Pat.#4254418:		Collision avoidance system using short pulse signal reflectometry
INVENTORS:		Cronson; Harry M., Lexington, MA
		Rao; Basrur R., Lexington, MA
		Drew; Prentis B., Kirkland, WA
		Ross; Gerald F., Lexington, MA
		Lerchenmueller; Werner, Bellevue, WA
ASSIGNEES:		Sperry Corporation, New York, NY
ISSUED:		Mar. 3, 1981
FILED:		Aug. 23, 1978
ABSTRACT: A collision avoidance system for rapid transit vehicles employing baseband radar principles in which signals with duration in the order of nanoseconds are transmitted down track along a surface wave transmission line. Reflections from a passive target located on the preceding vehicle are processed to establish the distance between the vehicles to within an accuracy previously unachievable.