Abstract: A magnetometer and method for measuring magnetic field strength particularly adapted for use in an electronic flux gate compass. A core of magnetic material in the shape of a toroid is coupled to a drive coil and to two sense coils oriented along orthogonal axes. A current limited, current source coupled to the drive coil periodically saturates the core, drives the core out of saturation at an intermediate current level, and saturates the core again. Each sense coil is coupled to a sense circuit which measures the current in the sense coil induced by the periodically changing flux density in the coil resulting from an external magnetic field coupled to the sense coil, produces a dc feedback signal to cancel out the external magnetic field, and provides the dc signal as an output representative of the external magnetic field strength along the axis of the sense coil. The dc signal is produced by synchronously detecting the amplified ac current in the sense coil.

Abstract: A variable attenuator comprises a plurality of attenuator stages connected in series along a transmission line signal path. Each attenuator stage comprises a resstive pi-section attenuating pad which may be selectively inserted into the signal path to increase attenuation along the path. Each series element of the pad is selectively inserted or removed from the signal path by opening or closing a parallel connected switching device, while each shunt element of the pad is selectively connected to or disconnected from ground by closing or opening a corresponding series connected switching device. The switching devices each comprise an NPN bipolar transistor and a PNP bipolar transistor, the emitter of each transistor being coupled to the emitter of the other and the collector or each transistor being connected to the collector of the other, to provide a low impedance AC signal path from collector to emitter when the transistors are active.