Hydrophone Case 



This is a 6-inch I.D. steel-wall pipe, 18 inches long with a 

 l/4-inch-ttdck wall. One end of this pipe is threaded, and an end- 

 cap is firmly screwed on; then a complete brazed joint is made around 

 the threaded joint. On the other end, a 6-3/16- by 1-inch brass 

 flange is brazed onto the pipe. This flange is machined for a PRP~ 

 902-64 0-ring, eight 7/l6-inch stud holes, and a standard 5-inch non- 

 tapered pips thread on the inside diameter. It will accomodate an 

 MI-2 mine hydrophone at present, but other hydrophones may be used 

 by attaching custom-made adapters on the 5-inch non-tapered pipe 

 thread. 



A No. CC1045 H.H, Buggie-cable feed-through gland is mounted on 

 the end-cap for the power and sigial cable. 



A treated wooden nose piece fits on the pipe end-cap for stream- 

 lining purposes, and is banded with 3/8-inch oval brass. 



The matching amplifier is shock mounted to the back cover of 

 the MI-2 mine hydrophone. 



The hangers (l/4- by 1-inch brass rectangular stock) are clamp- 

 type bands which attach the hydrophone assenfcly to the trawl cable. 

 The hangers can mount marlin-served shackles, or guarded sheaves can 

 be fabricated if the cable-shackle noise level should be annoying. 



Batteries 



The battery section of the telemeter contains Eveready batteries 

 No. 484, No. 960P, and No. 773. It is necessary to keep cardboard 

 spacers between (l) the No. 484 batteries to allow wire and plug 

 clearance and (2) the No. 96OP to provide insulation between bottom 

 of cells and chassis ground, wires, and plugs. Placing insulating 

 tape on the bottom of the cells provide an additional safety factor 

 against shorts. 



Maintenance 



It must be emphasized that for the proper performance of this 

 equipment, as far as water leaks are concerned;, the O-ring seals, 

 feed-th roughs, and rubber tubing must be properly inspected, cleaned, 

 and coated or packed with silicone high -vacuum grease before the 

 instrument is pit into operation. 



After each use of the instrument, the O-rings that seal the end 

 caps into the telemeter case and the O-ring that seals the MI-2 mine 

 hydrophone must be inspected, cleaned, and re-coated before re-use or 



15 



