5241 



HYDROGRAPHIC MANUAL 



Page 474 



flash the neon tube in the indicator, thereby registering the depth. This cycle is re- 

 peated at the rate of 20}^ times a second, resulting in as many soundings per second. 



The Dorsey Fathometer No. 1 is composed of four separate parts: the transceiver, 

 echo amplifier, indicator, and power supply. The transceiver, echo amplifier, and power 

 supply are nearly identical in circuit arrangements with those of the Dorsey Fathometer 

 No. 3. The functions of these parts are mentioned only briefly here, their construction 



PHOTOELECTRIC SLOT IN DISK LIGHT 



iV 20 5 rev 



TUBE "■ „„„„„H 



Ocean bottom 



Figure 104.— Schematic operating diagram of the Dorsey Fathometer No. 1. 



and functions being described in detail in 526 where the Dorsey Fathometer No. 3 is 

 described. 



5241. Transceiver 



The transceiver, or combined transmitting and receiving unit, operates on the 

 magnetostriction principle. It is a diaphragm type, intended for use in direct contact 

 with sea water, which requires that it be fitted into an opening cut in the bottom of 

 the vessel. It is relatively inefficient in energy conversion but possesses other qualities 

 favorable to shoal-water sounding. Back of the diaphragm are a number of nickel 

 tubes, which form the magnetostrictive element. Their physical dimensions are such 

 that they are broadly resonant at 17.5 kilocycles. A coil is wound around each nickel 

 tube to furnish the necessary magnetomotive force for transmitting, these same coils 

 introducing a voltage in the echo amplifier when the echo impinges on the diaphragm 

 of the transceiver. 



The transceiver installed in a hull mounting is shown in figure 105. 



