Signalling Lamps

©RN Communications Branch Museum/Library

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20 inch Signalling Projector Light

  The lamp is fully automatic and will burn steadily at all angles of elevation and maintain its focus for approximately 50 minutes (the life of a pair of carbon filiments). When in correct focus the lamp will give a beam of 2.6 degrees divergence and maximum candle power of 45 million. For signalling purposes the lamp can be moved 0.4 inches nearer the mirror and will then give a beam of 4.5 degrees divergence and about 10 million candle power. The ventilation of the projector is provided by an exhaust fan mounted at the top of the barrel. A rectangular steel duct arranged about three inches above the arc, and connected to the suction side of the fan, removes the fumes from the barrel. The reflector is cooled by means of a fish-tail nozzle at the bottom of the barrel, the lower part of this nozzle being open to the atomosphere. The lamp is approximately in the correct focal position when the engraved line on its baser co-incides with the engraving marked "F" on the lamp runner of the projector. In this position the positive crater (forward end) should be at the focus of the mirror, from the front surface of the reflector. This should be checked by using a steel distance rod exactly equal in length to the crater distance. This steel rod should be kept on or nerar the projector. When signalling the rear door of the projector should normally be left with the position marked top uppermost, but this door can be rotated until the most comfortable position for hand grip and shoulder rest has been obtained. The operating handle is capable of adjustment in three different positions to sit individual signalman. The shutter should be operated gently by means of light pressure of the fingers. Any strong pressure on the operating handle produces noise and may cause damage to the mechanism.

15 inch Dual Purpose Signalling Projector

  The 15 inch Dual Purpose Signalling Projector is designed for use either as a hand operated signalling projector or as a utility searchlight. It will replace the 10 inch Signalling Projector and the 20 inch Combined Searchlight and Projector. In this equipment a quartz iodide lamp is used instead of a carbon arc as the source of light, thereby achieving greater reliability with reduced maintenance. The projector can be operated at either of two power levels. For signallin gat normal ranges the lamp power is a nominal 400 Watts with a lamp life of approximately 100 hours. When the signalling range or weather conditions require it, or when the projector is being used for search purposes, a boost switch enables the lamp power to be increased to 800 wattes. Int his operating mode the life of the lamp is drastically reduced.
  Should the operational lamp fail for any reason, an alternative lamp fitted in the projector can be brough into action simply and rapidly by means of a change over handle. The projector is mounted on the standard spigot used for 10 inch signalling projectors.

!0 inch Signalling Projector and 10 inch Lightweight Signalling Projector

  In the 10 inch Signalling Projector the barrel is mounted in U-shaped tubular support arms which are fitted with a handle on each side for lifting purposes, and the design of the pedestal and barrel affords a high degree of accuracy of training and ease of manipulation. The signalling shutter is incorporated inside the front of the barrel and a front ring secures the glass in position outside the shutter. The glass reflector is fitted centrally in the back cover. The lamp when in focus has adispersion of 6 degrees giving a peak candle power of one million. A range of ten miles in bright sunlight with good weather may be expect in home waters.

  The 10 inch light weight 10 inch Signalling Projector was introduced into service for coastal craft, inshore minesweepers, auxilliary minesweepers Type B, seaward defence craft, fast patrol boats and other small craft as may be approved. It is designed for 24 volt supply and has been modified for Tungsten Halogen 24V/250W lamps.

5 inch Hand Signal Light - Aldis

  This is a modified Aldis which incorporates a watertight switch in the handle and is primarily for use in submarines and small craft where a more weatherproof light is required.

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  These signal lights give a peak candle power of 150,000 with a divergence of 6 degrees. A range of 5 miles in bright sunlight in good weather may be expected in home waters.

  The pistol grip is fitted with two triggers. The lower trigger is the switch handle which, when pressed, energises the lamp. This trigger should always be kept pressed when signalling. The upper trigger actuates the cylindrical signalling shutter.

Intermediate Signal Light

  The Intermediate Signal Light has the handle attached to both the front and rear portion of the body and it hinged at the bottom end of the handle. It has a dispersion of 10 degrees when using a pre-focus type lamp of 12V, 12W.

  The candle power of the beam can range from 2 to 2,000 and can be varied by means of a regulating switch fitted on the back of the lantern. The signal light is operated by a trigger key in the handle which works a cylindrical shutter covering the lamp and it can be a 12 unspillable battery.

Battery Operated Portable Signal Light

  These signal lights are designed for inter-ship communication between light craft in peace and war; and making special coloured signals requried during night torpedo attacks.

  The signal lights are constructed in two separate portions; the lower on containing the battery, the upper on containing the lamp and the actuating mechanism. The battery is thus kept clear of the mechanism, the electrical connections being made through rustless steel spring plungers. The signal light uses a 2.5 volts, 0.75 amps and can house a spare lamp in the handle.

