Most satellite dish actuators send a series of pulses to indicate their position. By counting pulses the positioner knows where the dish is pointing. It is possible to use a serial port and Linux with RTAI patches in order to count these pulses, thus

鸟菜.第四版,珍藏版，不错，强烈推荐，鸟菜.第四版，不错，强烈推荐，(Bird dish. Fourth edition, rare edition, good, strong recommendation, bird food. Fourth edition, good, strongly recommended,)