Patent attributes
An access cover to underground city infrastructure, particularly a cast iron or a cast iron-concrete cover provided with a cover detection sensor connected with a radio frequency signal transmitting antenna through a transmitter, characterized in that an antenna module (1) provided with a housing made of a material neutral to electromagnetic fields, preferably made of plastic, is installed in the through channel or hole (4) with variable cross-section, and removably fixed at the bottom to a sensor module (2) located underneath the bottom of the cover (3), provided with a battery powered, low current electronic system containing a radio transmitter and an acceleration sensor or a gyroscope and an appropriate controller which detects changes to the position of cover (3) in space and in time, whereby the surface area of the sensor module (2) is greater than the surface area of the through channel or hole (4).
