The present disclosure provides systems and methods directed to managing parking space utilization and, more particularly, to maintaining a usage record and controlling access to on-street and other public charging spaces for electric vehicles, plug-in hybrid electric vehicles and other vehicle types, such as high efficiency fuel powered vehicles, for which preferential parking may be desirable. The unit includes a fixed part and a rotary part arranged to grip a pipe to be rotated. A valve sensor generates a sensor signal indicative of an instantaneous parameter of the valve that changes between the deactuated and actuated positions. The contact surface is curved so that tape is in contact with different regions of the contact surface based on the amount of tape on each reel. Generated pulses from the pulse generator are supplied to both sides of the differential circuit and reflected signals from the transmission line are supplied to one side of the differential circuit.