A system is provided for detecting the output power of power amplifier circuitry in a transmitter of a mobile terminal. The nut is offset with respect to the longitudinal axis of the shaft of the bolt so that when the bolt is rotated by means of the nut, the bolt is caused to describe a circle of greater diameter than its own diameter, the amount of said offset being from about 0. A first test value, derived from the calculated spectral density estimate, is compared to a first threshold. The access device can be coupled to a screw head by sliding the outer sleeve relative to the inner sleeve and compressing the grasping elements. A repeater unit spans the wall joining the two antennas. In the case where the intermittent operation is stopped a number of times, subsequent intermittent operation may be prohibited.