ground station signal will be transmitted with respect to the time the ship 

 station signal was received. A constant velocity of propagation is assumed 

 and corrections are not normally made . 



a. Shipboard Equipment 



The timing of the entire system is controlled by a highly stable 

 100-kc crystal oscillator in the shipboard controller. Divider circuits are used 

 to produce signals for driving the distance-measuring circuits, gating delay 

 circuits and initiating pulses for the transmitter. 



The 100-kc timing signal is also fed to three synchro-resolver circuits 

 in the range units, along with the outputs of the appropriate dividers . The sig- 

 nals from the three resolver circuits (10, 100, and 1000 microseconds) are used 

 to measure the distance between the ship and the ground stations . 



A separate resolver system is used for each of the two ground stations, 

 so that the distance to each shore station is measured simultaneously. The 

 counting is done by a large vernier dial reading to 10 microseconds with a reso- 

 lution of 0.1 microsecond. The dial is coupled to a counter which reads tens, 

 hundreds, and thousands of microseconds, and thus indicates the distance to 

 each ground station in microseconds. 



Pulses from the range resolvers are directed to the indicator, where 

 they initiate the cathode-ray-tube sweep. The sweep is positioned by operation 

 of the ranger until it occurs simultaneously with the reception of the ground 

 station signal. The pulse which triggers the transmitter also triggers a fixed, 

 stationary sweep on which the transmitter signal is displayed. By adjusting each 

 ranger so that its ground station signal is in coincidence with the ship pulse, one 

 may read out the distance between ship and ground station on the vernier dial 

 and counter in loop-microseconds. 



The "A" ground station and "B" ground station signals are made to 

 appear on the left and right sides of the vertical cathode -ray-tube sweep. The 

 two signals are commutated at a high rate and thus appear continuously displayed 

 to the operator. 



Signals from both shore stations are received aboard ship on a single 

 receiver and a common antenna quarter-wave flat-top antenna. The incoming 

 signals are coupled to the receiver by an attenuator unit which amplifies the 

 signals from weak ground stations and shorts out those from the transmitter. 

 The receiver utilizes automatic gain control to equalize the strength of the sig- 

 nals from both ground stations . 



112 



artbur ZD.llittlf.Snr. 



