A New System for Preventing Collisions at Sea 



tions out and to occupy more territory, a much shorter 

 trumpet is employed, which is bell-mouthed and does not 

 require any support other than the central pivot, 



Plate No. 3. A vertical central section of the apparatus for 

 converting the inaudible waves of the echo into sounds which 

 are audible to the human ear. This apparatus is provided with 

 a thin, tightly drawn diaphragm. The atmospheric vibrations 

 cause this diaphragm to vibrate after the manner of the head 

 of a drum, and in moving it opens and closes electrical circuits 

 and causes bells of various sizes to ring. The circuit making 

 and breaking apparatus is shown in the smaller illustration. 

 Any degree of fine adjustment may be made by means of 

 the spindle, which is provided with a screw thread passing 

 through a support inside of the cylinder. Whatever pressure of 

 air there may be on the front of the diaphragm produces a 

 similar pressure inside of the cylinder. The air passes through 

 the felt, and through a small opening that is adjustable in the 

 connection through which the screw spindle passess. 



In Plate No. 4 we have a vertical central section of the 

 apparatus for recording the frequency and the amplitude of the 

 atmospheric vibrations that strike the diaphragm. A very 

 small and light rod is attached to the centre of the diaphragm 

 which passes to the rear and carries a pencil point that records 

 the vibrations on a strip of paper similar to trjat used in a 

 Morse instrument. When the operator moves the handle of 

 the siren downward, he not only opens the steam valve, but 

 closes an electric circuit which releases the mechanism of the 

 Morse instrument and allows about fourteen inches of the paper 

 to be fed out, all of which is shown in the drawings. 



The primary blast sent out by the siren is registered on the 



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