PUBLIC ADDRESS SYSTEMS 



135 



cover protects the parts from mechanical injury, and a cast iron case, 

 in which the whole assembly mounts, is provided for protection against 

 moisture. 



One of these receivers equipped with the largest projector provided, 

 will carry without serious distortion or overheating, power which is 



Fig. 13. 



about 27 miles above the zero level. With this output, it is possible 

 to project speech a distance of 1000 feet under ordinary weather 

 conditions and this has been done at several installations. 



On account of the different conditions encountered in installations 

 three types of horns have been used, shown in Fig. 12. Where it is 

 necessary to project the sound to great distances, a tapering wooden 



