(V-102 on Fig, 43) operates the Index relay of the slow-speed 

 recorder when switsh is in either the BUS or the 



position.. The first stage (V-101 on Fig, 43) is energized 

 by the chronometer when switch . is in the ] 

 position, and by the rectified 3-kc pulse from the magnetic tape 

 recorder when L is. In the position* 



(f) A l„?~kc low-pass filter which passes only the signal being 

 played back from the magnetic tape recorder, allowing it to be 

 recorded on the high-speed graphic level recorder „ 



26o Normally j, the only servicing required by the time tone amplifier will 

 be occasional tube replacement If more extensive servicing is necessary 

 the amplifier can be taken from the rack by removing the four screws 

 holding it to the tray a The control knobs must be removed from the front $ 

 but it is unnecessary to remove the front panel„ The time tone amplifier 

 employs three 6J5 tubes, two 6SJ7 tubes^ two 6v6 tubes, and one 6X5 tube„ 



27 „ The chronometer time control and phone monitor power supply (Fig, 44) 

 furnishes all operating voltages to the units described in paragraph 24o 

 It is located on the left side of the second shelf from the bottom of Rack 

 1, It employs a two-section filter with condenser input and supplies a 

 260-volt DC plate voltage and a 6„3~volt AC filament voltage. Negative 

 bias voltage is available between terminals 16 and 17 and is controlled by 

 the break-circuit chronometer to obtain time indexing on the original tapes 

 of the sound level recorders. Bias voltage is varied by means of R-202, 

 located on the under side of the power supply, 



28, The 110-volt AC input to this power supply is fused at 5 amperes on 

 the front panel of Rack 1 by the center fuse labeled L Y, 



This fuse also controls the 110-volt AC for Rack 2„ To remove the power 

 supply for servicing, disconnect the cables to it (all are at the rear of 

 the chassis) and remove the four screws located under the tray beneath the 

 four corners of the chassis. This power supply uses a single 5U4 tube. 



MONITOR AMPLIFIER AND LOUD-SPEAKER 



29 o The 124A monitor amplifier, used only to drive the monitoring loud- 

 speaker,, is located on the bottom shelf of Rack 1 Its input comes from 

 the Cannon receptacle marked on the rear of the Time Tone amplifier 

 chassis,- A . "control to regulate the output level from the 



speaker ia located on the bottom front panel of Rack !<= 



- 9 