  A rotating shutter is secured in friont and is fitted with four glass shades, namelyl; clear, neutral, red and green. Any of these shades can be brought in fron of the lamp by rotating the shutter. They are held in position by a spring click device. The approximate working ranges are one mile with the clear glass and half a mile with the remainder. The dispersion is approximately 18 degrees.

Lightweight Daylight Signalling Light (LDSL)

  The LDSL embodies a 3kW tungsten lamp of special design, capable of being flashed at 12 wpm and can be used on either a.c. or d.c. supplies with the appropriate alternative ancillary items (ventilation unit and control panel etc). Each LDSL has a horizontal divergence of 200 degrees and a vertical divergence of plug or minus 10 degrees.

WWII SIGNALLING TORCH

See also Lord Mountbatten's Signalling Lamp

Visual Signalling Special Transmitters

Infra-Red Signalling Lamps

  A V/S Special transmitter is essentially a lantern, similar in general design to an ordinary V/S lantern, fitted with a screen which prevents the passage of almost all the visible light radiated from the source and allows only the short-wave infra-red radiation t? be transmitted. Light from the transmitter is visible, for short distances only, as a deep red glow; the infra-red radiation cannot be detected without the aid of a special V/S Special receiver.

  A V/S Special receiver is an instrument that converts an image, formed by infra-red radiation received from the transmitter into a visible image. When a V/S Special transmitter is viewed by means of a V/S Special receiver, a spot of light is seen in a manner analogous to that in which light is.seen when a source of visible radiation is viewed by the unaided eye.

  As V/S Special transmitters radiate energy only in the near infra-red, which cannot be detected by the unaided eye, V/S Special apparatus provides a method of secure communication between two points, as long as no suitable type of receiving equipment for. interception is available. By the design of the transmitter, the dispersion of radiation can be controlled to minimise the risk cf enemy interception. These properties make the apparatus suitable for night screened-signalling or for use as navigational aids, the V/S Special transmitters, being used as signalling transmitters or as beacons. It should be remembered that, when using V/S Special methods for signalling, it is necessary either for the transmitting station to use a visual call-up or for the receiving station to keep a continuous watch; suitable apparatus is not at present available for the automatic reception of infra.-red signals.

  It is known that other countries have apparatus, similar to the V/S Special apparatus, in naval use and every effort should be made to detect and report enemy transmissions. Similarly, precautions must be taken when using transmitters on the assumption that the enemy has means of detection similar to our own. In general, therefore, the use of the transmitter, selected for a particular application, should be limited to the range and dispersion required. Special care must be taken in enemy waters.

V/S Special apparatus can be classified under the following headings.

Receivers.

  The term "V/S Special receivers" covers any apparatus (except television) capable of receiving infra-red radiation and transferring it to the eye as a visual image.

Transmitters.

V/S Special transmitters may be divided into two classes:-

(a)  Directing transmitters. These are used as navigational aids for directing craft along a defined line of bearing from the directing ship. The Lorenz beam principle is employed, i.e. two narrov; overlapping beams are produced and distinctive signals made with each to give indications of bearing.

(b)  Homing beacons and signalling' transmitters. These transmitters are used as navigational aids for homing craft to the ship displaying the homing beacon. They give either an all-round arc (e.g. Type 307) or a directional arc of'a fixed width which varies with the type of transmitter (e.g. Types 308*. 3^)* The majority of the beacons can be keyed to make coded signals or slow morse. No transmitter has been designed essentially for sending messages.

Trans-Receivers.

  These consist each of a transmitter and receiver, combined to form one unit. They are used in cases where the operation of both transmitter and receiver is required to be carried out by one operator. They are essential for use with "corner cube" reflectors. In this system, the operator transmits a beam which is picked up by a special reflector (known as a corner cube) and sent back to the operator. The system requires the receiver to be close to the source of transmission.

  It must be stressed that the performance obtained by any system of receivers and transmitters depends not only on the strength of the transmission but also on the sensitivity of the receiver. Since these vary under different conditions and, to a certain extent, from one instrument to another, it is essential that operators should know the individual performances of the instruments supplied to them.

  The following considerations affect the performance of V/S Special systems.
    (i) The accuracy of training of the transmitter. Transmissions are stronger in the centre of the beam and grow weaker
    towards the limits of dispersion.
    (ii) Atmospheric conditions and temperature. The transmission of infra-red is affected by fog in the same way as that of
    visible light.
    Also, the sensitivity of the receiver, and hence the greatest range of the system, is reduced at high temperatures.
    (iii) Condition of optical system and cleanliness of glass, screen, etc.
    (iv) Age of transmitter lamp.
    (v) Condition and endurance properties of transmitter battery.

The performance of the battery will drop after it has been in use for some time. Since both transmitters and receivers are affected by high temperatures, special steps have been taken to provide for efficient operaticn in the tropics.