Abstract: A shaft angle transducer particularly suited for use as a magnetic compass card for providing an output signal linear with angular movement over a wide range, such as plus and minus 40.degree., with no zero dead band. A member with a plurality of radial segments, each having relatively opaque and transparent portions, with the proportion of the portions changing from segment to segment to provide an output varying as a predetermined function of angular position. A sensor with radiation source and detector, with the segments moving between the source and detector, with the segments in a disc configuration and in a wheel configuration.

Abstract: The invention provides an equalizer or control unit to be used in conjunction with the present day type of parking meter. The control unit of the invention comprises an ultrasonic transmitter and receiver system which senses the presence of a parked vehicle, and which controls the parking meter in a manner such that the time remaining in the meter is returned to zero when the vehicle is driven away. The system to be described also controls the meter in a manner so as to prevent anyone from inserting coins into the meter after an initial parking interval has expired thereby to prevent the monopolization of the parking space by one vehicle over extended periods of time.