Abstract: A detector for a magnetic field having a low frequency compared to background EMF and having a magnitude approximately 1,000 times less than the EMF, the detector comprising: a pickup coil for capturing the magnetic field and the background EMF; an integrator coupled for receiving a signal having respective components representative of the magnetic field and the background EMF, the integrator having a time constant such that successive positive and negative polarity portions of the component representative of the background EMF cancel out one another in the integrator, but the component representative of the magnetic field results in a net output signal from the integrator, the net output signal being indicative of the magnitude of the magnetic field; and, a magnetic field strength output indicator responsive to the net output signal from the integrator, whereby the magnetic field can be detected with great sensitivity notwithstanding the background EMF.

Abstract: An antenna assembly for a cellular telephone reduces electrical signal interference caused by the close proximity of the antenna to the user's head. The antenna assembly includes a coil antenna mounted on the top of a telescoping rod member. Only the coil antenna is adapted for transmitting and receiving electrical signals. The coil antenna is electrically connected, via a coaxial cable, to a telephone transceiver circuit board. In operation, the telescoping rod member is extended until the coil antenna is positioned at a height above the user's head to minimize the transmission of electrical signals toward the user's head.