Beach Defense Illumination Equipment Anti-Motor-Boat Searchlights,

It is contemplated that spread beam searchlights will be used in conjunction with radio direction finders for the illumination of Motor Torpedo Boats. The direction will be telephoned from the direction finder to the searchlight. The searchlight will then go into action in the direction given. When the target is illuminated the ranges will be ascertained by the battery base and stations, and this information will then be sent to the gun batteries. Due to the narrowness of the concentrated beam 1.25 degrees spread of the searchlight it is necessary to spread the beam so that the target can be followed at close range, thereby facilitating accurate gunfire on the target. The subproject included the development and testing of an arrangement for spreading the beam of a 60-inch standard searchlight to conform with the following military characteristics The standard 60-inch searchlight shall be the basic unit Army modifications made in the standard unit shall not interfere with the normal long ranges of the lights The light shall provide for a 10 degree spread-beam, and also for a 15 degree spread beam provided this does not unduly complicate the mechanism involved The change from standard beam to spread beam, or vice versa, shall not require more than the minimum practicable time to effect, and preferably not more than 10 seconds The device to produce the spread beam shall be such that it can be attached to the searchlight in the field. As a result of service tests, the Coast Artillery Board indicated that the spread lens attachment Method No. 3 was the most satisfactory.