99? The tube complement of the amplifiers for each type of magnetic 

 recorder is as follows: 



MURQPHQNE CALTRON 



One 6B8 One 6SJ7 



One 6v6 One 6SQ7 



One 6E5 Two 6y6 



One 6X5 One 6E5 



One 6X5 



CHRONOMETER AMD CODE SWITCH 



100 A Hamilton break-circuit marine Chronometer (Fig, 11) , housed in a 

 shielded compartment, is located on the sliding tray at the top of Rack 3* 

 Two stop positions on the extension tracks permit the chronometer to be 

 slid out for the convenience of the operator, both for operating ease, and 

 for rewinding... In addition, a hold-down screw on the front right side 

 permits the slide tracks to be secured at an intermediate position and pre- 

 vents accidental jar or movement to the sliding tray, 



10ib The break-circuit Chronometer is mounted in its normal wood box 

 receptacle,. The cover has been removed, however, as the sliding cover to 

 the shielded compartment provides ample security for the chronometer and 

 at the same time makes it completely accessible for operation, and facilitates 

 rewinding „ 



102„ The function of the break-circuit chronometer is to interrupt the negative 

 bias applied to the tubes of the time tick pulse amplifier (time tick DC), 

 allowing the tubes to conduct once each second, except the 59th, in each minute,, 

 This energizes the time index relay and initiates the travel of the time index- 

 ing styli on the graphic level recorders, 



103=. At the same time the relay in the output circuit of the 3-kc oscillator 

 JLn the time tone amplifier is actuated, and 3-kc pulses, in synchronism with 

 the Chronometer, are recorded onto whichever magnetic tape recorder is opera- 

 ting. Therefore, as the signal is recorded on the tape, 3-kc tone signals 

 are simultaneously recorded at one-second intervals, 



104« A normally closed switch is located in the right-front corner of the 

 Chronometer box. This is the shot signal arrival coding switch. Pressing 

 this switch opens the bias control circuit manually and applies a secondary 

 time index to the graphic level recorder tapes and a secondary 3-kc tone 

 signal to the operating magnetic tape recorder. The code mark assists the 

 station operator in determining the exact time at which the signal arrived by 

 identifying its position with respect to the adjacent one-second indexes 

 from the break-circuit Chronometer, 



- 24 ■- 



