Abstract: A cover for a fill pipe opening of an underground fuel tank which contains a transmitter which will be activated when the cover is disturbed to transmit an alarm signal to a remote location. The signaling equipment is fully contained within the cover and the cover is sealed to protect the equipment from contamination. A rechargeable power source such as a battery is also contained within the cover, and it can be charged without breaking the sealed cover. The cover can be used in place of the existing cover without any modification to the fill line or fill access opening.