A method of servicing a wellbore comprising preparing a liquid plug, allowing the liquid plug to polymerize into a highly deformable elastic plug, and placing the highly deformable elastic plug into a wellbore. A detected member is positioned at one side of the position detecting sensor so as to be adjacent to or away from the position detecting sensor. The format defines transmission windows within an interval, each window occupying a part of that interval and having a frequency bandwidth profile, each said window being assignable for a transmission interval. Network-initiated access comprises a communication resource controller or other fixed network equipment sending a page request to the communication unit which responds with a page response message including the identification of the communication unit and an access control identifier. A transverse torsion-bar spring acts on the output lever, with an actuator adjusting a pretension of the torsion-bar spring.