removed for servicing by removing the front panel retaining screws. The 

 unit contains two 6J5 tubes, one 2050 tube, one VR150 tube, and one 5Y3 tube c 



GRAPHIC LEVEL RECORDERS 



42, The two Power Level graphic level recorders are located in the center 

 sections of Racks 2 and 3 (Figs, 7 and 10) , Fig, 47 is a schematic diagram 

 of a recorder circuit, These recorders provide a visual or graphic recording, 

 on waxed-paper tapa, of the shot arrival as received at the hydrophone and 

 amplified through either channel. The tapes are time indexed along the right- 

 hand edge by the amplified time impulses from the break-circuit chronometer, 



43 o Both recorders are mounted on extension tracks so that they may be pulled 

 out beyond the normal cabinet panel face (Fig, 8), The upper half of each 

 recorder panel folds back on the lower half, concealing the hinge and ex- 

 posing the controls of the recorder. Two knobs at the front of the chassis 

 facilitate sliding the recorders out until the latches on the sliding tracks 

 drop into stops, To return the recorders to the cabinet press down on the 

 latch handles on the moving slides and push easily on the whole unit until 

 it moves back into the cabinet, 



44, The graphic level recorder in Rack 2 is normally referred to as the 

 "slow-speed" recorder and normally operates at a paper speed of five mm,- per 

 second. The graphic level recorder in Rack 3 is normally referred to as the 

 "high-speed" recorder and operates at ten mm, per second^ providing a time 

 base twice the length of that of the "slow-speed" recorder, The "high- 

 speed" recorder is used to record the play -back of either of the two magnetic 

 tape recorders, 



45o When the signal strength of a shot arrival rises above the background 

 noise the automatic switching unit will fire, turning on the motors of both 

 graphic level recorders and actuating the time indexing stylus,, If the 

 "high-speed" recorder has its AI'uF control switch turned off, however, and 

 its motor switch on „ its motor will not be started. 



46, A careful analysis of the circuit connections will explain the opera- 

 tion of the "slow-" and "high-speed" graphic level recorders. The two 

 switches on the right front corner of each recorder chassis marked . 3 and 



control the recorder operation (Fig, 23 )<. When the switch is in 

 the UAl position the drive for the recorder paper and scriber will not 

 function unless the .. I switch is ON, thus providing 115 volt 60 cycle AC 

 to the recorder amplifier and the recorder motor. When the : switch is 

 off, no power will be supplied to either the amplifier or motor and the 

 recorder will not respond when the automatic switching unit fires. 



12 



