Abstract: A compass data converter converts 180X and 90X synchro compass data to 1/6 degree step data. 180X synchro data is converted by utilizing a 360X to 1/6 degree step data converter that divides the synchro rotation into six 60.degree. sectors providing a digital step data code representative thereof. A 180X converter further sub divides the 60.degree. sectors into 30.degree. sub sectors by selecting a synchro output in accordance with the step data code from the 360X converter and comparing the selected synchro output to ground to provide an additional step data digit. The converter for 90X data further sub-divides the 30.degree. sub-sectors into 15.degree. intervals by selecting two synchro outputs in accordance with the 360X step data code and the additional step data digit and scaling one of the selected synchro outputs to equal the other selected synchro output at the 15.degree. interval boundaries.

Abstract: The radar trigger and pretrigger generator determines the inherent component time delay through the radar modulator and transmitter during a first cycle of operation. During the next cycle of operation a pretrigger pulse is generated after a time corresponding to the previously measured delay and a trigger pulse is generated after a time corresponding to an operator selectable delay. The trigger pulse is used to trigger the radar modulator, which in effect, permits the operator to control the elapsed time between pretrigger pulse and transmitter firing in a fashion which is completely independent of circuit delay variances through the radar modulator and transmitter.

Abstract: A fast time constant circuit includes input and output amplifier means coupled together through an R-C network containing a series capacitor and a shunt-connected constant current source in which the level of current flow through the current source is regulated by means of a remote adjustable d.c. voltage source.

Abstract: Symbology is written on a radar plan position indicator display with a rotating beam deflection field. The PPI radar range is quantized into range increments and digital data representative of the symbology to be written are inserted into a shift register which is clocked in synchronism with the range sweeps to provide interleaved digital data to the video input of the display. The normal radar video data is combined with the symbology data so that the symbology and normal radar returns are simultaneously written in real time. A portion of the symbology generating apparatus provides a manual acquisition marker comprising a range ring and an azimuth geometric figure. A range switch gates a clock pulse signal into a range up/down counter for incrementing and decrementing the number therein, the digital output of the counter being representative of the range of the range ring.