housing, insulating material between the 

 different metals was used to reduce elec- 

 trolytic action. 



5. Economy and availability . 



Television equipment is costly and, 

 of the types available, the Image Orthicon 

 system costs the most. The higher cost had 

 to be borne, however, since this was the 

 only system which provided sufficient sen- 

 sitivity for our purposes. It was important 

 for us to reduce costs to a minimum and yet 

 to be able to secure the equipment for use 

 within a reasonable period of time. For- 

 tunately, a television system that met our 

 needs had been developed for the U. S. Navy 

 Bureau of Ships, as referred to by Sand 

 (1955). Some changes were required to meet 

 our specific requirements, but costs and 

 construction time were substjintially reduced 

 by adapting this previously developed sys- 

 tem to fit our needs. 



By using a noninterlaced system, we 

 eliminated the need for a synchronizing 

 generator and substantially reduced the cost. 

 Although some loss of resolution resulted, 

 the present unit has been satisfactory for 

 our use to date. A provision has been made 

 for attaching a synchronizing generator if 

 it becomes necessary. 



Power Source 



A major problem in operating tele- 

 vision equipment aboard vessels is that of 

 obtaining an adequate source of electric 

 power. Our system requires a regulated 60- 

 cycle supply of 110-120 -volt a.c. Small 

 vessels normally have 32-volt d.c. systems, 

 and conversion of these to 110-120 a.c. is 

 not practical. Larger vessels (over 100 

 tons) generally have 110-120 - volt d.c. sys- 

 tems. Our experience has been that conver- 

 sion to a.c. is often unsatisfactory because 

 the frequency varies beyond the maximum 

 permissible limit. In any event, installa- 

 tion of a converter is not practical for 

 short-term use. 



Research vessels often have a 110-120 

 a.c. system as part of their permanent 

 equipment. This may be adequate for tele- 

 vision if the frequency is well stablized 

 and if other items of equipment which could 

 cause interference are not operated from 

 the same system. 



Our solution to the problem of a 

 proper basic power source is the use of a 

 portcible gasoline-driven generator which 

 provides 2 1/2 kw. of 110-120- volt a.c, 

 bO +_ 3 cycles. This generator provides 

 sufficient current for one 1,000-watt un- 

 derwater light in addition to the basic 

 system requirement of 700 to 1,000 watts. 



As mentioned previously, we use a 

 noninterlaced scanning system which, to- 

 gether with elimination of the synchroniz- 

 ing generator, obviates problems associ- 

 ated with frequency instability. This 

 arrangement has the advantage of providing 

 greater tolerance to frequency variation 

 although some loss in picture resolution 

 results. 



Light s 



We have used artificial light in our 

 fishing-gear studies only when the camera 

 was mounted inside the cod end of the trawl. 

 In this instance, the lamps could be at- 

 tached easily and safely to the rigid cod- 

 end frame. Use of lights in other studies, 

 such as those of the forward parts of the 

 net, would require special considerations — 

 either that the lights be mounted on the 

 camera housing with a bracket, or suspended 

 from the part of the net to which the cam- 

 era is attached. 



Lighting problems encountered in 

 working with mounting stands, cages, or 

 other similar devices have not been serious 

 because lights may be very simply attached 

 to almost any carrying vehicle. The use 

 of lights complicates operations slightly, 

 in that an additional wire must be handled 

 with the camera cable. The light cable is 

 usually taped or lashed to the camera cable. 

 A single 1,000-watt diver's Ijunp has been 

 found to be adequate for most of our illu- 

 mination requirements. An illuminated 

 cod-end scene is shown in figure 2. 



OPERATION OF THE EQUIPMENT 



Since most of our work with under- 

 water television has been concerned with 

 the escapement of groundfish from otter 

 trawls, the following description will re- 

 late, for the most part, to methods used in 

 observations of this type of gear. 



