794 BELL SYSTEM TECHNICAL JOURNAL 



to the time of the synchronizing pulse is observed to be a function of the 

 rate of change of the saw-toothed wave form and the setting of the range con- 

 trol potentiometer which may be calibrated directly in units of range to the 

 target. The following range mark generator differentiates this coincidence 

 circuit output wave form and furnishes the desired amplification. Zero 

 range calibration is here provided by employing a sample of the zero time 

 refererce pulse and introducing this voltage into the range control circuit. 



^^MBte. RANGE-YARDS- 



^^i^HHik RANGE DIAL-i 



Fig. 61. — -Transmitter-receiver-indicator assembl\- as designed for SL-Naval Search 

 Radar equipment. 



Figure 61 illustrates the transmitter-indicator assembly of the SL naval 

 vessel search radar system. This system employs a PPI display with avail- 

 able range sweeps of 5, 25 and 60 nautical miles. The assembly shown to the 

 right of the main unit contains a variable range marker circuit of the type 

 just described. This range mark is positioned by means of the control 

 located toward the top of this unit and its calibration is observable through 

 a window located on the top panel. Here a ma.ximum measuring range in- 

 terval of 40,000 yards is available. Tn this application, the RC elements of 

 the wave generator are enclosed within an oven and maintained at a constant 

 temperature by thermostatic means. The accuracy achieved in this ex- 

 ample, without recourse to calibration means involving targets at known 



