5232 HYDROGRAPHIC MANUAL PaGE 464 



punched in the laminations which, when assembled, resemble a transformer core. 

 A few turns of rubber-covered wire are wound through the openings in such a way as to 

 include most of the nickel in the field of the windings. The cores are so dimensioned that 

 the entire unit has a natural frequency of vibration in water of 20 kilocycles. The 

 units are installed so the 4-inch dimension is vertical and the vibration of the horizontal 

 face of the transmitting unit, by the magnetostriction phenomenon, projects a beam of 

 supersonic sound downward into the water. 



The receiving unit is aft of the transmitting unit in the fish. The two units are 

 identical in every respect and may be used interchangeably. The separation between 

 the units is only 9 inches, thus practically eliminating any error due to separation (see 

 556), even for measurements of very shoal depths. 



The cables from the two units are led through two pipe fittings at the top of the 

 brass casting, and thence pass through two pipes that are screwed into these fittings 

 to form part of the supporting structure for the fish. These are rubber-covered, two- 

 conductor cables, covered with a flexible woven metal shield. The cable ends are 

 provided with plugs by which they are connected to the recorder cabinet. 



5232. Recorder Cabinet 



The recording mechanism is housed in a cabinet 21 inches long by 17 inches wide 

 by 10 inches high; the cabinet is an aluminum casting, with a glossy black finish. This 

 cabinet contains the entire recording apparatus, paper, echo amplifier, and phasing and 

 keying circuits. The total weight of the cabinet and all contents is 103 pounds. The 

 cabinet may be mounted on a vertical bulkhead or panel, or placed face up on deck or 

 on a table. The main door of the cabinet is hinged on the left, as one faces it, and accord- 

 ingly opens from right to left. This door is secured by two large wing nuts on the right 

 side. A small glass door in the main door covers the record paper and exposes about 

 2}^ inches of the fathogram before it is automatically wound on a take-up spool at the 

 right. Looking at the record in this position, with paper moving toward the right, the 

 profile of the bottom is disclosed in its natural position, that is, with the zero line, or 

 sea surface, at the top of the record. 



This cabinet is sprayproof and the instrument is designed to be operated in rather 

 severe weather, without harm to paper or mechanism. The glass door, through which 

 the fathogram is viewed, may be raised to permit access to the fathogram for making 

 notations thereon, either with black or colored pencil, or with a fountain pen. An 

 exhaust fan mounted in the cabinet removes the carbon dust formed on the paper and 

 dissipates any heat in the cabinet. 



Controls and other devices located on the front of the panel are: the phasing dial, 

 an index-adjuster knob, a gearsliift for changing from feet to fathoms or vice versa, a 

 reed tachometer, a governor adjuster, an amplifier sensitivity control, a 0- to 15-volt 

 d-c voltmeter, a fix-marker button, and a switch to turn on the electric bulbs which 

 illuminate the fathogram. On one side of the recorder cabinet is an off -on switch 

 and two manual motor-speed controls, one for rough and the other for fine adjustment. 

 On the left end of the recorder cabinet is a toggle switch by which the mark made on 

 the fathogram by the transmitted signal may be greatly reduced in intensity. The 

 three receptacles, into which the leads from the battery and transmitting and receiving 

 units are plugged, are on this same end. 



The important parts contained in the recorder cabinet are: the driving motor 

 and governor, recording mechanism, keying circuit, phasing mechanism, two motor 

 generators, and the echo amplifier. 



