An attitude sensor for determining camera orientation comprises gravity responsive means supported for movement to various positions in accordance with changes in camera orientation and fixed means for determining the gravity responsive means has moved to anyone of its positions. The gravity responsive means includes a plurality of discrete sections which have different degrees of light reflectivity or light transmissivity and are arranged to alternately occupy a predetermined location when the gravity responsive means is moved to respective ones of its positions. The fixed means includes photo-emitting means for directing light to whichever one of the discrete sections of the gravity responsive is occupying the predetermined location and photo-responsive means for providing a measure of light reflected from or transmitted by that one section.

An adaptive filtering system is disclosed. The system is used in a digital television receiver to extract low frequency vertical detail information from a comb filtered chrominance signal. This system provides wide bandwidth vertical detail information when the amplitude of the chrominance component of the composite video signal is low and narrower bandwidth vertical detail signals as the amplitude of the chrominance component increases. Adaptive filtering is accomplished by passing the comb filtered chrominance signal through a first low-pass filter, developing two reduced amplitude replicas of the filtered signal which are mutually supplementary. The ratio of the amplitudes of these two replicas is variable with a control signal. One replica is passed through a second low-pass filter and combined with the other replica to produce a vertical detail signal. The embodiment of the system that is disclosed includes means for developing a control signal that is proportional to the instantaneous amplitude of the chrominance component of the composite video signal.