542 HYDROGRAPHIC MANUAL PaGE 504 



The transceiver is housed in a east-steel tank (fig. 105), which can be installed in almost any type 

 of ship, it being only necessary to cast the holding ring of the housing to fit the slope of the ship's 

 bottom at the selected location. The transceiver must be installed so that its diaphragm is parallel 

 to the surface of the water. To reduce turbulence due to the projection of the housing beyond the hull, 

 a streamlined blister of steel plate or reinforced concrete is built around it, or on a wooden vessel it 

 can be made of wood bolted to the hull. As can be seen in figure 105, the transceiver is set in the hous- 

 ing in such a way as to form a watertight bottom, the transceiver's diaphragm being in contact with 

 sea water. Rubber gaskets between the transceiver and housing prevent any part of the transceiver 

 from being in direct contact with metal, to eliminate or dampen the effect of hull vibrations on it. It 

 is important to verify that all these gaskets are in place before the transceiver is installed. The 

 electric cable to the transceiver should be sheathed with a lead or copper covering, or be run in a con- 

 duit, where it passes through the bilge, to protect it from oil and water. 



Where a filter junction box is used with the Dorsej' No. 1, to introduce the polarizing current, it 

 should be located near the transceiver. 



Shielded cable should be used between all units. Although multiconductor cables may be used 

 in some cases, the following cables, without exception, should be individually and completely shielded 

 from source to terminus: (1) The 17.5-kc cable from power supply to transceiver; (2) the 17.5-kc 

 cable from power supply to echo amplifier; (3) the output of the echo amplifier to the indicator cabinet; 

 (4) the 1025-cycle cable from power supply to indicator cabinet; and (5) the 60-cycle 110-volt cable 

 to all parts. A high grade of cable suitable for marine use must be employed; only two sizes are needed 

 for the entire installation. The cable between the power supply and transceiver should be shielded, 

 low-capacity, two-conductor No. 10 stranded wire, insulated for 2,000 volts or more. The cables for 

 all other parts may be shielded No. 14 conductor, insulated for 2,000 volts or more. 



Where the cables are exposed to possible damage, they should be run through conduits. Kick 

 pipes should be used where they pass through decks or bulkheads. Watertight junction boxes must 

 be used at the unions of two or more cables. 



The longer cables should be bonded to the ship at intervals. Where practicable each separate 

 piece of equipment should be directly grounded but, if this is impracticable, the separate cables should 

 be all bonded together with wire and this wire grounded directly to the steel frame of the ship. 



542. DoRSEY Nos. 2 and 3 Installation 



All the instructions for installation of the Dorsey Fathometer No. 1 apply equally to the Dorsey 

 Fathometer Nos. 2 and 3, except for the size of the indicator and the installation of the sonic system 

 of the 312 Fathometer to work in conjunction with them. 



Since there are differences in the sizes and construction of the indicator cabinets of the Dorsey 

 Nos. 1, 2, and 3, each should be located with due regard to its weight and to affording accessibility to 

 its interior. The Dorsey No. 2 indicator cabinet should be located where there is a free space on each 

 side so that the doors can be opened, while the Dorsey No. 3 requires a space through which the front 

 may be opened through an angle of 90°, as well as clearance above it. Because of its weight, the Dorsey 

 No. 3 indicator cabinet should be supported on its base, in addition to any bulkhead fastenings. 



The Dorsey Fathometer Nos. 2 and 3 are combined sonic and supersonic instruments, and since 

 the sonic frequency of 1050 cycles is quite close in frequency to the 1025-cycle frequency of the cur- 

 rent of the motor driving the indicating mechanism, there is a possibility of strays, caused by the 1025- 

 cycle current, interfering when the sonic system is used. To guard against this, the 1050-cycle echo 

 amplifier and its input wires must be at least 10 feet from the power supply, the indicator cabinet, and 

 any wires carrying 1025-cycle current. It has been found convenient in some cases to locate this 

 sonic echo amplifier in the ship's hold near the hydrophone tanks. 



543. Veslekari Installation 



The factors governing the location of the indicator cabinet of the Dorsey Fathometers apply also 

 to the Hughes Veslekari graphic-recording instrument. There should be adequate room on each side 

 of the recorder cabinet to permit operation of the various controls, and sufficient space in which to 

 open the hinged front. J 



The high- and low-voltage batteries to operate the echo amplifier are contained in a box which 

 should be in the vicinity of the indicator cabinet. A charging panel and resistor for charging the 

 low-voltage batteries should be mounted near the battery box. The battery wires to the recorder 

 cabinet should be shielded. 



