loosening of the rectifier plates the noise can be remedied- by tightening 

 the bolt holding the plates together. 



Condensers having a total capacity of 12,000 microfarads 

 are connected across the output of the 7-volt DC supply,. Although 

 these are lo?/-voltage condensers, they nevertheless store considerable 

 energy over a long period of operation,, Therefore handle filament 

 leads with care, even after the unit has been turned off for some time c 



TIME TONE AMPLIFIER 



Description 



24o The time tone amplifier (Fig, 43) is the distribution center for the 

 entire SOFAR receiving system, as can be seen in Figs* 3 and 12= It is 

 located on the third shelf from the top of Rack 1„ The output of -which- 

 ever channel is in use is fed through the E control to this 

 amplifier and is then distributed from the system bus to the various 

 recorder units by means of selective switchings 



25» The time tone amplifier contains; 



(a) A headphone monitor amplifier for monitoring the signal on the 

 bus or the signal played back from the magnetic tape recorder a A low- 

 frequency rise equalizer counters the falling off of the headphone 

 response at low frequencies, A jack on the front of the third panel 

 from the top of Rack 1 is fed from the monitor amplifier,, 



(b) A 3-kc oscillator, the output of -which is controlled by the 

 Hamilton break-circuit chronometer, to time index the magnetic tape 

 recorders „ 



(c) A 2,5-kc to 3o5-kc band-pass filter used to separate the 3-kc 

 time-tone index from the recorded signal when the magnetic tape 

 recorder is played back onto the high-speed graphic level recorder - 



(d) A time-tone amplifier and rectifier which amplifies the 3-kc 

 tone separated by the band-pass filter and converts it into D0 o A 

 volume control for this amplifier is located on the right rear corner 

 of the chassis and is adjusted to provide good time indexing on the 

 high-speed graphic level recorder when the magnetic tape recorder is 

 played back n 



(e) A time-tick pulse amplifier which operates the txme indexing 

 relays on the sound level recorders whenever a pulse is initiated by 

 the break-circuit chronometer, The second stage of this amplifier 



- 8 ■- 



