [Feb. 19, 1962 (2)], No. 6353/62 and 6354/62. Heading G1A. [Also in Divisions F4, G2 and H1] A signalling system embodies a sodium vapour discharge lamp as a light source and to increase the signalling distance a filter is utilized at the receiving end, the filter transmitting the monochromatic radiation of the lamp but blocking the other wavelengths of the atmosphere. The signalling is performed by varying the power input to the lamp to produce flashes and in order to maintain the vapour pressure when the lamp input is interrupted or at a low value the lamp is provided with heating means, these means being controlled such that the vapour pressure remains substantially constant irrespective of the value of the signalling input. As shown, Fig. 1, a sodium vapour discharge lamp 13 having electrodes 11, 12 is supplied from a D.A. source 14 modulated for signalling by a modulating transformer 18, the circuit including a stabilizing resistor 15, a current limiting resistor 16 and a start switch 17. The receiver includes a filter 25, photo-electric cell 21 and a resistor 23 applying voltage variations to an A.C. amplifier 26 energizing an earphone or loudspeaker 27. In another system, Fig. 2 which is a modification of Fig. 1, three lamps 28 are connected in parallel across an A.C. source 29 through normally-open contacts 30 of a contactor 31, the contactor operating coil being connected across terminals 29 through a signalling key 32. Each lamp has a stabilizing inductance 33 and connected in parallel with the lamp and part of the inductance is a capacitor 34 to produce surge voltages when the key 32 is operated. In order to maintain the vapour pressure in the lamps when the contacts 30 are open each lamp has a heating resistor 35 connected across the terminals 29 through back contacts 37 of the contactor 31. When the key 32 is closed contacts 30 close and contacts 37 open whereby the resistors 35 are connected to terminals 29 through a resistor 36. Further to facilitate discharge through the lamps the lamp electrodes are kept heated by secondary windings 40 of transformers 38 having primary windings 39 connected directly to supply terminals 29. A lantern, Fig. 4, for the lamp 50 has a parabolic trough shaped reflector 52 in a housing 51 having a window 53, the housing being carried by brackets 55 secured to a vertical support 57 through vibration absorbing pads 59. The lamp is particularly intended for marine signalling where the light source is to be visible through a wide azimuthal angle, e.g. 360 degrees and to this end a number of lamps 61 may be mounted in a common plane on a ship mast 60, Fig. 5. Instead of the single lamps 61 as shown in Fig. 5 each lamp may be replaced by a number of lamps mounted one above the other in ladder-like formation.

Inventors

• 👤 Harold R Ruff
• 👤 Frederick E Large

Bibliographic Details